Thermal Energy Transfer

Thermal Energy Transfer• Thermal Energy – Energy created by the

movement of particles in a substance.

• Heat: Thermal energy that is transferred from one object to another

Three types of heat transfer:• Conduction

• Convection

• Radiation

• Requires contact between atoms; more energetic atoms collide with less energetic atoms and energy is transferred (solids with solids)

• Example: Warming a pot on a stove

Types of Energy Transfer - Conduction

• In a gas or liquid, atoms are free to move and as they warm they become less dense and rise. Atoms that are cold and denser will then descend and create a convection current. – (liquids/gas)

Types of Energy Transfer - Convection

• Energy is transmitted as photons (electromagnetic radiation)

• Ex. UV light, visible light, infrared light…• Think: The Sun!

Types of Energy Transfer - Radiation

• Video – Radiation , Conduction and Convection

Think about it!• What happens to hot air? Why?• Hot air rises because it is less dense.

• What do you think creates wind? • The unequal warming of the air creates

wind. Warm air (that is less dense) rises and replaces cold air (which is denser). Cold air descends to create a movement of air (convection current).

• Atmospheric Pressure – the pressure exerted by air on its surroundings due to the weight of the air

• Measured in kilopascals (kPa)• At sea level, the atmospheric pressure is

101.3 kPa (or 1 kg/cm3)

Atmospheric Pressure

Three factors that can reduce atmospheric pressure:

• Altitude – The higher you go, the pressure decreases

• Temperature – When warm air pushes into a cold air mass, pressure decreases. When cold air pushes into a region of warm air, the atmospheric pressure in that location increases.

• Humidity – The more water vapour in the atmosphere, the more the air is light (so more humidity = less pressure)

• Video – Atmospheric Pressure

• http://www.youtube.com/watch?v=jmQ8FWnM0fA

• As your altitude _____________, the density of the air _______________. Therefore, the atmospheric pressure _________________.

Layers of the Atmosphere

See Figure 1.8, page 19

Foldable• Figure 1.8 on page 19 has been copied for

you. Please cut along the dotted line only to create flaps that can be opened (you will record notes under these flaps) Glue along one side to place the diagram into your notes.

• The next few slides will review the layers of the atmosphere. You will record these notes under each flap.

Layers of the Atmosphere• Troposphere

– All water vapour is present here– All weather occurs here– From surface to ~10km– Temperature ranges from -50°C to 50°C

• Stratosphere– Ozone is present here– From 10km-50km– Temperature ranges -50°C to -30°C

Layers of the Atmosphere

Layers of the Atmosphere• Mesosphere

– Meteorites burn up here– Some ions are present here– From 50km to 85km– Temperature ranges from -30°C to -90°C

• Thermosphere– Aurora present– Some ions are present here– From 90km to 180km (space)– Temperature ranges from -90°C to over 200°C

Layers of the Atmosphere

• The movement of air at different ___________ also has an effect on atmospheric pressure. When ______ air pushes into an area of ______ air near the ground, the atmospheric pressure in that location ________. When ______ air pushes into a region of _______ air, the atmospheric pressure in that location ________.

• Video – Layers of the atmosphere

• http://www.youtube.com/watch?v=WaikvaAw2nk

To Do:

• Page 20 #5-8• Read page 20 and record definitions and

any important notes on humidity, specific humidity, relative humidity and dew point.

Answers page 20 #5-85. Thermal energy is transferred in the

atmosphere through radiation, convection, and conduction.

6. Radiation of thermal energy from Earth’s surface is the main method of heating air close to the surface.

7. Atmospheric pressure is caused by pressure exerted by the mass of air above any point on Earth’s surface.

8. Increasing temperature, humidity, and altitude