Bring a variety of goods originating -- in any way -- from natural resources. For example, you can have an egg, a wooden toy, a glass bottle of water, a book and a leather wallet. Ask children to tell you what all these objects have in common. If nobody can find the answer, explain that all of these objects are -- or are made of -- natural resources. The egg comes straight from nature, a wooden toy comes from a cut-down tree, glass has silica in the form of sand as its main ingredient and so forth.
Once students understand the connection between different objects, explain the definition of natural resources. Such resources are called "natural" because you can find them in nature, relatively undisturbed from human intervention. Natural resources can be plants, living organisms, as well as the earth's mineral wealth, such as petroleum and coal. However, when man removes these resources from their natural habitat and processes them (making glass goggles, wooden spatulas or any other object), they become industrial resources.
The depletion of natural resources is a critical problem mankind has to face. Explain that carelessly consuming resources without taking measures to conserve them can have multiple negative effects for the environment and people's standard of living. Show pictures of a water habitat after an oil spill (you can search for images from the spill in the Gulf of Mexico in 2010), photographs of deforestation and images of huge landfills with urban or industrial waste. Also mention solutions to these problems, such as recycling, less packaging and reforestation initiatives.
Ask children to open their notebooks on a blank page and have their pencils ready. On your mark, they must start writing as many products originating from a specific natural resource (wood or iron, for example) as they can. Allow students five minutes before asking them to put their pencils down, counting the correct answers and declaring the winner. For homework, ask children to write a short paragraph explaining how they can help the environment with just a simple daily task.