TOPIC 5

What is electromagnetic energy?

• Electromagnetic energy is a type of energy that is radiated, or given off, in the form of transverse waves from all matter that is not at absolute zero.

• Absolute zero – 0 Kelvin or -273° Celsius is the lowest possible temperature at which particles of matter have no motion. The higher the object’s temperature the more electromagnetic energy it will give off.

• Electromagnetic energy is distinguished by different wavelengths (Electromagnetic Spectrum pg. 15 ESRT)

What happens when energy waves come into contact with a material?

• Refract – or bent; as the energy passes through a materials of different densities, the direction of the wave is changed.

• Reflect/Scatter – when the energy bounces off the material and gets sent in various directions.

• Transmitted – when the energy passes through a material.

• Absorbed – when the energy is taken into the material.

How does texture and color affect amount of electromagnetic

energy being absorbed?

• Texture (roughness or smoothness) of a surface affects the amount of electromagnetic energy being absorbed.

• The rougher the surface the more energy it will absorb and the less it will refract.

• The darker the color of the surface the more energy it will absorb.

• Ex: Black surfaces – asphalt roads.

How can energy be transferred?• Energy moves from a region of high concentration

(source) to a region of low concentration (sink). Transfer of energy of a higher temperature to a lower temperature is called heat energy. Heat transfers can be accomplished in three different ways:

• Conduction – the transfer of heat energy from atom to atom or molecule to molecule when the vibrating particles collide. Occurs most affectively in solids.

• Convection – The transfer of heat by movement in fluids (gases and liquids) due to different densities. This creates convection currents – a circulatory motion.

• Radiation – The transfer of heat via electromagnetic energy. No medium is needed for the transfer. Sunlight is transferred this way.

What is transformation of energy?

A transformation of energy is the changing of one type of energy into another type of energy.

What are different ways energy can be transformed?

• Energy can be transformed in the following ways:

• Kinetic energy (energy a moving object has) into heat energy. Ex: Rubbing your hands together creates heat.

• Kinetic energy into potential energy (energy an object posses when not moving – stored energy). Ex: A moving car coming to a stop.

• Potential energy into Kinetic energy. Ex: A bolder sitting at the top of a cliff suddenly falls off.

What is mechanical energy?

Mechanical energy is the total amount of potential energy and kinetic energy

How is temperature related to kinetic energy?

• Temperature is a measure of the average kinetic energy of the particles in a body of matter.

• The greater the temperature the greater the average kinetic energy.

What is heat energy?

• The type of energy that is transferred from hotter to colder objects.

• It is measured in a unit called a Joule (quantity of heat needed to raise the temperature of one gram of liquid water by one degree Celsius.

What is specific heat?• The quantity it of heat needed (Joules) to raise the temperature of one gram of any substance one degree Celsius is called specific heat. (ESRT front cover)

• In simpler terms, specific heat is the resistance a material presents to heating up or cooling off. In other words, a material with a high specific heat takes a long time to heat up and a long time to cool off (visa versa).

An increase or decrease in energy and temperature can cause a material to change its state. What are the types

of changes of state?

• Melting – the changing of a solid into a liquid.

• Solidification (freezing) – the changing if a liquid into a solid. If the atoms are arranged in a pattern it is called crystallization.

• Evaporation (vaporization) – the changing if a liquid into a gas.

•Condensation – the changing of a gas (vapor) into a liquid.

•Sublimation – the changing of a gas directly into a solid or a solid directly into a gas without going through the liquid state. Ex: Dry Ice

What occurs as a material changes its state?

• When a material changes its state the temperature remains the same, because any energy being added to released in the system is being used to change states.

• When a substance goes from a solid to a liquid or a liquid to a gas the substance must gain heat.

• When a substance goes from a gas to liquid or a liquid to a solid, the substance must lose heat.

What is the related amount of energy used to change water into different states (ESRT front cover)?

• To change a solid into liquid water (melting), the energy that is gained is 334 Joules/gram

• To change a liquid into a solid (freezing), the energy that is released is 334 Joules/ gram

• To change a liquid into a gas (vaporization/evaporation), the energy that is gained is 2260 Joules/gram

• To change a gas into a liquid (condensation), the energy that is released is 2260 Joules/gram