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GCSE > Chemistry- Additional > Flashcards

Chemistry- Additional Flashcards

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1
Q

Describe how temperature and the collision theory work?

A

As temperature increases the particles have more energy therefore they move quicker and collide more often therefore they are more likely to overcome the activation energy as the collisions have more energy, this increases the rate of reaction

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2
Q

Describe how concentration and the collision theory work?

A

If it is more concentrated there are more reactant particles which make the collision more likely - low pressure
If there is more pressure the particles are more squashed so there is more frequent collisions, this increases the rate of reaction

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3
Q

describe how surface area and the collision theory work?

A

The smaller the pieces the larger the surface area therefore the particles have more area to work on so there are more frequent collisions, this increases the rate of reaction

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4
Q

How does a catalyst and the collision theory work?

A

A catalyst speeds up the rate of reaction without being changed or used up in the reaction, it also lowers the activation energy so more collisions are successful

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5
Q

Why are catalysts good in industry?

A
  • save money
    It increases the rate of reaction so it doesn’t have to operate for as long as it would without a catalyst
  • lowers temperature
    Reduces the amount of energy needed so saves money and is good for sustainable development
  • expensive
    But it never gets used up in the reaction
  • can be poisoned by impurities so the mixture has to be very clean
  • they only work for one kind of reaction
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6
Q

What is an exothermic reaction?

A

One which transfers energy to the surroundings usually in the form of heat and is shown as a rise in temperature

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7
Q

Give examples of an exothermic reaction?

A

Combustion
Neutralisation
Oxidation

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8
Q

How does a un reusable hand warmer work?

A

The iron turns into hydrated iron (II) oxide, sodium chloride is used as a catalyst

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9
Q

What are the advantages and disadvantages of a un reusable hand warmer?

A
  • only used once

- last for hours

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10
Q

How does a re usable hand warmer work?

A

A small metal disc in the plastic pack is used to start the exothermic reaction, a few metal particles are scrapped of which starts the crystallisation and spreads throughout the pack giving off energy, can be dissolved in heat

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11
Q

What are the advantages and disadvantages of an reusable hand warmer?

A
  • reversible

- last for 30 minutes

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12
Q

What is an endothermic reaction?

A

One which takes in energy from the surroundings usually in the form of heat and is shown by a fall in temperature

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13
Q

Give an example of an endothermic reaction?

A

Thermal decomposition

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14
Q

How do cold packs work?

A

The ammonium nitrate dissolves in the water and takes in energy from the surroundings making the pack cold

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15
Q

How do you get blue crystals?

A

Heat blue hydrated copper(II) sulfate crystals and it evaporates the water off leaving a white hydras copper sulfate powder, this is endothermic
Add a couple of drops of water to the White powder and you get blue crystals, this is exothermic

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16
Q

What is the collision theory?

A

Particles must collide with enough energy to overcome the activation energy, particles with less energy bounce off each other

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17
Q

What is a pH?

A

A measure of how acidic or alkaline a solution is

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18
Q

Where is acid on the pH scale?

A

0-6

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19
Q

What is an indicator?

A

A dye that changes colour depending on wether the substance is above or below a certain pH

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20
Q

What is a universal indicator?

A

A combination of dyes that turn colour as the pH changes, it is the best for estimating the pH of a solution

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21
Q

What do acids form in water?

A

Hydrogen ions

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22
Q

What is a base?

A

An substance with a pH greater than 7

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23
Q

What is an alkali?

A

An alkali is a base that dissolves in water to form hydroxide ions

24
Q

What is neutralisation?

A

A reaction between acids and bases

25
Q

What do you get when you react an acid with a base?

A

Acid+base>salt+water

26
Q

What do you get when you react an acid with metal?

A

Acid+metal>salt+hydrogen

27
Q

If the metal is more reactive what will happen?

A

The more reactive the metal the faster the reaction will go, or they will react explosively

28
Q

Why does copper not react with dilute acids?

A

Because its less reactive than hydrogen

29
Q

What is the speed of reaction indicated by?

A

The rate at which hydrogen bubbles are given off

30
Q

How do you work out that hydrogen is produced?

A

Squeaky pop test

31
Q

What is the equation for hydrochloric acid?

A

HCL

32
Q

What is the equation for sulphuric acid?

A

H2SO4

33
Q

What is the equation for nitric acid?

A

HNO3

34
Q

What happens when you mix a metal oxide with acid?

A

Acid+metal oxide>salt+water

35
Q

What happens when you mix a metal hydroxide and a acid?

A

Acid+metal hydroxide>salt+water

36
Q

What is ammonia useful for?

A

Ammonia can be neutralised by nitric acid to produce a fertiliser, the ammonia dissolves in water to make an alkaline solution, no water is produced and plants need it to make protein

37
Q

How do you make a salt with a base or insoluble base? (The method of crystallisation)

A

Add metal oxide and metal hydroxide to the acid
The solid will dissolve in the acid as it reacts
When the acid has been neutralised the excess solid will just sink to the bottom
Then filter the excess metal, metal oxide and metal hydroxide to get the salt solution
Or evaporate the water this makes the solution more concentrated to get pure solid crystals of the salt this is called crystallisation

38
Q

How do you make salts using an alkali?

A
  • Cant use the method above with alkalis as you wont be able to tell when the reaction has finished
    Add an indicator to show when the reaction has finished
    Then repeat adding the exact volume of alkali and acid so the salt is not contaminated by the indicator
    Then evaporate the water to crystallise the salts as usual
39
Q

How do you make insoluble salts?

A

Combine 2 salts that contain different soluble salts
Mix the two ions you need and the salt will precipitate out
Filter it from the solution, wash it than dry it again

40
Q

What is electrolysis?

A

Splitting up using electricty

41
Q

What does electrolysis require ?

A

It requires the electrolyte, this is a liquid to conduct electricity

42
Q

How do electrolytes conduct electricity?

A

Electrolytes contain free ions they are usually molten or dissolve ionic substances, the free ions conduct the electricity and make the whole thing work

43
Q

OIL RIG

A 
Oxidation
Is
Loss
Reduction
Is
Gain
44
Q

How does the electrolysis of sodium chloride solution work?

A

At the negative electrode 2 hydrogen ions accept 2 electrons and become a hydrogen molecule
At the positive electrode 2 cl- ions lose electrons and become one chlorine molecule
Sodium ions stay in solution as they are more reactive than hydrogen, and hydroxide ions from water are
Left behind, sodium hydroxide is left in the solution

45
Q

What happens if there is more than 2 free ions?

A

There will be some hydrogen and hydroxide ions

46
Q

What happens at the negative electrode?

A

At the negative electrode if metal ions and hydrogen ions are present the metal ions will stay in the solution, if the metal is more reactive than the hydrogen then the more reactive element will want to stay as an ion

47
Q

What happens at the positive electrode?

A

If OH- ions and halide ions are present than molecules of chlorine and bromine and iodine will be formed, if there is no halide then oxygen will be formed

48
Q

What do half equations do?

A

Show the reaction at the electrodes

49
Q

What are the useful products of sodium chloride?

A

Chlorine = bleach and plastics
Sodium hydroxide = soap
Hydrogen = margarine (hydrogen+ vegetable oils)

50
Q

What is the main ore of aluminium?

A

Bauxite

51
Q

What is left after you purify and mine aluminium?

A

A white powder of aluminium oxide is formed, this has to be extracted by electrolysis

52
Q

How do you do electrolysis of aluminium oxide?

A

Aluminium oxide has a high melting point do melting it would be 2 expensive
Therefore the aluminium has to be dissolved in molten cryolite
This decreases the melting point and makes it cheaper and easies
The electrolytes are made of carbon graphite because it is a good conductor of electricity
The aluminium forms at the negative electrode and the oxygen forms at the positive electrode
At the positive electrode the oxygen reacts with the carbon to form carbon dioxide therefore it has to be replaced every so often

53
Q

What is electroplating?

A

Uses electrolysis to coat the surface of one metal with another

54
Q

How does electroplating work?

A

The negative electrode is the metal object you want to plate and the positive electrode is the pure metal you want it to be plated with
The electrolyte has to contain ions of the plating metal

55
Q

What does electroplating do to the object?

A 
Attractive 
Cheaper
Conducts electricity 
Protect the object
Hardness of surface makes it resistant to scratching

GCSE (55 decks)

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