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GCSE Chemistry (C2) > Rates and Energy > Flashcards

Rates and Energy Flashcards

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1
Q

What two equations can be used to work out the rate of reaction?

A

Amount of reactant used ÷ time

Amount of product formed ÷ time

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2
Q

How can the average rate of reaction be found?

A

By measuring the time it takes for a certain amount of solid to appear in a solution

By measuring the amount of time it takes to collect a certain amount of gas

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3
Q

How can the rate of reaction at any given time be found?

A

From the gradient of the line on a graph of amount of product against time

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4
Q

What is the relationship between rate and time?

A

Rate is inversely proportional to time

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5
Q

How could a graph showing the rate of reaction be produced?

A

By measuring…

  • Mass/volume of gas produced
  • Changes in colour
  • Change in concentration
  • Change in pH

…over time

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6
Q

What is collision theory?

A

Chemical reactions can only happen if particles collide with sufficient energy

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7
Q

What is activation energy?

A

The minimum amount of energy for particles to collide/to start a reaction

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8
Q

What can increase the rate of reaction?

A
  • Temperature
  • Concentration of solutions
  • Pressure of gases
  • Surface areas of solids
  • Using a catalyst
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9
Q

Why do powders react faster than large pieces of solid?

A
  • They have a larger surface area
  • This means that there are more collsision in the same space of time
  • Therefore, the rate of reaction is faster
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10
Q

Why does increasing temperature increase the rate of reaction?

A
  • Increasing the temperature increases the speed of particles
  • This means they collide more frequency, increasing the rate of reaction
  • It also means they collide with more energy
  • This also increases the rate of reaction
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11
Q

Why does a small change in temperature have a large effect on the rate of reaction?

A

Because it increases both the speed of the collisions and energy of the particles

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12
Q

Why does increasing concentration increase the rate of reaction?

A
  • Particles in a solutions are moving randomly
  • If the concentration increases, there are more dissolved in the same volume
  • This means the particles are closer together so collide more often
  • This therefore increases the rate of reaction, because the frequency of reactions is increased
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13
Q

Why does increasing pressure increase the rate of reaction?

A
  • There are more molecules/particles in the same volume
  • This means they collide more frequently
  • Therefore the rate of reaction is increased
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14
Q

What happens to a catalyst during a chemical reaction?

A

Nothing, it is not used up

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15
Q

What do solid catalysts normally have and why?

A

A large surface area to make them as efficient as possible

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16
Q

Why do different reactions need different catalysts?

A

Catalysts often only work with one type of reaction

17
Q

Why does using a catalyst increase the rate of reaction?

A
  • The activation energy is lowered
  • This means that more of the collisions between particles result in a reaction
  • Therefore the rate of reaction is lowered
18
Q

What are many of the catalysts used in industry made of?

A

Transitions metals or their compounds

19
Q

What are the advantages of using catalysts in industry?

A
  • They do not need replacing very often
  • They reduce the time and energy needed for a reaction
  • This helps to reduce osts and environmental impact
  • If fossil fuels are burned to provide the energy for reactions, then catalysts will help conserve resources and reduce pollution/global warming
20
Q

What are the disadvantages of using catalysts in industry?

A
  • Some transition metals and their compounds are toxic and may cause harm if they get into the environment
  • They are expensive
  • Different ones are needed for different reactions
21
Q

What two areas of research offer possibilities for new or better catalysts?

A

Nanoscience and biological catalysts

22
Q

How is energy transfered in chemical reactions?

A

When bonds are broken or made

23
Q

What are exothermic reactions?

A

Reactions that transfer energy to the surroundings

This energy is often transfered as heat, so the surroundings heat up

24
Q

Give some examples of exothermic reactions

A
  • Combustion, such as burning fuels
  • Oxidation reactions, such as respiration
  • Neutralisation reactions
25
Q

What are endothermic reactions?

A

Reactions that take in energy from the surroundings

26
Q

What are the two ways to show that a reaction is endothermic?

A

Either causes a decrease in temperature or requires a constant supply of energy

27
Q

When some solid compounds are mixed with water, why might the temperature decrease?

A

Because an endothermic reaction is taking place as they dissolve

28
Q

Give an example of a type of reaction that needs to be heated continuously to keep it going

A

Thermal decomposition

29
Q

What is the relationship between the forward and reverse reactions in reversible reactions?

A

They are equal but involve opposite energy transfers

A reaction that is endothermic one way will be exothermic the other

30
Q

How much energy is released by the forward and reverse reactions of a reversible reaction?

A

The same amount of energy is released by both reactions (forwards and back)

31
Q

What type of reaction occurs when blue copper sulfate crystals are heated?

A

Endothermic

32
Q

What type of reaction occurs when water is added to anhydrous copper sulfate solution?

A

Exothermic

33
Q

Draw a balanced symbol equation showing how hydrated copper sulfate is reacted to make anhydrous copper sulfate

A

CuSO4 • 5H2O ⇌ CuSO4 + 5H2O

Hydrated copper sulfate ⇌ Anhydrous copper sulfate + water

34
Q

What can exothermic reactions be used to do and give an example of a product that uses this

A

They can be used to heat things

For example, a hand warmer

35
Q

What can endothermic reactions be used to do and give an example of a product that does this

A

They can be used to cool things

For example, cold packs

36
Q

Suggest the advantages and disadvantages of a re-usable hand warmer compared with a single use handwarmer

A

Advantage: Less waste/less matierals/resources used

Disadvantage: Has to be heated or needs energy to be used again, slower reaction, smaller temperature rise

37
Q

Suggest the advantages and disadvantages of a chemical cold pack compared with using an ice pack

A

Advantages: Can be used anywhere, can be stored easily

Disadvantage: Can only be used once, more waste, possibly more hazardous

GCSE Chemistry (C2) (5 decks)

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