Unit 3 - Heat Energy.

Lesson 1 : Heat and Temperature

Heat and Temperature
Heat is a form of energy , it can make things hot and it can do
work . Most of the heat on Earth comes from the sun .
Temperature is the movement of molecules in matter  kinetic energy
The molecules of matter move faster when it’s hot and slower
when it’s cold. Temperature is degree of hotness or coldness.
Temperature is measured with a thermometer

Heat is transfer of thermal energy from hot objects to cold objects.
Heat is the amount of molecules and their speed.

Sources of Heat Energy
The Sun
Friction
Fire
Electricity
Bending metals
Chemical reaction
Collision

Temperature and absolute zero
When an object gets hot, the molecules inside it move faster .
When it gets colder the molecules move slower .
Absolute zero is when the molecules stop moving - 0 K [Kelvin].

Celsius - Most common temperature scale worldwide:
 Freezing point of water is 0 o
C.
 Boiling point of water is 100 o
C.
Fahrenheit - The temperature scale used in the United States.

Temperature scale conversion
CK Tk = Tc + 273.15
CF TF = Tcx 9/5 + 32
KF TF = Tkx 9/5 − 459.67btopic

Heat flow
Heat is the flow of energy from warmer objects to colder objects because of
difference in temperature.
Heat only travels from a hotter place to a colder place.

Heat
travels by
Conduction

Convection

Radiation Fluids = liquids and gases

Conduction of Heat
The heat moves between the atoms.
Metals are good conductors of heat – their electrons can move.
Non-metals are heat insulators – poor conductors of heat.
Their electrons cannot move.c

Convection of Heat
Convection: The way heat energy move through fluids .
(Fluids = liquid or gas)
When fluid particles are heated, they move faster and further from each other.
The heat moves with the molecules.

Radiation of Heat
Radiation: Objects release heat energy as infrared radiation.
Hotter object releases more radiation.
Radiation can move through the vacuum of space.
Radiation passes by electromagnetic waves
(Unlike conduction and convection).
This is why we can feel the heat of the sun
although it is 150 million km away from Earth.

Most matter expands when heated and contracts when cooled.
The molecules push each other when heated  causes expansion

Heat Expand
Cool Contract

Different liquids expand / contract by different amounts.
Alcohol expands more than olive oil at the same temperature.
Olive oil expands more than water at the same temperature.

Heat expansion / contruction in Solids (metal) The metal ball can pass through the ring before heating.
The metal ball cannot pass through the ring after heating.
The metal ball can pass through the ring when it is cool again.

The water cycle During the day, the sun heats the Earth’s surface.
Some of the energy causes water from the sea to evaporate
and form clouds .

When the clouds condense due to cold

temperatures, we get rain .

Sea breeze - During the day the land gets hotter faster than
the seawater. The air above the land expands and rises.
cooler air from the surface of the sea flows to the land to replace this air.
The wind from the sea is called sea breeze .

Land breeze – During the night , the land gets cooler faster
than the sea. The air above the sea rises while cooler air from the
land flows to the sea to replace this air.
The wind from the land is called land breeze

The effects of the sun’s radiation vary depending on the type of surface.
In this investigation, you will compare the effect of heat absorption and
radiation on objects of different colors and reflectivity. You will then
investigate absorption and radiation on several types of surfaces: land,
represented by soil; ocean, represented by water; and urban areas,
represented by concrete.

The higher the temperature of the object, the higher the amount and more energetic the radiation it emits. A cool object still radiates energy but less than a hot object. Consider your hands as being warmed by the infrared radiation from a lamp for example. Though your hands also radiate energy, the lamp radiates energy to your hands at a much higher rate and thus your skin has a net gain in energy and an increase in temperature.

The appearance of a surface determines its rates of emission and absorption of radiation. In general, shiny coloured (e.g. white or silvery) and metallic surfaces emit or absorb radiation energy slowly since they reflect the radiation. Dark coloured (e.g. black) surfaces emit or absorb radiation energy more effectively. It is interesting to note that a good emitter of radiation is also a good absorber of radiation and vice versa.