Physical and Chemical Changes

1. Physical & Chemical Changes
Objectives:
3.1 Formulate hypothesis regarding the
causes of the changes in objects or
substances in the student’s
environment
3.2 Classify the changes in various
substances as either physical or
chemical changes

2. Types of Changes:
Two Types of Changes
Physical
Change
Chemical
Change

3. Physical Change:
 Does not change the chemical
composition or the nature of a substance
 Process is easily reversible
 Ex. Crumpling & smoothing out paper
 Ex. Freezing water and thawing ice
 Ex. Sublimation – from solid to gas
(ex. dry ice (CO2) or iodine)

4.  Key Words:
 Crush/Pulverize
 Melt
 Evaporation
 Condensation
 Sublimation
 Solidification
 Dissolve
Tells you a
physical change
occurred

5. Chemical Changes:
 Changes the chemical composition or
make-up of the substance
 New substances are formed with new
properties
 Not easily reversible
(Reversible only through chemical means
or reactions)
Rust

6. Signs of Chemical Changes:
Tells you a
chemical change
occurred
 Formation of a gas
 Formation of a precipitate
 Change in color
 Production of heat &/or light
 Increase or decrease in mass

7. Physical Change
-Sublimation
-Freezing
-Condensation
-Evaporation
-Pulverization (crush)
-Solidification
-Dissolving
Chemical Change
- Burning
- Neutralization
- Combustion
- Corrosion (rusting)

8. Which of the following are examples
of physical changes?
1. Melting Butter
2. Rusted Car
3. Dissolving Sugar
in Tea
4. Crushing Rock
6. Burning Wood
5. Condensation

9. Which of the following are examples
of chemical changes?
1. Cooking an egg
3. Sublimation of
Dry Ice
2. Rotting food
4. Freezing Rain
6. Crumpling
Paper
5. Burning a
candle

10. You carry out the following
steps of an experiment &
record your observations.
1. You place a powder in a test tube
2. You heat the test tube. You notice
that a colorless gas & a copper-
colored liquid are produced.
3. You collect the copper-colored liquid
& cool it. It becomes a solid.
Where did a chemical
change occur? A physical
change?

11. 5 Types of Chemical Change
 1. Synthesis is a reaction where 2 or more reactants
combine to form a new product
( A + B  AB)
 2. Decomposition is a reaction where a compound
separates into two or more compounds or elements.
(AB  A + B)
 3. Precipitation occurs when two solutions are
combined and an insoluble substance (precipitate)
forms.
(Solution + Solution  Solid)
 4. Acid Base Neutralization occurs when an acid
(pH1-6) and a base (pH 8-14) react to produce salt
and water.
(Acid +Base  Salt + Water)
 5. Oxidation occurs when substances react with the
oxygen. E.g. Combustion, rusting, respiration
(HydroCarbon + Oxygen  Carbon Dioxide + Water)

12. Conservation of Mass
 MASS REACTANTS = MASS PRODUCTS
 E.g. CH4 + 2 O2  CO2 + 2 H2O
 16g + 64g  44g + 36 g
 80g  80g
 Q. If you reacted 48 g of methane with 192 g of
oxygen, how many grams of product are formed?
 Q. If 108g of that was water, how many grams
of CO2 were there?

13. Activities:
 Physical Science Worksheet #2
 Workbook, Page 26, Q. 1,3
 Workbook, Page 88, Q. 1

14. References
 Student Study Guide – Physical
Science 416/436 - MEQ
 Science Quest – Grenier, Daigle,
Rheaume – 1998, Cheneliere
 Animation Factory Clip Art
 Microsoft Clip Art
 Google Images