Convection

LESSON 3

Energy Transfer

Conduction

Convection

Radiation

energy can be transferred in three ways

MRSTAV

Conduction

Conduction is the transfer of thermal energy through contact between substances

• the substances need to be in direct contact in order �for the energy to transfer

MRSTAV

Convection

• convection is the transfer of thermal energy through circulating currents in a fluid

MRSTAV

Heating Water In A Pot

• the bottom of the pot is in direct contact with the element on the stove
• heat energy from the element is transferred to the pot and then to the water at the bottom of the pot through conduction
• the water that heats at the bottom of the pot starts to move faster and the particles move farther apart
• the hotter water becomes less dense and starts to rise
• as the less dense water rises, it starts to cool
• as it cools it becomes more dense and starts to sink again
• this creates a convection current that cycles through the fluid

MRSTAV

Heating Water In A Pot

1. Particles at the bottom get heated first
2. Addition of heat = increase in movement
3. Colder particles fall (they’re more dense) and fill those spaces
4. Those particles then get heated
5. Those heated particles = increase in movement

MRSTAV

Convection

CONVECTION CURRENT

HOT WATER (less dense)

RISES

COOLER WATER (more dense)

SINKS

MRSTAV

GEOLOGY

Convection In The Geological Processes

• the mantle is warmed by the core of the earth
• the warmer mantle is less dense and rises towards the crust
• near the crust, it cools and start to sink down again
• this creates a convection current
• the movement of the mantle underneath the plates of the crust results in plate tectonics

​

Crust

MRSTAV

HEAT SINK

Heat Sink

• because of its high heat capacity, water acts as a heat sink
• a heat sink is something that absorbs heat but does not heat up much as a result
• this also creates convection currents called sea (or lake) breezes and land breezes

water absorbs HEAT, but doesn’t heat up much

MRSTAV

During the day, the sun shines on the land and the water

​

• the land (lower heat capacity) heats up quickly
• the water (higher heat capacity) heats up slowly

​

• the air over the warm land rises, creating a low pressure zone which
• the cool air from the water fill in (creating the breeze)

WARM AIR

LOW PRESSURE ZONE

COOL AIR

During the night, the sun stops shining

​

• the land (lower heat capacity) cools down quickly
• the water (higher heat capacity) cools down slowly

​

• the low pressure zone is now above the warmer water, and this creates a breeze coming from the land

COOL AIR

LAND BREEZE

WARM AIR

LOW PRESSURE ZONE

• Places that are located close to large bodies of water have higher temperatures �in the winter �and lower temperatures in the summer

Compare the climate of Vancouver to the climate of Toronto