Transcript Heat Transfer & The Natural Greenhouse Effect

HEAT TRANSFER &
The NATURAL GREENHOUSE EFFECT
TRAPPING HEAT
A “greenhouse” is any structure that is designed to take
in the sun’s energy and trap it as heat.
 The energy given off by the sun is called solar radiation.
 Some solar radiation is reflected back out of the
greenhouse but some of it hits surfaces within the
greenhouse and warms them up. These warm objects
warm up the air around them and the temperature of the
greenhouse goes up.
 The greenhouse is sealed so the warm air can’t escape
and the heat is trapped inside of it.

TRADITIONAL GREENHOUSE
The NATURAL GREENHOUSE EFFECT
Solar radiation strikes the Earth and one of two things
occur.
The energy is reflected by parts of the Earth back out
into space.

1.

Things such as clouds, ice and water are all capable of
reflecting solar radiation.
The energy is absorbed by areas on the Earth’s surface
and these surfaces become warm and heat up the air that
lies just above them.
2.

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The air becomes warm and the temperature goes up.
This warm air rises and the heat tries to escape into space.
GREENHOUSE GASES
Greenhouse gases are transparent (clear) gases that
allow the solar energy of the Sun through to hit the Earth
but do not allow the heat to escape.
 Its like a one-way door – light gets in but heat
can’t get out.

Greenhouse gases include carbon dioxide (CO2),
nitrous oxide (N2O) and methane (CH4).
 The most abundant of these gases in the atmosphere is
carbon dioxide. It is released in massive amounts through
combustion of fossil fuels such as coal, gasoline and oil.

The GREENHOUSE EFFECT
Albedo and Heat
The Earth reflects some light and absorbs other light. The
albedo of a surface is the percent of the incoming
radiation that is reflected. (It will determine if it heats up or
stays cool.)
 Objects that are duller and darker tend to have a higher
albedo than objects that are shiny and lighter in colour.
 Snow and ice have a much higher albedo than soil, open
water and forests.


Think of how “super bright” it seems to be outside
when you walk out of school on a winter day when
everything is covered in snow.
Thermal Energy Transfer


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Thermal energy is heat and the flow of heat is always
from the hotter object to the cooler object.
You can gain heat and lose heat but you do not
gain cold – that is the loss of heat.
Thermal energy is transferred from one object to
another in one of three ways:
1.
2.
3.
Radiation – the emission of energy as waves. (Example –
The suns energy reaches Earth as radiation.
Conduction – the transfer of thermal energy through direct
contact. (Example – An egg in a frying pan.)
Convection – the transfer of thermal energy through the
movement of particles. This method often involves liquids
and/or gases. (Example – Baking a cake in the oven.)
THERMAL ENERGY TRANSFER
THE END