Super Science: Conduction, Convection, and Radiation

Heat science is one of my favorites! First of all, let's start with how heat is made.

When an object moves very quickly, it generates heat. This is because when a molecule bumps into another molecule (everything is made up of many, many molecules) the molecules bump into other molecules and charges them off. Think of it like you have a line of dominoes stretching on and on and you push the first domino down. All of the other dominoes fall down, toppling over one another in a chain reaction.

The same goes for the molecules. Except, it's more like you have a bunch of beach balls bouncing around in a confined space. They keep on knocking into each other. The molecules bump into the other molecules over and over, faster and faster. Soon, they a generating a lot of heat.

This is convection. When a heat source brushes against, or rubs, or touches another thing, like a burner and a pot. (Solids, especially as medals, are the best conductors of heat because they have the most molecules) The burner generates heat, and the pot touching the burner begins to heat up. Then, it heats up the contents in it (water, vegetables, etc.). This is conduction at work! First the medal platform of the burner heats up, then the medal of the pot, and then the contents.

That brings us to radiation. Let's think about that burner. How does it heat up the pot, exactly? Radiation. The burner radiates heat.

The Sun has a radiation layer, or radiative layer. This is the layer that warms the Earth. The Sun radiates heat to Earth.

Radiation occurs when a object generating heat (the Sun, the burner) transfers it to another object (Earth, the pot). Like when a cat sits on your lap. You start feeling warm, and then warmer. The cat, (like all other mammals and warmblooded animals) is warm, and radiates heat to your lap. Conduction is also working in this case.

There is also another why for heat to transfer. This is called convection. Convection is when hot and cool air mingle together and make an even temperature. Wind currents help to make this process happen.

When the Sun heats the Earth, it does not heat it entirely evenly. There are warmer spots and cooler spots that can be very far, or very near, to each other. When the wind blows, it moves this air and mixes the different temperatures together. Sort of like when you're mixing a cake mix. There are dryer parts and wetter parts, like hotter and cooler air. When you stir, it becomes smooth and evenly mixed. When you stir, it's like when the wind blows. The wind currents are like the spoon. They mix the air to make the temperature even.

Let's think about that pot again. Conduction is working. The burner is hot, and when the metal meets metal, the pot heats up. When the pot (touching the content) is heated, the food inside of it is heated. Conduction is behind your food getting cooked.

Radiation is also at work. Heat is radiating from the burner, as it does from the Sun. This is also an important part of the process of cooking the food. Without radiation, conduction wouldn't have a chance to work.

Believe it or not, convection also plays a part in this. Conduction heats the air around the pot. It mixes in with the cooler air. Have you ever stood by the stove as your food is cooking? Notice how the air is warmer there, around the pot and in the kitchen, then it is out of the kitchen. If you are steaming your food, conduction is vital.

First the heat radiates from the burner, then it heats the metal top. Conduction brings heat to the pot, then to the food. Convection makes the air warm. If you are steaming veggies or another food you, convection is the cause of the steaming process ever getting finished, and started!

The next time you are cooking pasta, or steaming veggies, remember conduction, convection, and radiation. The next time you are playing with your dominoes, remember molecules. Remember the building blocks of heat.

-KittyLover8
© 2012