Physical and Chemical Change

Physical and Chemical Change

Objectives

• Comprehend that a change in of state is a physical change;

• Differentiate between physical change and chemical change;

• Give examples of physical change and chemical change.

Open Ended

What do you know about the different states of matter?

Open Ended

What is the difference between ice and water?

Open Ended

Is the material still water when it is turned into ice?

What are physical changes?

When you flatten a piece of a clay or cut it in half, you cause a physical change.

A physical change begins and ends with the same type of matter. Even though the caly has a different shape, it is still clay. You can cut, crush, tear, bend, ot stretch matter. Each action will cause a physical change.

Knitting causes a physical change. The yarn changes shape.

After a physical change, the physical properties of the matter change. However, the matter is still the same substance.

For example, an ice cube is solid water. If the ice cube warms, it melts. Now it is liquid water. If you pour that water into a kettle and heat it, you get steam. Steam is water in the form of a gas. Physical changes can be caused by wind, rain, freezing, and heating.

People use physical changes to create useful products.

For example, plastic, metal, and glass can be cut and molded into useful shapes. Rock can be sculpted.

Open Ended

Real - World Changes

How can you tell whether a physical change has taken place?

Physical changes happen around you all time. The sidewalks in your town or city are made of concrete. When the concrete is new, it is one solid piece. In time, chips and cracks form. Small pieces of concrete break off. Wind and rain carry the pieces away. Cracking and breaking are physical changes in the sidewalks.

Physical Changes in Materials

• Changes in solid materials when bent, pressed, hammered, or cut

• Changes in properties of materials when exposed to different temperatures - measure of hotness or coldness of matter - thermal energy is the total energy of the particles of a material

• Changes in properties of materials when mixed with the other materials

What are chemical changes?

Most bicycle frames contain iron. If you leave a bicycle outside for too long, the frame might rust.

Rust is a solid, brown substance. It forms when iron gets wet and reacts with oxygen in the air. Rust is neither iron nor oxygen, though it contains both of these elements.

The change from iron to rust is a chemical change.

A chemical change begins with one kind of matter and ends with another. A chemical change is also known as a chemical reaction.

All chemical reactions either give off energy or use energy. Chemical reactions may give off heat, light, or electricity.

What are common chemical changes?

Open Ended

In what way is a chemical change different from a physical change?