A hazard symbol tells you what kind of harm a substance can cause. A good SPM answer goes one step further and states the precaution that matches that harm.
This lesson is part of laboratory safety and investigation. Once you can read the symbols, continue with selecting suitable apparatus for a task.
What does each common symbol warn about?
Use the table below to check against your own textbook, which shows the full set for your syllabus.
| Symbol meaning | What it warns of | A matching precaution |
|---|---|---|
| Flammable | Catches fire easily | Keep away from flames and heat |
| Corrosive | Damages skin, eyes and metals | Wear goggles and gloves |
| Toxic | Can poison if swallowed, inhaled or absorbed | Work in a ventilated area, avoid contact |
| Explosive | Can blast under heat, shock or friction | Handle only as instructed, keep cool |
| Oxidising | Feeds a fire by supplying oxygen | Store away from flammable materials |
| Harmful to the environment | Damages living things in water or soil | Dispose of waste as directed, not down the sink |
How do I turn a symbol into a full answer?
Think in a chain of three links: hazard, risk, precaution. The hazard is the property, the risk is how it could hurt someone, and the precaution is the action that breaks the chain.
For a corrosive liquid, the hazard is that it burns skin. The risk is a splash while pouring. The precaution is to wear goggles and pour slowly over the bench tray.
Worked example: a storage scenario
A bottle of ethanol and a bottle of concentrated acid are both on one shelf near a Bunsen burner. The ethanol has a flammable symbol and the acid has a corrosive symbol.
Step 1. Name the hazards. Ethanol catches fire easily. The acid damages skin and eyes.
Step 2. Find the risks. A spark from the burner could ignite ethanol vapour. A spill of acid could reach a student’s hands.
Step 3. State the actions. Move the ethanol well away from the burner. Keep the acid in a tray low on the shelf, and wear goggles and gloves when pouring.
The mistake that costs marks
A common slip is to write “be careful” or “handle with care”. That names no action, so it earns nothing.
| Vague answer | Mark-earning answer |
|---|---|
| Be careful with the acid | Wear goggles and gloves because the acid is corrosive |
| Keep safe from fire | Keep ethanol away from the flame because it is flammable |
| Dispose of it properly | Pour the waste into the labelled waste bottle, not the sink, because it is harmful to the environment |
A mark-earning answer contains the symbol word, a “because”, and a specific action.
Check yourself
A technician finds a bottle with a toxic symbol that has spilled in a closed storeroom. State two sensible precautions and link each to the hazard.
Answer
Open windows or use extraction so the vapour does not build up, because toxic vapour can be inhaled.
Wear gloves and a mask while cleaning the spill, because toxic substances can be absorbed through the skin or breathed in.
A third acceptable point is to report the spill to the teacher instead of cleaning it up alone.
What to study next
Hazard symbols set the scene for choosing equipment. Continue with selecting suitable apparatus for a task, then try the investigation practice set.
To practise safety wording with a teacher, see online one-to-one Science tuition.