The document discusses two forms of energy: heat and light. It describes an experiment to demonstrate heat energy by having students feel which spoon (metal, plastic, or wooden) warms up fastest when placed in hot water. The metal spoon warms up fastest because metals are good conductors of heat, while materials like wood and plastic are insulators. Light is another form of energy, with the major source of light for Earth being the sun.

18. THE SUN IS THE MAJOR SOURCE OF LIGHT FOR THE EARTH