11' Melting and Boiling

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11. Melting and Boiling

• Scientific Enquiry Question

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• Raj wanted to investigate melting and boiling.
• He set up his apparatus safely and put on his
  safety glasses.
• The teacher put some crushed ice into the
  beaker.
• Raj put the thermometer into the ice.
• He lit the Bunsen burner so the beaker was
  heated gently.
• The graph shows how the readings on the
  thermometer changes.

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S
R
Q
P
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• (a). (i). Write a suitable title for the graph
• ___________________________________________
• (ii). What are the dependent and independent
  variables in this experiment?
• D.V. is ____________________________________
• I.V. is _____________________________________
• (iii). Using the graph for help how long did
  the experiment take? ____________________________
  
• (iv) What are the maximum and minimum
  temperature recordings on the graph?
• _____________ and _______________
• (v). What was the total temperature rise?
• ___________________________________________

Graph to show how temperature changes over time
when heated by a Bunsen
The temperature of the ice/water
Length of time the Bunsen is on for
15 minutes
Max 102 oC
Min -20 oC
122 oC
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• (b) Which letter on the graph shows
• (i) ice melting? ______ (ii) water boiling?
  ________
• (c) During the experiment, the beaker and its
  contents were quickly removed from the heat and
  weighed on a balance at the following times 0,
  5, 10 and 15 minutes
• (i) At which two times would you expect the
  readings on the balance to be the same?
• __________ minutes and __________ minutes
• (ii). Use scientific reasons to explain why they
  would be the same
• ___________________________________________
• ___________________________________________
• ___________________________________________

S
Q
5
0
Ice is melting at low temperatures with no loss
in mass. At higher temperatures water will start
to evaporate and during boiling water vapour is
lost to the atmosphere.
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• (d). Between which two of these times was the
  mass of the contents of the beaker changing most
  rapidly?
• __________ minutes and __________ minutes
• (ii). Use scientific reasons to explain why
• ______________________________________
• ______________________________________
• ______________________________________
• ______________________________________

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10
Steepest part of the graph. When melting the ice
the heat energy is being used to overcome the
forces holding the particles in their
crystal lattice (latent heat) so the temperature
does not go up. After 5 minutes the ice has all
melted so the heat energy is all transferred to
the water particles. When it starts to boil the
energy is used to by the particles to leave the
liquid and become a gas so the temperature no
longer goes up.
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• (e). Draw the equipment (with labels) to show
• how this experiment would be set up to work.
• Add very brief notes to point out any safety
• worries or hazards to be aware of.

Apparatus should be in centre of bench. Goggles
worn. Care with thermometer. Safe handling of
Bunsen. Hot apparatus
Thermometer Ice Beaker Gauze Tripod Bunsen
burner Heat proof mat
Heat
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• Coaching Notes
• What changes of state are we looking at?
• What is melting/freezing boiling/evaporating?
• What temperatures does pure water boil/melt?
• What safety issues?
• Read off data from the graph
• Time 0 mins Temperature is ?
• 2 ?
• 4 ?
• 6 ?
• 8 ?
• Extension Work
• Notice the temperatures MINUS 20 and PLUS 102 !!
• Can you explain what is going on? No mistakes
  have been made reading the thermometer.
• How could you test the water for impurities?
• Put the pattern seen in the graph into words
• i.e. _at_ point P .. then _at_ Q R S etc.

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• Extension Work
• Notice the temperatures MINUS 20 and PLUS 102 !!
• Can you explain what is going on? No mistakes
  have been made reading the thermometer.
• How could you test the water for impurities?
• Put the pattern seen in the graph into words
• i.e. _at_ point P .. then _at_ Q R S etc.