Energy and Heat Transfer

Forms of Energy

• Kinetic Energy: Energy of movement.

• Gravitational Energy: Energy stored in objects at a height.

• Elastic Energy: Energy stored in stretched objects (e.g., a spring).

• Chemical Energy: Energy stored in chemicals (e.g., fuels, batteries, food). Released by chemical reactions.

• Heat Energy:

• Light Energy:

• Sound Energy:

• Electrical Energy:

Energy Transformation: Energy always changes from one form to another.

Convection

• Liquids and gases expand when heated.

  • Particles in liquids and gases move faster when hot.

  • As a result, particles take up more volume.

    • The gap between particles widens, while the particles themselves stay the same size.

  • The liquid or gas in hot areas is less dense than the liquid or gas in cold areas, so it rises into the cold areas.

Conduction and Convection

• Thermal Conductivity: How good a material is at transferring thermal energy into and out of itself.

  • Metals are better at conducting than non-metals.

  • Insulators are materials that are bad at transferring thermal energy. Non-metals are very good at insulating.

  • The larger the thermal conductivity, the better it is at conducting.

  • The smaller the thermal conductivity, the better it is at insulating.

• Conductors

  • A conductor is a material that allows thermal energy to be transmitted through it easily.

    • All metals are good conductors.

    • When one end of a metal rod is put into a fire, the energy from the flame makes the atoms in the rod vibrate faster.

    • Since the atoms in the solid metal are close together, this increased vibration energy means that they collide with neighboring atoms more frequently.

    • Energy is passed on through the metal by these collisions, transmitting the energy. More frequent collisions increase the rate of transfer.