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AQA GCSE SCIENCE A

CHEMISTRY UNIT 2

Workbook

Limestone and building materials

Name: ……………………………………….. Date: ……………………………………

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Heating limestone

Safety notes

Wear eye protection

Do not touch the lime that is formed from heating limestone. It will be hot after heating and lime is an irritant even when it is cool.

1. Take some lumps of limestone. Examine the stone and describe its colour, texture and any other notable features briefly. Observation ………………………………………………………………………………………………………….

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2. Place a couple of lumps on a tripod and gauze and heat with a roaring Bunsen flame for 15 minutes. Take care; the lumps will become extremely hot. 3. While the lumps are being heated, take two more lumps of unheated limestone. Add a few drops of water and note any reaction. Observation ………………………………………………………………………………………………………….

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4. Returning to the lumps being heated, note any changes - particularly in colour. Take care; the lumps will be extremely hot. Observation ………………………………………………………………………………………………………….

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5. If possible, darken the room and note what happens when the flame is trained directly on the lumps Observation ………………………………………………………………………………………………………….

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6. Remove the lumps from the heat and allow them to cool to room temperature on the heatproof mat. Then take one of the heated pieces with your tongs. Gently try to crush it on the heatproof mat with the tongs. Try the same with a lump that has not been heated. Observation ………………………………………………………………………………………………………….

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7. Use tongs to place one of the lumps that has been heated in a test tube and then gently add a few drops of water with the dropping pipette. Make sure you are wearing eye protection. Observation ………………………………………………………………………………………………………….

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8. Now add more water to the test tube until it is about half full. Shake the test tube and pour off the clear liquid, half into one test tube and half into another. Add a few drops of Universal Indicator to one tube and record the pH using a colour chart. Observation ………………………………………………………………………………………………………….

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9. Place a straw into the clear liquid in the second tube and blow gently into the liquid through the straw. Observation ………………………………………………………………………………………………………….

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Explanations ………………………………………………………………………………………………………….

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Limestone has many uses. Look at the list - tick each one that uses limestone:

Use Limestone used? Construction

Roadstone coated Roadstone uncoated Railway ballast Concrete Cement Building stone Asphalt filler / mine dust Building lime Industrial

Agricultural / horticultural Iron & steel Specialist fillers Soda ash Sugar refining Glass

YouTube http://www.youtube.com/watch?v=KEKvcuBPZ20

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Questions 1. What happens to the mass of limestone when it is heated? 2. What is thermal decomposition? 3. What is the difference between quicklime and slaked lime? 4. Write down the chemical symbols to show the thermal decomposition of copper carbonate. 5. How could you test the gas given off to see if it is carbon dioxide?

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Limestone is used as a building material. Acid rain erodes limestone. Limestone contains calcium carbonate. The symbol equation for the reaction of calcium carbonate with hydrochloric acid is shown. CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g) Describe a test to show that carbon dioxide is produced in this reaction. Give the result of the test. ............................................................................................................................................

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Limestone quarries In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate. Limestone contains calcium carbonate. There is a large deposit of limestone under an area of natural beauty. A company wants to quarry this limestone and build a kiln near to the quarry to make cement. Area of natural beauty A quarry

• Explosives will be used to extract the limestone out of the ground. • Heavy machinery will be used to lift and crush the limestone. • Lorries will be used to transport the limestone to the kiln to make cement. • The lorries and the heavy machinery will use diesel fuel.

Quarrying limestone and making cement will have an impact on everything near the area. Describe the positive and the negative impacts of quarrying limestone and making cement.

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Start by using bullet points: Positive Negative

Write the above bullet points into good English ……………………………………………………………………………………………………..

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Explain the difference between cement, concrete and mortar ……………………………………………………………………………………………………..

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Match the compound to the formula

Calcium carbonate Ca(OH)2

Calcium oxide CaCO3

Carbon dioxide CaO

Calcium hydroxide CO2

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Science A Chemistry Limestone questions

Q1. Limestone has been called the Earth’s most useful rock.

(a) Limestone contains calcium carbonate, CaCO3.

(i) Complete the table to show the number of atoms of each element in the formula of calcium carbonate.

Calcium has been done for you.

Element Number of atoms in the formula CaCO3

Calcium, Ca 1

Carbon, C

Oxygen, O

(2)

(ii) The diagram below represents a carbon atom.

Use words from the box to label the parts of this atom.

bond electron molecule nucleus

(2)

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(b) At a cement works, limestone is mixed with clay and heated in a kiln.

Use the information in the diagram to answer these questions.

(i) Name the fuel that is used to heat the limestone and clay.

........................................................................................................................... (1)

(ii) Limestone contains calcium carbonate, CaCO3.

Draw a ring around the correct gas in the box to complete the sentence.

The gas formed when calcium carbonate decomposes is

argon.

carbon dioxide.

nitrogen.

(1)

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(c) The cement works starts to burn a different fuel.

Local residents are concerned because more children are suffering asthma attacks. Residents have also noticed that parked cars are becoming dirty because of smoke particles from the chimney.

The table shows the possible medical risk from smoke particles.

Particle size in mm Medical effect

Larger than 0.4 No medical risks known

0.3 and smaller Causes asthma attacks

0.2 and smaller May cause cancer

(i) Give two reasons why local residents are concerned about the cement works burning a different fuel.

1 ........................................................................................................................

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2 ........................................................................................................................

........................................................................................................................... (2)

(ii) The company operating the cement works stated that smoke particles from the chimney had not changed since it started burning the different fuel.

If you were a local resident, what evidence would you like to see to help you decide if the company’s statement is true or not?

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........................................................................................................................... (2)

(Total 10 marks)

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Q2. Limestone and the products of limestone have many uses.

(a) Limestone is quarried.

Photograph © Lonny Kalfus / Getty Images

Quarrying limestone has impacts that cause environmental problems.

Tick ( ) two impacts that cause environmental problems.

Impact of quarrying Tick ( )

Puts off tourists

Causes dust pollution

Increases jobs

Increases traffic

(2)

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(b) Limestone contains calcium carbonate, CaCO3. When it is heated calcium carbonate produces calcium oxide and carbon dioxide.

The word equation for this reaction is:

calcium carbonate → calcium oxide + carbon dioxide

(i) Complete the sentence.

The reaction when calcium carbonate is heated is called

thermal ........................................... (1)

(ii) 100 g of calcium carbonate was heated and produced 56 g of calcium oxide. Calculate the mass of carbon dioxide produced.

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....................................... g (1)

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(c) The flow chart shows the stages in the limestone cycle.

Complete the names of the calcium compounds formed in the flow chart.

(2)

(Total 6 marks)

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Q3. An old lime kiln made in the ground is shown.

(a) The thermal decomposition of calcium carbonate makes a white solid and carbon dioxide.

(i) Name a naturally occurring form of calcium carbonate.

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(ii) What does thermal decomposition mean?

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(iii) Suggest and explain the purpose of the coal.

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(iv) Write a word equation for the thermal decomposition of calcium carbonate.

................................... → ................................... + .................................... (2)

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(b) The diagrams show what happens when drops of cold water are added to the white solid formed by heating calcium carbonate.

(ii) What type of chemical reaction takes place?

........................................................................................................................... (1)

(ii) Give the chemical name of the solid formed. Give a use of this solid.

Name ................................................................................................................

Use ................................................................................................................... (2)

(Total 10 marks)

Q5. We can get many important substances from the Earth’s crust. Sometimes we can use

these substances straight from the ground.

(a) Which one substance in the list can be used straight from the ground?

Draw a ring around the correct answer.

gold iron lead calcium aluminium (1)

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(b) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate.

Rock salt is a mixture containing salt (sodium chloride) that we get from the Earth’s crust.

To get pure salt from rock salt we need to separate the pure salt from the other substances in the mixture.

Describe how you would obtain pure salt from rock salt in the laboratory. You should include in your answer the apparatus that you would use.

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(c) (i) Name the elements in pure salt.

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(ii) What is the chemical formula for pure salt?

............................................................................................................. (1)

(Total 9 marks)

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Q6. Lime (calcium oxide) is used in agriculture to reduce the acidity of soils.

Describe, as fully as you can, the reaction by which lime is made.

Name any other product(s).

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Q7. Portland cement was invented by Joseph Aspdin, a builder from Leeds. The flow diagram shows how cement is made.

(a) (i) Name the raw material X used to make cement.

.......................................................................................................................... (1)

(ii) In the kiln the raw materials are heated to about 1500°C. The limestone (calcium carbonate) is broken down at this temperature. Complete the word equation for this reaction.

calcium carbonate → ........................................ + carbon dioxide (1)

(iii) Suggest one major cost of this process other than the cost of the raw materials.

.......................................................................................................................... (1)

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(b) Cement can be used to make concrete. Name two substances that must be mixed with cement to make concrete.

1 .....................................................................

2 ..................................................................... (2)

(Total 5 marks)

Q8. Sea water contains magnesium ions. Magnesium oxide can be obtained from sea water using the following process.

(a) State the chemical name for limestone.

.................................................................................................................................... (1)

(b) Write a word equation for the action of heat on limestone.

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(c) State the chemical name for slaked lime.

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(d) Write a balanced chemical equation for the addition of water to quicklime.

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(e) How can magnesium hydroxide be separated from sea water?

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(f) Suggest and explain how magnesium could be obtained from magnesium oxide.

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(Total 9 marks)

Q9. Limestone is mainly calcium carbonate.

(a) Quicklime is produced by heating limestone.

(i) Complete the word equation for this reaction by writing the chemical name of the solid and the gas produced.

calcium carbonate → ................................. + ................................. . (2)

(ii) What is the name for this type of chemical reaction?

.......................................................................................................................... (1)

(b) Quicklime is used in self-heating cans.

The diagram shows a self-heating can designed to raise the temperature of coffee to 60 °C.

The button on the base of the can is pushed. The foil separator breaks, allowing water to mix with the quicklime. After about 3 minutes, the can is opened by the ring pull. Insulating materials are used inside the walls of the can to prevent either the lips or the fingers from being burned.

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(i) Explain why the coffee becomes hot.

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(ii) Suggest two reasons why it is not possible to re-use this self-heating can.

1 .......................................................................................................................

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2 .......................................................................................................................

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(Total 7 marks)

Q10. (a) Limestone is a hard rock that is used as a building material. Limestone was used by the Egyptians to make plaster.

Reaction 1 – calcium carbonate, CaCO3, was decomposed by heating limestone

CaCO3 → CaO + CO2

Reaction 2 – water was added to the solid produced to make slaked lime

CaO + H2O → Ca(OH)2

Reaction 3 – a mixture of slaked lime and water was used as plaster. After the plaster had set it became even harder with age

Ca(OH)2 + CO2 → CaCO3 + H2O

(i) Name the solid formed when calcium carbonate decomposed.

........................................................................................................................... (1)

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(ii) Use the reactions to explain how the plaster became even harder with age.

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(b) A gardener wanted to make a step up to his greenhouse door. He decided to use a mixture of cement and sand to make mortar.

He experimented using mixtures with different cement to sand ratios.

• The mortar mixtures were put in the same sized mould.

• Each mortar mixture was allowed to set hard.

• He then dropped a metal ball from increasing height_s until the set mortar cracked.

• He recorded his results in a table.

Volume of sand in cm3

Volume of cement in cm3

Height the metal ball dropped to crack the set

mortar in cm

800 100 17

700 100 24

600 100 30

500 100 36

400 100 37

300 100 48

200 100 54

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(i) What is the relationship between the volume of sand and the strength of the mortar?

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(ii) The gardener was not sure about some of his results.

Use the results to explain why.

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(Total 7 marks)

Q11. A limestone quarry is in an area of natural beauty and near several villages. The company operating the quarry wants planning permission to build a new cement works in the quarry.

The diagram shows some of the substances used and produced at a cement works.

(a) Limestone is mainly calcium carbonate, CaCO3. Write the correct number in the box to complete each sentence.

(i) The formula shows that calcium carbonate, CaCO3,

contains different elements.

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(1)

(ii) Calcium carbonate, CaCO3, contains a total number of atoms. (1)

(b) The company wants the new cement works because the nearest cement works is 100 km from the quarry. The company argues that a new cement works sited inside the quarry would reduce carbon dioxide emissions.

Suggest why the new cement works might reduce carbon dioxide emissions.

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(c) Residents from the villages near the quarry are concerned that there will be atmospheric pollution from the new cement works.

(i) Name and explain how one of the emissions from the chimney causes atmospheric pollution.

Name of emission: ...........................................................................................

Explanation: .....................................................................................................

........................................................................................................................... (2)

(ii) Suggest what the company could do to reduce this atmospheric pollution.

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........................................................................................................................... (1)

(Total 6 marks)

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Q12. Limestone contains calcium carbonate, CaCO3. At a cement works, limestone is mixed with clay and heated in a kiln.

(a) (i) When methane is burned in this process the waste gases contain carbon dioxide and nitrogen.

Explain why.

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........................................................................................................................... (2)

(ii) Complete the symbol equation for the thermal decomposition of calcium carbonate.

CaCO3 → ......................... + ......................... (2)

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(b) A different fuel is burnt at the cement works.

Suggest one reason the company may give for using this different fuel at the cement works.

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..................................................................................................................................... (1)

(c) The cement works continue to burn the different fuel.

Local residents are concerned because more children are suffering asthma attacks. Residents have also noticed that parked cars are becoming dirty because of smoke particles from the chimney.

The table shows the possible medical risk from smoke particles.

Particle size in mm Medical effect

Larger than 0.4 No medical risks known

0.3 and smaller Causes asthma attacks

0.2 and smaller May cause cancer

It is also recommended that to avoid damage to health, the concentration of any particles should be no higher than 2 parts per million (ppm).

Scientists were brought in to monitor the emissions from the cement work’s chimney. They positioned four sensors around the cement works to monitor airborne smoke particles.

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These four sensors only detect particle sizes larger than 0.5 mm and measure the concentration of particles in ppm. The scientists reported that the particle sensors showed that the average concentration of particles was 1.8 ppm. The scientists concluded that there was no risk to health.

(i) Explain why the local residents objected to the positions of the four sensors.

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(ii) What evidence did the scientists use to conclude that there was no risk to health?

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(iii) The local residents were still concerned that there was a risk to health, even though the average concentration of particles was 1.8 ppm.

Explain why.

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(Total 11 marks)

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Q13. Limestone is an important raw material.

The diagram shows a lime kiln. The limestone is heated by the burning coal.

(i) Suggest why hot air is blown into the lime kiln.

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..................................................................................................................................... (1)

(ii) Give two reasons why carbon dioxide is produced in the lime kiln.

Reason 1 .....................................................................................................................

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Reason 2 .....................................................................................................................

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(Total 3 marks)