Physical and Chemical Changes

1
Think about it
1. Whats 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?
2
Physical and Chemical Changes

• AGENDA
• Distinguishing and identifying changes
• Steel wool demonstration (this will get started
  early in the lesson, but we will revisit it
  several times.
• Guided practice to distinguish changes.
• Independent practice

• And how to tell the difference

3
Physical Change
Chemical Change

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

• Changes the way the atoms combine to form
  substances
• (new substances will have different physical
  properties)

4
Steel Wool Demonstration

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

5
Its a physical change if
Its a chemical change if

• It changes shape or size
• It dissolves.
• It changes phase (freezes, boils, evaporates,
  condenses)

• It burns
• Temperature changes without heating/cooling
• It bubbles (makes a gas)
• It changes color
• It forms any new materials

How are these different?
6
What kind of change is it if someone...

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

7
What kind of change is it if someone...

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

8
What kind of change is it if someone...

• Mixing vinegar and baking soda?
• Chemical change

9
Guided Practice (Left Side)For each of the
following examples

• Decide whether the changes is chemical or
  physical
• Justify your answer.

10
Boiling water is a physical change because the
liquid water changes state to become water vapor
when enough heat is added.
11

• Rusting (oxidation)

Chemcal
12
Physical or Chemical Change?

• Painting Wood
• PHYSICAL

13
Physical or Chemical Change?

• Burning Paper
• CHEMICAL

14
Physical or Chemical Change?

• Digestion of food
• CHEMICAL

15
Physical or Chemical Change?

• Sugar dissolving in water
• PHYSICAL

16
Physical or Chemical Change?

• A pond freezing in winter
• PHYSICAL

17
Physical or Chemical Change?

• Cutting wire
• PHYSICAL

18
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.
19
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.
20
Time (min) Mass (g) Mass (g) Color Color Other Observations Other Observations
  Room temp. Hot Room temp. Hot Room temp. Hot
0