N5 CHEM: RATE OF REACTION

4 signs of a chemical reaction:

Colour change

Temperature change

Precipitation

Effervescence

What is the difference between a chemical change and a physical change?

Physical change : reversible

Chemical change : irreversible, new substance formed

What is meant by exothermic

Energy exits and heat is given off

What is an endothermic reaction?

Energy is taken in from surroundings

What the 4 ways to speed up rate of reaction?

Decrease in particle size

Increase temperature

Increase concentration

Add a catalyst

What is a catalyst?

A substance that speeds up the rate of a chemical reaction and can be recovered at the end chemically unchanged

Explain how decreasing particle size speeds up rate of reaction.

As particle size decreases, surface area increases giving more opportunities for collisions.

Explain how increasing concentration increases rate of reaction.

As concentration increases, there are more reacting particle and so gives more opportunity for ‘bumps’

Why does increasing temperature speed up rate of a reaction?

Increase in temperature give the particles more energy and makes them collide more often.

What is the measure of concentration in gas?

Pressure

How to calculate average rate?

Change in quantity/Change in time

Why does average rate decrease as reaction proceeds?

Reactants are used up

Methods in how to measure the volume of gas produced:

Collection over water

Gas syringe

Cotton wool

How is the rate of a chemical reaction defined as?

Unit change per unit time