Sources and Effects of Heat Energy

An electric fan does not rely on the principles of expansion and contraction for its operation.

Mercury is traditionally used in clinical thermometers due to its high coefficient of thermal expansion.

Air expands the most for the same rise in temperature because gases generally have higher thermal expansion coefficients compared to liquids and solids.

A bimetallic strip is used in an electric iron to control the temperature by bending due to differential expansion of the two metals.

The Sun is the main natural source of heat energy for the Earth.

Heat is a form of energy caused by the movement of atoms and molecules in a substance.

When heated, solids, liquids, and gases generally expand due to an increase in the kinetic energy of their particles.

When materials are cooled, they generally contract as the kinetic energy of their particles decreases.

Expansion gaps in railway tracks help avoid damage by allowing the tracks to expand and contract with temperature changes without buckling.

A bimetallic strip is used in thermostats to control temperature changes by bending due to the differential expansion of two different metals.

A bimetallic strip is made of two different metals bonded together, which have different coefficients of thermal expansion.

Iron and brass are commonly used in bimetallic strips because they have different rates of thermal expansion.

Brass expands more than iron, steel, and aluminum at the same temperature due to its higher coefficient of thermal expansion.

Riveting is a process that uses heat expansion to join parts by driving a rivet through them.

Fixing a metal tyre over a wheel uses thermal expansion to fit the tyre tightly onto the wheel.

An axle is fixed into a wheel by heating the axle, which causes it to expand and fit tightly into the wheel.

Water is densest at 4°C. Below and above this temperature, its density decreases.

Water at 0°C is less dense than at 4°C because it starts to form ice, which is less dense than liquid water.

Heat is a form of energy associated with the movement of atoms, molecules, and other particles.

Heat in a substance is caused by the random motion of its particles, which is a measure of their kinetic energy.

Heat flows from a region of higher temperature (hot) to a region of lower temperature (cold).

Thermal expansion is the increase in size or volume of a material as its temperature increases.

Gases show the largest thermal expansion because their particles are free to move and occupy more space as temperature increases.

When solids are heated, the vibrations of their particles increase, causing them to move further apart and leading to expansion.

When solids are cooled, they generally contract as the kinetic energy of their particles decreases, causing them to move closer together.

When heated, mercury in a thermometer rises because it expands and moves up the tube.

Expansion in gases is caused by increased collisions of particles, which leads to an increase in pressure and volume.

When gases are heated in a closed container, the pressure increases because the particles move faster and collide more frequently with the container walls.

Cooling causes the contraction of a substance as the kinetic energy of its particles decreases, leading to a decrease in volume.

When water is cooled from 4°C to 0°C, it freezes and expands, which is why ice is less dense than liquid water and floats.

Ice floats on water because it is less dense than liquid water. When water freezes, its volume increases, decreasing its density.

The riveting process uses thermal expansion of solids to join parts by heating and expanding a rivet to fit tightly.

Glass is not commonly fastened using rivets because it is brittle and can shatter under the stress of riveting.

A bimetallic strip bends when heated because the two different metals it is made of expand at different rates. Typically, brass expands more than steel.

Bimetallic strips are commonly used in thermostats to control temperature by bending and activating a switch.

When the bimetallic strip in an electric iron bends, it disconnects the heating element, thereby controlling the temperature.

The heat from a fire triggers the fire alarm using a bimetallic strip, causing it to bend and complete an electrical circuit that sounds the alarm.

Gaps are left between railway track sections to allow for expansion and contraction due to temperature changes, preventing the tracks from buckling.

Bridges are built in sections with gaps to allow for expansion due to temperature changes, preventing structural damage.

If bridges are not designed for expansion, cracks can appear due to the stress caused by thermal expansion and contraction.

Metal bridges are at risk of fracture due to expansion if not properly designed to accommodate thermal changes.

Cement structures can crack due to dehydration, which causes shrinkage and stress within the material.

Crack control joints help manage natural cracking in slabs by providing a weakened plane that allows cracking to occur in a controlled manner.

In cold weather, pipes can burst when the liquid inside freezes and expands, causing the pipe to rupture.

The property of liquids used in thermometers is their expansion on heating, which allows them to rise in a tube as temperature increases.

Mercury and alcohol are commonly used in thermometers due to their predictable thermal expansion properties.

When heated, the liquid in a thermometer rises in the tube due to thermal expansion.

The normal human body temperature is approximately 98.6°F.

Heating allows the mercury to rise in a thermometer tube due to thermal expansion.

The typical temperature range of a body thermometer is from 35°C to 42°C, covering the range of normal and feverish body temperatures.

Ethanol is commonly used in alcohol thermometers due to its suitable thermal expansion properties.

The alcohol in an alcohol thermometer is typically dyed red for visibility.

Alcohol rises in a thermometer when heated because it expands, causing it to move up the tube.

When the thermometer cools down, the liquid contracts, causing it to descend in the tube.