What is Heat Energy?
Heat is a form of energy that is transferred between objects with different temperatures.
Heat energy always moves from a warmer material toward a material with a lower temperature.
The arm diagram shows a layer of heated air near the skin. If the air temperature around the arm is 780 F, heat energy moves away from the skin to the cooler air. The skin stops losing heat energy when the air around the skin is the same as the person’s body temperature, which is about 98.60 F. (FYI: My body temperature averages about 97.50 F.
Why Things Feel Hot or Cold!
When you touch an ice cube, the ice feels cold because heat energy from your skin is being lost to the ice. Temperature sensors in your skin send messages to your brain. When your skin loses heat energy, the message decoded by your brain is that you have touched something cold.
When you pick up a cup of hot chocolate, the cup feels hot because heat energy from the cup is being lost to your skin. The temperature sensors in your skin send messages to your brain. When your skin gains heat energy, the message decoded by your brain is that you have touched something hot.
1. Which diagram A or B, represents an environment in which heat energy moves from the skin to the air? (A)
2. Which diagram A or B, represents an environment in which heat energy moves from the air to the skin? (B)
Purpose: To demonstrate that the temperature sensors in your skin cannot accurately judge how hot or cold something is.
Three bowls with water of varying temperatures as shown. Use thermometers to measure and compare the temperatures.
Caution: The water temperature in each bowl must be safe enough to place your hands in.
Place your left hand in the bowl of icy cold water and your right hand in the warm water.
After about 15 seconds, move both hands to the center bowl of cool tap water.
The cool tap water feels warm to your left hand. The same bowl of cool tap water feels cool to your right hand.
Why does the water feels different to each hand?
Left Hand: The skin of the left hand in the icy water is at a lower temperature than the temperature of the cool tap water. Heat energy from the cool tap water is transferred to the left hand. When the skin takes in heat energy the message decoded by the brain is that the hand is touching something warm.
Right Hand: The skin of the right hand in the warm water is at a higher temperature than the temperature of the cool tap water. Heat energy from the right hand is transferred to the cool tap water. When the skin loses heat energy the message decoded by the brain is that the hand is touching something cool.