Discover Reversible Changes: When Materials Change and Change Back!

A physical change happens when a material changes its shape, size, or form. You can see physical changes all around you every day!

A reversible change is a special kind of physical change. It means the material can go back to how it was before. Nothing is lost or destroyed it just changes and then changes back!

When ice gets warm, it melts and becomes water. That is a physical change! But you can put the water back in the freezer and it becomes ice again. This is a reversible change.

You can see this with juice popsicles too. When a popsicle melts, it turns into liquid juice. Put it back in the freezer and it becomes solid again!

Chocolate and butter work the same way. When they get warm, they become soft or liquid. When they cool down, they become hard again. The material stays the same it just changes form!

You can change the shape of some materials and then change them back. This is also a reversible change!

When you squish playdough or clay into a new shape, you can always squish it back. The material stays the same only the shape changes. You can make a ball, then a star, then a ball again!

When you fold paper into a boat or airplane, you can unfold it to get a flat sheet again. When you bend a pipe cleaner into a circle, you can straighten it back out. When you stretch a rubber band, it snaps back to its original shape when you let go!

Physical Change: A physical change is when a material changes its shape, size, or form. You can see a physical change when you fold paper or melt ice. The material is still the same material it just looks different.

Reversible Change: A reversible change is a change that can be undone. You can make the material go back to how it was before. Melting ice is reversible because you can freeze the water again!

Solid: A solid is a material that has a firm shape, like an ice cube, a stick of butter, or a frozen popsicle. Solids feel hard or firm when you touch them.

Liquid: A liquid is a material that flows and takes the shape of its container, like water, melted chocolate, or juice. When a solid melts, it becomes a liquid.

Melting: Melting is when a solid gets warm and turns into a liquid. Ice melts into water. Chocolate melts into a soft, runny liquid when it gets warm.

Freezing: Freezing is when a liquid gets very cold and turns into a solid. Water freezes into ice. Juice freezes into a popsicle. Freezing is the reverse of melting!

Reshape: To reshape means to change something into a new shape. You can reshape playdough by squishing it, rolling it, or pressing it flat. You can reshape it again and again!

You can try these activities to see reversible changes for yourself!

• Put an ice cube on a plate and watch it melt. Then put the water in the freezer and watch it freeze again.
• Roll playdough into a ball, then press it flat, then roll it into a snake. You can always change it back!
• Fold a piece of paper in half, then unfold it. The paper goes back to its flat shape.
• Stretch a rubber band gently and let it go. Watch it snap back to its original shape.
• Bend a flexible straw and then straighten it out again.

You already know that materials around you can look and feel different. You know that some things are hard and some things are soft. This helps you understand how materials can change!

As you learn about reversible changes, you are building a strong foundation for understanding how the world around you works. Every time you see ice melt or reshape your playdough, you are a scientist making observations!

Learning about reversible changes is part of a bigger topic called Changes. In this chapter, you explore how materials around you can change in different ways.

As you keep learning about science, you will discover that not all changes are reversible. Some changes are irreversible, which means the material cannot go back to how it was before. For example, when you burn paper or cook an egg, you cannot undo those changes. Understanding reversible changes now helps you compare them to irreversible changes later!

You will also connect what you learn here to the idea of states of matter solids, liquids, and gases. When ice melts into water, it changes from a solid state to a liquid state. This is a reversible physical change because you can freeze the water back into a solid. These ideas all work together to help you understand how materials behave in the world around you.