Risk assessment: hazards and matched controls
Key idea: Risk depends on both a hazardous property and the chance and severity of exposure. Choose precautions that interrupt the specific route to harm, using the supplied reagent and method information.
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Guided lessons · coming soon
Guided lesson
Guided steps
- Identify the hazardous property.
- Connect the hazard, exposure and risk.
- Match each precaution to the route it interrupts.
- Write the gas risk and two matched controls.
- Check the exposure route and gas controls.
- Explain why gloves and goggles leave an inhalation gap.
- Explain which hazards remain after removing the flame.
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ContinueA precaution is useful when it interrupts a credible route to harm. Link the hazardous property, possible exposure and control rather than attaching “wear goggles” to every experiment.
Check your understanding 1 Find the hazardous property
A solvent is flammable. Vapour could reach a nearby flame while it is poured. Identify the hazardous property, rather than the exposure event or a precaution.
Show answer
The hazardous property is flammability. Vapour meeting a flame is a route to ignition. Removing the flame interrupts that route, while other controls address other routes.
Hazard, exposure and risk
A hazard can cause harm: a corrosive solution, flammable vapour or hot glass. Assess risk by considering how likely exposure is and how serious the harm could be under the proposed conditions. A splash reaching the eye is a possible event; its likelihood depends on the quantities, handling and precautions.
Read the supplied hazard information and the school’s approved method. Controls must suit the reagent, concentration and operation. Plan precautions alongside the measurements, using the experimental-planning lesson.
Match a control to the route
| Hazard and possible harm | A relevant control | Risk that remains |
|---|---|---|
| Corrosive liquid splashes into eyes | Use splash goggles and a pipette filler; handle the approved small quantities carefully. | Goggles do not control inhalation of vapour. |
| Irritant powder is breathed in | Weigh the given small mass gently, without raising dust, in the specified ventilated area. | Goggles do not stop dust being inhaled. |
| Flammable vapour ignites | Remove ignition sources; use the approved water-bath method and ventilation if heating is required. | A flame-free heat source does not remove the vapour hazard. |
| Hot glass burns skin | Let it cool and use suitable handling equipment. | Glass that looks unchanged may still be hot. |
Check the disposal and emergency arrangements before starting. After a splash or spill, follow the school’s response procedure and alert the supervisor. Protective equipment complements containment and safe handling; it does not replace them.
Guided practice 1
Manage an inhalation risk
Problem
An experiment produces a small amount of a gas that must not be inhaled. State the risk and two matched control measures.
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Hints
Hint 1
route
Name how the gas could cause harm before choosing a control.
Hint 2
hierarchy
Contain the gas at source and reduce the amount that could escape.
Show solution step by step
State hazard and risk
Method
State that the gas is harmful by inhalation and may escape into the breathing zone.
Reason
A risk statement links the hazardous property to a credible exposure route.
Working
Answer
Hazard: harmful gas; risk: inhalation if released.
Control exposure
Method
Carry out the small-scale reaction in a functioning fume cupboard.
Reason
The cupboard removes escaped gas, while small quantities reduce the possible exposure.
Working
Answer
Control = fume cupboard + minimum practicable scale.
Quick check
Do not identify gases by smelling them. Observation and specified gas tests must avoid direct inhalation.
Check your understanding 2 Check the gas controls
For the harmful gas above, choose the exposure route, a ventilation control and a way to reduce the amount that could escape.
Show answer
Inhalation is the route. A functioning fume cupboard removes escaped gas, while a small approved scale limits the amount available. Gloves and goggles may still be needed for contact/splash risks, but do not replace ventilation.
Check that the precaution targets the hazard
Check your understanding 3 Assess a proposed control
A given reaction produces a harmful gas. A learner proposes gloves and goggles but no ventilation control. Explain the gap and a suitable change.
Show answer
Gloves and goggles protect against relevant contact or splash hazards, but they do not control gas entering the breathing zone. Use the school’s functioning fume cupboard and small scale; retain the other protection required by the reagents and school method. Do not identify the gas by smelling it.
Check your understanding 4 Evaluate a heating plan
A flammable solvent needs warming. A learner replaces a Bunsen burner with the approved water bath and says the experiment now has no risk. Explain why that conclusion is too strong.
Show answer
Removing the flame addresses one ignition source. Flammable vapour and hot apparatus remain hazards, so the approved ventilation, quantities, handling and other ignition controls still matter. Link each remaining hazard to a suitable control in your explanation.
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Syllabus and review details
- GCE A-Level H2 Chemistry 2027 · 9476-2027
9476 (2027), complete syllabus
Last reviewed: