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S2 GCSE Chemistry Unit 2 > Topic 3 - Different Types of Chemical Reactions > Flashcards

Topic 3 - Different Types of Chemical Reactions Flashcards

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1
Q

What are some of the ways in which a chemical reaction can be recognised?

A
  • Colour change.
  • The formation of a precipitate.
  • The formation of a gas.
  • A temperature change.
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2
Q

What are the three ways to classify a chemical reaction?

A
  • Energetics
  • Redox
  • Type of reaction
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3
Q

What is an exothermic reaction?

A

An exothermic reaction is a reaction in which heat is given out.

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4
Q

What is an endothermic reaction?

A

An endothermic reaction is a reaction in which heat is taken in.

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5
Q

Name some exothermic reactions.

A 
Neutralisation
Displacement
Combustion
Hydration of anhydrous salts
Rusting
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6
Q

Name some endothermic reactions.

A

Thermal decomposition
Electrolysis
Dehydration of hydrated salts

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7
Q

Bond-breaking is …

A

Endothermic

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8
Q

Bond-making is …

A

Exothermic

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9
Q

All chemical possess (blank) in their bonds.

A

Internal energy.

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10
Q

What is the overall energy change in a reaction?

A

The overall energy change in a reaction is a balance of the energy taken in when bonds break in the reactants and the energy released when bonds form in the products.

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11
Q

What is thermal decompostion?

A

Thermal decomposition is the process by which a substance/compound breaks down when heated.

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12
Q

Describe the effect of heat on metal carbonates.

A
  • Some metal carbonates decompose on heating.
  • All Group 1 carbonates are stable to heat except lithium carbonate.
  • All Group 2 carbonates and transition metal carbonates decompose when heated.
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13
Q

Give the general equation for the thermal decomposition of a metal carbonate.

A

Metal carbonate —> Metal oxide + Carbon dioxide

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14
Q

Describe the effect of heat on copper (II) carbonate.

A

Copper (II) carbonate (often called ‘copper carbonate’) is a green solid.
• When copper (II) carbonate is heated it decomposes to the black solid copper (II) oxide and carbon dioxide gas is released.
• The solid loses mass due to the release of carbon dioxide gas:
CuCO3 —> CuO + CO2

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15
Q

Describe the effect of heat on calcium carbonate.

A

Calcium carbonate is a white solid with the formula CaCO3.
• It is the main chemical in limestone and marble.
• It is insoluble in water.
• It is used to remove acidic impurities from the iron ore in the blast furnace.
• On heating, calcium carbonate decomposes to form calcium oxide and carbon dioxide:
CaCO3 —> CaO + CO2
• During heating the solid glows orange. There is a loss in mass due to the release of carbon dioxide gas.

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16
Q

In the production of iron ore, calcium carbonate is used in the blast furnace. Why is this?

A

Calcium carbonate is used to remove acidic impurities from the iron ore in the blast furnace.

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17
Q

Calcium carbonate undergoes thermal decomposition in a …

A

Lime kiln

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18
Q

Calcium carbonate is also referred to as …

A

Limestone

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19
Q

What are the uses of calcium carbonate (limestone)?

A
  • Limestone is used in agriculture to neutralise acidity in soil water. Calcium carbonate reacts with acids reducing the acidity of the soil.
  • Calcium carbonate is also used as an antacid in the stomach to reduce excess stomach acidity.
  • Calcium carbonate is used in the extraction of iron. It decomposes to calcium oxide and is reacts with acidic impurities in the iron ore and removes them from the iron.
  • Limestone is used as a building material.
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20
Q

Describe the inputs and outputs of a lime kiln.

A

Limestone (calcium carbonate) is decomposed into lime (calcium oxide) industrially in a lime kiln.

  • Limestone + coke (coke is a fuel with a high carbon content and few impurities) in at the top of the lime kiln.
  • Exhaust gases out at the top of the sides.
  • Hot air in at the bottom of the sides.
  • Lime/quicklime (calcium oxide) out at the bottom.

The hot air is blown into the lime kiln to burn the coke and heat the calcium carbonate until it decomposes.
The exhaust gases mainly consist of carbon dioxide and air.

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21
Q

How is limestone obtained?

A

Limestone is quarried.

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22
Q

What are the positive aspects of limestone quarrying?

A
  • Provides employment.
  • Provides better transport links.
  • Provides landfill sites.
  • Provides a local resource for construction and agriculture.
  • Puts more money into the local economy.
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23
Q

What are the negative aspects of limestone quarrying?

A
  • Destroys hedgerows, which are the habitat of many animals and birds.
  • Creates an eyesore.
  • Causes dust pollution.
  • Causes noise pollution.
  • Increases the traffic in the region.
24
Q

What is the ‘atmosphere’?

A

The atmosphere is a collection of gases that surround the Earth.

25
Q

What is the ‘air’?

A

The air is the atmosphere near the surface.

26
Q

What is the composition of the atmosphere today?

A 
79% Nitrogen
20% Oxygen
<1% Noble gases
Water vapour
0.03% Carbon dioxide
27
Q

What was the composition of the atmosphere during the first billion years of the Earth’s existence?

A

The atmosphere on the Earth during this period was formed by intense volcanic activity, with large proportions of carbon dioxide, hydrogen sulfide, methane, ammonia and water vapour.

28
Q

How did changes in the atmosphere occur over the millions of years?

A

Changes in the atmosphere occurred slowly over millions of years due to several biological and chemical processes:

  • Photosynthesis (using up carbon dioxide and releasing oxygen).
  • Bacteria converting ammonia to nitrogen.
  • Carbon dioxide dissolving in water and reacting to form carbonate rocks.
  • Carbon, from carbon dioxide, being trapped in plants and animals forming fossil fuels over time.
29
Q

For how long has the composition of the atmosphere today lasted?

A

For 200 million years the proportion of different gases in the atmosphere has been much the same as it is today.

30
Q

Why is the composition of the atmosphere still changing today?

A

Increased use of fossil fuels and deforestation are causing an increase in the percentage of carbon dioxide in the atmosphere.

31
Q

Who proposed the theory of continental drift?

A

Continental theory was proposed by Alfred Wegener in 1912.

32
Q

What evidence did Wegener use to support his theory?

A

Wegener used the following evidence to help explain his theory:

  • The shape of continents - e.g. South America would fit almost exactly into Africa.
  • The fossils found in continents that he proposed had once been joined were very similar.
  • There were similar species of animals found in continents that he proposed had once been joined, and none of these animals had ever been able to survive in water.
33
Q

Why was Wegener’s theory not accepted by other scientists at the time?

A

Wegener’s theory was not accepted by other scientists at the time as he could not provide a mechanism to explain how the continents moved.

34
Q

Where do earthquakes and volcanoes occur?

A

At the boundaries between tectonic plates.

35
Q

What is rusting?

A

Rusting is the reaction of iron with water and air producing hydrated iron (III) oxide.

36
Q

What is the chemical name of rust and its symbol form.

A

Rust is hydrated iron (III) oxide.

Fe2O3.XH2O.

37
Q

What conditions/factors are required for rusting to occur?

A
  1. Air (oxygen)

2. Moisture (water in the air)

38
Q

Can steel rust?

A

Steel is an alloy of iron containing between 0.2 and 2% carbon. Steel is stronger than iron. The iron in steel also rusts.

39
Q

What are some of the methods used to protect iron from rusting?

A
  1. Barrier methods
    - Painting
    - Oiling (with oil or grease)
    - Plastic coating
    - Plating/metal coating (with chromium or tin, or through galvanisation with zinc)
  2. Sacrificial protection
    - Bars of magnesium can be attached to the sides of ships and oil rigs.
    - Iron can be coated in zinc (galvanisation, barrier method and sacrificial protection). Protects in case the metal is scratched and provides a barrier of zinc oxide.
  3. Alloying
    - Stainless steel is an alloy that is resistant to corrosion.
40
Q

What is a barrier method?

A

Preventing the surface of the iron coming into contact with water and air by using a barrier or protective layer.

41
Q

What is sacrificial protection?

A

Putting a more reactive metal (higher up in the reactive series) in contact with the iron or steel. The more reactive metal reacts first, leaving the iron intact.

42
Q

What is alloying?

A

An alloy is a mixture of two or more elements, at least one of which is a metal. Alloys have metallic properties. Alloys are often stronger and more resistant to corrosion than the pure metals they are made from. Stainless steel is an alloy that is resistant to corrosion.

43
Q

Only iron and steel (blank), other metals (blank).

A

Rust

Corrode

44
Q

What is a redox reaction?

A

A redox reaction is one in which oxidation and reduction occur at the same time.

45
Q

What is oxidation?

A

Oxidation is described as the gain of oxygen, loss of electrons or loss of hydrogen.

46
Q

What is reduction?

A

Reduction is described as the loss of oxygen, gain of electrons or gain of hydrogen.

47
Q

Reduction is the (blank) of oxidation.

A

Reverse

48
Q

What is combustion?

A

Combustion happens when a substance burns in air, producing oxides and releasing heat.

49
Q

Give some examples of redox reactions.

A

Rusting
Combustion of fuels
Displacement reactions

50
Q

What is a displacement reaction?

A

A displacement reaction is one in which a more reactive element will form ions and cause ions of a less reactive element to change to atoms. This process involves the transfer of electrons. The more reactive element displaces the less reactive element from a compound.

51
Q

What are the two main types of displacement reaction?

A
  • A solid metal reacting with a solution containing metal ions.
  • A solid metal reacting with a solid metal oxide.
52
Q

Describe the observations and apparatus required for an experiment when magnesium is burnt directly in air (oxygen). Write down the symbol equation for the combustion reaction.

A

Magnesium

Apparatus:

  • Gas jar containing pure oxygen
  • Combustion spoon
  • Magnesium ribbon

Method:

  • Using a blue flame from the Bunsen burner, light the magnesium ribbon until it catches fire.
  • Move the magnesium ribbon into the gas jar using the combustion spoon.

Observations: Magnesium is a grey metal that burns with a bright white light, releasing heat and forming a white powder (magnesium oxide).

2Mg + O2 —> 2MgO

53
Q

Describe the observations and apparatus required for an experiment when sulfur powder is burnt directly in air (oxygen). Write down the symbol equation for the combustion reaction.

A

Sulfur

Apparatus:

  • Gas jar containing pure oxygen
  • Combustion spoon
  • Sulfur powder

Method:

  • Using a blue flame from the Bunsen burner, light the sulfur powder until it catches fire.
  • Move the sulfur powder into the gas jar using the combustion spoon.

Observations: Sulfur is a yellow powder which melts to a brown/red liquid and burns with a blue flame releasing heat and forming a colourless, pungent and choking gas called sulfur dioxide.

S + O2 —> SO2

54
Q

Describe the observations and apparatus required for an experiment when copper (II) oxide is reduced. Write down the symbol equation for the redox reaction.

A

Reduction of copper (II) oxide

Apparatus:

  • Delivery tubing
  • Glass tube
  • Heat source (such as a Bunsen flame)
  • Porcelain boat containing copper oxide
  • Combustion of excess hydrogen at the end of the glass tube

Method:

  • Metal oxides such as copper (II) oxide (often called ‘copper oxide’) can be reduced using hydrogen gas. The hydrogen is passed over the heated metal oxide.
  • The excess hydrogen is burned to prevent flammable hydrogen gas building up in the laboratory.

Observations:

  • Black copper oxide changes to a pink colour; condensation collects inside the tube.
  • The copper oxide is reduced to copper because the copper (II) oxide loses oxygen; loss of oxygen is reduction.
  • The hydrogen is oxidised to water because hydrogen gains oxygen; gain of oxygen is oxidation.
  • This reaction is a redox reaction because both oxidation and reduction are occurring simultaneously.

CuO + H2 —> Cu + H2O

55
Q

Name some oxidation and reduction reactions which occur in industrial processes.

A
  1. Iron manufacture
    - In the manufacture of iron in the blast furnace, iron ore (containing iron (III) oxide) is reduced to iron.
    - Fe2CO3 + 3CO —> 2Fe + 3CO2
    - Iron (III) oxide is reduced to iron because the iron (III) oxide loses oxygen; loss of oxygen is reduction.
    - Carbon monoxide (CO) is oxidised to carbon dioxide (CO2) because carbon monoxide gains oxygen; gain of oxygen is oxidation.
    - This reaction is a redox reaction because both oxidation and reduction are occurring simultaneously.
  2. Aluminium manufacture
    - In the manufacture of aluminium, aluminium ore (aluminium oxide) is reduced to aluminium by electrolysis.
    - Al3+ + 3e- —> Al
    - Aluminium ions gain electrons; gain of electrons is reduction.
  3. Haber Process
    - In the haber process, nitrogen reacts with hydrogen to form ammonia.
    - N2 + 3H2 —>/

S2 GCSE Chemistry Unit 2 (8 decks)

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