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chemistry gcse > topic 7 - rates of reactions and energy changes > Flashcards

topic 7 - rates of reactions and energy changes Flashcards

1
Q

what core practical investigates the effect of changing the conditions of a reaction on the rates of reaction?

A
  • measure production of gas between HCl and marble chips
    -> size of marble ships changes (smaller chips = larger surface area - faster rate)
  • observe a colour change in reaction between sodium thiosulfate and HCl (changing conc. - greater number of particles - faster rate) - x dissapears
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2
Q

suggest a practical method which can be used to determine the rate of a given reaction?

A
  • using amount of product used or formed over time
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3
Q

what is the formula for the rates of reaction?

A

amount of reactant used / time
or
amount of product formed / time

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4
Q

what is units of rate of reaction given as?

A

g/s or cm3/s

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5
Q

how can you measure the amount of reactant used?

A

if a gas you can measure volume using a gas syringe

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6
Q

what is the collision theory?

A

when the reacting particles collide with enough energy

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7
Q

what is the minimum amount of energy required in the collision theory called?

A

activation energy

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8
Q

what ways increase frequency/energy of collisions?

A

-increasing temperature
-pressure
-concentration
-surface area
-catalyst

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9
Q

what is the effect of increasing the temperature on the energy of collisions (rate of reaction)?

A
  • increases rate of reaction
  • increases kinetic energy so they collide more frequently and energetically
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10
Q

what is the effect of increasing the concentration on the energy of collisions (rate of reaction)?

A
  • increases rate of reaction
  • increases number of particles in a given volume and increases frequency of collisions
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11
Q

what is the effect of increasing the surface area on the energy of collisions (rate of reaction)?

A
  • increases rate of reaction
  • increases surface available for collisions
  • increases frequency of collisions
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12
Q

what is the effect of increasing the pressure on the energy of collisions (rate of reaction)?

A
  • increases rate of reaction
  • increases number of particles in given volume
  • increases frequency of collisions
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13
Q

how do you interpret graphs of mass, volume or concentration of reactant/products over time?

A
  • draw tangent to curves and use slope to measure rate of reaction
  • gradient = rate of reaction
    -> steeper line = increase in rate
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14
Q

what is a catalyst?

A

substances that speed up chemical reactions without altering the products of the reaction, being itself unchanged chemically and in mass at end of reaction

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15
Q

what does adding a catalyst do?

A

decrease the activation energy - provide alternate pathway and increases proportion of particles with energy

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16
Q

what are enzymes?

A

biological catalysts

17
Q

why is yeast an important enzyme?

A

used in production of ethanol as is fermented from sugars
-> then used in alcoholic drinks

18
Q

what is the theory of the conservation of energy?

A

energy is neither created or destroyed

19
Q

what type of reaction is salt dissolving in water?

A

either exothermic or endothermic

20
Q

what type of reaction is neutralisation?

A

exothermic

21
Q

what type of reaction is displacement?

A

exothermic or endothermic

22
Q

what type of reaction is a precipitation?

A

exothermic

23
Q

describe an exothermic reaction

A

one that transfers energy to the surroundings from the system
- temperature of surroundings increase

24
Q

give examples of exothermic reactions (4)

A

combustion, neutralisation, many oxidation reactions, hand warmers

25
Q

describe an endothermic reaction

A

one that takes in energy from the surroundings to the system
- temperature of surroundings decrease

26
Q

give examples of endothermic reactions

A

decomposition

27
Q

what type of reaction is breaking bonds and why?

A

endothermic - energy supplied to break reactant bonds

28
Q

what type of reaction is making bonds and why?

A

exothermic - energy released when bonds in products are formed

29
Q

what is the overall heat energy change for an exothermic reaction?

A

more heat energy released in making bonds in products that in breaking bonds in reactants

30
Q

what is the overall heat energy change for an endothermic reaction?

A

less heat energy is released in forming bonds in products then required in breaking bonds of reactants

31
Q

what is the calculation for energy change?

A

energy in - energy out (using polymer drawings)

32
Q

what does a negative energy change mean?

A

reaction is exothermic

33
Q

what does a positive energy change mean?

A

reaction is endothermic

34
Q

explain the term activation energy

A

the minimum amount of energy by colliding particles for a reaction to occur

35
Q
A

chemistry gcse (9 decks)

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