Intro to Thermal Energy

Before watching the video, students are likely to think of heat as a form of energy rather than the movement of thermal energy, and they are likely to define temperature in simple terms of how hot or cold something is.

Before watching the video, students should know that adding energy to a substance heats it up and removing energy from a substance cools it down.

The Sun, heaters, light bulbs, ovens, stoves, fires, car engines, rubbing our hands together, and hand warmers are examples of heat in our everyday lives. Common sources of heat, other than the Sun, can be classified as being caused by electrical flow, chemical reaction (including burning), or friction.

We sometimes need to cool things in our everyday lives to keep food fresh or at temperatures that we like, to keep people comfortable inside buildings, to cool our bodies when we exercise, to treat fevers or heat exhaustion, and so on.

Water freezes when it gets cold—that is, when energy is removed from it. Ice melts when it gets warm, or when energy is added to it.

Although students might think that “cold” is moving into their hand, thermal energy is moving from their hand to the ice cube. Thermal energy moves from hotter areas into colder areas. The transfer of thermal energy from your hand to the ice cube makes your hand feel colder.

Temperature measures the average kinetic energy of the atoms or molecules that make up an object. As thermal energy is added to an object, the object’s molecules move faster. When the molecules move faster, they have more kinetic energy. So the temperature increases.

As thermal energy is transferred to the chocolate, its molecules vibrate faster and faster. Eventually they vibrate fast enough that they start to slide past each other and move around. As this happens, the chocolate changes from a solid to a liquid.

Thermal energy moves from water vapor in the air around the glass into the cold drink. As the water molecules in the air lose energy, they slow down and move closer together. As this happens, the water vapor condenses into a liquid on the outside of the glass.

Yes. Thermal energy always moves from an area with a higher temperature to an area with a lower temperature. So, if you place a block of ice in contact with a substance that has an even lower temperature, such as liquid nitrogen or dry ice, then thermal energy would move from the ice to the colder substance.

You need to minimize the amount of thermal energy that moves into the drink from the warmer air around it. Putting it in a thermos or vacuum-insulated tumbler is one way to do this. The lack of air between the two layers of the container slows down the transfer of thermal energy. Another way to do this is to surround your cup with a material that has a lot of air space in it, such as cardboard or foam. The air space slows down the movement of thermal energy.

A chemical reaction inside the hand warmer releases thermal energy. This thermal energy moves from the hand warmer into your hands