Chemistry Flashcards
(110 cards)
0
Q
What is the symbol for sodium?
Including information
A
23
Na
11
11 protons
11 electrons
12 neutrons
1
Q
What are elements?
A
Substances made up from one type of atom.
2
Q
What’s a compound?
A
What is formed when two or more elements combine together.
3
Q
What are the charges and masses of protons, neutrons and electrons?
A
Protons: +1 / mass 1
Neutron: 0 / mass 1
Electron: -1 / 0.001
4
Q
What is the mass number and atomic number of an element?
A
Mass number: the total number of atoms, all protons, electrons and neutrons.
Atomic number: number of protons (and electrons)
5
Q
Where are protons, neutrons and electrons found?
A
Protons and neutrons are in the centre of the nucleus.
Electrons are found in shells around the nucleus.
6
Q
Info about the periodic table
A
The elements are arranged in columns called groups and rows called periods.
Atoms are represented by chemical symbols.
Group 1 are the alkali metals
Group 2 are the alkaline earth metals
Group 7 are the halogens
Group 0 are the noble gasses
The majority is made up of metals.
The further down the table / group, the more reactive the element is.
7
Q
What is an electronic configuration / structure?
A
The amount of electrons on the shells of elements and the way it’s drawn, shells in order holding 2,8,8,2…
8
Q
What is the electronic structure for argon?
40
Ar
18
A
2,8,8.
9
Q
What do elements in the same group have in common?
A
They have the same number of electrons on their highest energy level e.g. Group 1 have one electron in their highest energy level / shell.
10
Q
What is an ionic bond?
A
It is when a metal reacts with a non metal and ions are formed.
The elements want a full outer shell.
Metal atoms lose one or more electrons to form positively charged ions (because if they lose electrons then there will be more protons than electrons) and the non metals gain he electrons to form negatively charged ions (as there would be more electrons).
The oppositely charged ions attract each other strongly forming an ionic bond.
An example of an ionic bond is between lithium and fluorine as Li has one electron on it’s outer shell (which it wants to lose) and F has 7 electrons on its outer shell (and it needs one more for a full outer shell).
Atoms are lost or gained.
11
Q
What’s a covalent bond?
A
It is when a non metal reacts with a non metal and molecules (group of bonded atoms) are formed.
The elements want a full outer shell.
An example of this is by a water molecule of H2O as oxygen has 6 electrons on it’s outer shell and hydrogen has 1 so two H atoms can share electrons with the oxygen atom to form H2O
Atoms are shared between the elements.
12
Q
How would sodium and chlorine bond?
A
By an ionic bond.
13
Q
How many atoms and elements are in: C2H5OH
A
3 elements
9 atoms
14
Q
What happens to atoms in chemical reactions?
A
They rearrange themselves to form new substances.
Atoms are neither created nor destroyed so the number and type of atom stays the same before and after the reaction, meaning the mass of products = the mass of reactants.
This means we can write chemical equations to represent reactions. (Word equations give names, symbol equations show the numbers and types of atoms)
When symbol equations are written, they must be balanced / equal on both sides.
15
Q
How do you balance an equation?
A
You can only change the large number in front of the symbol. Never change the small (subscript) numbers as this would change the formula of the substance.
16
Q
Balance the equations:
H2 + Cl2 ~ HCl
Ca + O2 ~ CaO
Na + H2O ~ NaOH + H2
A
H2 + Cl2 ~ 2HCl
2Ca + O2 ~ 2CaO
2Na + 2H2O ~ 2NaOH + H2
17
Q
What is the scientific name and chemical formula for limestone?
A
Calcium Carbonate
CaCO3
18
Q
What happens when a carbonate reacts with an acid?
A
All carbonates produce a salt, water and CO2 gas when reacting with an acid.
19
Q
What is another name for calcium hydroxide solution?
A
Limewater, used to test for CO2 (turning cloudy).
20
Q
What happens to metal carbonates when heated strongly enough?
A
They decompose to the metal oxide and CO2.
21
Q
What is the limestone reaction cycle?
A
Calcium carbonate
CaCO3
+ heat
Calcium oxide
CaO
+ little water
Calcium hydroxide
CaOH
+ more water and filter
Calcium hydroxide solution
Limewater
+ CO2
CaCO3
22
Q
What are the uses of calcium hydroxide?
A
As it’s an alkali, it’s used to neutralise acids e.g. for soil within farming
Not very soluble but dissolves slightly to make limewater
It reacts with CO2 to form limestone
23
Q
What is cement?
A
A substance made by mixing limestone with clay and heating it strongly which is ground up to make a fine powder.
24
What is mortar?
Cement mixed with sand and water to hold bricks and buildings together.
25
What's concrete?
A material made by adding aggregate (small stones and crushed rocks) to cement, water and sand.
26
What are the pros and cons of limestone quarrying?
Pros:
More employment opportunities for locals
More customers and trade for local businesses
They are often restored
Can often mean that the roads will be improved too
```
Cons:
Loss of habitats and wildlife
More traffic
Dust and noise
Air and noise pollution
```
27
What is thermal decomposition?
The breaking down if a substance due to heat
28
What is the word and symbol equation for the thermal decomposition of limestone?
Calcium carbonate > heat > calcium oxide +
carbon dioxide
CaCO3 > heat > CaO + CO2
29
What is the order of reactivity of the elements from most to least: magnesium, copper, iron, potassium and carbon
```
Potassium
Magnesium
Carbon
Iron
Copper
```
30
Complete the displacement equation:
| Copper oxide + carbon ~
Copper oxide + carbon ~ CO2 + copper
31
What's an ore?
A rock containing enough metal to make it economically worthwhile to extract the metal.
32
What's an alloy?
A mixture of metals (and sometimes non metals) e.g. Brass is a mixture of copper and zinc.
33
What is it called when oxygen is removed by a reaction?
Reduction
34
What is it called when oxygen is added by a reaction?
Oxidisation
35
Metals such as gold, which are very low in the reactivity series, don't react with anything else so are found on their own or within rocks so can be separated physically.
However, most metals are found as compounds e.g. Iron oxide so they need to be separated by chemical reactions.
What is the method of separating the iron and oxygen?
Displacement
Metals can be extracted from compounds by displacement by using a more reactive element to 'boot out' the less reactive element e.g. Using carbon to separate iron and oxygen.
Reduction takes place as the carbon gains oxygen and iron is separated.
36
How is iron extracted?
In a blast furnace
Iron oxide is concentrated then is reduced in the blast furnace by using carbon.
It's them separated but still has impurities, 96% iron, and the impurities make it hard and brittle.
Removing carbon and impurities makes pure iron but is too soft.
37
Give 2 uses and properties of aluminium
Uses:
Within aircrafts
Foil
Properties:
Low density
High in reactivity
Resistant to corrosion
Has to be extracted using electrolysis - expensive
Aluminium alloys are stronger and have more uses than pure aluminium
38
Give 2 uses and properties of titanium
Uses:
Turbine blades in a jet engine
Aircraft engines
Properties:
Strong
Resistant to corrosion
It can be reduced by carbon but the carbon reacts with the metal, making it brittle
39
What are the 5 ways copper can be extracted?
```
Smelting
Displacement
Electrolysis
Phytomining
Bioleaching
```
40
What's smelting?
Heating the ore strongly in a furnace.
It produces impure copper which can be purified by electrolysis however this process requires huge amounts of heating and electricity.
41
What's displacement?
When a more reactive element is used to 'boot out' the less reactive element e.g. Using carbon to separate iron and oxygen.
Reduction takes place as the carbon gains oxygen and iron is separated.
Displacement with copper occurs when solutions of copper compounds are reacted with a metal that is more reactive than copper, such as scrap iron, to displace the copper.
42
What's electrolysis?
Using electricity to extract copper from a copper solution using electricity.
It's done by a circuit and, in the copper sulphate solution, there are 2 carbon electrons; the positive - anode and the negative - cathode.
The electricity passing through the circuit causes the metal to separate from the solution and form on the cathode and gas is produced on the anode.
43
What's phytomining?
A method of extracting copper done by plants absorbing copper compounds from the ground.
Then the plants, rich in copper, are burned to produce ash, high in copper, which is then extracted.
44
What's bioleaching?
A method of extracting copper by using bacteria to produce solutions which contain copper compounds.
45
Why is coper good for electrical wiring?
Because it's a good conductor of heat but doesn't react with water. It can be bent but is hard enough to keep shape.
This makes it useful for pipes, water tanks and heating systems too.
46
What are transition metals?
Elements from the central block of the periodic table.
They are all metals and have similar properties. They are good conductors of heat and electricity and, although strong, they can be bent and hammered into shape, making the good for buildings, vehicles, pipes and containers.
47
Pros and cons of metals in construction?
```
Pros:
They're strong
Can be shaped
Can be made into flexible wires
Good electrical conductors
```
Cons:
It causes pollution and uses up limited resources
Metals are more expensive than materials like concrete.
Iron and steel can rust
48
Name 3 types of steel:
Low-carbon steel: easily shaped
High-carbon steel: hard
Stainless steel: resistant to corrosion
49
What is crude oil?
A mixture of many different compounds.
50
What is the process where crude oil is separated into useful components?
Fractional distillation
Crude oil contains many different compounds that boil at different temperatures. This means we can separate the mixture of liquids by distillation. Simple distillation of crude oil can produce liquids that boil within different temperature ranges.
These liquids are called fractions.
51
What are most of the compounds in crude oil?
Hydrocarbons
This means that their molecules contain only carbon and hydrogen.
Most of these hydrocarbons are alkanes with the formula C(n) H(2n + 2).
An example of the molecular formula from crude oil is ethane which is a hydrocarbon: C2H6
52
What's an alkane?
Saturated hydrocarbons
| They contain as many hydrogen atoms as possible in their molecules.
53
What are features of fractions with low boiling points?
They burn more easily
They're less viscous - have low viscosity (not very thick or sticky)
They burn with clean flames so produce little smoke
54
When fuel and hydrocarbons burn, gasses are produced. What is the issue with carbon monoxide?
It's a toxic gas.
55
When fuel and hydrocarbons burn, gasses are produced.
| What is the issue with sulphur dioxide?
It causes acid rain.
56
When fuel and hydrocarbons burn, gasses are produced.
| What is the issue with nitrogen oxide?
It causes acid rain
57
When fuel and hydrocarbons burn, gasses are produced.
| What is the issue with carbon dioxide?
It contributes to global warming / greenhouse effect.
58
Burning any fuel that contains carbon produces CO2. Incomplete combustion of these fuels can produce carbon monoxide and tiny, solid particulates (small solid particles).
What is the problem with particulates?
They reflect sunlight so they cause global dimming.
59
What happens when hydrocarbons burn completely?
They are oxidised to carbon dioxide and water.
60
Info on alkanes:
| Saturated or unsaturated, general formula, an example
Saturated hydrocarbon
General formula is Cn H2n+2
Example: ethane (C2 H6), methane and propane
61
Info on alkenes:
| Saturated or unsaturated, general formula, an example
Unsaturated hydrocarbon (containing carbon - carbon double bond)
General formula is Cn H2n
Example: ethene C2 H4
62
Advantages and disadvantages of biodiesel
Advantages:
It makes little contribution to CO2 levels (because the CO2 given off when it burns was taken from the atmosphere by plants as they grew)
Disadvantages:
The plants that are grown for biodiesel use large areas if farm land.
63
What are biofuels?
Fuels made from plant or animal products which is renewable.
Biodiesel is made from vegetable oils extracted from plants.
64
Advantages and disadvantages of ethanol
Advantages:
It's a biofuel from sugar so is renewable
Can be stored an d distributed
Can be mixed with petrol
Disadvantages:
Requires large areas of farmland
65
Advantages and disadvantages of hydrogen
Advantages:
Only produces water when burned
Disadvantages:
It's a gas so it takes up a large volume, making it difficult to store in the quantities needed for combustion.
Can be produced from water by electrolysis but requires a lot if energy
66
What's cracking?
The process of large hydrocarbon molecules being broken down into smaller molecules.
67
What are the two methods of cracking?
Heating a mixture of hydrocarbon vapours and steam to a very high temperature.
Passing hydrocarbon vapours over a hot catalyst.
68
During cracking, thermal decomposition takes place producing smaller molecules, some alkanes and some alkenes. What's an alkene?
Small molecules. They're unsaturated hydrocarbons as they contain fewer hydrogen atoms than alkanes, with the same number of carbon atoms.
69
What bond do alkenes have?
A double bond between 2 carbon atoms meaning that it is more reactive than alkanes.
70
Give ways which alkanes and alkenes differ:
| 5
```
Alkenes are unsaturated
Alkenes have a double bond
Alkenes have a different general formula
Alkenes have fewer hydrogen atoms than the corresponding alkane
Alkenes are more reactive
```
71
What happens when alkanes and alkenes are added to bromine water?
Alkanes: nothing
Alkenes: due to being more reactive (double bond) they react with the bromine water by turning it from orange to colourless.
72
What's a monomer?
Small molecules used to make polymers (large molecules).
Small reactive molecules that react together in repeating sequences to form a very large molecule (a polymer).
73
What's a polymer?
Large molecules made up from small molecules (monomers) joined together.
A substance (e.g. Plastic) made from very large molecules made up of many repeating units (e.g. Polythene).
74
What's polymerisation?
The reaction to make a polymer.
The reaction of monomers (small molecules) to make a polymer (substance made from very large molecules called polymers.
E.g. Ethene > poly(ethene) And propene > poly(propene)
75
What are alkenes used for?
Making polymers such as poly(ethene) and poly(propane).
| Plastics we use such as bag, bottles and toys are made from alkenes.
76
What are the 2 ways ethanol can be made?
1) By the fermentation of sugar rom plants using yeast. Enzymes in the yeast cause the sugar to convert to ethanol and CO2. This method is used to make alcoholic drinks.
2) By the hydration of ethene. Ethene is reacted with steam at a high temperature within a catalyst (a substance increasing chemical reactions without reacting itself).
The ethene is obtained from crude oil by cracking.
77
What's the word equation for the fermentation of sugar using yeast?
Sugar/glucose —> ethanol + carbon dioxide
78
What's the word equation for the hydration of ethene
Ethene + steam —> ethanol
79
How are biodegradable plastics made?
From plant material.
| An example is a polymer made from cornstarch which is used as biodegradable food packaging.
80
What does biodegradable mean?
Being capable of being broken down and decomposed by bacteria and living organisms, avoiding pollution.
81
What is a smart polymer?
Also called shape memory polymers, they are able to change back to their original shape when temperature or conditions are changed,
E.g. The material used for stitching wounds that changes shape when heated to body temperature.
82
What are the 2 methods vegetable oils are extracted from seeds, nuts and fruits?
1) Crushing and pressing the plant materials, followed by removing water and impurities.
2) Distilling the plant material mixed with water. The oil is then separated from the mixture of water and oil.
83
What is meant by hardening vegetable oils?
Vegetable oils can be hardened by reacting them with hydrogen a 60°C with a nickel catalyst. This makes gem solid at room temperature, suitable for spreading.
84
What's an emulsifier?
A substance which helps keeps immiscible liquids (e.g. Oil and water) mixed so they don't separate into layers.
85
How do emulsifiers work?
If we shake, stir or beat liquids like, oil and water, together tiny droplets form that can be slow to separate, known as an emulsion.
Emulsifier molecules have a small hydrophilic part and a long hydrophobic part. The hydrophilic part (or 'head' ) is attracted to water. The hydrophobic part (or 'tail' ) is attracted to oil.
The hydrophobic 'tail' parts of lots of emulsifier molecules go into each oil droplet, meaning the droplet is surrounded by hydrophilic parts.
This keeps the oil droplets apart in the water, preventing them from joining together and separating out.
```
Hydrophilic = water loving
Hydrophobic = water hating
```
86
What products require emulsifiers?
```
Milk
Cream
Water based paints
Ice cream
Cosmetic creams
Salad dressings
```
87
Pros and cons of using emulsifiers and oils in foods
Pros:
Vegetable oils are high in energy and important nutrients
They contain unsaturated fats, better than saturated fats
Emulsifiers stop water and oil separating, making the food smoother, creamier and more palatable
Cons:
Animal and hydrogenated vegetable oils contain saturated fats, linked to heart disease
High in fat
88
What's the structure of the earth from the centre to the outside?
```
Inner core
Outer core
Mantle
Crust
Atmosphere
```
89
What's the percent of gasses in our atmosphere today?
```
Nitrogen 78%
Oxygen 21%
Argon 0.9%
Carbon dioxide 0.04%
Trace amounts of other gasses
```
90
What are tectonic plates and why do they move?
Huge slabs if rock that make up the earth's crust and top part of the mantle.
They move due to convection currents in the mantle beneath them due to energy released by the decay of radioactive elements heating up the mantle. The movement causes earthquakes, mountains, volcanoes etc. on plate boundaries.
91
What was Alfred Wegener's theory of the continents?
He had the theory of continental drift that the countries and continents used to be one based on the findings of similar fossils and rock on country borders.
The theory wasn't accepted at first because he couldn't explain why the continents moved.
92
What is the earth's atmosphere believed to be like billions of years ago?
In the first billion years, the surface was covered with volcanoes that released carbon dioxide, water vapour and nitrogen.
As the earth cooled, most of the water vapour condensed to form oceans so the early atmosphere was mainly CO2 and water vapour. Some scientists believe there was also nitrogen and possibly some methane and ammonia.
In the next 2 billion years, bacteria, algae and plants evolved. The algae and plants used carbon dioxide for photosynthesis and produced oxygen. This meant, as the number of plants increased, the amount of carbon dioxide decreased and oxygen increased.
93
There are many theories as to how life on earth actually began.
One theory states that the compounds needed came from reactions involving hydrocarbons and ammonia with lightning providing energy. This linked to the Miller-Urey experiment.
What is the Miller-Urey experiment?
An experiment in 1952 by scientists Miller and Urey.
They based it on what scientists at the time through was in the early atmosphere.
They used a mixture of water, ammonia, methane and hydrogen and a high voltage spark to simulate lightening.
After a week, they found that amino acids, the building blocks for protein, had been produced.
94
Amino acids are made from the elements carbon, hydrogen, oxygen and nitrogen. In the Miller-Urey experiment, why was a mixture of water, ammonia, methane and hydrogen used?
They contain all the elements needed to make amino acids.
Water has hydrogen and oxygen, ammonia has nitrogen and hydrogen, methane contains carbon and hydrogen and hydrogen is hydrogen.
95
What are theories about the beginning of life on earth (other than the Miller-Urey experiment.)?
The theories have changed since 1950 but scientists have been able to produce amino acids with other mixtures of gasses.
One theory suggests that these organic molecules formed a 'primordial soup' and that the amino acids in this mixture combined to make proteins from which life began.
Many other theories have been proposed but they are all unproven so we cannot be sure about any of the theories.
96
How much CO2 is in our atmosphere?
For 200 million years, CO2 levels have remained the same as natural processes, such as death, respiration and feeding by animals and plants, were at balance but recently, CO2 levels have risen drastically.
97
Why have CO2 levels risen recently?
Due to the large increase in burning fossil fuels.
98
Plastic waste that contains polymers made from C3H6 and similar monomers causes environmental problems. Bullet point why?
```
Non biodegradable
Can't be broken down
Last for a very long time
Takes up space in landfill
Incineration produces CO2
Made from crude oil - using finite resources
```
99
What are fractions?
Liquids with different boiling ranges separated from a mixture of liquids. (Crude oil).
We can separate a mixture of liquids by distillation.
100
How does fractional distillation work?
Crude oil is vaporised and sent into a fractionating column, a tall tower hot at the bottom and cooler at the top.
The vapours move up the column, getting cooler as they go up.
The hydrocarbons condense to liquids when they reach the level that is at their boiling point. Different liquids collect on different levels.
(hydrocarbons with small molecules have the lowest boiling points so are collected at the top and vise versa)
101
How can ethanol be produced?
By the fermentation of sugar using yeast (sugar/glucose -> ethanol + carbon dioxide)
By the hydration of ethene
(Ethene + steam -> ethanol)
102
Why are emulsions useful?
They're thicker
They're getting at coating
The have a better texture
103
Wha are examples of emulsions?
Ice cream
Salad dressing
Mayonnaise
Cosmetics
104
What's formed when an alkali metal reacts with oxygen and with water?
Metal + oxygen -> metal oxide
Metal + water -> metal hydroxide + hydrogen
105
What are the benefits of oils?
```
It provides energy
Higher boiling point than water
Cook faster
Better flavour
Contains nutrients
```
106
What are properties of titanium and aluminium?
Low density
Resistant to corrosion
Al - power lines and plane bodies
Ti - hip joints
107
What are the properties of copper?
Good conductor of heat and electricity
Bent into shape
Hard
Non reactive
Cu - cooking pans and electrical wiring
108
Properties of impure iron
Strong
Brittle
Obtained from the blast furnace
109
How's stainless steel made?
Forming an alloy with steel and chromium
