While students have experienced light and dark, they may have never given the two much thought. Teaching children about light and dark is best accomplished through hands-on activities and experiments that can be done both in and out of the classroom. Prior to plunging right into the activities, make sure that the students understand that darkness is the absence of light.
The most prominent light source on the planet Earth is the sun. Take the children outside and explain that the sun provides light and heat for all of Earth's inhabitants. Have the children step in and out of the shade and explain that the shade occurs when the light is blocked by an object like a tree or building. Sunglasses can also be used to demonstrate a shade or dark effect. Provide fun facts about the sun. Tell them that if the sun were hollow, more than 1 million Earths could fit inside of it. Be sure the children do not look directly at the sun. Return to the classroom and show the children pictures of the sun.
Close all of the curtains in the classroom and turn off the lights. If the room is still bright, move to another location such as a gym or cafeteria where the students can see pitch darkness. Be sure the students are seated and know not to walk around during the experiment. Explain to the children that what they are experiencing is darkness. Ask the children what they can see, if anything. With the assistance of parents or other teachers, shine one large flashlight and several small flashlights into the room. Explain that the light from the moon and stars breaks through the darkness of nighttime and provides light. Be sure the children understand that unlike the sun and stars, the moon is not a light source itself but rather reflects the light from the sun.
Identify various types of light sources from around the room, including fluorescent lighting, light bulbs and monitors. Ask the children to think of other items that create light, including televisions, street lights, car headlights, cell phones, fireflies and candles.
Light is necessary for things to grow on the planet. Use a plant to demonstrate how the leaves will grow toward the light. Put a similar plant into complete darkness in a cabinet or closet. Have the students monitor the plants for an extended period of time and journal any differences between the two.