C2.4 Rates and energy Flashcards Preview

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Flashcards in C2.4 Rates and energy Deck (16):
1

What does rate of reaction mean?

how quickly a reaction takes place

2

How can you find the rate of reaction?

measuring how much reactant is used
measuring how much product is formed

3

What is collision theory?

particles must collide with a certain amount of energy before they can react-effective collisions speed up a reaction

4

What is activation energy?

the minimum amount of energy required for a reaction to occur

5

What does the gradient of a line on a graph tell us about rates of reactions?

the steeper the slope the faster the rate of reaction

6

What increases the rate of reaction?

surface area
temperature
concentration
adding a catalyst

7

What effect does surface area have on the rate of reaction?

rate of reaction increases-more particles exposed-more effective collisions

8

What effect does temperature have on the rate of reaction?

reaction happen faster as temp.increases-more energy-higher collision frequency-more particles reaching activation energy

9

What effect does concentration have on the rate of reaction?

increasing concentration increases frequency of effective collisions-more particles-more 'crowded'-increases rate of reaction

10

What effect does a catalyst have on the rate of reaction?

catalysts speed up rate of reaction-not used up in reaction-reduces energy costs

11

What is an exothermic reaction?

gives off heat to their surrounding (temp.increase)

12

What is an endothermic reaction?

takes in heat from its surroundings (temp. decrease)

13

What energy changes are involved in a reversible reaction?

reversible reactions absorb exactly the same amount of energy it releases. usually: first reaction is exo second is endo

14

What is an example of an exothermic reaction?

copper sulphate solution + magnesium powder
super saturated sodium ethanoate + "seed"

often used in hand warmers-reusable

15

What is an example of an endothermic reaction?

ammonium nitrate + water
iced packs for sports injuries

16

What do thermal decomposition reactions need?

to be heated continuously to keep the reaction going