2.1 Flashcards
(109 cards)
1
Q
What is an element?
A
Same atoms
2
Q
What is a compound?
A
Different atoms chemically bonded
3
Q
How do you split a compound ?
A
Chemical reaction
4
Q
What is in a mixture?
A
Different elements or compounds not chemically combined
5
Q
How do you separate a mixture?
A
Physical techniques
6
Q
What physical techniques can separate mixtures?
A
Filtration
Distillation
Crystallisation
7
Q
What is a molecule?
A
Any of the same elements chemically joined
8
Q
Why is found in the nucleus of an atom?
A
Protons
Neutrons
9
Q
Where are the electrons found in the atomic structure ?
A
Shells
10
Q
What is the charge of an atom?
A
0
11
Q
Why is there no overall charge of atoms?
A
Electrons are cancelled out by protons
12
Q
On the periodic table which number is the atomic number?
A
Smaller number
13
Q
What is the atomic number
A
Number of protons
14
Q
Where is the mass number on the periodic table?
A
Biggest number
15
Q
What is the mass number?
A
Total of protons and neutrons in the nucleus
16
Q
How do you calculate number of neutrons ?
A
Mass number - atomic number
17
Q
Why do elements react?
A
Full outer shell
18
Q
What are boiling points of ionic compounds? Why?
A
Very high
Electrostatic forces require lots of heat energy to break
19
Q
Can ionic compounds conduct electricity ? Why?
A
No
Ions cannot move because of the electrostatic forces of attraction.
20
Q
When can ionic compounds conduct electricity? Why?
A
Molten or dissolved in water
Breaks electrostatic forces
Ions can now move and carry current
21
Q
Why does ionic bonding contain?
A
Transfer of electrons of non metals and metals
22
Q
What does covalent bonding contain?
A
Shared electrons of non metals
23
Q
What are the properties of simple covalent molecules?
A
Low melting and boiling points
Usually gases or liquids at room temp
Do not conduct electricity
24
Q
What holds the atoms in each covalent molecule together?
A
Strong covalent bonds
25
What holds the molecules together in a covalent molecule?
Weak intermolecular forces
26
Why does it not take much energy to turn a simple covalent molecule into a gas?
Weak intermolecular forces are easily broken with little energy
27
Why do simple covalent molecules not conduct electricity?
They do not have an overall electric charge
28
What are the 4 giant covalent molecules?
Diamond
Graphite
Fullerenes
Silicon dioxide
29
What is diamond made of and how are these atoms bonded?
Carbon atoms with 4 covalent bonds to other carbon atoms
30
What are the properties of diamond and why do these occur?
Extremely hard
Very high melting point
Because of the large number of strong covalent bonds
31
What is graphite made of and how are the atoms bonded?
Carbon atoms with 3 covalent bonds
32
Why is graphite very soft?
It has layers which are not strongly held together as there aren't covalent bonds between layers - only weak intermolecular forces
Layers can then slide over each other
33
Why can graphite conduct electricity and heat?
Each atom has a spare electron due to only having 3 covalent bonds.
The delocalised electrons can move and conduct electricity and heat.
34
What can fullerenes be used for?
Drug delivery into the body
Lubricants
Catalysts
Nanotubes for reinforcing materials e.g. Tennis rackets
35
How are fullerenes structured?
Hexagonal rings of carbon
36
What elements does silicon dioxide contain?
Oxygen and silicon
37
Why does silicon dioxide have a high melting point?
Contains a large number of covalent bonds
38
What are the forces between oppositely charged ions called?
Strong electrostatic forces
39
Why can metals conduct heat and electricity?
Because of their delocalised electrons
40
Why can metals be bent and shaped?
The layers of atoms slide over each other
41
What are alloys?
2 or more different metals
42
Why are alloys harder than pure metals?
Different story sized atoms of metals distort the layers in the structure, making it more difficult for layers to slide over each other
43
What do shape memory alloys do?
| Give an example.
Return to their original shape
Nitinol is used in dental braces
44
How are thermosoftening polymers structured?
Individual, tangled polymer chains with weak intermolecular forces between them.
45
How are thermosetting polymers structured?
Polymer chains with cross-links between them so they do not melt when heated.
46
What happens when a thermosoftening polymer is heated? Why?
| What happens when it is cooled?
It melts when heated because the intermolecular forces are easily broken.
Turns back to solid when cooled.
47
What happens when a thermosetting polymer is heated? Why?
Does not melt.
| Strong cross links are not broken by heat.
48
What's the difference between low density ploy(ethene) and high density poly(ethene)?
They are produced using different catalysts and reaction conditions.
LDPE = weak, lower usable temperature (85 degrees), many branches on polymer molecules
HDPE = strong, higher usable temperature (120 degrees), few branches on polymer molecules
49
What is nanoscience?
Structures that are 1-100 nanometres in size
50
What are nanoparticles used for?
```
Catalysts
Coatings e.g. Paints
Cosmetics e.g. Sun creams, deodorants
Stronger and lighter construction materials
Highly selective sensors
New computers
```
51
How do nanoparticles work?
They have a high surface area to volume ratio
52
What are the masses of protons, neutrons and electrons?
```
Proton = 1
Neutron = 1
Electron = very small
```
53
What is the mass number?
Total number of protons and neutrons
54
What is an isotope?
Atoms of the same element with a different number of neutrons
55
What is the relative atomic mass (Ar) of an element?
It compares the mass of the atoms of the element with the 12C (carbon 12) isotope.
It is an average value for the isotopes of the element.
56
What is the relative formula mass (Mr) of a compound?
The sum of the relative atomic masses of the atoms in the numbers shown in the formula
57
What is the relative formula mass of a substance in grams known as?
One mole of that substance
58
What is good about instrumental methods?
Accurate
Sensitive
Rapid
Useful when the amount of sample is small
59
What technique is used to detect artificial colours in food?
Paper chromatography
60
How does gas chromatography linked to mass spectroscopy work?
Different substances, carried by a gas, travel through a column packed with a solid material at different speeds, so that they become separated
Number of peaks on the output of a gas chromatograph shows the number of compounds present
Position of the peaks on the output indicates the retention time
Mass spectrometer can identify substances very quickly and accurately and can detect very small quantities
61
What can a mass spectrometer also do?
Give the relative molecular mass of each of the substances separated in the column
This is given by the molecular ion peak
62
How do you calculate the percentage of an element in a compound?
Use the relative mass of the element in the formula and the relative formula mass of the compound.
(Mass of element / Relative formula mass) x 100%
63
How do you calculate the empirical formula of a compound?
Use the percentages or masses of the elements in the compound.
Find the ratio of elements in the compound
64
Why is it not always possible to obtain the calculated amount of product?
The reaction may not go to completion as it is reversible
Some of the product may be lost when it is separated from the reaction mixture
Some of the reactants may react in way different from the expected reaction
65
What is the percentage of product obtained called?
Yield
66
How do you calculate percentage yield?
(Actual mass of product / Expected mass of product) x 100%
67
Hoe is a reversible reaction represented?
2 arrows in opposite directions
68
What are the 2 ways of working out rate of reaction?
Amount of product formed / time
Amount of reactant used / time
69
What is activation energy?
The minimum amount of energy particles must have to react
70
What are the 4 ways of increasing the rate of reaction?
Increase temp
Increase pressure of reacting gases
Increase concentration of reactants in solutions
Increase surface area of solid reactants
71
How does increasing temperature increase the rate of reaction?
Increases the speed of reacting particles so they collide more frequently and more energetically
72
How does increasing pressure of reacting gases increase the rate of reaction?
Increases the frequency of collisions
73
How does increasing the concentration of reacts in solutions increase rate of reaction?
Increases frequency of collisions
74
How does increasing the surface area of solid reactants increase rate of reaction?
Increases frequency of collisions
75
What are catalysts?
Something that changes the rate of reaction but is not used up during the reaction
76
What do different reactions need?
Different catalysts
77
Why are catalysts important in industrial processes?
They speed up the rate of reaction so reduce costs
78
What happens during chemical reactions in terms of energy?
Energy is transferred to or from the surroundings
79
What is an exothermic reaction?
A reaction that transfers energy to the surroundings
80
Give examples of exothermic reactions
```
Combustion
Neutralisation
Oxidation reactions
Self-heating cans
Hand warmers
```
81
What is an endothermic reaction?
A reaction that takes in energy from the surroundings
82
Give examples of endothermic reactions
Thermal decomposition
| Sports injury packs
83
What happens if a reversible reaction is exothermic in one direction?
It is endothermic in the other direction
84
What does (s), (l), (g) and (aq)mean?
Solid
Liquid
Gas
Aqueous
85
What can you react with acids to make soluble salts? And how do you react them?
Metals - not all metals are suitable (some too reaction and some not enough)
Insoluble bases - base is added to acid until no more will react and the excess is filtered off
Alkalis - an alkali can be used to show when the acid and alkali have completely reacted to produce a salt solution
86
How can you produce solid salts from salt solutions?
Crystallise the salt solution
87
How do you make insoluble salts?
Mixing appropriate solutions of ions so that a precipitate is formed
88
How can precipitate be used?
To remove unwanted ions from solutions e.g. In treating water for drinking or treating sewage
89
What is a base?
Metal oxides and hydroxide
90
What is an alkali?
A soluble hydroxide
91
The particular salt produced between an acid and a base/alkali depends on...
The acid used
| The metal in the base or alkali
92
Which salts are produced by:
Hydrochloric acid
Nitric acid
Sulfuric acid
Chlorides
Nitrates
Sulfates
93
What is formed when ammonia dissolves in water? What is this used to produce?
An alkaline solution
| Ammonium salts
94
What are ammonium salts important for?
Fertilisers
95
What do hydrogen ions make solutions go?
| What do hydroxide ions make solutions go?
Acidic
| Alkaline
96
What is the pH scale?
A measure of the acidity or alkalinity of a solution
97
What happens in a neutralisation reaction?
Hydrogen ions react with hydroxide ions to produce water
98
What happens to the ions when an ionic substance is melted or dissolved in water?
They are free to move in the liquid or solution
99
What is electrolysis?
When you pass an electric current through ionic substances that are molten or in solution to break them down into elements
100
What is an electrolyte?
The substance broken down by electrolysis
101
What happens to the positively charged ions during electrolysis?
What about the negatively charged ions?
Move to the negative electrode (cathode)
Move to the positive electrode (anode)
102
What is a use of electrolysis?
| Give examples of this use.
Electroplating
E.g. Copper plating
Silver plating
103
What happens at the negative electrode?
Positively charged ions gain electrons (reduction)
104
What happens at the positive electrode?
Negatively charged ions lose electrons (oxidation)
105
If there is a mixture of ions, what do the products formed depend on?
The reactivity of the elements involved
106
How is aluminium manufactured using electrolysis?
Electrolysis of molten mixture of aluminium oxide and cryolite
Aluminium forms at negative electrode
Oxygen forms at positive electrode
Positive electrode is made of carbon, which reacts with oxygen to form carbon dioxide
107
What does the electrolysis of sodium chloride solution produce?
Hydrogen
Chlorine
Sodium hydroxide solution
108
How are sodium hydroxide solution and chlorine important reagents for the chemical industry?
Sodium hydroxide = production of soap
Chlorine = production of bleach and plastics
109
Why is cryolite used to extract aluminium?
It reduces the energy costs as molten cryolite has a lower melting point the aluminium oxide
