Define Celsius Scale
Reading of thermocouple thermometer:
At 100oC the current is 68 mA
At 0oC the current is 0 mA
Now the current is 52 mA, what is the
corresponding temperature?
Find the unknown temperature 
Define heat capacity C (h.c.)
Define specific heat capacity (s.h.c).
Explain the meaning of s.h.c. of aluminium
900 Jkg-1oC
What is the heat capacity of a pot
of soap if 640 000 J of energy is
needed to raise its temperature
from 20C to 100 C?
Define power
Kilowatt-hour is a unit to measure __________
1kWh
= ___________ J
By experiment, the s.h.c. of water is 4200 Jkg-1C1.
What does it mean?
The word specific means ____________
Calculation of Energy
The power of an electric heater is 2500 W.
How much energy generated by this heater in
half an hour?
An experiment is carried out to measure the
heat capacity of a copper block.
The initial reading of the joulemeter is 215
100 J and the final reading is 220 830 J. The
temperature of the block rises 15ºC.
(a)
What is the heat capacity of the block?
(b)
State one assumption made in the calculation.
The power of a florescence tube in classroom is
about 60W. There are 5 florescence tubes in
classroom.
How much electrical energy is used in one
period of time (50 minutes) in Joule and in
kilowatt-hour?
If the cost of 1 kWh is about $0.6, what is the
cost of electrical energy for 1 period of lesson?
Mixtures
When a cup of water at 20OC is
mixed with another cup of water
at 30OC, what is the final
temperature ?
20OC
1kg
+
30OC
2 kg
High specific heat capacity of water
s.h.c. of water = 4200Jkg-1OC-1
The high specific heat capacity of water will cause the
following consequences:
• it stores a large amount of ______ when it is heated up
• it gives out a large amount of _______ when it cools
down
• it heats up or cools down more slowly than other liquids
High specific heat capacity of water
Living organisms
• Living ____________ contain a high
proportion of water
• Water helps maintain a __________ body
temperature when environmental
temperature changes rapidly
High specific heat capacity of water
Climatic effects
• The land heats up very fast during the day
than the sea because the ______________ of
soil is much less than water.
• The sea cools down more slowly than the _____
during the night.
• The average summer and winter temperature
in ___________ vary less than inland areas.
High specific heat capacity of water
Water as a coolant
• Materials used for cooling are called ________
• For example, water is used in a ________ to
cool a car’s engine, in large air _____________
1. How much energy is needed to heat 100g of water
from 10OC to 30OC ?
2. 60000J of energy is transferred to 3kg of copper
initially at 20OC.
Find the final temperature of the copper.
3. A 2-kW electric heater supplies energy to a 0.5-kg
copper kettle containing 1kg of water.
Calculate the time taken to raise the temperature
by 10OC.