Physical & Chemical Changes

Objectives:3.1 Formulate hypothesis regarding the

causes of the changes in objects or substances in the student’s

environment3.2 Classify the changes in various substances as either physical or chemical changes

Types of Changes:

Two Types of Changes

Physical Change

Chemical Change

Physical Change:

Does not change the chemical composition or the nature of a substance

Process is easily reversible

Ex. Crumpling & smoothing out paperEx. Freezing water and thawing iceEx. Sublimation – from solid to gas

(ex. dry ice (CO2) or iodine)

Key Words:Crush/PulverizeMeltEvaporationCondensationSublimationSolidificationDissolve

Tells you a physical change

occurred

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

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

Physical Change-Sublimation-Freezing-Condensation-Evaporation-Pulverization (crush)-Solidification-Dissolving

Chemical Change

- Burning- Neutralization- Combustion- Corrosion (rusting)

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

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

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?

Activities:

Physical Science Worksheet #2

Student Study Guide – Mod 1-14 - 1-16

References

Student Study Guide – Physical Science 416/436 - MEQ

Science Quest – Grenier, Daigle, Rheaume – 1998, Cheneliere

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