9.3- Energy transfer in air and water

Heat transfer

Heat transfer = the movement of thermal energy from area of higher temp. to area of lower temp.

Heat transfer can occur by1. Radiation2. Conduction3. Convection

Recall

Energy from Sun

UV radiationHigh energyVisible lightInfrared radiation

Low energy

Heat transfer by radiation

• Radiation= emission of energy as waves

• When Sun’s radiation reaches Earth, matter such as land, water or air are heated up

• Warmed matter then - transfer its heat to cooler matter - Or re-emits heat as infrared radiation

Heat transfer by conductionConduction = transfer of heat through direct contactUsually takes place in solid

Think of domino effect:

During conduction, hotter particles pass their energy on to cooler particles in the solid

Notice particles do NOT move to the new location. They stay put.

Heat transfer by convection

Convection = transfer of heat through movement of particles

Usually occur in fluids (liquids and air)

During convection:

- Heated water rises to the top, forming an upward convection current

- The hot water contacts cooler air at the surface

- This hot water cools and sink to the bottom, forming a downward convection current.

Heat transfer summary video:https://www.khanacademy.org/partner-content/mi

t-k12/mit-k12-physics/v/heat-transfer

Energy transfer in the atmosphere

• Energy absorbed by atmosphere is unevenly distributed

Air at equator is warmer

Air at higher latitude is cooler

Energy transferred in the atmosphere by convection currentAir at equator heated upBecome less denseRises above colder airColder air is more dense; thus, sinks pushing the hotter air upwardsHot air then spread out towards the poles & cool down

• Ocean currents driven by 3 factors:

1. Prevailing winds

2. Convection3. Uneven concentration of salts in ocean water

Energy transfer in the ocean

creates surface currents moving warm water

creates deep currents

Thermohaline circulation: the continuous flow of water in ocean because of the differences in water temperature

and salinity (salt level)

If this conveyor belt is disrupted, the climate will change

Thermohaline circulation

• Warm surface water moves towards the poles as it gets

- colder & - saltier due to evaporation of water and sea ice

formation

• Colder, saltier water sinks to ocean floor• Warmer surface water flows from equator to the

poles to fill in the space for colder, saltier water

Video conveyor belt

• http://www.youtube.com/watch?v=FuOX23yXhZ8 (NOA)

• http://www.youtube.com/watch?NR=1&v=SdgUyLTUYkg&feature=endscreen (One ocean)

• http://www.youtube.com/watch?v=02NRKzemXYE (Al gore)

Learning check

1. Which of the following has the highest capacity for storing thermal energy?

a. air b. metalc. large body of water (ocean) d. land

2. Which of the following is the most effective heat sink?a. air b. metalc. large body of water (ocean) d. land

3. Compared to inland regions, the climates of regions close to oceans and large bodies of water tend to be b. colder in winter and warmer in summer c. milder in winter and cooler in summer

P334-339 textbook