Question

Discuss the effects that heat has on matter. Give at least 5 Sentence

Answer 1

THE EFFECTS OF HEAT ON MATTER
Introduction
When heat is added to a body, various things can result:
• expansion
• increase in temperature
• change of state
• chemical change
The first three of these are physical changes which we will look at in more details
Expansion
When heat is added to a solid, the particles gain energy and vibrate more vigorously about their fixed
positions, forcing each other further apart. As a result expansion takes place. Similarly, the particles in
a liquid or gas gain energy and are forced further apart. The degree of expansion depends on the
substance.
For a given rise in temperature a liquid will expand more than a solid. Gases expand enormously on
heating, causing a possible explosion if the gas is in a confined space.
In a fire, the thermal expansion of steel beams, concrete and glass can cause considerable damage,
especially if expansion takes place at different rates, setting up stresses in the material or structure.
Liquids in drums and pans may overflow when heated. This is due to the fact that liquids expand at a
greater rate than solids.
Thermostats
The fact that different substances can expand by different amounts is used in some heat detectors in fire
alarm circuits, or as a switch in an electrical heating device.
A bimetallic strip is used which is made of two metals fixed together.
When the metals expand on heating, one expands more than the other causing the bar to curve. The
curved bar touches on electric contact and sets off the alarm
This can also be used to break and make electrical contact as the temperature rises and falls in ovens,
heater etc.,
Some automatic sprinkler heads operate when an expanding liquid breaks a bulb and releases the water
jet. These can be designed to operate at different temperatures.
Allowances need to be made for expansion and contraction due to normal variation in temperatures,
especially in large metal structures such as bridges, railway lines, power cables.
Solids expand in three dimensions, but very often only the change in length is important. To calculate