Learning outcomes
- Distinguish a hazard, a risk and a precaution.
- Identify realistic hazards in common physics experiments.
- Suggest precautions that directly reduce a stated risk.
- Recognise unsafe positioning and electrical arrangements.
- Write concise safety answers.
3.1 Hazard, risk and precaution
A hazard is something with the potential to cause harm. A risk describes what harmful event could occur and, where relevant, how likely or serious it is. A precaution is an action that reduces the likelihood or consequence of that harm.
For hot water, the hazard is high temperature, the risk is a burn from spilling or touching it, and a suitable precaution is to use a stable heatproof surface, avoid overfilling and allow the apparatus to cool before handling.
3.2 Mechanical hazards
Clamp stands can topple, masses can fall and glass objects can roll from a bench. Place heavy bases flat, keep equipment away from the edge, tighten bosses and clamps, and position a tray or soft landing below falling masses when appropriate.
A suspended load should not be placed above feet or delicate apparatus. A stretched spring may recoil if overloaded, so stay within the elastic range and use eye protection when there is a credible snapping or ejection risk.
3.3 Thermal and glass hazards
Hot liquids and heaters cause burns. Use heatproof mats, low volumes, suitable containers and tongs or insulation when needed. A thermometer must not be used as a stirrer, and glass should be checked for cracks.
The safest answer is specific to the setup. ‘Wear gloves’ is not automatically correct because bulky gloves may reduce grip. A better precaution may be to let the water cool, handle the beaker by a safe part, or use a clamp.
3.4 Electrical hazards
School experiments normally use low-voltage supplies, but short circuits can overheat wires and cells. Include a switch, limit current with a resistor, avoid connecting a cell directly across an ammeter, and open the switch between readings when heating would alter the experiment.
Mains electricity should not be introduced into improvised student circuits. Keep water away from electrical equipment and ensure damaged insulation is not used.
3.5 Writing a safety response
State the chain in one sentence: ‘The hot beaker could cause burns, so place it on a heatproof mat and allow it to cool before moving it.’ This identifies the risk and the action.
Avoid generic statements such as ‘be careful’ or ‘wear safety equipment’ without naming the hazard. Eye protection is appropriate when splashes, fragments, snapping wire or falling objects could reach the eyes.
Worked examples
Circuit safety
Hazard: a high current heats the resistance wire. Risk: the wire can burn skin and its resistance changes. Precaution: use a low current, close the switch only while taking a reading and do not touch the wire immediately.
Pendulum safety
Keep the swing amplitude small and ensure the bob cannot strike a person or fragile apparatus. Secure the clamp stand and keep the path clear.
Practical focus
Investigation or training activity
Inspect four experimental setups and write one hazard–risk–precaution statement for each. Reject any precaution that does not directly address the identified risk.
Examination guidance
- Do not invent a hazard that is not present in the diagram.
- Link the precaution to the risk.
- “Be careful” earns no scientific credit.
- For electrical tests, mention low voltage, current limiting or opening the switch where relevant.
- For hot apparatus, remember that it may remain hot after heating stops.
Check your understanding
- What is a hazard?
- Give one risk from a loose clamp stand.
- Why should a switch be opened between resistance readings?
- When is eye protection especially relevant?
Answers
- A source with the potential to cause harm.
- It may topple and falling apparatus may injure someone or break.
- To reduce heating and keep the wire temperature and resistance more constant.
- When splashes, fragments, snapping components or ejected objects are possible.
