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 20C 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-1C-1.

The word specific means ____________

What does it mean?

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?

When a cup of water at 20OC is mixed with another cup of water at 30OC, what is the final temperature ?

2020OOCC 3030OOCC+

1kg 2 kg

MixturesMixtures

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 waterHigh specific heat capacity of water

High specific heat capacity of waterHigh specific heat capacity of water

Living organismsLiving organisms

• Living ____________ contain a high proportion of water

• Water helps maintain a __________ body temperature when environmental temperature changes rapidly

High specific heat capacity of waterHigh specific heat capacity of water

Climatic effectsClimatic 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 waterHigh specific heat capacity of water

Water as a coolantWater 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.