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GCSE Combined Science > Chemistry Paper 2 > Flashcards

Chemistry Paper 2 Flashcards

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1
Q

What is the formula for a mean rate of reaction in terms of reactants?

A

quantity of reactant used/time taken

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2
Q

What is the formula for a mean rate of reaction in terms of products?

A

quantity of reactant product formed/time taken

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3
Q

How can you measure the quantity of a reactant or product?

A

In grams or in cm3

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4
Q

What are the two possible units for rate of reaction?

A

g/s or cm3/s (where s is seconds)

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5
Q

How could you measure the rate of a reaction from a graph?

A

Draw a tangent to the curve and calculate the gradient.

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6
Q

What is “collision theory”?

A

The theory that chemical reactions only occur when particles collide with sufficient energy

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7
Q

What five factors can affect the rate of a reaction?

A

Temperature, surface area of a solid, concentration of reactants in solution, pressure of gases, catalyst

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8
Q

State the effect of increasing the surface area on the rate of a reaction

A

Increases the rate

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9
Q

Explain why increasing the surface area increases the rate of a reaction

A

More particles are available to collide there are therefore more frequent collisions between reactants.

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10
Q

State the effect of increasing the concentration on the rate of reaction

A

Increases

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11
Q

Explain why increasing the concentration increases the rate of reaction

A

More concentrated means more particles in solution, therefore more frequent collisions between reactants.

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12
Q

State the effect on increasing the pressure of a gas on the rate of reaction

A

Increases

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13
Q

Explain why increasing the pressure of a gas increases the rate of a reaction

A

Less space for the particles to move around in, therefore more frequent collisions

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14
Q

State the effect of increasing the temperature on the rate of reaction

A

Increases

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15
Q

What is the activation energy?

A

The amount of energy a particle needs before it will be able to react when it collides with another particle

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16
Q

Explain why increasing the temperature increases the rate of reaction

A

Increases the speed at which particles move therefore more frequent collisions.
Increases the number of particles which have the activation energy therefore more collisions result in a reaction.

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17
Q

What is a catalyst?

A

Something which changes the rate of a reaction but is not used up in that reaction

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18
Q

How do catalysts speed up reactions?

A

They provide another route for the reaction to take place which has a lower activation energy.

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19
Q

What is a reversible reaction?

A

A reaction which can go from reactants to products but also from products to reactants

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20
Q

What chemical symbol represents a reversible reaction?

A

⇌

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21
Q

If a reaction is exothermic in the forward direction what will it be in the reverse direction?

A

Endothermic

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22
Q

What is dynamic equilibrium?

A

The point in a reversible reaction when the forward and reverse reactions are occurring at the same rate

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23
Q

How is the amount of reactant changing at equilibrium?

A

It is not changing

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24
Q

How is the amount of product changing at equilibrium?

A

It is not changing

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25
Q

(HT) What is Le Chatelier’s principle?

A

When a reaction at equilibrium is changed, it will seek to counteract that change

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26
Q

(HT) A reaction is exothermic in the forward direction. What will occur if the temperature is increased?

A

The backward reaction will increase as it is endothermic and will reduce the temperature

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27
Q

(HT) A reaction is at equilibrium when some product is removed. What will occur?

A

The forward reaction will increase as that will increase the amount of product

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28
Q

(HT) How does increasing the pressure affect equilibrium?

A

Favours the side with fewer gaseous molecules

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29
Q

What is crude oil?

A

A mixture of hydrocarbons

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30
Q

What is a finite resource?

A

One that will run out

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31
Q

Why is crude oil a finite resource?

A

Because it takes longer to form than the rate at which we are using it up

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32
Q

What is a hydrocarbon?

A

A compound made of atoms of carbon and hydrogen only

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33
Q

What is a general formula?

A

A mathematical formula which allows you to work out the chemical formula of a substance

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34
Q

What is an alkane?

A

A hydrocarbon with only single bonds

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35
Q

Name the first four alkanes

A

Methane, ethane, propane, butane

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36
Q

What is the general formula for alkanes?

A

Cn + H2n+2

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37
Q

How does boiling point change with the length of an alkane?

A

The longer the alkane, the higher its boiling point

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38
Q

How does viscosity change with the length of an alkane?

A

The longer the alkane, the more viscous (the thicker) it is

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39
Q

How does flammability change with the length of an alkane?

A

The longer the alkane, the less flammable it is

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40
Q

What is fractional distillation?

A

A process used to separate mixtures substances with different boiling point

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41
Q

What are the steps involved in fractional distillation?

A

Crude oil is vaporised, different molecules rise up the fractionating column and cool down. Condense at different points on the column.

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42
Q

Why is fractional distillation important?

A

Because the different fractions have different uses

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43
Q

What is a fuel?

A

A substance which when reacted with oxygen releases energy

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44
Q

Name five fuels we obtain from crude oil

A

Petrol, diesel, kerosene, heavy fuel oil and liquefied petroleum gases

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45
Q

What other uses are there for products of fractional distillation?

A

Solvents, lubricants, polymers and detergents

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46
Q

What is combustion?

A

The reaction of a fuel with oxygen

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47
Q

What are the products of complete combustion?

A

Carbon dioxide and water

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48
Q

When does incomplete combustion occur?

A

When there is not enough oxygen present

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49
Q

What is cracking?

A

The process of breaking down a long hydrocarbon into smaller hydrocarbons

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50
Q

What are the products of cracking?

A

Short alkanes and alkenes

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51
Q

Why is cracking important?

A

Because smaller hydrocarbons are more useful than longer ones

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52
Q

What are the two types of cracking?

A

Catalytic and steam cracking

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53
Q

What are alkenes

A

A different type of hydrocarbon which is more reactive than an alkane

54
Q

What are alkenes used for?

A

As a starting material to make more useful chemicals

55
Q

How do you test for an alkene?

A

React it with bromine water

56
Q

What is the colour change when an alkene reacts with bromine water?

A

Turns from orange to colourless

57
Q

What is chemical analysis?

A

The process of establishing what chemicals are present in a substance

58
Q

In everyday language what is a “pure” substance?

A

A substance that has had nothing added to it and is in its “natural” state

59
Q

In chemistry what is a “pure” substance?

A

A substance made of a single element or compound

60
Q

How can pure substances be distinguished from impure ones?

A

By their melting/boiling points

61
Q

Describe the melting and boiling points of pure substances

A

One very specific temperature

62
Q

Describe the melting and boiling points of impure substances

A

They change state at a range of temperatures

63
Q

What is a formulation?

A

A complex mixture designed as a useful product

64
Q

Give three examples of formulations

A

Fuels, cleaning agents, paints, medicines, alloys, fertilisers and foods

65
Q

What is chromatography?

A

A process to separate the constituents of a mixture

66
Q

In paper chromatography, what is the stationary phase and what is the mobile phase

A

Paper is stationary, solvent (usually water or ethanol) is mobile

67
Q

How can chromatography show the difference between pure and impure substances?

A

Pure ones will not separate into a number of spots

68
Q

How is the Rf value calculated?

A

Distance moves by spot/ distance moved by solvent

69
Q

What does a substance’s Rf value depend on?

A

How soluble it is in the solvent

70
Q

In chromatography, why must the substances be placed on a pencil line?

A

Pencil will not dissolve in the solvent

71
Q

In chromatography why must the solvent height be lower than the pencil line

A

So that the substance does not into the solvent off the paper

72
Q

How can hydrogen be tested for?

A

Makes a squeaky pop when a splint is placed in it

73
Q

How can oxygen be tested for?

A

Relights a glowing splint

74
Q

How can carbon dioxide be tested for?

A

Buble through limewater, turns it milky (cloudy)

75
Q

How can chlorine be tested for?

A

Bleaches damp litmus paper white

76
Q

What is the approximate proportion of nitrogen in Earth’s current atmosphere?

A

80%

77
Q

What is the approximate proportion of oxygen in Earth’s current atmosphere?

A

20%

78
Q

Which gases are in small proportions in the current. atmosphere?

A

Noble gases, water vapour, carbon dioxide

79
Q

When Earth was formed which planets was its atmosphere similar to?

A

Venus and Mars

80
Q

What do Mars and Venus’s atmospheres comprise of?

A

Carbon dioxide with little or no oxygen

81
Q

What produced the gases present in Earth’s early atmosphere?

A

Volcanoes

82
Q

Which gases were present in Earth’s early atmosphere?

A

Carbon dioxide water vapour and nitrogen with small amount of methane and ammonia

83
Q

Why have theories about Earth’s early atmosphere developed and changed over time?

A

Evidence is limited and it was billions of years ago

84
Q

By what process do algae and plants produce oxygen?

A

Photosynthesis

85
Q

Write the word equation to represent photosynthesis

A

carbon dioxide + water -› oxygen + glucose

86
Q

How did the world’s oceans form?

A

The Earth’s temperature cooled, causing water vapour in the air to condense

87
Q

How did the oceans reduce atmospheric levels of carbon dioxide in Earth’s early atmosphere?

A

Carbon dioxide dissolved in the oceans

88
Q

How did algae and plants reduce levels of carbon dioxide in Earth’s early atmosphere?

A

By photosynthesising

89
Q

What was formed when shells of organisms made using dissolved carbon dioxide fell to the bottom of the ocean and were covered and compressed?

A

Sedimentary rock

90
Q

What was formed when plants that grew millions of years ago died and were trapped and compressed under rocks?

A

Coal

91
Q

What was formed when plankton that lived in the ocean millions of years ago died and were trapped and compressed under rocks?

A

Crude Oil and Natural Gas

92
Q

Name three greenhouse gases

A

Water Vapour, Carbon Dioxide, and Methane

93
Q

Describe the wavelength of radiation that comes from the sun and is reflected by the Earth

A

From the Sun: short wave,
From the Earth: long wave

94
Q

What happens to the long wave radiation that is reflected from the Earth in the atmosphere?

A

It is absorbed by greenhouse gases

95
Q

What is the name given to the process that warms up the surface of the Earth?

A

The greenhouse effect

96
Q

What human activities increase carbon dioxide levels?

A

Deforestation and burning fossil fuels

97
Q

What human activities increase methane levels?

A

Farming animals and landfill

98
Q

What is the name given to the increasing average temperature of the Earth?

A

Climate Change

99
Q

Name an effect of climate change

A

Increased flooding, changes in rainfall patterns, frequency of storms, amount of water in a habitat etc…

100
Q

What is the name given to the total amount of carbon dioxide and other greenhouse gases emitted over the full lifecycle of a product, service or event?

A

Carbon footprint

101
Q

What is produced from the complete combustion of a hydrocarbon fuel?

A

Carbon dioxide and water

102
Q

Which products could be produced from an incomplete combustion of a hydrocarbon fuel?

A

Carbon dioxide, water, carbon monoxide, carbon particulates

103
Q

Which gas is produced when fuels are burned and contain sulfur impurities?

A

Sulfur dioxide

104
Q

Which gases are produced when nitrogen and oxygen react in the very high temperatures of a car engine?

A

Oxides of nitrogen

105
Q

What are the effects of carbon monoxide?

A

A toxic gas

106
Q

What are the effects of sulfur dioxide?

A

Causes respiratory problems and acid rain

107
Q

What are the effects of the oxides of nitrogen?

A

Causes respiratory problems and acid rain

108
Q

What are the effects of particulates of fuels?

A

Cause global dimming and health problems for humans

109
Q

What do humans use resources for?

A

Warmth, shelter and food

110
Q

What are finite resources?

A

Resources that will run out

111
Q

What is sustainable development?

A

Development that meets the needs of the current generations without compromising the ability of future generations to meet their own needs

112
Q

Give an example of a natural product that has been replaced by a synthetic product

A

Cotton has been replaced by polyester

113
Q

What is potable water?

A

Water that is safe to drink

114
Q

In the UK how is potable water produced?

A

Passing fresh water through filter beds and sterilising

115
Q

How is water sterilised?

A

Using chlorine, ozone or ultraviolet light

116
Q

What is desalination?

A

Removal of salt from sea water

117
Q

In what two ways can desalination be carried out?

A

Reverse osmosis or distillation

118
Q

What is the main disadvantage of desalination?

A

It requires a large amount of energy

119
Q

In what kinds of locations is desalination carried out?

A

Ones where there is limited supply of fresh water

120
Q

What needs to be removed from sewage and agricultural waste water?

A

Organic matter and harmful microbes

121
Q

What needs to be removed from industrial waste water?

A

Organic matter and harmful chemicals

122
Q

How is sewage treated?

A

Screening, sedimentation, anaerobic digestion, aerobic biological treatment

123
Q

(HT) Name two new ways of extracting copper from low-grade ores

A

Phytomining and bioleaching

124
Q

(HT) What is a low grade ore?

A

Rock with only a small amount of metal compound in it

125
Q

(HT) How is phytomining carried out?

A

Plants absorb metal compounds, are harvested and then burned to produce ash

126
Q

(HT) How is bioleaching carried out?

A

Bacteria are used to produce a leachate solution

127
Q

(HT) How can copper be produced from the products of phytomining or bioleaching?

A

Electrolysis or displacement with scrap iron

128
Q

What is a life cycle assessment?

A

A way of assessing the environmental impact of a product across its entire life cycle

129
Q

What are the four stages in a product’s life cycle?

A

Extracting and processing raw materials, manufacturing and packaging, use and operation, disposal distribution at each stage.

130
Q

Why is it important to reduce use, recycle and reuse products?

A

Reduces the use of limited resources, energy sources and environmental impacts

131
Q

Give an example of a product that can be reused

A

Glass

132
Q

Give an example of a product that can be recycled

A

Metal

GCSE Combined Science (6 decks)

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