# Rate of reaction

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## Reacting particle model

Chemical reactions take place when particles collide.

The rate of the reaction depends on the number of successful collisions between the reacting particles, the higher the number of successful collisions that take place, the faster the reaction.

The rate of reaction can be increase by increasing the concentraion, raising the temperature, or the pressure.

-As the concentration increases, there are more reacting particles in a smaller space, this increasing the number of successful collisions between reacting particles, increasing the rate of reaction also.

-As the temperature increases, the particles gain kinetic energy and therefore move around more quickly, this means the number of successful collisions increases as the particles collide more due to lots of movement.

-Increases in pressure forces the particles together, meaning more successful collisions will take place and therefore increasing the rate of reaction.

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## Successful collisions

The rate of reaction depends on the successful collision frequency, this describes the number of successful collisions between reacting particles per second.

For a successful collision to occur, the reacting particles need to have enough energy to react.

-As the concentration increases, the number of collisions per second increases, and so the rate of reaction increases.

-As the temperature increases the reactants have more kinetic energy, so collisions are more energetic and frequent, so more likely to be successful.

-Increasing the pressure in gases forces particles closer together, increasing collision frequency.

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## Graphs and tables

BOTH TABLES AND GRAPHS CAN SHOW WHEN A REACTION HAS FINISHED:

• On a graph, the line will be horizontal.
• In a table, the numbers will stop chaning.

BOTH TABLES AND GRAPHS CAN BE USED TO COMPARE THE RATE OF REACTION:

• On graphs, the steeper the line, the faster the reaction.
• In a table, the larger the change between readings, the faster the reaction.
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## Key definitions

RATE OF REACTION - the speed with which a chemical reaction takes place.

CONCENTRATION - the amount of chemical dissolved in a certain volume of solution, high       concentration means lots of something a space, low means not much is in       the space.

KINETIC ENERGY - the energy that moving objects have.

COLLISION FREQUENCY - the number of successful collisions between reacting particles that happen in a second.

REACTANTS - chemicals which are reacting together in a chemical reaction

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