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Chemistry > Materials and Processes > Flashcards

Materials and Processes Flashcards

1
Q

What is a cell?

A

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

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2
Q

What is a cell made from?

A

Cell is comprised of two metals in contact with an electrolyte

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3
Q

How does a voltmeter work?

A

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

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4
Q

What does the size of the potential difference depend upon?

A

The type of electrode and the concentration of the electrolyte

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5
Q

What is a battery?

A

Two or more cells connected together in series

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6
Q

How do you calculate total voltage of a battery?

A

The sum of the voltage of all cells

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7
Q

What are rechargeable batteries?

A

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

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8
Q

What is potential difference?

A

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

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9
Q

What two things about the electrodes affect the voltage output?

A

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

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10
Q

How do you know which electrode is which?

A

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

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11
Q

What is a fuel cell?

A

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

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12
Q

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

A

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

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13
Q

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

A

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

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14
Q

What are the advantages of a hydrogen fuel cell?

A
  • No need to recharge
  • Less toxic waste at end of life
  • Only water produced
  • Fuel can be added (longer lifetime)
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15
Q

What are the disadvantages of a hydrogen fuel cell?

A
  • Hydrogen is explosive (must be stored safely)
  • Lack of infrastructure
  • Mainly produced by fossil fuels
  • Electrolysis of water requires energy
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16
Q

What is corrosion?

A

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

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17
Q

What is rust?

A

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

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18
Q

What does rusting require?

A

Rusting requires both oxygen and water.

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19
Q

What occurs after corrosion?

A

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

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20
Q

What are the two methods of protecting metals from corrosion?

A

Barrier and sacrificial protection

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21
Q

How does barrier protection work?

A

Oxygen and water cannot reach the surface

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22
Q

How does sacrificial protection work?

A

More reactive metal corrodes in place of the less reactive metal

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23
Q

What are three examples of barrier protection?

A
  • Coating with paint or plastic
  • Oiling or greasing
  • Electroplating with a less reactive metal
24
Q

Give two examples of sacrificial protection

A
  • Blocks of more reactive metal
  • Galvanising (form of coating where when it is scratched the coating reacts instead)
25
Q

What is an alloy?

A

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

26
Q

What are alloys of iron called?

A

Steels

27
Q

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

A

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

28
Q

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

A

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

29
Q

Why is chromium used for sacrificial protection in stainless steel?

A

Chromium is more reactive than iron, this reduces corrosion

30
Q

Why can aluminium be left unpainted?

A

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

31
Q

What are alloys of copper and tin known as?

A

Bronze

32
Q

What are alloys of copper and zinc known as?

A

Brass

33
Q

What are alloys of aluminium used for?

A

Plane bodies as they are low density

34
Q

What is a benefit of Nitinol?

A

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

35
Q

What does 24 Karats mean?

A

100% gold

36
Q

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

A

In Karats

37
Q

Why is gold alloyed with other precious metals?

A
  • To increase its hardness
  • To change the colour
  • To make the material cheaper
38
Q

What is soda lime glass made out of?

A
  • Sand
  • Limestone
  • Sodium carbonate
39
Q

What is Borosilicate glass made of?

A
  • Sand
  • Boron trioxide
    (it has a higher melting point)
40
Q

How are ceramics made?

A

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

41
Q

What affects the melting point of a polymer?

A
  • 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
42
Q

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

A

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

43
Q

What is the difference between HDPE and LDPE?

A

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

44
Q

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

A

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

45
Q

What are the conditions for the Haber process?

A

450° C
200 atm
An iron catalyst

46
Q

Why is the temperature of 450° C used?

A

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

47
Q

Why is a pressure of 200 atm used?

A

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

48
Q

What is NPK fertiliser?

A

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

49
Q

What is nitrogen used for in plants?

A

Amino acids / Protein

50
Q

What is phosphorus used for in plants?

A

DNA, root growth, and flower production

51
Q

What is potassium used for in plants?

A

General growth, and crop yield

52
Q

What are the problems with using manure as fertiliser?

A
  • Parasites can inhabit the manure
  • The quantity of N, P, and K varies
53
Q

Where do we get the nitrogen from for NPK fertiliser?

A

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

54
Q

Where do we get potassium for NPK fertiliser from?

A

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)

55
Q

Where do we get the phosphorus for NPK fertiliser from?

A

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)

Chemistry (5 decks)

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