C2 - chemical resources

Question 0

What is the lithosphere?

Answer 0

The outer layer of the earths crust.

Question 1

What does the lithosphere comprise of?

Answer 1

The lithosphere is relatively cold and rigid and compromises the crust and top part of the mantle.

Question 2

How is information about earth collected and why in this way?

Answer 2

The crust is too thick to drill through, so most of our information about the earth is collected from seismic waves produced by earthquakes and man-made explosions.

Question 3

What is the mantle and its properties?

Answer 3

The mantle is the zone between the core and the crust. It is cold and rigid just below the crust, but at greater depths it is hot and non-rigid and able to move.

Question 4

Why does the temperature of the mantle increase with depth?

Answer 4

Because the earth’s core transfers energy.

Question 5

What moves the earths plates slowly?

Answer 5

Convection currents.

Question 6

What is subduction?

Answer 6

Oceanic crust is denser than continental crust. When these plates collide, the oceanic plate (which is called at the margins) sinks, pulling more of the plate down, and partly melting as it reaches the hotter part of the mantle.

Question 7

What is plate tectonic theory?

Answer 7

Plate tectonic theory suggests that Africa and South America could once have been one land mass.

Question 8

What is the evidence for plate tectonic theory?

Answer 8

It explains a wide range of evidence.

It has been discussed and tested by many scientists.

In the 1960s, new sea floor spreading evidence was found. Subsequent research led to Wegener’s theory slowly becoming accepted.

Question 9

What does magma rise up through the earth’s crust?

Answer 9

Because it is less dense than the crust.

Question 10

What are the properties of iron-rich basalt rock?

Answer 10

Iron-rich basalt rock comes from runny lava in slower volcanic eruptions.

Question 11

What are the properties of silica-rich rhyolite rock?

Answer 11

Silica-rich rhyolite rock comes from thick lava in explosive eruptions.

Question 12

How can hardness of materials be compared?

Answer 12

By rubbing them together.

Question 13

Why is limestone soft?

Answer 13

Limestone is a sedimentary rock. It is made from soft sediments compressed and cemented together. This makes limestone quite soft.

Question 14

Why is marble harder than limestone?

Answer 14

Marble is a metamorphic rock formed when limestone is changed by heat and pressure, and is typically composed of an interlocking mosaic of carbonate crystals. Marble is harder than limestone because it has been baked.

Question 15

Why is granite very hard?

Answer 15

Granite is formed when magma cools and solidifies. It is an igneous rock with interlocking crystals. This makes it very hard.

Question 16

What is thermal decomposition?

Answer 16

Thermal decomposition is a reaction where one substance breaks down on heating to give at least two new substances.

Question 17

What is the thermal decomposition of limestone (calcium carbonate)?

Answer 17

Calcium carbonate –> calcium oxide + carbon dioxide

CaCOthree –> CaO + COtwo

Question 18

How is cement made?

Answer 18

Cement is made when limestone is heated with clay.

Question 19

How is concrete made?

Answer 19

Concrete is made by mixing cement, sand and small stones with water.

Question 20

What is a composite material?

Answer 20

Composites contain at least two materials which can be distinguished. e.g reinforced concrete

Question 21

Why is reinforced concrete a better construction material then concrete?

Answer 21

• concrete is strong under compression but weak under tension
• if heavy loads are applied to a beam, the concrete will bend. This creates tension and compression. The tension cracks the concrete
• reinforced concrete is harder and more flexible than concrete, so is a better construction material

Question 22

What are the advantages of recycling copper?

Answer 22

• it has a fairly low melting point so the energy cost to melt is low
• it reduces the need for mining, saving reserves and the environmental problems caused by mining
• it keeps the cost of copper down

Question 23

What are the disadvantages of recycling copper?

Answer 23

• the small amounts used in electrical equipment are difficult to separate
• valuable ‘pure’ copper scrap must not be mixed with less pure scrap, such as solder
• less copper is mined so there are fewer mining jobs
• the actual separating process may produce pollution
• a lot of copper is thrown away as it is difficult to persuade people to recycle it

Question 24

What solution is used in the purification of copper by electrolysis?

Answer 24

An electrolyte of copper(II) sulfate solution is used.

Question 25

Why occurs at the anode in the electrolysis of copper?

Answer 25

The positive anode loses mass as the copper dissolves.

Question 26

Why occurs at the cathode in the electrolysis of copper?

Answer 26

The negative cathode gains mass as pure copper is played into it.

Question 27

Why does the concentration of the copper(II) sulfate electrolyte stay the same during electrolysis?

Answer 27

Because as the impure copper anode dissolves, pure copper is played on to the cathode at the same rate.

Question 28

What electron half equation happens at the anode during copper purification?

Answer 28

Cu - 2e(little minus) –> Cu(two plus)

Question 29

What electron half equation happens at the cathode during copper purification?

Answer 29

Cu(two plus) + 2e(little minus) –> Cu

Question 30

What is oxidation and reduction?

Answer 30

Oxidation - loss of electrons

Reduction - gain of electrons

Question 31

What’s an alloy?

Answer 31

Alloys are mixture containing at least one metal.

Question 32

What do different alloys contain?

Answer 32

• amalgam, contains mercury (this is used for filling teeth)
• brass, contains copper and zinc
• solder, contains lead and tin

Question 33

What is nitinol (nickel titanium)?

Answer 33

It’s a smart alloy which is used to make spectacle frames; it returns to its original shape after being bent if it is put in hot water.

Smart alloys are becoming more important as new ways to use them are found.

Question 34

What’s a smart alloy?

Answer 34

They return to their original shape after being heated to a certain temperature.

Question 35

What accelerates rusting?

Answer 35

Acid rain and salt water.

Question 36

What is the word equation for rusting?

Answer 36

iron + oxygen + water –> hydrated iron(III) oxide

This is an oxidation reaction be use iron reacts with oxygen forming an oxide.

Question 37

Why doesn’t aluminium corrode in moist air?

Answer 37

Because it has a protective layer of aluminium oxide, which, unlike rust, does not flake off the surface.

Question 38

Steel is harder and stronger than iron and steel is less likely to corrode than iron. True of false?

Answer 38

True.

Question 39

What’re the advantages and disadvantages of aluminium car bodies compared to steel car bodies?

Answer 39

Aluminium is lighter and more resistant to corrosion than steel. However, steel costs less and is stronger.

A lighter aluminium body means fuel economy is improved. Because aluminium corrodes slowly, the car will also last long.

Question 40

What is the word equation for the haber process?

Answer 40

Nitrogen + hydrogen ammonia

Question 41

What is the balanced symbol equation for the haber process?

Answer 41

Ntwo + 3Htwo 2NHthree

Question 42

What are the optimum conditions for the haber process?

Answer 42

• use a catalyst made of iron
• raise the temperature to about 450•C
• use high pressure (about 200 atmospheres/20 MPa)
• recycle any unreacted nitrogen and hydrogen

Question 43

Why are these the optimum conditions for the haber process?

Answer 43

• the iron catalysts increase the ROR but not the PY
• high pressure increases the PY of ammonia
• a high temperature increases reaction rate
• a high temperature breaks down ammonia, reducing PY

-the optimum temperate is around 450•C. Although the yield is not very high, the rate is fairly quick. This is the best compromise.

Question 44

What increases costs of chemical manufacture?

Answer 44

When the pressure is raised (increasing the plant costs) and the temperature is raised (increasing the energy costs).

Question 45

What decreases costs of chemical manufacture?

Answer 45

When catalysts are used, unreacted starting materials are recycled and automation is used (reducing wage bills).

Question 46

What considerations determine the conditions used to manufacture a chemical?

Answer 46

Both the reaction rate and percentage yield need to be high enough to give a sufficient daily yield of product

A low percentage yield can be accepted if the reaction can be repeated many times with recycled starting materials

Optimum conditions give the lowest cost

Question 47

What is the word equations for making salt?

Answer 47

Acid + base –> salt + water

Acid + metal carbonate –> salt + water + carbon dioxide

Question 48

Why do fertilisers need to be soluble?

Answer 48

So they can be absorbed by plants roots as only dissolved substances are small enough to be absorbed

Question 49

How do fertilises increase crop yield?

Answer 49

Replacing essential elements used by the previous crop providing extra essential elements and providing nitrogen that is incorporated into plant protein resulting in increased growth

Question 50

What is eutrophication?

Answer 50

Eutrophication is when:

• Fertilises are washed off fields
• Fertiliser in the water increase the nitrogen and phosphate levels in ponds lakes and rivers
• These chemicals cause algal bloom
• Aerobic bacteria use up all the oxygen in the water and feed on the dead and decaying plants
• Most living organisms die

-excessive use of fertilisers can also pollute water supplies

Question 51

In what to ways is salt mined in Cheshire?

Answer 51

Mining from the ground as rocksalt and solution mining by pumping in water and extracting saturated salt solution.

Question 52

Mining can lead to subsidence. What is subsidence?

Answer 52

The ground above a mine can sink causing landslips and dear prying homes. Salt at the surface, particularly brine solution, can escape and effect habitats.

Question 53

What are the election half equations at the cathode and anode during the electrolysis of brine?

Answer 53

At the cathode, hydrogen is made, electrons are gained so this is reduction:
2H+ + 2e- –> Htwo

At the anode chlorine is made, electrons are lost so this is oxidation:
2Cl- – 2e- –> Cltwo

The ions not discharged make sodium hydroxide solution:
Na+ + OH- –> NaOH

Question 54

How is sodium chloride solution separated?

Answer 54

By electrolysis.

Hydrogen is made at the negative cathode.

Chlorine is made at the positive anode.

Sodium hydroxide forms in solution.

Hydrogen and chlorine are reactive so it is important to use inert electrodes so that the products for react before they are collected an the electrodes do not dissolve.

Question 55

What are sodium hydroxide and chlorine involved in making?

Answer 55

Household bleach, chemicals, solvents, plastics, paints, soaps, medicines and food additives.

Question 56

How do you produce a fertiliser from the reaction of an acid and an alkali?

Answer 56

The alkali is titrated with the acid using an indicator to find out the quantities needed before the main batch is made (this is repeated until the results are consistent)

Although the acid and alkali have now reacted completely to produce a neutral solution of ammonium sulfate fertiliser, this is contaminated with indicator solution

The titration results are used to repeat the experiment using the correct quantities

The dissolved fertiliser is heated to evaporate most of the water off, then left for the remaining solution to crystallise. The crystals are then filtered off.