Chemistry Flashcards
1
Q
What are elements
A
A substance that is made of only one sort of atom
2
Q
How many different elements are there
A
Around 100
3
Q
Where are elements shown
A
In the periodic table
4
Q
What do the groups in the periodic table contain
A
Elements with similar properties
5
Q
What are atoms of each element represented by
A
A chemical symbol
6
Q
What are atoms nucleus’ made up of
A
Protons, neutrons and around which there are electrons
7
Q
What are the relative electrical charges
A
Proton +1
Neutron 0
Electron -1
8
Q
What are the number of electrons equal to in an atom
A
The number of protons in the nucleus
9
Q
Do atoms have an overall electric charge
A
No
10
Q
What do all atoms of a particular element have
A
The same number of protons
11
Q
What do atoms of different elements have
A
Different numbers of protons
12
Q
What is an element’s atomic number
A
The number of protons it has
13
Q
What is an element’s mass number
A
The sum of the protons and neutrons
14
Q
What do electrons occupy
A
Particular energy levels. Each electronic an atom is at a particular energy level (in a particular shell). The electrons in an atom occupy the lowest available energy levels (innermost available shells)
15
Q
What do elements in the same group in the periodic table have
A
The same number of electrons in the highest energy level (outer electrons) and this gives them similar chemical properties
16
Q
What are noble gases
A
Elements in group 0
17
Q
Why are noble gases unreactive
A
Their atoms have stable arrangement of electrons
18
Q
What happens when elements react
A
The atoms join in with other atoms to form compounds. This involves giving, taking or sharing electrons to form ions or molecules.
19
Q
What do compounds formed of metals and non-metals consist of
A
Ions
20
Q
What are compounds formed from non-metals consist of
A
Molecules
21
Q
How are the atoms held together in molecules
A
By covalent bonds
22
Q
What can chemical reactions be represented by
A
Word equations or by symbol equations
23
Q
Why are the mass of the products equal to the mass of the reactants in a chemical reaction
A
No atoms are lost or made during a chemical reaction
24
Q
Why is it economical to extract metal from ores
A
What is contained in the metal. The economics of extraction may change over time
25
What happens before metal is extracted and purified
Ores are mined and may be concentrated
26
Where are unreactive metals such as gold found
In the earth as the metal itself
27
What do metals found as compounds require
Chemical reactions to extract the metal
28
What metals can be extracted from their oxides by reduction with carbon
Metals that are less reactive than carbon e.g. Iron oxide is reduced in the blast furnace to make iron
29
Which metals are extracted by electrolysis of molten compounds
Metals that are more reactive than carbon, such as aluminium
30
Why are certain metals expensive
The use of large amounts of energy in the extraction of them
31
How can copper be extracted through smelting
Heating copper rich ores in a furnace. The copper can be purified by electrolysis. The supply of copper rich ores is limited and is depleting
32
Why are new ways of extracting copper from low-grade ores being researched
To limit the environmental impact of traditional mining. Copper can now be extracted by phytomining, or by bioleaching
33
What are all substances made from
Atoms
34
How can copper be obtained from solutions of copper salts
Electrolysis or by displacement using scrap iron
35
What metals cannot be extracted from their oxides by reduction with carbon
Aluminium and titanium
36
Why are current methods of extraction expensive
There are many stages in the process
| Large amounts of energy are needed
37
Why should we recycle metals
Extracting metals uses limited resources and is expensive in terms of energy and effects on the environment
38
How much iron from the blast furnace contains iron
96%
39
Why does iron from the blast furnace have limited uses
The impurities make it brittle
40
What are most iron converted into
Steels
41
Why are steels alloys
They are mixtures of iron with carbon
42
What do some steels contain
Other metals
43
What can alloys be designed to have
Properties for specific uses. Low carbon steel is easily shaped, high carbon steel is hard, and stainless steels are resistant to corrosion
44
What are most metals in everyday use
Alloys
45
What are pure copper, gold, iron and aluminium too soft for
Many uses and so are mixed with small amounts of similar metals to make them harder for everyday use
46
What are transition metals
The elements in the central block of the periodic table. They are good conductors of heat & electricity and can be bent or hammered into shape
47
What are transition metals useful as
Structural materials and for making things that must allow heat or electricity to pass though them easily
48
What kind of properties do copper have
Properties that make it useful for electrical wiring and plumbing
49
Why are aluminium and titanium useful metals
Low density and resistance to corrosion
50
What do compounds formed from metals and non metals consist of
Ions
51
What do compounds formed from non metals consist of
Molecules. In molecules the atoms are held together by covalent bonds
52
What is CaCO3
Limestone. It can be quarried and used as a building material
53
What is limewater
A solution of calcium hydroxide in water.
54
What is limestone
A naturally occurring resource that provides a starting point for the manufacture of cement and concrete
55
What is thermal decomposition
When one substance chemically changes into at least two new substances when it's heated
56
What happens to limestone when it is heated
It thermally decomposes to make calcium oxide (CaO) and carbon dioxide (CO2)
57
What metal carbonates decompose in the same way as limestone
Magnesium, copper, zinc and sodium. However, not all carbonates of metals in group 1 can be decomposed by the temperature reached on a Bunsen burner
58
What does calcium oxide react with water to produce
Calcium hydroxide (Ca(OH)2), an alkali that can be used in the neutralisation of acids e.g. acidic soil
59
What is limewater
A solution of calcium hydroxide in water. It can be used as a test for carbon dioxide, the carbon dioxide turns the limewater cloudy.
60
What does limewater react with carbon dioxide to produce
Calcium carbonate.
| Calcium hydroxide + carbon dioxide = calcium carbonate + water
61
What do carbonates react with acids to produce
Carbon dioxide, a salt and water.
Calcium carbonate + sulphuric acid = calcium sulfate + carbon dioxide + water
The type of salt produced depends on the acid e.g. a reaction with hydrochloric acid would make a chloride
62
Which other carbonates react with acids
Copper, zinc, sodium and magnesium
63
What damages limestone
Acid rain
64
How is cement made
Powdered limestone heated in a kiln with powdered clay
65
How is mortar made
Cement mixed with sand and water
66
What is aggregate
Water and gravel
67
How is concrete made
Cement mixed with sand and aggregate
68
Advantages of limestone
Widely available and cheaper than granite and marble
Does not rot when wet, like wood and cannot be gnawed away by insects
Fire resistant
Does not corrode like many metals
Can be used to neutralise acidic soil and lakes
Neutralises sulphur dioxide, a cause of acid rain
The quarry and associated businesses provide jobs
69
Disadvantages of limestone
Low tensile strength
Quarrying processes create noise and dust pollution
Quarrying destroys habitats
Transportation of limestone causes noise and pollution
Cement factories create a lot of dust, which can cause breathing problems for those nearby
70
What is the reactivity series
```
Potassium K
Sodium Na
Calcium Ca
Magnesium Mg
Aluminium Al
CARBON C
Zinc Zn
Iron Fe
Tin Sn
Copper C
```
71
What is electrolysis
The breaking down of a substance using electricity
An electrolyte conducts the electricity - because of the free ions
Electrolytes are often metal salt solutions made from the ore or molten metal oxides
Electrons are taken away from the (positive) anode and given away to the (negative) cathode.
As ions lose/gain electrons they become atoms/molecules and are released
72
How is electrolysis used to purify copper
Electrons are pulled off copper atoms at the anode, causing them to go into the solution as Cu2+ ions.
Cu2+ ions near the cathode gain electrons and turn back into copper atoms
The impurities are dropped at the anode as a sludge, while pure copper atoms bond to the cathode
73
What is an anode
A big lump of impure metal which will eventually dissolve
74
What is a cathode
A thin piece of pure metal that the pure metal atoms bond to
75
What is Bioleaching
Using bacteria to separate copper sulfide. The bacteria get energy from the bond between sulfur and copper, separating out the copper from the ore in the process. The leachate (the solution produced by the process) contains copper, which can be extracted by e.g. filtering
76
What is Phytomining
Growing plants in soil that contain copper. The plants cant use or get rid of the copper so it gradually builds up in the leaves. The plants can be harvested, dried and burned in a furnace. The copper can be collected from the ash left in the furnace
77
What is crude oil
A mixture of a very large number of compounds
78
What are most of the compounds in crude oil consist of
Molecules made of hydrogen and carbon atoms (hydrocarbons). Most of these are saturated hydrocarbons called alkanes, which have the general formula CnH2n+2
79
What are the first four alkanes
Methane CH4
Ethane C2H6
Propane C3H8
Butane C4H10
80
What is fractional distillation
Separating the many hydrocarbons in crude oil into fractions, each of which contains molecules with a similar number of carbon atoms. This is done by heating the crude oil and evaporating it. It is then allowed to condense at a number of different temperatures.
81
What do some properties of hydrocarbons depend on
The size of their molecules. These properties influence how hydrocarbons are used as fuels
82
What are the trends of hydrocarbons
The shorter the molecules:
The less viscous (thick) the hydrocarbon is
The more volatile (runny) it is
The lower its boiling point and the temperature at which they condense and vaporise
The more flammable it is
83
How does viscosity help decide how the hydrocarbon is used
The really viscous hydrocarbons are used for lubricating engine parts and for covering roads
84
What do most fuels, including coal, contain
Carbon and/or hydrogen and may also contain some sulfur
85
What is released into the atmosphere when a fuel burns
Carbon dioxide
Water (vapour)
Sulfur dioxide
Oxides of nitrogen
86
What may particulates contain
Soot (carbon)
| Unburnt fuels
87
What happens during combustion of hydrocarbon fuels
Energy is released and the carbon and hydrogen in the fuels are oxidised
88
What are the causes of acid rain
Sulfur dioxide and oxides of nitrogen.
When the sulfur dioxide mixes with clouds it forms dilute sulphuric acid. This then falls as acid rain.
In the same way, oxides of nitrogen cause acid rain by forming dilute nitric acid in clouds
89
What is the cause of global warming
Carbon dioxide
90
What is the cause of global dimming
Solid particles (particulates)
91
What is partial combustion
When some of the fuel does not burn, because there is not enough oxygen.
Under these conditions, solid particles (particulates) and carbon monoxide is released.
92
How can sulfur emissions be reduced
Power stations can use Acid Gas Scrubbers which take the harmful gases out before they release their fumes into the atmosphere
93
What are the two types of biofuels
Ethanol and Biodiesel
94
What is ethanol
A biofuel produced from fermented plant material and is used to power cars in some places. It's often mixed with petrol to make a better fuel.
95
What are the pros of ethanol
The CO2 released when it's burnt was taken in by the plant as it grew, so it's 'carbon neutral'.
It's widely available
96
What are the cons of ethanol
Engines need to be converted before they'll work with ethanol fuels
There are worries that as demand for it increases farmers will switch from growing food crops to growing crops to make ethanol - this will increase food prices
97
What is biodiesel
A fuel produced from vegetable oils e.g. rapeseed oil and soybean oil. Biodiesel can be mixed with ordinary diesel fuel and used to run a diesel engine.
98
What are the pros of biodiesel
It is carbon neutral
Engines don't need to be converted
It produces much less sulfur dioxide and 'particulates' than ordinary diesel or petrol
99
What are the cons of biodiesel
We can't make enough to completely replace diesel
Its expensive to make
It could increase food prices like using ethanol could
100
What is cracking
A process used to turn hydrocarbons into smaller, more useful molecules. It involves heating the hydrocarbons to vaporise them. The vapours are either passed over a very hot catalyst or mixed with steam and heated to a very high temperature so that thermal decomposition reactions then occur.
101
What are the products of cracking
Alkanes and unsaturated hydrocarbons called alkenes. Alkenes have the general formula CnH2n.
102
How can you test for an alkene
By adding the substance to bromine water. An alkene will decolourise the bromine water, turning it from orange to colourless. This is because the double bond has opened up and formed bonds with the bromine
103
How can ethanol be produced with ethene
Ethene (C2H4) can be hydrated with steam (H20) in the presence of a catalyst to make ethanol
104
Advantages and disadvantages of producing ethanol with ethene
Advantages: Ethene is cheap and not that much of it wasted
Disadvantages: Ethene is made from crude oil and is non renewable. This could mean ethene may become very expensive
105
How can ethanol be produced with renewable resources
It can be fermented by yeast using sugar
| Sugar = carbon dioxide and ethanol
106
Advantages and disadvantages of producing ethanol with renewable resources
Advantages: It uses simpler equipment, the ethanol made could be used as a cheap fuel in countries that don't have oil reserves for making petrol and is renewable
Disadvantages: The ethanol isn't very concentrated and so has to be distilled and then purified.
107
What is polymerisation
Joining together lots of small alkenes molecules (monomers) to form very large molecules (polymers)
108
What does the earth consist of
A core, mantle and crust and is surrounded by the atmosphere
109
What are tectonic plates
The Earth's crust and upper part of the mantle cracked into a number of large pieces
110
Why do the tectonic plates move at relative speeds of a few centimetres a year
Convection currents within the Earth's mantle driven by heat released by natural radioactive processes
111
What are the proportions of different gases in the atmosphere
Around 80% nitrogen
Around 20% oxygen
Small proportions of various other gases, including carbon dioxide, water vapour and noble gases.
This has been the same for about 200 million years
112
What was Phase 1 of the evolution of the Earth
Intense volcanic activity during first billion year
| Volcanoes released gases that formed the early atmosphere and water vapour that condensed to form the oceans.
113
What was Phase 2 of the evolution of the Earth
Plants and algae evolved. CO2 dissolved in the oceans and the plants and algae also absorbed it and produced O2 by photosynthesis.
Most of the carbon from the carbon dioxide became 'locked up' in sedimentary rocks as insoluble carbonates (limestone) and fossil fuels
114
What was the early atmosphere mostly made of
Mostly CO2 and virtually no oxygen. There may have also been water vapour, and small amounts of methane and ammonia. This is quite like the atmospheres of Mars and Venus today
115
What was limestone formed from
The shells and skeletons of marine organisms
116
What do fossil fuels contain
Carbon and hydrocarbons that are the remains of plants and animals
117
What was Phase 3 of the evolution of the Earth
The build up of oxygen killed off many early organisms, but allowed more complex organisms to evolve and flourish.
The oxygen also created the ozone layer (O3) which blocked harmful rays from the Sun and allowed humans to evolve
118
What is the Primordial soup theory
The Earth's early atmosphere contained hydrocarbons, ammonia and other gases
Lightning struck and caused a chemical reaction which produced amino acids
The amino acids collected in a 'primordial soup'
The amino acids gradually combined to produce organic matter and eventually evolved into simple organisms
119
What did Miller and Urey do
Carried out an experiment to prove the primordial soup theory in the 1950's. They sealed the gases in their apparatus, heated them and applied electrical charge for a week.
They found that amino acids were made, but not as many as there are on Earth
120
What are natural stores of CO2
The oceans but increased amounts of carbon dioxide absorbed by the oceans has an impact on the marine environment
121
What is air
A mixture of gases with different boiling points and can be fractionally distilled to provide a source of raw materials used in a variety of industrial processes
122
How is air separated
Air is filtered to remove dust
It's then cooled to around -200 degrees and becomes a liquid
During cooling water vapour condenses and is removed
CO2 freezes and is removed
The liquified air then enters the fractionating column and is heated slowly
The remaining gases are separated by fractional distillation. O2 and argon come out together so another column is used to separate them
123
What can polymers be used as
```
New packaging materials
Waterproof coatings for fabrics
Dental polymers
Wound dressings
Hydrogels
Smart materials (including shape memory polymers)
```
124
Why do many polymers lead to problems with waste disposal
Many polymers are not biodegradable and so cannot be broken down by microbes
125
Why can plastic bags break down more easily
They are being made from polymers and corn starch
126
How can you tell an oil is unsaturated
It contains double carbon bonds and reacts with bromine water
127
How can you harden or hydrogenate unsaturated vegetable oils
Reacting them with hydrogen in the presence of a nickel catalyst at about 60 degrees.
The hydrogen adds to the double carbon bonds.
128
Why are hydrogenated oils useful in spreads and in cakes and pastries
They have higher melting points so they are solids at room temperature
129
What kind of properties do emulsifiers have
Hydrophilic and hydrophobic. The head is hydrophilic and the tail is hydrophobic. The head dissolves in water and the tail dissolves in oil.
130
What does hydrophilic mean
Water loving
131
What does hydrophobic mean
Water fearing
132
Oils do not dissolve in ...
... water
133
Oils can be used to produce ...
... emulsions.
134
What are emulsions made up of
Lots of tiny droplets of one liquid suspended in another liquid. There are oil in water and water in oil emulsions. Emulsions are thicker than either oil or water.
135
What are emulsifiers
Molecules that turn oil/water mixtures into emulsions
136
What are emulsions' special properties
Provide better texture
Thicker
Creamier
Better at coating
137
Advantages and disadvantages of using emulsifiers
Advantages: Stop emulsions from separating out and this gives them a longer shelf life. Emulsifiers allow food companies to produce food that's lower in fat but still has a good texture.
Disadvantages: Some people are allergic to certain emulsifiers e.g. egg yolk
138
What benefits do vegetable oils have for cooking
They have higher boiling points than water and so can be used to cook foods at higher temperatures than by boiling. This produces quicker cooking and different flavours but there is more fat in the food.
139
Why are vegetable oils and fuels important
They provide a lot of energy and nutrients.
140
How are oils extracted
The plant material is crushed and the oil is removed by squashing the crushed material through metal plates.
141
What can you extract oils from
Some fruits, seeds and nuts
142
What does distillation do
Refines oil, and removes water, solvents and impurities
143
What can solvents do
Be used to get oil from plant material
| Oil can also be separated using a centrifuge
