School
laboratories can be hazardous places. A risk assessment should
be carried out before every experiment.
A risk assessment looks at the hazards and how they can be reduced
to acceptable levels. Information on hazards can be found in books
or from safety cards.
Effect of acid on magnesium
Put a piece of magnesium ribbon into a boiling
tube
Measure out 30cm3 of dilute hydrochloric
acid and add it to the boiling tube.
Observe the reaction and test the gas given off
with a lit wooden spill.
Risk assessment Look at the experiment and decide on what precautions
should be taken to make the risks acceptable. Roll over the headings
to see the answers.
Hydrochloric acid
May cause burns and irritation if in contact with
skin, mouth or eyes.
Magnesium
Metal is flammable, especially if in powder form.
Hydrogen
Flammable gas formed during the reaction.
Wooden spill
Flame as a source of ignition.
Hydrochloric acid
Wear lab coat and safety glasses to protect from splashes.
Use acid from a bench-top bottle. Place boiling tube in
a rack. Take care when measuring out acid. If acid comes
into contact with skin or mouth, wash out immediately with
lots of water.
Magnesium
Use no more than 3cm of magnesium ribbon and do not place
directly into any flame.
Hydrogen gas
The amounts of hydrogen produced are very small and are
highly unlikely to pose a real danger.
Take care with the lit wooden spill and test the gas at
arms length.
Make the assessment
You must decide if you can do the experiment
safely. If the hazards are reduced and the right precautions taken,
does the experiment seem to be too risky or not?
Do a risk assessment for all your experiments
and you should be safe in the laboratory.