catalysts

what is a catalyst

A catalyst is a substance that increases the rate of a chemical reaction. The presence of a catalyst is one of several factors that influence the rate of chemical reactions. (Other factors include the temperature, concentration, and surface area of reactants.) A catalyst isnt a reactant in the chemical reaction it speeds up. As a result, it isnt changed or used up in the reaction, so it can go on to catalyze many more reactions. Q: How is a catalyst like a tunnel through a mountain? A: Like a tunnel through a mountain, a catalyst provides a faster pathway for a chemical reaction to occur.

how catalysts work

Catalysts interact with reactants so the reaction can occur by an alternate pathway that has a lower activation energy. Activation energy is the energy needed to start a reaction. When activation energy is lower, more reactant particles have enough energy to react so the reaction goes faster. Many catalysts work like the one in the Figure 1.1. The catalyst brings the reactants together by temporarily bonding with them. This makes it easier and quicker for the reactants to react together. Q: In the Figure 1.1, look at the energy needed in the catalytic and non-catalytic pathways of the reaction. How does the amount of energy compare? How does this affect the reaction rate along each pathway? A: The catalytic pathway of the reaction requires far less energy. Therefore, the reaction will occur faster by this pathway because more reactants will have enough energy to react.

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catalysts in living things

Chemical reactions constantly occur inside living things. Many of these reactions require catalysts so they will occur quickly enough to support life. Catalysts in living things are called enzymes. Enzymes may be extremely effective. A reaction that takes a split second to occur with an enzyme might take many years without it! More than 1000 different enzymes are necessary for human life. Many enzymes are needed for the digestion of food. An example is amylase, which is found in the mouth and small intestine. Amylase catalyzes the breakdown of starch to sugar. You can see how it affects the rate of starch digestion in the Figure 1.2. A: The starches in the cracker start to break down to sugars with the help of the enzyme amylase. Try this yourself and see if you can taste the reaction.

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instructional diagrams

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questions

a catalyst is a reactant in the reaction it catalyzes.

a. true

-->  b. false

a catalyst is used up in the reaction it catalyzes.

a. true

-->  b. false

the compound that speeds up the breakdown of starch to sugar in your mouth is

a) an enzyme.

b) called amylase.

c) also found in your small intestine.

-->  d) all of the above

more than 1000 different enzymes are necessary for human life.

-->  a. true

b. false

the presence or absence of a catalyst is the only factor that affects the rate of a chemical reaction.

a. true

-->  b. false

diagram questions

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