Energy TransferEARTH SCIENCE

• SC.6.E.7.1 Differentiate among radiation, conduction, and convection, the three mechanisms by which heat is transferred through Earth’s system.

Florida Benchmarks

• Density is the mass per unit volume of a substance.

• For example, a sandwich bag full of foam and a sandwich bag full of sand. Have different densities.

• Differences in density can cause movement in the atmosphere, water movement, and rock movement.

What is Density?

How is energy transferred by radiation?• Radiation is the transfer of energy as

electromagnetic waves.• EM waves do not need any type of material

to travel through.• The sun transfers energy to Earth by

radiation. For example, there is nothing but empty space between the Sun and the Earth.

• Radiation can transfer energy to objects that are not in direct contact.

Heat

How does the sun heat Earth?

How is energy transferred by radiation?

• The sun is almost 150 million km away but is the major source of energy for processes on Earth.

• Solar radiation can be reflected, scattered, or absorbed.

• Solar radiation is reflected mostly at the North Pole and South Pole because the ice caps reflect the Solar radiation like a mirror.

• Solar radiation is absorbed by the asphalt in a parking lot because the dark color absorbs the solar radiation.

Where does radiation occur on Earth?

How is energy transferred by convection?• Convection is the transfer of energy due to

the movement of matter.• Convection occurs because most matter

becomes less dense when it gets warmer.• Convection currents form as warm and cool

matter rise and fall due to temperature and density differences.

• Boiling water is an example of convection, hot water rises and as it cools the water sinks to the bottom of the pot.

Heating Up

• Energy moves through the atmosphere as warm air rises and cool air sinks. For example hot air balloon rises. This convection is responsible for most of our weather systems. Warm wet air rises up into the atmosphere rises and when the air cools, the air loses the ability to hold water and precipitation occurs.

• Ocean water has different densities due to temperature and the amount of salt in the water. For example, at the beach and as you swim in the water you feel cooler water at your feet. This convection is responsible for currents like the Gulfstream. The Gulf Stream influences the climate of the east coast of North America from Florida to Newfoundland, and the west coast of Europe.

Where does convection occur on Earth?

How is energy transferred by conduction?

• Conduction is the transfer of energy from one object to another object through direct contact.

• When objects touch, their particles interact.

• The greater the energy difference, the faster the transfer of energy by conduction occurs.

Ouch

• Energy can transfer by conduction from warm ground to cool air at Earth’s surface. Have you ever walked on the sand on a beach, how hot was it?

• Warm air can transfer energy to cooler water and cause evaporation. If water vapor transfers energy to air, the water vapor can condense.

• Energy can be transferred in rock by conduction, but very slowly. For example, when I was at the Grand Canyon, In the late afternoon the rocks were very hot to the touch.

Where does conduction occur on Earth?