National 5 Chemistry: Unit 1 Section 1 - Rates of Reaction

Vocabulary flashcards covering chemical reaction signs, factors influencing reaction rates, catalysts, and methods for measuring and calculating the speed of reactions.

Product

A new substance formed in all chemical reactions.

Reactants

The substance you started with

Signs of a chemical reaction

1. Colour change

2. Gas production

3. Temperature change

4. Change in odur

5. Sound produced

6. Precipitate formed

Exothermic reaction

A reaction in which energy exits, resulting in an increase in the temperature of the surroundings.

Endothermic reaction

A reaction in which energy enters, resulting in a decrease in the temperature of the surroundings.

Rate of reaction

The rate of reaction is how quickly reactants are changed into products

Collision Theory

Collision theory states that a chemical reaction only occurs when particals collide with enough energy and in the correct orientation for a reaction to occur

Particle Size

• If you decrease partical size the rate of reaction will increase. This is because more surface area is available for reactions to take place on

• If you increase partical size the rate of reaction decreases

Concentration

• If you increase concentration the rate of reaction will increase. This is because there are more reactants particals present to react

• If you decrease concentartion the rate of reation will decrease.

Temperature

• If you increase temperature the rate of reaction will increase. This is because particals have gained more energy and ate more likely to collide and react.

• If you decrease temperature the rate of reaction will decrease.

Catalyst

A catalyst is a substance that increases the rate of reaction without being used up or chemically changed

Catalyst poisoning

Is when impurities block the active site of a catalyst reducing the number of successful collisions and slowing down the reaction

Regeneration

Is the process of restoring a catalyst so that it can work effectively again

Enzymes

Biological catalysts that catalyse reactions in living things.

Average Rate Formula

$$\text{Average Rate} = \frac{\text{Change in Mass or Volume}}{\text{Change in Time}}$$

$$g\,s^{-1}$$

• Mass lost of reactants formula

• Mass and time

$$cm^3\,s^{-1}$$

• Measuring volume of gas

• Volume and time

Reaction Graph Steepness

Indicates the speed of the reaction; the steeper the line is, the faster the reaction is.

Graph Leveling Off

Occurs on a reaction graph when the reactants are used up and the reaction stops.