Ca (OH) 2 (s) + CO2 (g) CaCO3 (s) + H2O (l)

Which describes a way to speed up the collisions between calcium hydroxide and carbon dioxide molecules to produce calcium carbonate faster?

Lower the temperature.

Use larger pieces of calcium hydroxide.

Lower the pressure.

Reduce the volume of the container.

The only answer that makes sense here is the last one. By reducing the volume of the container, you increase the pressure within the container. By LeChatelier's Rule, this will favour the right side of the reaction (i. e. the products), where there are fewer gas molecules. Lowering the pressure will have the opposite effect. Lowering the temperature in general reduces the speed of reactions because particles then have lower kinetic energy and therefore do not collide with one another as often. Using larger pieces of calcium hydroxide will also lower the rate of the reaction because you decrease the effective surface area of the compound capable of interacting with carbon dioxide.