Physical and Chemical Changes Background Information for Teachers, Parents and Caregivers

This page provides information to support educators and families in teaching K-3 students about physical and chemical changes. It is designed to complement the Physical and Chemical Changes topic page on BrainPOP Jr.

Before beginning this topic, we highly recommend reviewing the movies Solids, Liquids, and Gases and Changing States of Matter for review. This movie will introduce physical and chemical changes of matter and explore different examples. We recommend pausing the movie and discussing scenes together and having children come up with their own examples.

Review with children that everything is made up of matter. Then point out different items and have children describe their properties. Remind children that a property is a trait that tells you something about the object. For example, clay is thick, brown, and soft. A physical change happens when matter changes size, shape, or form. You can make physical changes to clay by molding it into a pot or flattening it out. The substance is still clay—its shape is just different. The substance also has some of the same properties.

Brainstorm other physical changes together. How can you make physical changes to a piece of paper? You can rip it, cut out a shape, paint or color on it, or fold it in different ways. The paper might look different, but it is still paper. The substance itself did not change. When you add food coloring to water, the water goes through a physical change. It’s still water, just a different color. It still has many of the same properties. When you break a glass vase, it goes through a physical change. It looks different, but it’s still glass. Explain to children that when you freeze water, it goes through a physical change. It’s still water, just in a different state. You can melt the ice and it will become water again. When a candle melts, the wax goes through a physical change. It is still made of the same substance, even though it is not a solid. When the wax cools down, it will harden again. Help children understand that in some cases, physical changes can be undone, or reversed.

Point out physical changes all around us. When we get a haircut, our hair goes through a physical change. When grass gets mowed, it goes through a physical change. When we paint walls, they go through a physical change, too. When rock gets weathered by wind, land goes through physical changes. You may want to watch the Slow Land Changes movie for extension.

Explain to children that after a substance goes through a chemical change, it becomes a different substance. The substance before and after a chemical change can have very different properties. For example, bread dough goes through a physical change after it is baked. The dough and the bread have very different properties. They look, smell, and taste different. Help children understand that chemical changes cannot be undone. You cannot turn bread back into dough! Explore other chemical changes together. For example, when milk sours, it goes through a chemical change. Sometimes you can smell and even see the difference. If you leave a slice of apple out, the nutrients will go through chemical changes and the apple will turn brown. When metals is exposed to air and water, the metal goes through a chemical change and rusts. When wood is burned, it goes through a chemical change that cannot be reversed. Help children understand that chemical changes happen all around us. When tree leaves change color in the fall, they are going through chemical changes. When flowers die, they also go through chemical changes.

There are no set rules on how to tell if something is a physical or chemical change. But, you can help children ask questions about the substance to make an educated decision. Did the substance’s properties change drastically? Can the change be undone? Was heat needed to spark the change or was heat released during the change? Encourage children to think about the substance before and after the change. They can make inferences and use inquiry skills to explore and understand.