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The steeper the line on the graph is, the faster the rate of reaction is.
In theory, reactions should be faster at the start of the graph because there are more reatants left to react together to make the product.
This graph shows how temperature, concentration and amount of reactants are factors of how the rate of reaction can be affected.

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The amount of monkeys would be called the concentration because there is a certain number of monkeys within a certain area. To get an idea of how the concentration (amount) of reactants affects the rate of reaction just think of the monkeys as the reactants in a reaction. More monkeys in a small area interact more often which means more noise.