What is the required practical for investigating rate factors?

The required practical for investigating rate factors is to measure the rate of a reaction by observing a colour change.

In this practical, you will investigate how different factors affect the rate of a chemical reaction. The reaction you will be observing is between sodium thiosulphate and hydrochloric acid. When these two substances react, they produce a precipitate of sulphur which clouds the solution and eventually makes it opaque. By timing how long it takes for the solution to become opaque, you can measure the rate of the reaction.

To investigate how temperature affects the rate of reaction, you will carry out the experiment at different temperatures. You can do this by heating the sodium thiosulphate solution before adding the hydrochloric acid, or by carrying out the experiment in a water bath at a controlled temperature. You should find that the reaction happens faster at higher temperatures.

To investigate how concentration affects the rate of reaction, you will carry out the experiment with different concentrations of sodium thiosulphate or hydrochloric acid. You can change the concentration by adding water to the solution. You should find that the reaction happens faster when the concentration is higher.

To investigate how surface area affects the rate of reaction, you could use a solid reactant and change its surface area by crushing it into a powder or using larger pieces. You should find that the reaction happens faster when the surface area is larger.

Remember to keep all other factors constant while you are changing one factor. This is to ensure that any changes you observe in the rate of reaction are due to the factor you are investigating, and not due to some other factor.