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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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