Sec 2 Flashcards
(318 cards)
1
Q
Chapter 10
What are two essential substances that cells require to survive?
A
Nutrients and oxygen
2
Q
Chapter 10
Explain the need for a transport system in multicellular organisms.
A
Since there are as much as billions of cells in a multicellular organism, most cells lie far away from the source of essential substances and a transport system is an efficient way for cells to obtain these essential substances.
3
Q
Chapter 10
What is the similarity and difference between diffusion and osmosis?
A
They are similar in how both processes involve the overall movement of particles from a region of higher concentration to a region of lower concentration. Osmosis is the overall movement of water molecules only while diffusion is the overall movement of all particles through a partially permeable membrane.
4
Q
Chapter 10
How is diffusion used to ensure that there is enough oxygen in the cell?
A
Since the cell is constantly using up oxygen, the concentration of oxygen inside the cell is lower than the concentration of oxygen outside the cell. The diffusion gradient is maintained which means that oxygen keeps diffusing into the cell and thus, diffusion ensures that there is enough oxygen in the cell.
5
Q
Chapter 10
How is the exchange of gases in a leaf during photosynthesis an example of diffusion?
A
In the presence of light, photosynthesis occurs where carbon dioxide is used up and oxygen is produced by the leaf. Carbon dioxide diffuses in and oxygen diffuses out. These processes thus show that diffusion plays a pivotal role in the exchange of gases in a leaf during photosynthesis.
6
Q
Chapter 10
What is the definition of osmosis?
A
Osmosis is the net/overall movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane.
7
Q
Chapter 10
What is the definition of diffusion?
A
Diffusion is the overall movement of particles from a region of higher concentration to a region of lower concentration.
8
Q
Chapter 10
What is water potential?
A
Water potential can be thought of as the “concentration” of water in a substance.
9
Q
Chapter 10
What is the difference between a cell bursting and crenation?
A
A cell bursts when it is placed in a solution which has higher water potential as compared to the water potential in cell’s cytoplasm. Water moves from the solution into the cell via osmosis, causing the cell to expand and burst. A cell crenate when it is placed in a solution which has lower water potential as compared to the water potential in cell’s cytoplasm. Water moves from the cell into the solution via osmosis, causing the cell to crenate.
10
Q
Chapter 10
How do animals avoid the bursting and crenation of cells?
A
Animals maintain roughly a similar solute concentration both inside and outside the cell
11
Q
Chapter 10
What is the difference between a plant cell becoming plasmolysed and turgid
A
The cell sap of the plant cell has to have a lower water potential than the surrounding solution which means that water will diffuse from the solution into the cell and the plant cell would then expand and become turgid. While the cell sap of the plant cell has to have a higher water potential than the surrounding solution which means that water will diffuse from the cell into the solution which means that the cytoplasm will shrink away from the cell wall, becoming plasmolysed.
12
Q
Chapter 10
What is a transport system in a plant made of?
A
The roots and vascular bundles.
13
Q
Chapter 10
What are the two flows in the plant transport system?
A
The upward flow of water and mineral from the roots to the leaves and there is a downward flow of food molecules from the leaves to the roots.
14
Q
Chapter 10
How are water and mineral salts taken into a plant?
A
Water and mineral salts from the soil diffuses into root hair cells which are located at the ends of roots.
15
Q
Chapter 10
What are the functions of the xylem tissue and phloem tissue respectively?
A
The xylem tissue transports water and minerals from the roots to the leaves while the phloem tissue is in charge of the transport of leaves to the roots.
16
Q
Chapter 10
What is the definition of transpiration pull?
A
Transpiration is the upward pull of water as water is evaporated from the leaves which means that there is a low water potential at the leaves and water will move into the leaves via osmosis from the roots.
17
Q
Chapter 10
In the phloem tissue, what is the overall flow of the transport of food substances?
A
The overall flow of the transport of food substances inside the phloem is downwards.
18
Q
Chapter 10
State two features of a root hair cell.
A
It is a long outgrowth of a root cell which increases surface area to volume ratio. The cell vacuole of a root hair cell contains cell sap which is concentrated with mineral salts.
19
Q
Chapter 10
Why is it that as organisms get bigger, simple diffusion/osmosis is no longer enough to supply the needs of the organism?
A
As organisms get bigger, the surface area to volume ratio gets smaller which means that it is not efficient to use simple diffusion and osmosis for the supply of essential substances and nutrients as these essential substances and nutrients are unable to reach the cells fast enough for cellular respiration and waste is not able to be disposed of fast enough.
20
Q
Chapter 10
What are the components of blood?
A
Plasma, red blood cells, white blood cells and platelets.
21
Q
Chapter 10
What is plasma made of and what is the function of it?
A
Plasma is made of mainly water and its function is to act as a solvent for many substances and transport them from one part of the body to another.
22
Q
Chapter 10
What are 2 characteristics of red blood cells and what is their function?
A
The characteristics of red blood cells is that they have a biconcave shape and that they do not have a nucleus. Red blood cells take in and release oxygen through diffusion.
23
Q
Chapter 10
State 10 components of the human transport system
A
Blood which contain red blood cells, white blood cells, plasma and platelets, blood vessels, veins, arteries, capillaries and the heart
24
Q
Chapter 10
State and explain the function and importance of the heart
A
The heart is a muscular pump that keeps the blood circulating quickly and continuously, ensuring that blood is delivering oxygen and nutrients to your cells and removing waste products.
25
Chapter 10
| State and explain the function and importance of veins
Veins are a type of blood vessel that is thin and has less elastic walls compared to arteries and carry mostly de-oxygenated blood towards the heart.
26
Chapter 10
| State and explain the function and importance of arteries
Arteries are a type of blood vessel that is thick, elastic and has muscular walls to withstand high pressure as oxygenated blood is carried away from the heart.
27
Chapter 10
| State and explain the function and importance of capillaries
Capillaries are a type of blood vessel which very thin, has one-cell thick walls to allow easy diffusion of substance. Capillaries connect arteries to veins and form a vast network linking to the cells of the body. Capillaries carry oxygen and nutrients to the cells and carry carbon dioxide and waste produced away from the cells.
28
Chapter 10
| State and explain the function and importance of white blood cells
White blood cells are involved in defending the body against both infectious diseases and foreign materials. They are produced in the bone marrow and have a short lifespan.
29
Chapter 10
| State and explain the function and importance of platelets
Platelets are irregularly shaped cell fragments that form clots to stop excessive bleeding.
30
Chapter 10
| Describe the process of double circulation
Double circulation in the human body is like two "loops" of blood flow and the heart is like two pumps, maintaining the loops. One part pumps deoxygenated blood to the lungs to get rid of carbon dioxide and gain oxygen while the other part pumps this re-oxygenated blood to the rest of the body.
31
Chapter 10
| Why must the human transport system work with other organ systems?
The human transport system, which is the circulatory system, supplies oxygen and nutrients to our bodies by working with the respiratory system. At the same time, the circulatory system helps carry waste and carbon dioxide out of the body.
32
Chapter 11
| State the three main types of nutrients in food which can also be used to produced energy
Carbohydrates, proteins and fats/lipids.
33
Chapter 11
| State 3 reasons why we need food
We need food to provide us with energy for our daily activities such as walking, grow new cells and tissues and repair worn-out tissues
34
Chapter 11
State and explain how digestion is important in allowing food molecules to be broken down and absorbed by the body through diffusion.
Since most food that we eat is made up of large, complex and insoluble molecules, the molecules cannot be absorbed by the body as they are too large to cross the partially permeable surface membrane. As such, the body needs to break down these molecules into small and soluble forms that can diffuse from the digestive system into the bloodstream and to other cells.
35
Chapter 11
| State some sources of carbohydrates, proteins and lipids that can be found in common foodstuffs
Carbohydrates can be found in rice, proteins can be found in meat and lipids can be found in butter
36
Chapter 11
| State the characteristics and functions of carbohydrates for the human body
Carbohydrates can be found in the form of starch, sugar or cellulose and can be soluble or insoluble in water. Carbohydrates provide an immediate source of energy and also makes up part of the fibre that the body cannot digest. Fibre passes out undigested and forms the bulk of our faeces.
37
Chapter 11
| State the characteristics and functions of fats/lipids for the human body
Fats/lipids are made up of glycerol and fatty acids and is insoluble in water. Fats/lipids are mainly used as a storage of energy and prevents the body from losing too much heat.
38
Chapter 11
| State the characteristics and functions of proteins for the human body
Proteins are made up of several small molecules called amino acids and can be soluble or insoluble in water. Proteins are mainly used to make new cells for body growth and repair worn-out tissue. Proteins is also used to make more complex proteins called enzymes.
39
Chapter 11
| State and explain the function and importance of enzymes in digestion.
Enzymes are protein molecules that speed up the chemical digestion of the food molecules.
40
Chapter 11
| State 5 five characteristics of enzymes
Enzymes are complex proteins that speed up the rate of chemical reactions. Enzymes remain unchanged at the end of the reaction. Enzymes are specific in their action and only speed up one kind of reaction. Enzymes are sensitive to temperature and pH. Only a small amount is required to affect a large amount of reactants.
41
Chapter 11
| How does temperature affect the enzyme
If the temperature is too low, the enzyme will be inactive but if the temperature is too high, the enzyme will be denatured and lose its unique protein molecule shape, and will stop working as a result.
42
Chapter 11
| How does pH affect the enzyme
Enzymes have an optimum pH level and can only function within a narrow pH range. Outside this range, denatured will occur
43
Chapter 11
Identify what enzyme acts on starch, maltose, proteins, and fats/lipids respectively and state what are the final products of digestion.
Amylase acts on starch which produces maltose, maltase acts on maltose which produces glucose, protease acts on proteins which produces animo acids and lipase acts on fats/lipids which produces fatty acids and glycerol.
44
Chapter 11
| Name the 5 stages of digestion in order
Chewing, digestion in the stomach, digestion in the small intestine, absorption and defaecation.
45
Chapter 11
| Identify the 6 parts of the alimentary canal
Mouth, oesophagus/gullet, stomach, small intestine, large intestine and anus.
46
Chapter 11
| What happens in the mouth after eating food
The teeth cuts and grinds the food into smaller, pieces, increasing the surface area to volume ratio. The salivary glands which contains enzymes such as salivary amylase digests starch into maltose. The tongue pushes food around the mouth while we chew, and to the back of the mouth and into the oesophagus.
47
Chapter 11
| What happens in the oesophagus after eating food
The oesophagus is a muscular tube about 25cm long. It transports food down through the process peristalsis. The muscles of the oesophagus contract above the ball of food, pushing it down. Muscles relax below the ball of food, widening the tube for it to move down.
48
Chapter 11
| What happens in the stomach after eating food
The muscles of the stomach contract and relax to break down the food into even smaller pieces, and mix the food with gastric juices. Mixing is important as the gastric juices contain enzymes like protease, as well as hydrochloric acid.
49
Chapter 11
| What are the functions of hydrochloric acid in the stomach
Hydrochloric acid creates and acidic environment which is the optimal pH for the proteases in the stomach to work and help kill bacteria.
50
Chapter 11
| What happens in the small intestine after eating food
Partially digested from the stomach moves to the small intestine, which is aided in digestion by and connected to the liver and gallbladder, and the pancreas. Food is mixed with bile, intestinal juice and pancreatic juice in order to complete digestion. The final molecular products of digestion are then absorbed into the bloodstream here
51
Chapter 11
What digestive fluid does the liver, small intestine and pancreas respectively, and what enzymes are inside this digestive fluid
The liver produces bile which contains no enzymes, the small intestine produces intestinal juice and contains the enzymes maltase, protease and lipase and the pancreas produces pancreatic juice and contains the enzymes pancreatic amylase, protease and lipase.
52
Chapter 11
| Describe the process of emulsification
Emulsification is the process where large fat droplets are physically digested by bile which is a digestive fluid produced in the liver into smaller fat droplets.
53
Chapter 11
| How is food absorbed into the bloodstream in the small intestine?
After physical and chemical digestion are completed in the small intestine, the food molecules are absorbed into the bloodstream through the processes like diffusion. Only small food molecules pass through the walls of the small intestine and blood vessels. The small food molecules enter the bloodstream and are transported throughout the body.
54
Chapter 11
| What happens in the large intestine when after eating food
Undigested food from the small intestine passes into the large intestine, where no digestion occurs. In the colon, water, mineral salts, and any remaining nutrients are absorbed. The rectum stores what is left as faeces, which leave the body through the anus in the process of defecation.
55
Chapter 11
| Identify 5 digestive juices and how they contribute to the digestive process
Saliva contains salivary amylase that digests starch into maltose. Gastric juices contain the enzyme protease that digests proteins as well as hydrochloric acid. Bile helps in physically breaking down large fat droplets into smaller fat droplets in a process called emulsification. Intestinal juice contains the enzymes maltase which digests maltose, protease that digests proteins and lipase which digests fats/lipids. Pancreatic juice contains the enzymes pancreatic amylase which digests starch, protease which digests proteins and lipase which digests fats/lipids.
56
Chapter 12
| What is reproduction?
It is the process by which organisms produce new organisms like themselves.
57
Chapter 12
| Why is reproduction important?
Reproduction ensures the transfer of genetic information from one generation to another, and the continuity of a species.
58
Chapter 12
| State and explain the function and importance of the sperm duct
The sperm duct is a muscular tube that carries sperms from the testes to the urethra.
59
Chapter 12
| State and explain the function and importance of the male sex glands
The male sex glands secrete fluids containing nutrients and enzymes. The nutrients and enzymes provide the sperms with the energy to move.
60
Chapter 12
| State and explain the function and importance of the penis
The penis becomes erect when sexually excited. Sperms are ejaculated through the penis during sexual intercourse.
61
Chapter 12
| State and explain the function and importance of the urethra
The urethra is a tube which leads to the outside of the body through the penis. During sexual intercourse, sperms pass from the testes, into the sperm ducts and then into the urethra. The sperms pass to the outside of the body through the urethra.
62
Chapter 12
| State and explain the function and importance of the testis (plural: testes)
The testes produce sperms and male sex hormones
63
Chapter 12
| State and explain the function and importance of the scrotum
The scrotum is a sac outside the body that holds each testis and provides an environment where the sperms can develop at their ideal temperature.
64
Chapter 12
| Why does the male reproductive cell have a tail?
The male reproductive cell has a tail as it the movement of the tail helps it to swim towards the female reproductive cell.
65
Chapter 12
| State and explain the function and importance of the fallopian tube/oviduct
The fallopian tube/oviduct is a muscular tube connecting the ovary to the uterus. The wall of the oviduct contracts to push the egg along the oviduct towards the uterus.
66
Chapter 12
| State and explain the function and importance of the ovary
The ovary produces eggs and female sex hormones.
67
Chapter 12
| State and explain the function and importance of the uterus
The uterus is a pear-shaped organ with thin muscular walls. The inner surface of the uterus is covered with a layer called the uterine lining. This is also the site where fertilised embryo will develop
68
Chapter 12
| State and explain the function and importance of the cervix
The cervix is a ring of muscle at the lower end of the uterus.
It is kept closed during pregnancy and widens during childbirth.
69
Chapter 12
| State and explain the function and importance of the vagina
The vagina is a muscular tube. It joins the cervix to the outside of the body. It is also where sperm is deposited and through which the baby is born.
70
Chapter 12
| State and explain the female reproductive cell and its characteristics
The female reproductive cell is an egg and it contains a nucleus.
71
Chapter 12
| Define puberty
Puberty is the period when an adolescent becomes capable of sexual reproduction.
72
Chapter 12
| At what ages does puberty start
Ages 10-14
73
Chapter 12
| Why do people grow more during puberty?
During puberty, the body produces a higher amount of growth hormones
74
Chapter 12
| What body systems are affected at the end of puberty for each gender?
For boys, they will have heavier bones and an increase in muscle growth. For girls, they will experience an increased amount of fat tissues at the breasts, hips and pubic region.
75
Chapter 12
| State 5 effects of puberty for boys and 4 effects of puberty for girls
Boys will experience the growth of facial hair, the enlargement of the voice-box which leads to the deepening of the voice, the increase in the size of the penis and testes, the production of sperm and ejaculation occurs and hair starts to grow in the pubic region. Girls will experience hair growth in the armpits, enlargement of the breasts and uterus while the hips broaden, the menstrual cycle begins and hair starts to grow in the pubic region.
76
Chapter 12
| Define menstruation
Menstruation is the discharge of the broken down tissues of the uterus, unfertilised egg and blood.
77
Chapter 12
| State the 4 stages of the menstrual cycle
Menstruation, repair and growth of the uterine lining, ovulation and the further thickening of the uterine lining
78
Chapter 12
| From which days does menstruation occur during the menstrual cycle
Days 1-5
79
Chapter 12
| From which days does the repair and growth of the uterine lining occur during the menstrual cycle?
Days 6-10
80
Chapter 12
| From which days does ovulation occur during the menstrual cycle?
Days 11-17
81
Chapter 12
| From which days does the further thickening of the uterine lining occur during the menstrual cycle?
Days 18-28
82
Chapter 12
| State and explain the repair and growth of the uterine lining during the menstrual cycle
The uterine lining grows thicker and becomes very rich in blood capillaries.
83
Chapter 12
| Define ovulation
When a mature egg is released into the fallopian tube/oviduct
84
Chapter 12
| Why does the uterine lining remain thick during days 18-28 of the menstrual cycle?
The uterine lining remains thick to supply the embryo with nutrients and oxygen for growth
85
Chapter 12
| What happens during sexual intercourse?
During sexual intercourse, the erect penis is inserted into the vagina. The penis ejaculates semen (which contains sperm) into the upper end of the vagina. The sperms will then swim up to the uterus into the oviducts and one of the sperms may get to fuse with the egg cell.
86
Chapter 12
| Define fertilisation
Fertilisation is the process where the nucleus sperm fuses with the nucleus of the egg.
87
Chapter 12
| How does a woman get pregnant?
When sperm is deposited in the vagina during sexual intercourse, the sperm will travel up the uterus through the oviduct to the egg. If an egg is present in either oviduct, fertilisation may take place and the nucleus of the sperm and nucleus of the egg fuse. The fertilised egg divides repeatedly to form a ball of cells called the embryo. The embryo moves into the uterus and is implanted in the uterine lining and thus, the woman is pregnant.
88
Chapter 12
| What happens during pregnancy?
During pregnancy, the embryo develops into a foetus or unborn baby.
89
Chapter 12
| What happens during birth?
At the end of a pregnancy, the muscles of the uterus contract to push out the fully formed baby, the cervix enlarges to allow the baby to pass through and thus, the woman gives birth.
90
Chapter 12
| Define heredity
Heredity is a process by which characteristics are passed down genetically from one generation to the next.
91
Chapter 12
| What is premarital sex?
Premarital sex is the act of having sexual intercourse before a couple is married.
92
Chapter 12
| What problems come with premarital sex?
Unwanted pregnancies and sexually transmitted diseases
93
Chapter 12
| What is abortion?
Abortion is the deliberate termination of a pregnancy.
94
Chapter 12
| When does an abortion usually carried out?
Abortion is usually carried out within the first 12 weeks of pregnancy.
95
Chapter 12
| What are 3 reasons for abortion
The child may be born physically or mentally handicapped. The mother is physically and/or mentally incapable of supporting the child. The unwanted pregnancy resulted from rape.
96
Chapter 12
| How is an abortion carried out?
During an abortion, a doctor surgically removes the embryo or foetus from the uterus.
97
Chapter 12
| Why are birth control methods used and what do they prevent?
Birth control methods are used to prevent pregnancies through preventing ovulation, fertilisation or the implantation of the embryo.
98
Chapter 12
| Identify 5 methods of birth control
Not having sexual intercourse at all (abstinence). Withdrawal of the penis just before ejaculation. The rhythm method. The use of chemicals such as spermicides and contraceptive pills. The use of mechanical devices such as condoms, diaphragms and intra-uterine devices.
99
Chapter 12
| What is the temporary birth control method Rhythm method?
Couples who practise this method do not have sexual intercourse during the fertile period (ovulation) of the woman's menstrual cycle.
100
Chapter 12
| What is the temporary birth control method of using spermicide?
Spermicide is a chemical that kills or blocks sperms from entering the uterus. It comes in gel form, aerosol foams and foaming tablets and is inserted into the vagina before sexual intercourse. However, it is not reliable when used on its own and is usually used with a condom or diaphragm.
101
Chapter 12
| What is the temporary birth control method of using a diaphragm/cap?
The diaphragm is a dome-shaped rubber cup with an elastic rim. It is inserted into the vagina and placed over the cervix. The diaphragm is impermeable to sperms and so, prevents sperms from entering the uterus. Hence fertilisation does not occur.
102
Chapter 12
| What is the temporary birth control method of using a condom?
A condom is a thin rubber tube used to cover the erect penis before sexual intercourse. It is impermeable to sperms and hence, sperms cannot enter the uterus and fertilisation will not occur. It is also impermeable to bacteria and viruses. This also protects the user from getting sexually transmitted diseases.
103
Chapter 12
| What is the temporary birth control method of using an Intra-uterine device (IUD)
The IUD is a piece of plastic or metal that is inserted into the uterus by a doctor. IUDs can also come in different forms. The IUD disrupts the function of the uterus by preventing the embryo from implanting in the uterus lining. This method provides effective protection for a long period of time.
104
Chapter 12
| What is the temporary birth control method of using contraceptive pills
Contraceptive pills contain certain female sex hormones which prevent ovulation. They disrupt the function of the ovary by preventing the release of a mature egg each month. These pills must be taken under a doctor's prescription and are reliable when a woman adheres to the instructions. However, she may suffer from some side effects.
105
Chapter 12
| Identify 2 permanent birth control methods
Vasectomy and tubal ligation
106
Chapter 12
| Why are permanent birth control methods permanent?
Permanent birth control methods permanently prevent fertilisation by disrupting the functions of parts of the reproductive system.
107
Chapter 12
| What is the permanent birth control method of using vasectomy?
Vasectomy involves tying and cutting part of both sperm ducts during surgery. This disrupts the function of the sperm ducts. Sperms will not be ejaculated during sexual intercourse and thus the male will not be able to make his partner pregnant and thus fertilisation will not occur since sperms are absent.
108
Chapter 12
| What is the permanent birth control method of using tubal ligation?
Tubal ligation involves tying and cutting both oviducts during surgery. This disrupts the function of the oviduct and prevents sperm cells from meeting the egg cell. Thus, fertilisation will not occur.
109
Chapter 12
| What is a sexually transmitted infection?
An infection transmitted from one person to another through sexual intercourse is called a sexually transmitted infection (STI)
110
Chapter 12
| Identify 3 sexually transmitted infections
Human Immunodeficiency Virus (HIV), Syphilis and Gonorrhoea
111
Chapter 12
| How does one get a sexually transmitted infection?
During sexual intercourse, bodily fluids are exchanged in the reproductive systems. Bacteria or viruses in those bodily fluids can enter the circulatory system of his or her sexual partner through their sexual reproduction system. Some sexually transmitted infections may also be spread through contaminated blood or childbirth.
112
Chapter 12
| Explain what Human Immunodeficiency Virus (HIV) does to the body and is it curable or treatable?
HIV attacks the immune system and causes the person to lose immunity and protection against common infections. A person infected with HIV may suffer from severe weight loss, lung infections, and brain infections, amongst other symptoms. Currently, HIV is not curable but is treatable.
113
Chapter 12
| Explain what Syphilis does to the body
A person infected with syphilis may suffer from common symptoms such as rashes and painless sores. If left untreated, syphilis may lead to blindness, inability to move parts of the body, heart failure, insanity and even death.
114
Chapter 12
| Explain what gonorrhoea does to the body
Symptoms and signs of gonorrhoea are swelling, pain, and pus at the infected areas. If left untreated, the bacterial infection can spread and affect other organ systems.
115
Chapter 12
| How do you treat gonorrhoea and syphilis and why does it work?
Since gonorrhoea and syphilis are both bacterial infections, antibiotics can be used to treat them.
116
Chapter 12
| State 6 ways to prevent getting infected with STIs and control their spread
We can avoid having multiple sex partners, avoid sharing instruments, ensure that only needles that are free from bacteria and diseases are used, using condoms during sexual intercourse to reduce the risk of infection, not abusing drugs or charging injection needles and ensuring that donated blood is screened for HIV and safe for use.
117
Chapter 12
| What are some complications of abortions
Parts of the sexual reproductive system may become infected or damaged which can lead to the disruption of the system's function and may cause difficulties in getting pregnant again
118
Chapter 13
| Define electric current
An electric current is the rate of flow of electric charge.
119
Chapter 13
| State the SI unit of current
The SI unit of current is the ampere (A).
120
Chapter 13
| Describe conventional flow
Conventional flow is the flow of current from the positive terminal of a battery to the negative terminal
121
Chapter 13
| Describe electron flow
Electron flow is the flow of electrons from the negative terminal to a positive terminal
122
Chapter 13
| How is a circuit diagram useful?
A circuit diagram helps us see if the electrical components are connected correctly
123
Chapter 13
| List the components of an electric circuit.
Wires, dry cell, switch, light bulb and resistor
124
Chapter 13
| What is in a series circuit?
In a series circuit, the electrical components are joined one after another to form a single loop. Electric current passes through a single path in a series circuit.
125
Chapter 13
| What is in a parallel circuit?
In a parallel circuit, the electrical current is divided into branches. Electrical components are connected in each branch. Electric current passes through all branches.
126
Chapter 13
| Describe and explain the difference in the brightness of two bulbs when they are arranged in series and in parallel
Bulbs are brighter when arranged in parallel because
| current is faster.
127
Chapter 13
| How would other circuit components be affected if one component is removed in a series and parallel circuit?
The components won’t work in series, but will still work in parallel circuit.
128
Chapter 13
How would you connect the electrical appliances in
your home, in series or in parallel? Why?
Parallel. If one appliance is switched off, the others can still work.
129
Chapter 13
| How do we measure current and how is it the device correctly placed?
We measure current using an ammeter and must be placed in series in a circuit
130
Chapter 13
| Electrical charges needs _____ to push them along a circuit
energy
131
Chapter 13
| How do electrical charges flow?
electric charges flow from a point of higher
| potential to a point of lower potential
132
Chapter 13
| What is a condition that is needed for electric current to flow
An electric current can flow only when there is a potential difference (V) or p.d.
133
Chapter 13
| Define potential difference
The potential difference (or p.d.) between any two
points is the amount of energy needed to move one
unit of electric charge from one point to another.
134
Chapter 13
| What is the SI unit of potential difference
The SI unit of potential difference is the volt (V).
135
Chapter 13
| What does 1 volt of potential difference mean?
1 volt of potential difference means that 1 joule
| of energy is needed to move 1 unit of charge.
136
Chapter 13
| How do we measure potential difference and how is the device correctly placed?
We measure potential difference using a voltmeter and must be connected in parallel to the circuit
component
137
Chapter 13
| What is a resistor?
An electrical component resists or hinders the flow
of electric charges when it is connected in a
circuit.
138
Chapter 13
The higher the __________ in a component, the higher the potential difference needed to move electric charge through the component.
resistance
139
Chapter 13
| Define resistance
The resistance of a component is the ratio of the potential difference across it to the current flowing
through it.
140
Chapter 13
| How do you find resistance?
Resistance = Voltage ÷ Current
141
Chapter 13
| What is the SI unit of resistance?
The SI unit of resistance is the ohm (Ω).
142
Chapter 13
| How do you increase the resistance of a component?
Increase its length, cross-sectional area and type of material the component is made of
143
Chapter 13
How does adding a fixed resistor in parallel in a circuit with a fixed resistor already make the light bulb glow brighter compared to adding a fixed resistor in series which makes the light bulb glow dimmer
Adding another resistor in parallel decreases the resistance in the circuit. Hence, the current flowing through the light bulb increases and thus, the light bulb glows brighter.
144
Chapter 13
| What is a variable resistor (rheostat) and what do we use it for?
A variable resistor or rheostat allows us to adjust the
| resistance in a circuit. Rheostats are used to adjust the sound volume of radios and the brightness of light bulbs.
145
Chapter 13
| How does a variable resistor work?
When the slider is on the left, the short resistance
wire offers low resistance. When the slider is on the
right, the long resistance wire sets up a higher resistance.
146
Chapter 13
| List 5 effects of an electric current
A chemical effect, magnetic effect, heating effect, lighting effect and sound effect
147
Chapter 13
| What is electrolysis?
It is the use of electricity to break down compounds into their elements
148
Chapter 13
| What is electroplating?
The coating objects with metals using electricity
149
Chapter 13
| How is a telephone an example of the magnetic effect of an electric current?
The diaphragm is attached to the springs that are fixed to the earpiece. When a current flows through the wires, the soft-iron bar becomes an electromagnet. The diaphragm becomes attracted to the electromagnets. As the person on the other end of the line speaks, his voice causes the current in the circuit to change. This causes the diaphragm in the earpiece to vibrate, producing sound.
150
Chapter 13
| How is the light bulb an example of the heating effect of an electric current?
The current flows through the highly coiled filament and the current causes the filament to heat up. The filament glows and gives out light.
151
Chapter 13
| Define the power of a circuit component
The power of a circuit component is the amount of electrical energy converted to other forms of energy per unit time by the component.
152
Chapter 13
| What is the SI unit of power
The SI unit of power is the watt (W)
153
Chapter 13
| What does one watt of power mean?
One watt of power means that in one second, one joule
| of energy is converted to other forms of energy.
154
Chapter 13
| What does a power rating of an appliance tell us?
The power rating of an appliance tells us the rate an appliance converts electrical energy into other forms of energy.
155
Chapter 13
| How do you calculate energy?
Energy = Power × Time
156
Chapter 13
| What is the formula for power?
Power = Energy ÷ Time
157
Chapter 13
| State 2 hazards of electricity
Electrical fires and electric shocks and electrocution
158
Chapter 13
| How does an electrical fire occur using an example?
Large currents can occur when electrical circuits are damaged, misused or do not work properly. For example, inserting too many plugs into the same power socket may draw a large current. The large current generates heat, which may melt the
insulation and cause a fire.
159
Chapter 13
| How does an electric shock or electrocution occur using an example of a damaged kettle?
When large currents pass through a person’s body, he will experience an electric shock or electrocution. In the damaged kettle, the wire at high potential is
disconnected from the heating coil and touches the metal. The electric potential of the casing increases and there is a large difference between the ground and the kettle. Hence, if a person touches the metal casing, a current flows through his body into the ground and he will experience an electric shock.
160
Chapter 13
| How do you prevent electrocution?
Switch off and pull out the plug from the socket before cleaning fans, television sets, computers and toasters. Never use electrical gadgets in wet places, because water can conduct electricity through your body. Do not touch electrical appliances with wet hands. Avoid getting water into the sockets of appliances. Do not use an appliance until you are sure it is dry. Call an electrician to repair damaged appliances or
electrical cables.
161
Chapter 13
State three safety features found in all
household electrical circuits to deal with large currents
Earth wire, fuse and circuit breaker.
162
Chapter 13
| How does the earth wire prevent large currents?
The earth wire provides a path of low electrical resistance. The large current flows directly from the live wire into the ground or earth.
163
Chapter 13
| How does the fuse prevent large currents?
The fuse makes use of the heating effect of an electric current to switch off a large current. A large current causes a short, thin wire in the fuse to heat up and melt.
164
Chapter 13
| How does the circuit breaker prevent large currents?
When the current in one part of the circuit is too large, the main circuit breaker can be switched on which cuts electricity but usually, the circuit breaker for that part is turned on.
165
Chapter 14
| What can a force be?
A force can be a 'push' or 'pull'.
166
Chapter 14
| What are the two types of forces?
Contact and non-contact forces.
167
Chapter 14
| The contact force that acts on two materials rubbing against each other is called ________.
Friction
168
Chapter 14
| State 3 non-contact forces
Gravitational, magnetic and electrostatic
169
Chapter 14
| What is the gravitational force?
Gravitational force is the force that attracts objects
| to planets.
170
Chapter 14
| What is magnetic force?
Magnetic force is the force exerted by a magnet on magnetic materials such as iron and steel.
171
Chapter 14
| What is a non-contact force?
A force that acts on an object without touching it
172
Chapter 14
Illustrate gravitational force using the example of
weight and ocean tides.
Gravitational force is responsible for the movement of high and low tides in harbours, ports and coastal areas.
The tides are also caused partly by the moon’s gravity pulling on the waters of the ocean.
173
Chapter 14
| What is electrostatic force?
Electric charges that do not flow in an electric circuit are called static electricity.
174
Chapter 14
| What is the difference between the electrostatic force of attraction and repulsion?
Unlike charges attract each other. The force acting on the positive and negative charges is called the electrostatic force of attraction. Like charges repel
each other. The force acting on the negative charges is called the electrostatic force of repulsion.
175
Chapter 14
| What is the difference between the magnetic force of attraction and repulsion?
Unlike charges attract each other. The force acting on the poles is called the magnetic force of attraction. Like poles repel each other. The force acting on the poles is called the magnetic force of repulsion.
176
Chapter 14
| Define weight
Weight is the force that the earth exerts on objects.
177
Chapter 14
| What is the SI unit of force?
Newtons (N)
178
Chapter 14
| What instruments do we use to measure force?
An extension spring balance and a compression spring balance
179
Chapter 14
| What is an extension spring balance?
The spring in an extension spring balance stretches when a pulling force acts on it and a pointer attached to the spring indicates the amount of force
acting on the spring.
180
Chapter 14
| What is a compression spring balance?
The spring in a compression spring balance compresses when a pushing force acts on it and a pointer attached to the spring indicates the amount of force acting on the spring.
181
Chapter 14
Why is the force of gravity (weight) is different on
different massive objects, e.g. planets
This is because the strength of an object's gravity has a direct relationship with the size of the object.
182
Chapter 14
| What is the difference between the mass and weight of an object?
Mass is the measure of the quantity of matter in a body. Weight is the measure of the force exerted on the body
183
Chapter 14
| State 5 effects of forces on an object
Forces can change the shape or size of objects, move a stationary object, change the direction of a moving object, change the speed of a moving object and stop a moving object.
184
Chapter 14
| Define speed
Speed is the distance travelled per unit time.
185
Chapter 14
| What is the formula for speed?
Speed = Distance travelled/Time taken
186
Chapter 14
| What is the SI unit for speed?
m/s
187
```
Chapter 14
Where is the effort, load and pivot in a first-class lever?
```
The effort and load are at both ends of the lever with both forces pushing down and the pivot is located in between them.
188
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Chapter 14
Where is the effort, load and pivot in a second-class lever?
```
The effort and pivot are located at both ends of the lever and the load is located in between them. The effort is pushing up while the load is pushing down.
189
```
Chapter 14
Where is the effort, load and pivot in a third-class lever?
```
The load and pivot are located at both ends of the lever and the effort is located in between them. The effort is pushing up while the load is pushing down
190
Chapter 14
| Define pressure
Pressure is the amount of force acting perpendicularly
| on a unit area.
191
Chapter 14
| How do you calculate pressure?
Pressure= Force/Area
192
Chapter 14
| What is the SI unit for pressure
N/m² (Pascal)
193
Chapter 14
| How does atmospheric pressure work using the example of a straw?
By sucking through the straw, we lower the air pressure in the straw. The higher atmospheric
pressure outside the straw pushes the liquid up the
drinking straw.
194
Chapter 15
| What is energy?
Energy is the ability to do work.
195
Chapter 15
| What is the SI unit of energy and work done?
The SI unit of energy and work done is the
| joule (J).
196
Chapter 15
| How much energy does it take to do one joule of work?
One joule of energy is needed to do one
| joule of work.
197
Chapter 15
| How do you calculate work done?
Work done = force x distance moved
198
Chapter 15
| What are the 2 conditions in which must be fulfilled for work to be done?
A force must act on an object and the object must move in the same direction as the force.
199
Chapter 15
| What happens when work is done on an object?
When work is done on an object, energy is converted from one form to another.
200
Chapter 15
| What is the law of conservation of energy?
Energy cannot be created or destroyed.
201
Chapter 15
Describe the changes in energy using the
bowstring as an example.
When an archer pulls the bowstring, chemical potential energy in the muscles is converted to elastic potential energy in the bowstring. When the archer releases the bowstring, elastic potential energy in the bowstring is converted to kinetic energy in the moving arrow.
202
Chapter 15
| What are non-renewable sources of energy?
Sources of energy that are limited and will run out eventually.
203
Chapter 15
| Identify 1 source of non-renewable source of energy
Fossil fuels
204
Chapter 15
| What is the energy conversion of the burning of fossil fuels in power stations
Chemical potential energy to heat to kinetic energy to electrical energy.
205
Chapter 15
| What is the energy conversion in motor vehicles
Chemical potential energy to heat to kinetic energy
206
Chapter 15
| What are petrol, diesel, kerosene and natural gas used for?
Petrol is used for fuel for cars and motorcycles, diesel is used for fuel for buses, taxis, and lorries, kerosene is used for fuel in jets and natural gas is used as fuel for cooking.
207
Chapter 15
| What happens when fossil fuels are burnt, how does it cause global warming and why is it bad for the environment?
When fossil fuels are burnt, carbon dioxide
gas is produced. Carbon dioxide gas traps heat from the sun in the earth’s atmosphere and causes global
warming. Global warming causes ice in the polar regions to melt, raising sea levels. It also brings about erratic and destructive weather patterns.
208
Chapter 15
| What are renewable sources of energy?
Renewable sources of energy are sources of energy that can be sustained or renewed indefinitely.
209
Chapter 15
| What are biofuels?
Biofuels are derived from animal and plant matter such as water hyacinth and sugar cane. Biofuels are burnt to produce energy, like fossil fuels. Thus, the energy conversion for biofuels is the same as that for fossil
fuels
210
Chapter 15
| What is the negative impact on the environment of using biofuels?
Carbon dioxide produced when biofuels are burnt
also contribute to global warming. However, the plants that produce these biofuels take in carbon dioxide during photosynthesis which partially offsets the heat trapped.
211
Chapter 15
| What is geothermal energy?
Geothermal energy is derived from hot rocks deep underground in volcanic areas. By drilling deep into the earth, water flowing through huge underground pipes is heated into steam.
212
Chapter 15
| What is the energy conversion in geothermal power stations?
Heat to kinetic energy to electrical energy?
213
Chapter 15
| What are 2 uses of geothermal energy?
The steam from heated water in geothermal power stations can be used to heat homes and buildings.
It can also generate electricity.
214
Chapter 15
| What are the negative impacts on the environment of using geothermal energy?
Some types of geothermal power stations extract
poisonous substances such as hydrogen sulfide or arsenic from deep underground. The land around the geothermal power stations may sink when material is extracted, causing damage to buildings and roads. The flow patterns of rainwater may also be significantly
affected.
215
Chapter 15
| How does solar energy work and what is the energy conversion in solar cells?
The energy in sunlight can be directly converted into
| electrical energy by solar cells. The energy conversion in solar cells is light energy to electrical energy.
216
Chapter 15
| What are the uses of solar energy?
The energy in sunlight can be used to heat water. Some solar heaters can channel the heated water
(steam) to drive a turbine to generate electrical energy.
Solar cells can directly convert sunlight into
electrical energy.
217
Chapter 15
| What is the impact of using solar energy?
No harmful substances or pollutants are produced when solar cells generate electricity.
218
Chapter 15
| What is wind energy?
Wind energy is an energy source that converts the
| energy of moving air (wind) into electricity by rotating one or more turbines.
219
Chapter 15
| What is the energy conversion in wind turbines?
Kinetic energy to electrical energy.
220
Chapter 15
| What is the use of wind energy?
Wind energy provides electrical energy for households and research stations, especially in remote areas.
221
Chapter 15
| What are the negative impacts of using wind energy?
The wind blades of turbines may cause a significant
number of deaths of birds and bats. The rotating wind turbines produce some low-frequency noise, including infrasound which may cause some people to feel nauseous and experience headaches.
222
Chapter 16
| Sound must travel through a ______
Medium.
223
Chapter 16
| Why can we not hear sound through a vacuum?
Vibrations of the source of the sound are not passed on to the surrounding molecules because there are not any.
224
Chapter 16
| What is sound caused by?
Vibrations of matter
225
Chapter 16
| What happens when we beat a drum?
When the drum membrane moves to the right, the
surrounding air molecules are pushed closer together. In turn, the air molecules move and collide with other air molecules. When the drum membrane moves to the left, it creates an area with few air molecules.
The side-to-side motion (vibration) of the drum skin causes the air molecules near it to also move from side to side in a regular pattern. This helps to carry the sound energy away in a moving pattern
226
Chapter 16
| How does sound move away from the source?
Sound moves in ripples away from the source
227
Chapter 16
| What is the speed of sound in a solid and why is it so?
5000-6000m/s
In a solid, when molecules at one end start to vibrate, energy is transferred to the neighbouring molecules very rapidly. This is because the molecules are packed very closely together.
228
Chapter 16
| What is the speed of sound in a liquid and why is it so?
1500m/s
When molecules at one end start to vibrate, energy is transferred to the neighbouring molecules less rapidly. This is because the molecules of a liquid are not packed as closely together as those of a solid.
229
Chapter 16
| What is the speed of sound in a gas and why is it so?
300m/s
When molecules at one end start to vibrate, energy is transferred to the neighbouring molecules slowly. This occurs within a gas as the molecules are far apart from one another
230
Chapter 16
| How do hearing aids aid our hearing?
Sound occurs when a vibrating object disrupts the air around it. The vibrating air molecules, in turn, cause
structures within the ears to vibrate. The vibrations pass the sound energy to our ears and the brain translates the vibrations into information. A hearing aid increases the loudness of sounds by producing greater vibrations of air molecules.
231
Chapter 16
| What is the external ear and what does it do?
The external ear is the cup-like flap that collects the
| sound.
232
Chapter 16
| What is the ear canal and what does it do?
The ear canal channels the sound to the eardrum.
233
Chapter 16
| What is the eardrum and what does it do?
The eardrum is a flap of skin that vibrates according to the frequency of the sound coming in.
234
Chapter 16
| Identify the 3 bones in the ear and explain what they do
The three bones are the hammer, anvil and stirrup. These bones transfer the vibrations to the inner ear.
235
Chapter 16
| What is the cochlea and what does it do?
The cochlea is a shell-shaped chamber that vibrates according to different frequencies.
236
Chapter 16
| What are the ear nerves and what do they do?
The ear nerve in the inner ear detect the vibrations and change them into electrical signals. Then, they transfer these signals to the brain which interprets the sound.
237
Chapter 16
| What is the frequency of sound?
The frequency of sound is the number of cycles per second made by the vibrating source of sound.
238
Chapter 16
| What is the pitch of a sound?
The frequency of sound
239
Chapter 16
| What is one unit of frequency?
One unit of frequency is one hertz (Hz).
240
Chapter 16
| What is one hertz?
One hertz is one cycle per second.
241
Chapter 16
| What is the range of sound that humans can hear?
Humans can hear sounds ranging from 20 Hz to
| 20,000 Hz.
242
Chapter 16
| How do you increase the loudness of a sound?
Increase the size of the vibrations
243
Chapter 16
| Identify 5 ways sound is used in society
Warning of danger, entertainment, communication, sonar, ultrasound and technology
244
Chapter 16
| How is sound used as a warning of danger
Sound can be used as an alarm. We shout to warn or alert others of a disaster. Loud sirens warn people of approaching danger or alert people of an emergency
vehicle.
245
Chapter 16
| How is sound used as a method of entertainment?
Sound can also be used for our listening pleasure. These sounds are pleasant to our ears. People may pay to enjoy pleasing sounds such as investing in a sound system to listen to music at home.
246
Chapter 16
| How is sound used as a method of communication?
We talk in order to communicate with one another.
247
Chapter 16
| What is sonar?
Sonar is a technique that uses sound to gather information about the environment. For example,
sonar of the ocean floor can provide information about underwater conditions as well as objects surrounding the ship.
248
Chapter 16
| What is ultrasound and how is it used in society?
Ultrasound is defined as sound with frequencies above 20,000 Hz, which cannot be heard by the human ear. Ultrasound is used in hospitals to observe the internal organs without the need for an operation. One example of ultrasound being used in society is that ultrasound allows doctors to observe foetuses in pregnant mothers, detect cancers and observe tumours in the body.
249
Chapter 16
| What is noise?
Noise is a collection of notes that is unpleasant and may even be harmful.
250
Chapter 16
| What are some negative impacts of noise?
Noise can cause annoyance or health problems
251
Chapter 16
| How do you measure the loudness of sound?
The loudness of sound is measured in decibels (dB)
252
Chapter 17
| The degree of hotness or coldness of an object is measured by the object's __________
Temperature.
253
Chapter 17
| What is the SI unit of temperature?
Kelvin (K)
254
Chapter 17
| What happens when a substance is heated?
When a substance is heated, it undergoes expansion and increases in volume.
255
Chapter 17
| What happens when a substance is cooled?
When a substance is cooled, it undergoes contraction and decreases in volume.
256
Chapter 17
| Why do thick glass cups crack when hot water is poured into them?
The glass on the inside expands more quickly than the outside when heated
257
Chapter 17
Expansion and contraction may cause ______ to
________ that are constantly exposed to the
__________.
damage, structures, environment
258
Chapter 17
What happens when telephone wires and electrical cables are exposed to cold weather and what has been done to prevent it?
When telephone wires and electrical cables are exposed to cold weather, they may snap which is why the wires and cables are strung loosely from pole to pole.
259
Chapter 17
| What happens when tiled and concrete pavement cables are exposed to hot weather and what has been done to prevent it?
Excessive expansion on very hot days can cause concrete to crack. Tiles on a pavement may also pop out. To get around these problems, expansion gaps are laid between concrete slabs and tiles. This provides space for tiles and concrete slabs to expand without any damage.
260
Chapter 17
| Why do we use a special type of glass that expands very little when heated?
If boiling water is poured into a thick glass, the glass is likely to crack due to the uneven expansion of the glass. Hence, most of the glassware found in the home and in the laboratory are made of a special type of glass. Unlike ordinary glass, this special type of glassware is less likely
to crack when hot liquids are poured into it as it expands less than ordinary glass
261
Chapter 17
| What happens when water pipes are exposed to hot weather and what has been done to prevent it?
Water pipes and oil pipelines can expand on hot days, causing them to burst. Hence, expansion bends are made in these pipes. This allows the pipes to expand without any damage.
262
Chapter 17
| What happens when MRT and railway tracks are exposed to hot weather and what has been done to prevent it?
Railway tracks can bend and twist due to expansion in hot weather. Hence, expansion gaps in the tracks provide space for the tracks to expand without any damage on hot days
263
Chapter 17
| What happens when bridges are exposed to hot weather and what has been done to prevent it?
Bridges may expand up to a meter in hot weather. Thus, bridges have expansion gaps or a free end resting on rollers. This allows the metal structures to expand without any damage on hot days.
264
Chapter 17
| How is expansion used to open a tight-fitting lid on jars?
The lid of the jar can be immersed in warm water for a few minutes, causing the metal lid to expand more than
the glass jar. This loosens the lid and allows us to unscrew it easily.
265
Chapter 17
| What are rivets and how are they used?
When red-hot, the rivet is put into position. It is hammered into a head and then allowed to cool. As the rivet cools, it contracts and pulls the steel plates together.
266
Chapter 17
| What are bimetallic strips used for?
They are used for appliances that rely on temperature regulation.
267
Chapter 17
| How do bimetallic strips work?
A bimetallic strip consists of two different metals that expand at different rates when heated.
268
Chapter 17
| How does heat flow?
Heat flows from a region of higher temperature to a region of lower temperature.
269
Chapter 17
| What are the 3 ways heat can flow?
Conduction, convection and radiation.
270
Chapter 17
| What is conduction?
Conduction is the process of heat transfer through a medium or material without any movement of the medium or material.
271
Chapter 17
| Why does a carpet feel warm when touched?
It feels warm as a carpet does not conduct heat away easily from the body when touched as it is a bad conductor of heat.
272
Chapter 17
| Why does marble feel cool when touched?
It feels cool as marble conducts heat away easily from the body when touched as it is a good conductor of heat.
273
Chapter 17
| What are insulators used for?
They are used to reduce the amount of heat from
| being transmitted from one place to another.
274
Chapter 17
| Why is it that when you warp paper around a metal rod and put a flame directly below the paper, the paper does not burn?
This is because the heat is conducted away from the paper quickly by the metal and thus the paper is never hot enough to burn.
275
Chapter 17
| What are conductors used for?
Conductors are used whenever heat has to be quickly transferred from one place to another.
276
Chapter 17
| How are radiators used in temperate climates?
In temperate climates, radiators keep rooms warm during the winter. Radiators quickly conduct heat away from the heat source before they can warm the air around them.
277
Chapter 17
| How are insulators used in warm climates?
Walls and buildings are made of brick and other insulating materials. In warm climates, the insulating materials help to reduce heat gain by conduction.
278
Chapter 17
| What is convection?
Convection is the transfer of heat from one place to
| another by the movement of fluids
279
Chapter 17
| Why are air conditioners placed on the ceiling?
At the top, the gas gets cooled and contracts. This causes volume to decrease. Since Density = mass/volume, the gas is now denser. The cooler/denser air sinks to the bottom. The warmer and less dense air gets displaced by the cooler air and rises to the aircon unit. This cycle is repeated forming a convection current, which ensures fair cooling of the room.
280
Chapter 17
| Why are heating systems placed on the floor?
At the bottom, the gas gets heated and expands. This causes volume to increase. Since Density = mass/volume, the gas is now less dense. The Warmer and less dense rises to the top The cooler and denser gas gets displaced by the warmer gas and sinks to the bottom. This cycle is repeated forming a convection current, which ensures fair heating of the room.
281
Chapter 17
| What is radiation?
Radiation is the transfer of heat, in the form of waves, from one place to another. It does not require a medium for transmission.
282
Chapter 17
| What are the 3 factors that affect the rate of radiation?
Nature of the surface, the total surface area of the body and temperature of the body.
283
Chapter 17
| How does the nature of the surface affect the rate of radiation?
The darker and rougher the surface, the higher the rate of radiation or absorption. The lighter and smoother the surface, the lower the rate of radiation or absorption.
284
Chapter 18
| Physical changes are _________ and do not involve the _________ of new substances
reversible, formation
285
Chapter 18
| Chemical changes are ____________ and result from ________ reactions
irreversible, chemical
286
Chapter 18
| How do you represent chemical changes?
Word equations
287
Chapter 18
| What are the components of a word equation?
Reactants, conditions and products
288
Chapter 18
| What are the reactants of a word equation?
Substances present at the start of the reaction
289
Chapter 18
| What are the conditions of a word equation?
Factors required for the reaction to take place
290
Chapter 18
| What are the products of a word equation?
Substances present at the end of the reaction
291
Chapter 18
| What is the word equation of the burning of hydrocarbons?
Methane + Oxygen >heat> Carbon Dioxide + Water
| MOHCDW
292
Chapter 18
| The products of a chemical reaction have different __________ from that of _________
properties, reactants.
293
Chapter 18
| Why does a light stick glow when bent?
A light stick contains two chemicals that are kept separate in an external casing and a smaller, thinner tube on the inside. When the stick is bent, the inner tube breaks and releases the chemical inside it into the surrounding solution. As the two chemicals react, light is given off.
294
Chapter 18
| What is thermal decomposition?
Thermal decomposition is a process in which a single substance is broken down into two or more simpler substances by the effect of heat.
295
Chapter 18
| What is the word equation for when sugar is heated for too long?
Sugar >heat> Carbon + Water vapour
| SHCWV
296
Chapter 18
| What is oxidation?
Oxidation refers to a process in which a substance reacts with oxygen.
297
Chapter 18
| Oxidation also occurs in __________ and ________ __________
combustion, cellular respiration
298
Chapter 18
| What is combustion?
Combustion refers to the combination of a substance with oxygen in the presence of heat. One or more new substances may be produced.
299
Chapter 18
| When does complete combustion occur?
Complete combustion occurs when there is an abundant supply of oxygen.
300
Chapter 18
| What is cellular respiration?
Cellular respiration is the process in which living cells of plants and animals take in oxygen to release the
energy stored in glucose.
301
Chapter 18
| How can we prevent iron from rusting?
Painting, coating with a layer of oil and surrounding the iron with a drying agent
302
Chapter 18
| Is photosynthesis a chemical change or a physical change?
Photosynthesis is a chemical change
303
Chapter 18
| Alkalis taste ______ and have a ________ feel
bitter, slippery
304
Chapter 18
| What happens when acids react with alkalis?
When acids react with alkalis, a chemical reaction
| called neutralisation occurs.
305
Chapter 18
| What is an indicator?
An indicator is a substance that changes colour
depending on whether the solution being tested is
acidic or alkaline.
306
Chapter 18
What happens when blue litmus paper is dipped in
acid and alkali?
The blue litmus paper turns red when dipped in acid and remains blue when dipped in alkali.
307
Chapter 18
| What happens when red litmus paper is dipped in acid and alkali?
The red litmus paper remains red when dipped in acid and turns blue when dipped in alkali.
308
Chapter 18
| How does the universal indicator work?
The Universal Indicator indicates the strength of acids or alkalis through a colour change. The colour change from pH 1 to pH 14 is Red, Orange, Yellow, Green, Blue, Indigo and Violet (ROYGBIV)
309
Chapter 18
| What is the word equation for acid etching?
Metal + Acid > Salt + Hydrogen
| MASH
310
Chapter 18
| What is the word equation for when dilute acid reacts with carbonate
Dilute Acid + Carbonate > Salt + Water + Carbon Dioxide
| ACSWC
311
Chapter 18
| In a chemical reaction, the mass of the product(s) is the ___ as the mass of the reactants.
same
312
Chapter 18
| In a chemical reaction, the atoms of the reactants _________ to form new products
rearrange
313
Chapter 18
| State 4 ways chemical changes benefit us
Cooking food, cleaning and fertilisers, manufacturing of useful products and decomposition of dead organisms.
314
Chapter 18
| Explain the negative effects of chemical change that is burning.
Burning and combustion in cars and factories release air pollutants, such as soot and toxic gases, in the atmosphere. Gases such as sulfur dioxide in the atmosphere dissolve in the falling rain and lead to acid rain. Acid rain corrodes buildings and other structures. Polluted air leads to difficulty in breathing and increases the risk of respiratory illnesses. Acid rain destroys plants and kills fishes and other aquatic life.
315
Chapter 18
| Explain the negative effects of chemical change that is rusting
When iron rusts, structures such as bridges become corroded and unsafe. These structures need to be repaired and replaced, causing the loss of finite natural resources.
316
Chapter 18
| What is one example of a word equation of combustion
Petrol + Oxygen >heat> Carbon Dioxide + Water Vapour
317
Chapter 18
| What is the word equation of photosynthesis
Carbon Dioxide + Water >Sunlight & Chlorophyll> Glucose + Oxygen
318
Chapter 18
| What is the word equation when acids and alkalis (Neutralisation)
Acid + Alkali > Water + Salt
| AAWS
