C2.4 Rates and energy Flashcards
What does rate of reaction mean?
how quickly a reaction takes place
How can you find the rate of reaction?
measuring how much reactant is used
measuring how much product is formed
What is collision theory?
particles must collide with a certain amount of energy before they can react-effective collisions speed up a reaction
What is activation energy?
the minimum amount of energy required for a reaction to occur
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
What increases the rate of reaction?
surface area
temperature
concentration
adding a catalyst
What effect does surface area have on the rate of reaction?
rate of reaction increases-more particles exposed-more effective collisions
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
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
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
What is an exothermic reaction?
gives off heat to their surrounding (temp.increase)
What is an endothermic reaction?
takes in heat from its surroundings (temp. decrease)
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
What is an example of an exothermic reaction?
copper sulphate solution + magnesium powder
super saturated sodium ethanoate + “seed”
often used in hand warmers-reusable
What is an example of an endothermic reaction?
ammonium nitrate + water
iced packs for sports injuries
