CSEC Physics Syllabus - Effective for examinations from May - June 2015
Section B - Thermal Physics and Kinetic Theory
Macroscopic Properties and Phenomena
Phases of Matter
Specific Objective 2.6
distinguish among solids, liquids, and gases;
Specific Objective 2.7
use the Kinetic theory to explain the different macroscopic properties of solids, liquids, and gases;
Expansion
Specific Objective 2.8
explain observations of the effects of thermal expansion;
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Example 1
Explain in terms of the kinetic theory of gases:
a) how the air inside a bicycle tire keeps the tire inflated and hard, and can support the weight of the cyclist
b) how the pressure in a car tire increases and the tires get hot when the car is driven fast.
Solution
The Kinetic Theory of Matter states that matter is made up of tiny particles and these particles are in constant motion. For gases, these particles have the most kinetic energy, are spaced further than solids and liquids, and are in constant motion; colliding with each other and their container.
a) The air inside the bicycle tire keeps the tire inflated, hard, and can support the weight of the cyclist due to the pressure. The air particles occupy the entire space of their container, the tire. They constantly bombard the inside walls of the tire and each other producing an air pressure inside the tire. Recall, Pressure is the force applied to an object over a specific area; therefore, when the air particles collide with the inside walls of the tire, they exert a force on an extremely small area producing air pressure in the tire. This pressure is sufficient enough to keep the tire inflated, hard, and support the weight of the cyclist.
b) The pressure in a car tire increases
Example 2
Explain why:
a) the glass surrounding the bulb of a thermometer is thin even though this makes it fragile
b) the mercury level inside the capillary tube will not immediately rise to its final steady level when a thermometer is first placed in a warm liquid
c) an alcohol-filled thermometer might be preferred to a mercury-filled one by an Arctic explorer
d) in a clinical thermometer the bulb is not quite full of mercury at room temperature.
Solution
a)
Example 3
A lump of ice, wrapped in a piece of copper gauze, is weighted down in a test tube of water as seen in the figure below. Explain how the water can be heated to the boiling point at the top of the tube without the ice melting.
Solution
Example 4
a) A glass stopper is jammed inside the glass neck of a bottle. Explain why running hot water over the bottle's neck may help to loosen the stopper.
b) Explain why a glass bottle is likely to crack if very hot water is poured inside it when the glass is cold.
Solution
a)
Example 5
The figure below shows a device that switches off a domestic appliance when it reaches the desired temperature.
a) What is this device called?
b) Name TWO domestic appliances that make use of this device.
c) What electrical property must material Z possess?
d) What materials could be used for X and Y?
e) Explain why bending occurs when the device is heated.
Solution
a)
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