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Controlling Chemical REACTIONS

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on 5 January 2015

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Transcript of Controlling Chemical REACTIONS

There are several factors that can cause the rate of a chemical reaction to
1) Increase surface area of reactants
2) Increase in temperature
3) Increase in concentration of reactants
4) Use of a catalyst
Exothermic and
Endothermic Reactions
Exothermic reaction
- a reaction that

For an exothermic reaction to start, a tiny amount of activation energy is needed. Once a few molecules react, they will provide activation energy for the remaining molecules to react.

Endothermic reaction
- a reaction that

In an endothermic reaction, the energy of the products is greater than the energy of the reactants.

There are several factors that affect the rate of a chemical reaction:
1) Surface area of reactants
2) Temperature
3) Concentration of reactants
4) Use of a catalyst
5) Use of an inhibitor
Why does the surface area of a reactant influence the rate of this reaction?
ANSWER: Increasing the surface area allows more particles to react, and this increases the rate of reaction.
Energy and Reactions
Activation energy - the minimum amount of energy needed to start a chemical reaction

ALL chemical reactions require a certain amount of activation energy to get started.

activate - to set in motion, to make active

How might you make water from hydrogen gas and oxygen gas? Where does the activation energy come from?
Controlling chemical reactions
How is temperature related to chemical reaction rates?

ANSWER: As you saw in the Alka Seltzer lab, reaction rates are faster at higher temperature.
What is concentration?
ANSWER: Concentration is the amount of a substance in a given volume.

If you increase the concentration of the reactants, you supply more particles to react.
What is a catalyst?
ANSWER: A catalyst is a substance that increases the rate of a reaction by lowering the activation energy.

Catalysts aren't always permanently changed in a reaction.

A biological catalyst is called an enzyme.
Why are catalysts
necessary for life?
Many chemical reactions necessary for life happen at temperatures that would kill living things. Enzymes are necessary to allow these reactions to occur at safe temperatures.
What is an inhibitor and how does it work?
ANSWER: An inhibitor is a material used to decrease the rate of a reaction. It works by preventing reactants from coming together.
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