Think about it:

1. What’s the difference between cutting and burning a piece of wood?

2. How should the mass of the products (results of each process) compare to the original piece of wood?

And how to tell the difference

Physical and Chemical Changes

AGENDA:1.Distinguishing and identifying changes

2.Steel wool demonstration (this will get started early in the lesson, but we will revisit it several times.

3.Guided practice to distinguish changes.

4.Independent practice

Physical Change

• Substance may seem different, but the way the atoms combine is the same.

Chemical Change

• Changes the way the atoms combine to form substances

(new substances will have different physical properties)

Steel Wool Demonstration

• We will be taking observations every 5 minutes for this demonstrations

It’s a physical change if

• It changes shape or size

• It dissolves.• It changes

phase (freezes, boils, evaporates, condenses)

It’s a chemical change if

• It burns• Temperature changes

without heating/cooling

• It bubbles (makes a gas)

• It changes color• It forms any new

materials

How are these

different?

What kind of change is it if someone...

•Tears up paper?•Physical change•Mixes salt and water?•Physical change

What kind of change is it if someone...

•Burns paper?•Chemical change•Evaporates salt water?•Physical change

What kind of change is it if someone...

•Mixing vinegar and baking soda?

•Chemical change

Guided Practice (Left Side):For each of the following examples

• Decide whether the changes is chemical or physical

• Justify your answer.

Boiling water is a physical change because the liquid water changes state to become water vapor when enough heat is added.

• Rusting (oxidation)

Chemcal

Physical or Chemical Change?

•Painting Wood

•PHYSICAL

Physical or Chemical Change?

•Burning Paper

•CHEMICAL

Physical or Chemical Change?

•Digestion of food•CHEMICAL

Physical or Chemical Change?

•Sugar dissolving in water

•PHYSICAL

Physical or Chemical Change?

•A pond freezing in

winter•PHYSICAL

Physical or Chemical Change?

•Cutting wire•PHYSICAL

Law of Conservation of Mass

Matter can never be created or destroyed.

This means:During any physical or chemical change, the total mass of all substances before and after the change remains the same.

Sometimes, measuring all the components of a change is difficult.Example: if you boiled water, it would be difficult to measure the mass of all the water vapor.

Temperatures influence on chemical changes

This means:During any physical or chemical change, the total mass of all substances before and after the change remains the same.

As with the steel wool demonstration, adding energy in the form of heat typically speeds up the change.

Time (min)

Mass (g) Color Other Observations

  Room

temp.

Hot Room

temp.

Hot Room temp.

Hot

0