Physics

Chapter 4

HEAT

Knowledge – Part A

• What is meant by

heat?

temperature?

thermal equilibrium? ( the characteristics)Specific heat capacity?Latent heat of fusion or vaporisation?

Knowledge – Part B ( formulae)

• Q = Pt

• Q = mcө

• Q = ml

• Student will be ask the meaning of each of symbols and which situation to apply for each of this formula.

Understanding

• Graph of temperature against time

( Heating / cooling curve)T/oC

t/ minutes

Q = mcө

Q = mcө

Q = ml

Q = ml

Solid state

Solid liquid

Liquid gas

liquid state

gaseous state

Q = mcө

Stress on the change of temperature ( Q = mcө)Constant temperature ( Q = ml)Phase changesReminder that Q = Pt

Understanding• Sea breeze

i. The specific heat capacity of land is lower than that of sea.

ii. During daytime, the air above land is hotter than the air above the sea.

iii. Since hot air is less dense than cold air, it rises upward.

iv. Cool air from the sea, known as sea breeze then flows to land replacing the hot air.

A similar picture featuring land breeze is given and student is asked to explain the phenomenon as shown above.

Understanding

• Importance of low specific heat capacity and high capacity.

Low c , conductor, for cooking utensils ( made from metal), heats up faster, bigger change in temperature.

High c, insulator, for pot handle ( made from wood, plastic), store more heat, slower change in temperature.

This will help to answer question on decision making ( paper 2 section C )

e.g. to choose a cooking utensil material with low c is chosen because of it heats up

faster. material with low density is chosen because it is

lighter making it more portable.

Paper 3

A. Reading of a thermometer. Given diagrams of thermometers taken at different

time , the student is able to read and write down to correct decimal places and units for each of these diagrams.

B. Tabulate data : Refer to construct 3 in PEKA Physics

C. Transferring of data or plotting of graph. Labeling of axes with symbols and units Correct scale Transfer the data accurately Drawing of a best fitted/smooth line/ curve

D. Information from the graph State relationship between variables Calculate gradient and write down the units. Show how to get the values of y for given values of x

and vice versa. (using dotted line) Extrapolation of graph.