GCSE Chemistry

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 calcium hydroxide
CaO + H₂O ===> Ca(OH)₂
Reaction 3 - a mixture of calcium hydroxide and water was used as plaster . After the plaster had set it became even harder with age
Ca(OH)₂ + CO₂ ===> CaCO₃ + H₂O
Name the solid formed when calcium carbonate decomposed

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 calcium hydroxide
CaO + H₂O ===> Ca(OH)₂
Reaction 3 - a mixture of calcium hydroxide and water was used as plaster . After the plaster had set it became even harder with age
Ca(OH)₂ + CO₂ ===> CaCO₃ + H₂O
use the reactions to explain how the plaster became even harder with age (3)

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 cemeny works in the quarry . The diagram shows some of the substances used and produced at cement works
tthe company wants the new cement works because the nearest cement works is 100km from the quarry . The company argues that a new cement works sited inside the quarry would reduce carbon dioxide emmsions . Suggest why the new cement works might reduce carbon dioxide emmisions

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 cemeny works in the quarry . The diagram shows some of the substances used and produced at cement works .
Residents from the villages near the quarry are concerned that there will be atmopsheric pollution from the cement works . Name and explain how emmisions from the chimmney causes atmospheric pollution and what the company should do to reduce this atmopsheric pollution

give one piece of evidence that led to Wenger's idea being accepted

Margerine is manufactured using "hard" plant oils . A margerine company tested several plant oils to deterimine their hardness for use in its margerine . In the test iodine solution was used to find the iodine value . The units are grams of iodine that react with 100g of oil . Plant oils with lower iodine values are harder and are less unsaturated
The company stated that some of the plant oils were brown and that this may have affected the results . Explain why the company considered the colour of the plant oils to be a problem with this test

Copper was considered to be the most suitable material to use for hot water pipes . PEX is now used as an alternative material for hot water pipes . Copper is extracted from its ore by a series of processes .
* The low grade ore is powdered and concentrated
* smelting is carried out in an oxygen flash furnace . This furnace is heated 1100°C using a hydrocarbon fuel . The copper ore is blown into the furnace with air , producing impure , molten copper .
* Oxygen is blown into ther impure , molten copper to remove any sulphur . the copper is cast into rectangular slabs
* the final purification of copper is done by electrolysis
PEX is made by a series of processes
* Fractional distilation
* cracking
* polymeristation
* conversion of poly(ethene) into PEX
suggest the possibel environmental advntages of using PEX instead of copper for hot water pipes (4)

In recent years we have become more aware of the need to recycle glass used glass bottles can be recycled if they are put into bottle bankssuggest one reason why light bulbs should not be put into bottle banks (1)

very few glass bottles are reused
suggest one reason why (1)

new glass bottles cane be also produced by heating , at 1700°C , a mixture of the following raw materials
sand (silicon dioxide)
soda ash (sodium carbonate)
limestone (calcium carbonate)
explain why the use of recycled glass to make glass bottles uses less carbon dioixde than making glass bottles from raw materials (2)

the bar chart shows the percentages of glass bottles produced and the percentages of glass bottles put into bottle banks in the UK
tMore green glass bottles are put into bottle banks than are made in the UK . Suggest one reason why . (1)

suggest and explain one result from the percentage of clear glass produced in the UK (2)
Suggest and explain one problem resulting from the percentaege of clear glass bottles produced in the UK (2)

Most power stations in the UK burn coal . Coal was formed from tree-like planst over millions of years . Suggest why burning wood instead of coal would help to reduce our carbon footprint (3)

Give one reason why Wegner's idea was not accepted in 1915 (1)

the theory of plate tectonics is used to explain why earthquakes occur . Explain how earthquakes occur (2)

Calcium oxide is used in a self heating can . 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 seperator breaks , allowing water to mix with the calcium oxide . 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 of the lips or the fingers from being burned
1) Explain why the coffee becomes hot
2) suugest why it is nogt possible to re-use this self heating can

Explain how propene molecules form a polymer (3)

explain what the formula Na₂CO₃ shows about the compound (2)

explain the environmental benifits of using biodiesel as a sustainable , low pollution fuel (3)

Crude oil is the source of many useful materials . Crude oil is seperated into fractions by fractional distilation
Describe how the Naptha fraction seperates from the other fractions

suggest 2 reasons why all alkanes with fewer carbon atoms are better fuels than the alkane with the formula
C₃₀H₆₂ (2)

the burning of fossil fuels has caused the % of carbon dioxide in the atmosphere to increase above 0.03% . Explain why (2)