6.2.4

Predict and explain, using the collision theory, the qualitative effects of particle size, temperature, concentration and pressure on the rate of a reaction.

Independent variables	Time, Surface area of marble chips
Dependent variable	Volume
Controlled variables	Mass of marble chips, Concentration and volume of hydrochloric acid, Temperature of surroundings, Volume of water in the inverted measuring cylinder
Collision theory explanations	The larger the surface area, the faster the reaction should be because in a powdered solid, the particles can easily come into contact with the surrounding reactant. But in solid substance, only the particles on the surface can come into contact with a surrounding reactant. So as surface area increases, rate increases dramatically too.
Gradient represents:	Rate of reaction
Units for gradient	cm3/sec
Reasons for differences in graphs	The results don’t exactly support the collision theory otherwise the line for the powder would be the steepest showing the fastest rate of reaction. However, for other types of marble chips the line is steeper as the surface area increases.