The energy involved in change of state
4 marks · NormalYou are asked to investigate the melting of naphthalene in the laboratory.
List two pieces of equipment you need to measure the temperature at fixed time intervals as naphthalene melts.
Explain one safety precaution you should take when carrying out this investigation.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) Thermometer and stopwatch (or data logger).
(b) Heat naphthalene in a water bath, not directly, as it is flammable. Or: Wear safety goggles to protect eyes from splashes.
Also accept: Data logger; Use of goggles as safety
Common mistakes: Failing to mention indirect heating; Giving an irrelevant safety
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Identifies thermometer as equipment for measuring temperature
B2 (a) · 1 mark · Identifies stopwatch or timer for timing intervals
B3 (b) · 1 mark · Names or explains a relevant safety precaution (such as use of water bath for flammable naphthalene)
B4 (b) · 1 mark · Safety precaution is accurate and relevant to naphthalene melting
Worked solution
a) You need a thermometer to measure the temperature as naphthalene melts, and a stopwatch (or timer) to record each time interval.
b) Naphthalene is flammable, so it should be heated in a water bath rather than directly with a Bunsen burner. Alternatively, wear goggles to protect your eyes from hot materials.