Answer:
Greenhouse gases are gases that trap heat in the Earth's atmosphere and contribute to the greenhouse effect. One example of a heat-trapping greenhouse gas is carbon dioxide (CO2).
When infrared radiation (heat) from the sun enters the Earth's atmosphere, some of it is absorbed by the Earth's surface and some is reflected back into space. However, greenhouse gases in the atmosphere, such as CO2, absorb some of the reflected infrared radiation and trap it in the atmosphere, preventing it from escaping into space.
The reason greenhouse gases are able to trap heat is because of the way their molecules interact with infrared radiation. Infrared radiation is a type of electromagnetic radiation that has a specific wavelength. When this radiation comes into contact with greenhouse gas molecules, the molecules are able to absorb the radiation and become excited.
This excitation causes the molecules to vibrate and rotate, which generates heat. This heat is then re-emitted in all directions, including back towards the Earth's surface, which further contributes to the warming of the planet.
The more greenhouse gases there are in the atmosphere, the more heat they are able to trap, and the warmer the Earth's surface becomes. This is why the increasing levels of greenhouse gases in the atmosphere, such as CO2, are a major concern when it comes to climate change.