0.6 - Assessing practical risks and precautions
Assess how a practical procedure could cause harm, then choose a precaution that reduces that particular risk. Worked examples link chemical and apparatus hazards to exposure, likelihood and seriousness across a range of practicals.
Hazard, Risk and Precaution
A hazard is the thing that can cause harm. In chemistry, the hazard might be a corrosive solution, a flame, hot glassware, an irritating gas, a sharp broken tube, an electrical supply, or a moving piece of apparatus.
Risk
Risk is the chance that a hazard will cause harm in the particular procedure, together with how serious that harm could be.
Risk depends on context. Dilute hydrochloric acid has a lower risk when a few drops are added with a dropping pipette than when a burette is being filled above eye level, because the possible exposure is different. A hot tripod presents a lower burn risk while it cools in a designated place than if a student picks it up immediately after heating. It remains hot and must still be treated as a hazard.
A precaution is an action that reduces the chance of harm or reduces how serious the harm would be. Strong answers link the precaution to the risk:
- weak: "Be careful."
- better: "Wear safety goggles because dilute acid could splash into the eyes."
- stronger: "Fill the burette below eye level using a funnel because sodium hydroxide solution could splash from the top of the burette."
Model a Risk Evaluation
To evaluate a risk, work through four linked questions:
- What is the hazard?
- How could it cause harm in this exact procedure?
- How likely and how serious is the harm?
- What specific precaution would reduce the risk?
Here is a model for an acid-alkali titration using sodium hydroxide solution in a burette and dilute sulfuric acid in a conical flask.
| Step in the procedure | Hazard | Risk in this procedure | Suitable precaution |
|---|---|---|---|
| Filling the burette | Sodium hydroxide solution can irritate or damage skin and eyes | The solution could splash from the top of the burette, especially if it is filled above eye level | Fill the burette below eye level and wear safety goggles |
| Swirling the conical flask | Acid and alkali are being mixed | Liquid could splash out of the conical flask | Swirl gently and keep the conical flask on the bench |
| Reading the burette | Glass burette clamped vertically | The burette could fall or break if the clamp is loose | Clamp the burette securely before adding solution |
Notice the pattern: each precaution is matched to the hazard and the way harm could happen. "Wear PPE" on its own is too vague, because it does not say which risk is being reduced.
When reading a new procedure, consider the chemicals and apparatus, the quantities and concentrations, and how they will be handled. A familiar chemical can present a different risk when it is heated, sprayed or used in a larger amount.
Choosing Specific Precautions
A suitable precaution must change something about the procedure. It might reduce exposure, reduce the amount used, control the apparatus, separate the student from the hazard, or make the outcome less serious.
| If the risk is... | A suitable precaution is likely to... | Example answer shape |
|---|---|---|
| Liquid splashing into eyes | protect eyes or reduce splashing | "Wear safety goggles because the acid could splash." |
| Harmful gas being breathed in | reduce inhalation | "Use the approved small-scale quantities and good ventilation; a fume cupboard may be needed because sulfur dioxide can irritate the lungs." |
| Burns from hot apparatus | prevent touching hot equipment | "Use tongs and allow the apparatus to cool before handling." |
| Fire from a flammable liquid | keep fuel away from ignition sources | "Keep the alcohol bottle stoppered and away from the lit spirit burner." |
| Broken glass | make the apparatus stable | "Clamp the burette securely so it does not fall and break." |
| Electrical equipment near solution | reduce contact between liquid and electrical parts | "Use a low-voltage supply and keep the leads dry." |
Do not force every answer to include safety goggles. Safety goggles are often suitable for splashes, but they do not control inhaling a gas, a hot tripod, an unstable clamp, or a flammable fuel bottle. Likewise, "tie long hair back" is useful near flames, but it is not a good answer for a corrosive solution splashing during a titration.
Risks Across Specification Practicals
The specification expects you to apply risk evaluation across a range of practicals, including the Chemistry core practicals. You do not need a separate memorised safety paragraph for each one. You need to recognise the practical context and choose a precaution that fits.
| Practical context | Example risk to evaluate | Suitable linked precaution |
|---|---|---|
| Simple distillation of water or chromatography of inks | Distillation apparatus can cause burns; chromatography solvents may be flammable or irritating | Let hot distillation glassware cool; keep flammable chromatography solvents away from ignition sources |
| Adding calcium oxide or calcium hydroxide to dilute hydrochloric acid | Acid or alkaline powder can damage eyes; dust may be inhaled and reaction heating can cause splashes | Add small amounts with a spatula, stir gently, avoid raising dust, and wear safety goggles |
| Preparing hydrated copper sulfate crystals | Warm acid and copper sulfate solution can irritate skin or eyes; hot apparatus can burn | Use a water bath where required, heat gently, wear safety goggles, and handle hot apparatus with tongs |
| Electrolysis of copper sulfate solution | Copper sulfate solution could splash near electrical equipment; wet leads or contacts could make the setup unsafe | Use a low-voltage supply, keep leads and electrical contacts dry, and secure the electrodes before switching on |
| Acid-alkali titration | Acid or alkali could splash while filling or swirling | Fill the burette below eye level, clamp it securely, and swirl gently |
| Rate reaction with marble chips and hydrochloric acid | Acid could splash; gas pressure can build if apparatus is blocked | Use a suitable gas syringe or delivery tube setup and check it is not sealed in a way that pressure can build dangerously |
| Ion tests, including flame tests and gas tests | Flames, hot wires, irritating gases, corrosive reagents | Use a flame test wire carefully, keep hair and loose clothing away from flames, and do not inhale gases directly |
| Alcohol combustion temperature-rise practical | Alcohols are flammable; apparatus becomes hot | Keep fuel bottles stoppered and away from the flame, use a heatproof mat, and cap the spirit burner when finished |
Some precautions control more than one risk, but the answer still needs the link. For example, "use small volumes" is creditworthy when it reduces the amount of corrosive liquid that could splash or the amount of harmful gas produced. It is not creditworthy if it is written as a vague habit with no practical reason.
Evaluate and Suggest
Evaluating a risk means judging how likely or serious the harm is in the procedure and how a precaution reduces it. For example, a blocked gas outlet creates a greater pressure risk than a clear outlet; the control should address that blockage.
A linked explanation might read:
"The main risk is that sodium hydroxide solution could splash from the burette into the student's eyes while the burette is being filled. The student should fill the burette below eye level and wear safety goggles. This reduces the chance of splashing into the eyes and protects the eyes if a splash occurs."
Now try the skill more independently.
The best safety answers are usually short, but they are not generic. They name the hazard, describe the risk in the procedure, and choose a precaution that would actually reduce that risk.
Evaluate risk by linking hazard, possible harm, likelihood or seriousness, and a specific precaution matched to the practical procedure.