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Understanding that heat is a form of energy that can make things feel warm.
Have you ever wondered why a metal slide feels like an oven on a sunny day, or why a cup of cocoa warms up your cold hands?
Heat is a type of energy that makes things feel warm or hot. We can't see heat, but we can definitely feel it! The biggest source of heat for our whole planet is the Sun. It sends heat energy through space to warm our air, water, and land. Another common source of heat is fire. We use fire to cook our food and keep our homes warm in the winter. Even your own body makes heat energy to keep you alive!
1. Imagine placing a black t-shirt on a sidewalk in the bright sun. 2. After minutes, touch the shirt. 3. The shirt feels hot because it soaked up the heat energy from the Sun!
Quick Check
What are two common sources of heat energy mentioned in this section?
Answer
The Sun and fire.
Heat is always on the move! It has a very important rule: heat always travels from warmer things to cooler ones. If you hold an ice cube in your hand, the heat moves from your warm skin into the cold ice. This makes the ice melt! The heat will keep moving until both things are the same temperature. This is why hot soup eventually cools down if you leave it on the table; the heat moves from the soup into the cooler air.
1. You put a cold metal spoon into a bowl of hot soup. 2. The heat energy moves from the soup (the warmer object) into the spoon (the cooler object). 3. Soon, the handle of the spoon feels warm to your touch!
Quick Check
If you touch a cold window with your warm hand, which way does the heat move?
Answer
The heat moves from your warm hand to the cold window.
How do we know exactly how hot something is? We use a tool called a thermometer. A thermometer measures temperature, which is a way to describe how much heat energy something has. Most thermometers have a red liquid inside. When the liquid gets warm, it expands and moves up the tube. When it gets cold, it moves down. We measure this in units called degrees.
1. Look at a thermometer in a classroom. It might say degrees. 2. Take it outside on a snowy day. The red line will drop down to degrees. 3. The lower the number, the less heat energy there is!
Which of these is the biggest source of heat for the Earth?
If you put a warm blanket on a cold bed, where does the heat go?
A thermometer is used to measure how heavy an object is.
Review Tomorrow
Tomorrow, try to remember the 'Golden Rule' of heat: which way does it always move?
Practice Activity
Find three things in your house that give off heat (like a toaster or a lightbulb) and tell a grown-up how you know they are sources of energy.