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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;
• state 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).

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.

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 than using a 100 cm³ measuring cylinder.