Both conduction and convection are methods of energy transfer that require particles. However, convection occurs in liquids and gases where the particles, although farther apart, are free to move. Although the particles in liquids are closer together than gases, they are still able to move and flow.
When particles are near a heat source, they gain thermal energy, causing them to vibrate and move more quickly. This leads to the particles moving further apart, making the gas or liquid less dense.
It’s important to note that individual particles don’t change in size or become less dense; instead, the overall gas or liquid becomes less dense.
1. The moving particles with a lot of thermal energy rise and transfer energy to the particles at the top, replacing the particles with little thermal energy.
2. Particles at the top, which as a whole are cooler and denser, fall to take the place of the high-energy particles.
The constant cycling of particles is called a convection current. The particles rise and fall, transferring energy to colder regions.
Consider the example of water heating in a pot:
1. The pot is heated from the bottom.
2. The particles at the bottom of the pot start to vibrate more as they are heated.
3. These particles then transfer heat energy to other areas of the pan and the water molecules at the bottom of the pot.
4. Due to the heating process, convection currents form within the water inside the pot.