Plastics
3 Minutes
Plastics and polymers for kids: learn why plastic takes thousands of years to decompose and how natural polymers differ. An English science lesson.
- How monomers bond to form polymer chains
- Differences and examples of natural and synthetic polymers
- Soil test comparing cloth and plastic decomposition
What this lesson teaches
Plastics are synthetic materials made of long molecular chains called polymers, which take hundreds to thousands of years to break down in the ground. They persist in the environment because their chemical bonds are extremely strong and do not decompose easily in soil.
How polymers are formed
A polymer is a large chemical structure created when many small units called monomers link together. The word monomer means a single molecule. In a polymer, these individual molecules join together through strong chemical bonds to form a continuous long chain. These tough chemical linkages are found in plastics as well as in many other everyday items.
Natural and synthetic polymers
- Natural polymers are materials obtained directly from living things like plants and animals.
- Examples of natural polymers include plant fibers such as cotton and jute, along with fur jackets made from animal hair.
- Synthetic polymers are artificial materials that humans make by combining specific chemicals.
- Examples of synthetic polymers include everyday plastic carry bags, plastic water bottles, and PVC pipes.
Comparing decomposition in soil
An experiment using moist soil demonstrates how the two types of polymers break down at completely different rates. When a piece of a cloth bag and a piece of a plastic cover are buried in moist soil for one week, only the cloth piece shows slight signs of decomposition. The synthetic plastic cover remains completely unchanged. Natural polymers degrade easily in soil, whereas synthetic polymers take an exceptionally long time to break apart.
The long breakdown time of plastics
Everyday plastic items, such as small plastic tea cups, can take more than a thousand years to fully decompose once thrown on the ground. Because the chemical bonding in a synthetic polymer is so strong, it takes centuries for the soil to react with the material and break those bonds apart. If humans continue to discard synthetic polymers, these products will persist for thousands of years and cause great destruction to the world. Using natural polymers instead of synthetic plastics helps keep waste from piling up in the earth.