Physical and Chemical Changes Chapter 8 Lesson 5

What do you see?

What are physical changes? Change of state is an example of physical change Ice cubes are water that is solid and when they melt, the substance is still water. The liquid can even evaporate and change into gas, but it is still water. Some physical changes be easily reversed When sugar is mixed with water, the sugar dissolves in the water. You could evaporate the water and collect the vapor. The sugar would be left behind in the container A physical change alters the form of an object WITHOUT changing what type of matter is. Changes in size and shape are examples of physical changes Sharpening your pencil, tearing a piece of paper, breaking glass are all examples

Examples Answer= C Water is changed from a liquid to a solid. Changes of state are examples of physical changes

What do you think? Answer=B Dissolving sugar is a reversible process. Many physical changes can be reversed

You try… Answer=D Making sugar water is reversible. Once again, physical changes can be reversed.

What are chemical changes? CHEMICAL CHANGES- occur when atoms link together in new ways to create substances different from the original substances If you combine baking soda with vinegar, a chemical change occurs. The baking soda changes and bubbles form=The bubbles are a new substance Also, a new white solid is left behind that has formed different properties than the vinegar and baking soda. During chemical reactions, atoms in the baking soda and vinegar link together in new ways.

How can you spot a chemical change? Chemical changes produce new substances that have different properties than the previous ones You can often see, hear, or smell the formation of new substances as a chemical change occurs Chemical changes include: Change in color is a sign of chemical change When metals corrode (rust) it is a sign of chemical change Bubbles are a sign of a chemical reaction Heat and light (candles)

Examples Answer= D A rotting pear has chemical properties that have changed within. It will usually change color when it is rotten.

Let’s try another… Answer= A. Anything that has been burned or rusted creates a new type of matter. When there is a new substance it is a chemical change

You try… Answer= D Once again, anything that burns will cause a new substance=chemical change