Materials and Processes

Question 1

What is a cell?

Answer 1

A cell is a redox system containing chemicals which react together to release electrical energy

Question 2

What is a cell made from?

Answer 2

Cell is comprised of two metals in contact with an electrolyte

Question 3

How does a voltmeter work?

Answer 3

A voltmeter has a very high resistance, so when connected in series, it restricts current flow and measures the potential difference between electrode

Question 4

What does the size of the potential difference depend upon?

Answer 4

The type of electrode and the concentration of the electrolyte

Question 5

What is a battery?

Answer 5

Two or more cells connected together in series

Question 6

How do you calculate total voltage of a battery?

Answer 6

The sum of the voltage of all cells

Question 7

What are rechargeable batteries?

Answer 7

Rechargeable batteries batteries in which the reaction is reversible by connecting the battery to mains and reversing the current through it and all the reactants run out no more power is being outputted

Question 8

What is potential difference?

Answer 8

It’s a measurement of the difference in reactivity between the metals used in a cell, we call these, the reference electrode and the test electrode

Question 9

What two things about the electrodes affect the voltage output?

Answer 9

If the metals are farther apart, in the reactivity series, they will produce a greater voltage
If the test electrode is less reactive than the reference electrode, then the voltage is negative

Question 10

How do you know which electrode is which?

Answer 10

The reference electrode is connected to a positive terminal of the voltmeter

Question 11

What is a fuel cell?

Answer 11

An electrical cell that generates electricity as long as oxygen and fuel are supplied

Question 12

What happens at the negative electrode of a hydrogen fuel cell?

Answer 12

-Hydrogen molecules are converted to hydrogen ions
-An oxidation reaction occurs
-Hydrogen irons travel through the electrolyte
-Electrons travel through the circuit generating current

Question 13

What happens at the positive electrode in a hydrogen fuel cell?

Answer 13

-Hydrogen ions react with oxygen producing water
-A reduction reaction occurs

Question 14

What are the advantages of a hydrogen fuel cell?

Answer 14

• No need to recharge
• Less toxic waste at end of life
• Only water produced
• Fuel can be added (longer lifetime)

Question 15

What are the disadvantages of a hydrogen fuel cell?

Answer 15

• Hydrogen is explosive (must be stored safely)
• Lack of infrastructure
• Mainly produced by fossil fuels
• Electrolysis of water requires energy

Question 16

What is corrosion?

Answer 16

A gradual destruction of materials by reactions with substances in the environment

Question 17

What is rust?

Answer 17

Rust is hydrated iron oxides and hydroxides formed during the corrosion of iron

Question 18

What does rusting require?

Answer 18

Rusting requires both oxygen and water.

Question 19

What occurs after corrosion?

Answer 19

The corroded oxide layer, flakes away and allows the metal beneath it corrode

Question 20

What are the two methods of protecting metals from corrosion?

Answer 20

Barrier and sacrificial protection

Question 21

How does barrier protection work?

Answer 21

Oxygen and water cannot reach the surface

Question 22

How does sacrificial protection work?

Answer 22

More reactive metal corrodes in place of the less reactive metal

Question 23

What are three examples of barrier protection?

Answer 23

• Coating with paint or plastic
• Oiling or greasing
• Electroplating with a less reactive metal

Question 24

Give two examples of sacrificial protection

Answer 24

• Blocks of more reactive metal
• Galvanising (form of coating where when it is scratched the coating reacts instead)

Question 25

What is an alloy?

Answer 25

Alloy is a mixture of the metal with other elements, metallically bonded

Question 26

What are alloys of iron called?

Answer 26

Steels

Question 27

What are the three types of steel, their properties and uses?

Answer 27

Low Carbon Steel - Easily Shaped - Car Bodies High Carbon Steel - Strong But Brittle - Construction Stainless (Cr and/or Ni) - Corrosion Resistant - Cutlery

Question 28

What does it mean if the carbon content of steel is higher?

Answer 28

The higher the carbon content, the harder it is for layers to slide making a less malleable material, more brittle

Question 29

Why is chromium used for sacrificial protection in stainless steel?

Answer 29

Chromium is more reactive than iron, this reduces corrosion

Question 30

Why can aluminium be left unpainted?

Answer 30

The more reactive than iron, aluminium forms, a layer of aluminium oxide, which is unreactive

Question 31

What are alloys of copper and tin known as?

Answer 31

Bronze

Question 32

What are alloys of copper and zinc known as?

Answer 32

Brass

Question 33

What are alloys of aluminium used for?

Answer 33

Plane bodies as they are low density

Question 34

What is a benefit of Nitinol?

Answer 34

Nitinol is a shape memory alloy. This means it reforms to its original shape when heated and cooled.

Question 35

What does 24 Karats mean?

Answer 35

100% gold

Question 36

How do you represent the percentage of gold in a gold alloy?

Answer 36

In Karats

Question 37

Why is gold alloyed with other precious metals?

Answer 37

- To increase its hardness - To change the colour - To make the material cheaper

Question 38

What is soda lime glass made out of?

Answer 38

- Sand - Limestone - Sodium carbonate

Question 39

What is Borosilicate glass made of?

Answer 39

- Sand - Boron trioxide (it has a higher melting point)

Question 40

How are ceramics made?

Answer 40

Ceramics are made by shaping wet clay, and then heating it in a furnace. Both pottery and bricks are made this way.

Question 41

What affects the melting point of a polymer?

Answer 41

- The longer, the chain, the stronger, the intermolecular forces - The type of monomer also affect the strength of intermolecular forces - The stronger, the intermolecular forces holding change of a polymer together, the higher the melting point

Question 42

What are the two types of polyethene and how do we get them?

Answer 42

High density polyethene HDPE and Low density polyethene LDPE are made using different conditions

Question 43

What is the difference between HDPE and LDPE?

Answer 43

HDPE has strong intermolecular forces where as LDPE has weak intermolecular forces due to branches and its chains

Question 44

What is the difference between a thermosoftening and a thermosetting polymer?

Answer 44

A thermosetting polymer has cross links/covalent bonds, and therefore does not melt when heated, but instead burns

Question 45

What are the conditions for the Haber process?

Answer 45

450° C 200 atm An iron catalyst

Question 46

Why is the temperature of 450° C used?

Answer 46

If the temperature is too high, the yield ammonia is too small If the temperature is too low, the reaction rate will slow down and the yield per hour is lower Lower yield is accepted for a faster rate of reaction

Question 47

Why is a pressure of 200 atm used?

Answer 47

If the pressure is too, low, yield of ammonia, will be too low If the pressure is too high, the experiment equipment needed will be more expensive to set up and maintain Lower yield is accepted in turn for a cheaper process

Question 48

What is NPK fertiliser?

Answer 48

A formulation that contains carefully measured quantities of salts (nitrogen, phosphorus, and potassium)

Question 49

What is nitrogen used for in plants?

Answer 49

Amino acids / Protein

Question 50

What is phosphorus used for in plants?

Answer 50

DNA, root growth, and flower production

Question 51

What is potassium used for in plants?

Answer 51

General growth, and crop yield

Question 52

What are the problems with using manure as fertiliser?

Answer 52

- Parasites can inhabit the manure - The quantity of N, P, and K varies

Question 53

Where do we get the nitrogen from for NPK fertiliser?

Answer 53

Reacting ammonia from the Haber process with nitric acid (this process has a 35% atom economy for nitrogen)

Question 54

Where do we get potassium for NPK fertiliser from?

Answer 54

It’s obtained through mining, either as potassium sulphate (this has a 44.8% atom economy for potassium) or as potassium chloride (this has a 52.3% atom economy for potassium)

Question 55

Where do we get the phosphorus for NPK fertiliser from?

Answer 55

It is extracted from phosphate rock through reactions with acids: - Sulphuric acid (the products are monocalcium phosphate, calcium sulphate, and waste) - Nitric acid (the products are phosphoric acid and calcium nitrate) - Phosphoric acid (the product is calcium phosphate)