11. 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.

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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.

S

R

Q

P

(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 proof mat

Heat

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. @ 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 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. @ point P …..; then @ Q ; R; S etc.