# Melting and Boiling

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```					11. Melting and Boiling

Scientific Enquiry Question
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.
110
temperature                         SS
100      in ºC

90

80

70

60

50                                 RR

40

30

20

10
Q
Q
0
15
–10   P                 time in minutes
P
–20

–30
(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?
___________________________________________
(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
___________________________________________
___________________________________________
___________________________________________
(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
______________________________________
______________________________________
______________________________________
______________________________________
(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.

Thermometer

Ice

Beaker
Gauze

Tripod
Bunsen burner
Heat
Heat proof mat
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
How could you test the water for impurities?
Put the pattern seen in the graph into words
i.e. @ point P …..; then @ Q ; R; S etc.
Extension Work:
Notice the temperatures MINUS 20 and PLUS
102 !!
Can you explain what is going on? No
thermometer.

How could you test the water for impurities?

Put the pattern seen in the graph into words
i.e. @ point P …..; then @ Q ; R; S etc.

```
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 views: 19 posted: 6/13/2012 language: pages: 9