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Core Science > Chemistry > Flashcards

Chemistry Flashcards

1
Q

What are elements

A

A substance that is made of only one sort of atom

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2
Q

How many different elements are there

A

Around 100

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3
Q

Where are elements shown

A

In the periodic table

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4
Q

What do the groups in the periodic table contain

A

Elements with similar properties

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5
Q

What are atoms of each element represented by

A

A chemical symbol

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6
Q

What are atoms nucleus’ made up of

A

Protons, neutrons and around which there are electrons

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7
Q

What are the relative electrical charges

A

Proton +1
Neutron 0
Electron -1

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8
Q

What are the number of electrons equal to in an atom

A

The number of protons in the nucleus

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9
Q

Do atoms have an overall electric charge

A

No

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10
Q

What do all atoms of a particular element have

A

The same number of protons

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11
Q

What do atoms of different elements have

A

Different numbers of protons

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12
Q

What is an element’s atomic number

A

The number of protons it has

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13
Q

What is an element’s mass number

A

The sum of the protons and neutrons

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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)

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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

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16
Q

What are noble gases

A

Elements in group 0

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17
Q

Why are noble gases unreactive

A

Their atoms have stable arrangement of electrons

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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.

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19
Q

What do compounds formed of metals and non-metals consist of

A

Ions

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20
Q

What are compounds formed from non-metals consist of

A

Molecules

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21
Q

How are the atoms held together in molecules

A

By covalent bonds

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22
Q

What can chemical reactions be represented by

A

Word equations or by symbol equations

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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

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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

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25
Q

What happens before metal is extracted and purified

A

Ores are mined and may be concentrated

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26
Q

Where are unreactive metals such as gold found

A

In the earth as the metal itself

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27
Q

What do metals found as compounds require

A

Chemical reactions to extract the metal

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28
Q

What metals can be extracted from their oxides by reduction with carbon

A

Metals that are less reactive than carbon e.g. Iron oxide is reduced in the blast furnace to make iron

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29
Q

Which metals are extracted by electrolysis of molten compounds

A

Metals that are more reactive than carbon, such as aluminium

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30
Q

Why are certain metals expensive

A

The use of large amounts of energy in the extraction of them

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31
Q

How can copper be extracted through smelting

A

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

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32
Q

Why are new ways of extracting copper from low-grade ores being researched

A

To limit the environmental impact of traditional mining. Copper can now be extracted by phytomining, or by bioleaching

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33
Q

What are all substances made from

A

Atoms

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34
Q

How can copper be obtained from solutions of copper salts

A

Electrolysis or by displacement using scrap iron

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35
Q

What metals cannot be extracted from their oxides by reduction with carbon

A

Aluminium and titanium

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36
Q

Why are current methods of extraction expensive

A

There are many stages in the process

Large amounts of energy are needed

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37
Q

Why should we recycle metals

A

Extracting metals uses limited resources and is expensive in terms of energy and effects on the environment

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38
Q

How much iron from the blast furnace contains iron

A

96%

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39
Q

Why does iron from the blast furnace have limited uses

A

The impurities make it brittle

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40
Q

What are most iron converted into

A

Steels

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41
Q

Why are steels alloys

A

They are mixtures of iron with carbon

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42
Q

What do some steels contain

A

Other metals

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43
Q

What can alloys be designed to have

A

Properties for specific uses. Low carbon steel is easily shaped, high carbon steel is hard, and stainless steels are resistant to corrosion

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44
Q

What are most metals in everyday use

A

Alloys

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45
Q

What are pure copper, gold, iron and aluminium too soft for

A

Many uses and so are mixed with small amounts of similar metals to make them harder for everyday use

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46
Q

What are transition metals

A

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

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47
Q

What are transition metals useful as

A

Structural materials and for making things that must allow heat or electricity to pass though them easily

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48
Q

What kind of properties do copper have

A

Properties that make it useful for electrical wiring and plumbing

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49
Q

Why are aluminium and titanium useful metals

A

Low density and resistance to corrosion

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50
Q

What do compounds formed from metals and non metals consist of

A

Ions

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51
Q

What do compounds formed from non metals consist of

A

Molecules. In molecules the atoms are held together by covalent bonds

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52
Q

What is CaCO3

A

Limestone. It can be quarried and used as a building material

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53
Q

What is limewater

A

A solution of calcium hydroxide in water.

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54
Q

What is limestone

A

A naturally occurring resource that provides a starting point for the manufacture of cement and concrete

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55
Q

What is thermal decomposition

A

When one substance chemically changes into at least two new substances when it’s heated

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56
Q

What happens to limestone when it is heated

A

It thermally decomposes to make calcium oxide (CaO) and carbon dioxide (CO2)

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57
Q

What metal carbonates decompose in the same way as limestone

A

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

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58
Q

What does calcium oxide react with water to produce

A

Calcium hydroxide (Ca(OH)2), an alkali that can be used in the neutralisation of acids e.g. acidic soil

59
Q

What is limewater

A

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
Q

What does limewater react with carbon dioxide to produce

A

Calcium carbonate.

Calcium hydroxide + carbon dioxide = calcium carbonate + water

61
Q

What do carbonates react with acids to produce

A

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
Q

Which other carbonates react with acids

A

Copper, zinc, sodium and magnesium

63
Q

What damages limestone

A

Acid rain

64
Q

How is cement made

A

Powdered limestone heated in a kiln with powdered clay

65
Q

How is mortar made

A

Cement mixed with sand and water

66
Q

What is aggregate

A

Water and gravel

67
Q

How is concrete made

A

Cement mixed with sand and aggregate

68
Q

Advantages of limestone

A

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
Q

Disadvantages of limestone

A

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
Q

What is the reactivity series

A 
Potassium      K
Sodium          Na
Calcium         Ca
Magnesium   Mg
Aluminium     Al
CARBON       C
Zinc                Zn
Iron                 Fe
Tin                   Sn 
Copper           C
71
Q

What is electrolysis

A

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
Q

How is electrolysis used to purify copper

A

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
Q

What is an anode

A

A big lump of impure metal which will eventually dissolve

74
Q

What is a cathode

A

A thin piece of pure metal that the pure metal atoms bond to

75
Q

What is Bioleaching

A

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
Q

What is Phytomining

A

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
Q

What is crude oil

A

A mixture of a very large number of compounds

78
Q

What are most of the compounds in crude oil consist of

A

Molecules made of hydrogen and carbon atoms (hydrocarbons). Most of these are saturated hydrocarbons called alkanes, which have the general formula CnH2n+2

79
Q

What are the first four alkanes

A

Methane CH4
Ethane C2H6
Propane C3H8
Butane C4H10

80
Q

What is fractional distillation

A

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
Q

What do some properties of hydrocarbons depend on

A

The size of their molecules. These properties influence how hydrocarbons are used as fuels

82
Q

What are the trends of hydrocarbons

A

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
Q

How does viscosity help decide how the hydrocarbon is used

A

The really viscous hydrocarbons are used for lubricating engine parts and for covering roads

84
Q

What do most fuels, including coal, contain

A

Carbon and/or hydrogen and may also contain some sulfur

85
Q

What is released into the atmosphere when a fuel burns

A

Carbon dioxide
Water (vapour)
Sulfur dioxide
Oxides of nitrogen

86
Q

What may particulates contain

A

Soot (carbon)

Unburnt fuels

87
Q

What happens during combustion of hydrocarbon fuels

A

Energy is released and the carbon and hydrogen in the fuels are oxidised

88
Q

What are the causes of acid rain

A

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
Q

What is the cause of global warming

A

Carbon dioxide

90
Q

What is the cause of global dimming

A

Solid particles (particulates)

91
Q

What is partial combustion

A

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
Q

How can sulfur emissions be reduced

A

Power stations can use Acid Gas Scrubbers which take the harmful gases out before they release their fumes into the atmosphere

93
Q

What are the two types of biofuels

A

Ethanol and Biodiesel

94
Q

What is ethanol

A

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
Q

What are the pros of ethanol

A

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
Q

What are the cons of ethanol

A

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
Q

What is biodiesel

A

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
Q

What are the pros of biodiesel

A

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
Q

What are the cons of biodiesel

A

We can’t make enough to completely replace diesel
Its expensive to make
It could increase food prices like using ethanol could

100
Q

What is cracking

A

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
Q

What are the products of cracking

A

Alkanes and unsaturated hydrocarbons called alkenes. Alkenes have the general formula CnH2n.

102
Q

How can you test for an alkene

A

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
Q

How can ethanol be produced with ethene

A

Ethene (C2H4) can be hydrated with steam (H20) in the presence of a catalyst to make ethanol

104
Q

Advantages and disadvantages of producing ethanol with ethene

A

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
Q

How can ethanol be produced with renewable resources

A

It can be fermented by yeast using sugar

Sugar = carbon dioxide and ethanol

106
Q

Advantages and disadvantages of producing ethanol with renewable resources

A

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
Q

What is polymerisation

A

Joining together lots of small alkenes molecules (monomers) to form very large molecules (polymers)

108
Q

What does the earth consist of

A

A core, mantle and crust and is surrounded by the atmosphere

109
Q

What are tectonic plates

A

The Earth’s crust and upper part of the mantle cracked into a number of large pieces

110
Q

Why do the tectonic plates move at relative speeds of a few centimetres a year

A

Convection currents within the Earth’s mantle driven by heat released by natural radioactive processes

111
Q

What are the proportions of different gases in the atmosphere

A

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
Q

What was Phase 1 of the evolution of the Earth

A

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
Q

What was Phase 2 of the evolution of the Earth

A

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
Q

What was the early atmosphere mostly made of

A

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
Q

What was limestone formed from

A

The shells and skeletons of marine organisms

116
Q

What do fossil fuels contain

A

Carbon and hydrocarbons that are the remains of plants and animals

117
Q

What was Phase 3 of the evolution of the Earth

A

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
Q

What is the Primordial soup theory

A

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
Q

What did Miller and Urey do

A

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
Q

What are natural stores of CO2

A

The oceans but increased amounts of carbon dioxide absorbed by the oceans has an impact on the marine environment

121
Q

What is air

A

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
Q

How is air separated

A

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
Q

What can polymers be used as

A 
New packaging materials 
Waterproof coatings for fabrics
Dental polymers 
Wound dressings
Hydrogels 
Smart materials (including shape memory polymers)
124
Q

Why do many polymers lead to problems with waste disposal

A

Many polymers are not biodegradable and so cannot be broken down by microbes

125
Q

Why can plastic bags break down more easily

A

They are being made from polymers and corn starch

126
Q

How can you tell an oil is unsaturated

A

It contains double carbon bonds and reacts with bromine water

127
Q

How can you harden or hydrogenate unsaturated vegetable oils

A

Reacting them with hydrogen in the presence of a nickel catalyst at about 60 degrees.
The hydrogen adds to the double carbon bonds.

128
Q

Why are hydrogenated oils useful in spreads and in cakes and pastries

A

They have higher melting points so they are solids at room temperature

129
Q

What kind of properties do emulsifiers have

A

Hydrophilic and hydrophobic. The head is hydrophilic and the tail is hydrophobic. The head dissolves in water and the tail dissolves in oil.

130
Q

What does hydrophilic mean

A

Water loving

131
Q

What does hydrophobic mean

A

Water fearing

132
Q

Oils do not dissolve in …

A

… water

133
Q

Oils can be used to produce …

A

… emulsions.

134
Q

What are emulsions made up of

A

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
Q

What are emulsifiers

A

Molecules that turn oil/water mixtures into emulsions

136
Q

What are emulsions’ special properties

A

Provide better texture
Thicker
Creamier
Better at coating

137
Q

Advantages and disadvantages of using emulsifiers

A

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
Q

What benefits do vegetable oils have for cooking

A

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
Q

Why are vegetable oils and fuels important

A

They provide a lot of energy and nutrients.

140
Q

How are oils extracted

A

The plant material is crushed and the oil is removed by squashing the crushed material through metal plates.

141
Q

What can you extract oils from

A

Some fruits, seeds and nuts

142
Q

What does distillation do

A

Refines oil, and removes water, solvents and impurities

143
Q

What can solvents do

A

Be used to get oil from plant material

Oil can also be separated using a centrifuge

Core Science (3 decks)

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