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.

Questions	Answers
Independent Variable	Surface area of CaCO3 chips (i.e. powder, chips #2 etc.)
Dependent Variable	Volume of CO2 produced
Controlled Variables	Volume of HCl, mass of CaCO3, stop watch, inverted measuring cylinder, top pan balance.
Using collision theory explain the following shape of the graphs at the start of the reaction.	The larger the surface area of CaCO3 the faster the rate of reaction. This is because in a solid only the particles on the surface can collide successfully hence if it is powdered more particles can come into contact with the other reactant.
What does the gradient of the graph at any one point represent?	Rate of reaction
What are the units for the gradient of the graph?	cm3/seconds
Discuss the reasons for the differences in the shape of the graphs.	The larger the surface area of CaCO3 the steeper the graph should be, due to an increase in rate of reaction.