Rates of ReactionChemical Reactions – Year 8 Science

Rates of ReactionWhen do we want to change the rate of a reaction?

What can we use to change the rate of reaction?

Fukushima, JapanOn 11 March 2011, the Number 3 Reactor at the Fukushima Daiichi Nuclear Plant exploded due to an uncontrolled nuclear reaction.

Rates of reactionThe reaction rate is a measure of how quickly a chemical reaction occurs.

How can the rate of a reaction be changed to make a slow reaction happen quickly or make a fast reaction slow down?

CatalystsA catalyst is a chemical that can speed up a chemical reaction but is still present once the reaction has finished. Catalysts are not reactants because they are not changed by the reaction.

The catalysts in living things are called enzymes. Enzymes in the human body help to digest the food you eat more quickly.For example, the lactase enzyme helps humans digest lactose which is found in dairy products.

lactase enzymeLactose glucose + galactose

Rates of reactionThe reaction rate can also be increased by;- increasing the amount of reactants that are combined- Increasing the concentration of the reactants - Increasing the surface area of the reactants- Increasing the temperature of the reaction- Increasing the pressure that the reaction occurs at

Fukushima, JapanA Nuclear ReactionControl rods can be lowered into the reactor to slow the nuclear reaction (creating less electric power), or raised to speed it up (creating more electric power).

Changing the rate of reactions

Think about some basic reactions that you have seen at home and in the lab.

How could you speed them up or slow them down?

How could you change these?

- Dissolving salt in water- Keeping cheese from going mouldy- Stopping iron from rusting

Next class…

- Investigate the effect of temperature on a reaction (practical)

- Answer the following questions:- What is the rate of a reaction?- State five different methods of changing the rate of

a reaction.- How does heating increase the rate of a reaction?- What is a catalyst?- How do you know that a catalyst is not a reactant?- What is an enzyme?