SCIM1040 Lecture Notes - Lecture 3: Arboriculture, Tidal Power, Atmospheric Convection
5 Jun 2018
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SCIM1040- Lecture 3
Energy
People have learned how to change energy from one form to another so that we can do work
more easily and live more comfortably.
Energy is found in different forms such as:
➢ Light energy
➢ Heat or infrared energy
➢ Electrical energy
➢ Magnetic energy
➢ Sound energy
➢ Kinetic energy – energy of movement
➢ Gravitational potential energy – stored energy dependent on height
➢ Elastic potential energy – stored energy in materials as the result of stretching, twisting,
bending or compressing
➢ Chemical energy
➢ Nuclear energy
Temperature
the temperature of a small cup of boiling water is the same as the temperature of a large pot of
boiling water, even if the large pot of boiling water is much bigger (more mass) than the cup and
has millions and millions more water molecules.
The liquid (mercury or coloured alcohol) of the thermometer expands as temperature increases
and contracts as temperature decreases.
* Do not use mercury thermometers!!!
Heat
In reference to the temperature example, a large pot having a larger mass of boiling water and
millions and millions more moving water molecules, will have more heat energy BUT the same
temperature of 100°C.
Many different types of energy can be converted into heat energy. Light, electrical, chemical,
nuclear and sound can each cause a substance to heat up by increasing the speed of its moving
particles.
Reversible changes in heat are are physical changes where no new substance is produced, just
changes in state.
Heat may cause new substances to be produced e.g. when burning wood, cooking food, popping
corn, and frying an egg
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Methods of heat energy transfer
Conduction always occurs from a higher temperature object to one of a lower temperature.
Occurs as particles move faster and further apart so passing on their kinetic energy to other particles
by colliding with them, and hence transferring heat energy to adjacent molecules
Good conductors of heat are also good conductors of electricity because they have free electrons
that can move.
Occurs best in solids because the particles are closer together (tightly packed) more than liquids and
gases.
Most metals are excellent conductors of heat. e.g., copper, platinum, gold, iron.
Poor conductors of heat are called insulators. e.g., wood, glass, most plastics, air and water.
Convection
Examples of convection:
A room heater creates a convection current by warming air at the bottom which rises and cooler air
at the top sinks to the floor to replace the air that rose. The process continues making the room
warmer.
Land breezes (night) and sea breezes (day) are due to convection currents.
Atmospheric convection - produces winds.
Heating water in a saucepan.
Radiation
Examples of radiation occurring are:
Heat from the Sun warming your face.
Heat from a fire – when you stand in front of the fire, your front gets warm while your back is still
cool.
What is the electromagnetic spectrum
High energy gamma rays and X-rays are not received on Earth from stars but are made on Earth.
Light energy
We see planets and our Moon in our Solar System because they reflect light from the Sun to Earth.
We see objects on Earth because they reflect light to our eyes (or they make their own light such as
hot objects).
Lenses can also be used to bend light
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
People have learned how to change energy from one form to another so that we can do work more easily and live more comfortably. Energy is found in different forms such as: Gravitational potential energy stored energy dependent on height. Elastic potential energy stored energy in materials as the result of stretching, twisting, bending or compressing. The liquid (mercury or coloured alcohol) of the thermometer expands as temperature increases and contracts as temperature decreases. In reference to the temperature example, a large pot having a larger mass of boiling water and millions and millions more moving water molecules, will have more heat energy but the same temperature of 100 c. Many different types of energy can be converted into heat energy. Light, electrical, chemical, nuclear and sound can each cause a substance to heat up by increasing the speed of its moving particles.
