Topic 5 Energy

Energy is the ability to do work or cause change Kinetic energy: energy of motion  faster objects have more kinetic energy Temperature is a measure of how fast molecules are moving  hotter objects have more kinetic energy (molecules are moving faster) Absolute Zero: theoretically the lowest temperature possible; no energy is given off -273  C or 0 Kelvin

Potential energy: energy related to position or phase  higher objects have more potential energy Law of Conservation of Energy: Energy cannot be created or destroyed, it can only change form

Potential energy can be converted into kinetic energy to provide power

Electromagnetic Energy/Radiation Travels in transverse waves at the speed of light (3 x 10 8 m/s) Wavelength: distance from crest to crest Frequency: number of waves per second (bigger wavelength = lower frequency

The entire range of electromagnetic radiation (distinguished from one another by their wavelength) is called the electromagnetic spectrum

WHAT HAPPENS TO ELECTROMAGNETIC ENERGY (RADIATION) ONCE IT REACHES EARTH? Radiation is reflected – bounced back at the same angle they arrived Radiation is scattered – reflected/refracted in various directions Radiation is refracted - bent Radiation is transmitted – pass through the material Radiation is absorbed (taken in as heat energy)

Surface Properties light vs. dark smooth vs. rough

Energy Transfer 1) Radiation: transferred by EM waves through empty space

2)Conduction: energy is transferred by vibrating molecules All metals are good conductors (a material that is NOT a good conductor is called an insulator)

3) Convection: energy is transferred by movement of fluids due to differences in temperature and density

CONDUCTION – MOLECULES TRANSFER KINETIC ENERGY (KE) THROUGH VIBRATIONS OR COLLISIONS SOLIDS BEST FOR CONDUCTION MOLECULES CLOSE TOGETHER

Heat is infrared energy that flows from a warmer object or area to a cooler one In solids, the closer the molecules, the better they conduct heat In fluids, heat causes molecules to move faster and spread out, making them less dense and therefore the “heat” rises

Specific Heat Heat energy is measured in Joules: the amount of heat needed to raise the temperature of 1 gram of water 1  C Different substances heat up at different rates; the amount of heat needed to raise the temperature of 1 gram of a substance 1  C is its specific heat

Liquid water has a higher specific heat than all other naturally occurring substances; therefore, water heats up and cools down slower than equal masses of any other substance Heat = mass x ΔT x sp. Heat

Phases/States of Matter

 Increasing temperature requires the addition/ absorption of heat energy.  Decreasing temperature requires the release of heat energy.

Evaporation is when liquid becomes a gas below the boiling point Evaporation is a “cooling process” because the water absorbs heat from the surroundings, cooling it down

334 J/g2260 j/g

Latent Heat Latent heat is a form of potential energy gained or lost during a phase change What happens to temperature when you boil water?

Temperature does NOT change during a phase change! Solid  Liquid: Heat = mass x Heat of fusion Liquid  Gas: Heat = mass x Heat of vaporization