After planning an investigation, the next step is to think about what equipment to use, and how to conduct the experiment safely.
A risk assessment should be carried out when planning. The safety aspects of each part of the plan have to be considered in detail. It is important to identify the dangers, state the potential risks and what has to be done to minimise the risk to yourself and others in the laboratory.
For example when using a power pack attached to the mains there is a danger of electrocution (identify the danger). Water spilled on the power pack could cause an electric shock (potential risk) . Do not use the power pack close to sinks and taps (minimising the risk).
If electric current is going to be used, the potential hazards need to be identified to ensure that it’s used safely. This might affect the power supply used and even the connecting leads. The hazards also need to influence the general running of the experiment and how and where the equipment is used.
The next step is to think about the most appropriate equipment to use. For example, the length of a pendulum could be measured using a 50 cm rule, a metre rule or a 20 m tape measure. In different circumstances one of these might be more accurate than others, which would affect the choice.
If you need to measure 20 cm of string then a 50 cm rule would give a more accurate length than using a metre rule or a 20 m tape measure. Also, using balances that measure mass to the nearest 0.01 g will give a more accurate measurement then using ones that measure mass to the nearest gram.
If you need to measure out 5 cm3 of liquid then a 10 cm3 measuring cylinder would give a more accurate volume then using a 100 cm3 measuring cylinder.