Physical and Chemical Changes
AKS 11: Distinguish between a physical and chemical change
Concept of Change
Matter: anything that has mass and volume
Change: the act of altering a substancePhysical or Chemical
Physical ChangePhysical change: a change that
occurs that does not change the identity of the substance.
Does NOT result in the production of a new substance
CAN be reversed easily by physical means
Can you think of ways I can make PHYSICAL changes to a piece of paper?
TearingCuttingRipping/shreddingFoldingGluing Writing on it
Physical Change Examples Melting ice(change in state or phase)
Freezing Kool-aid Tearing paper Bending a wire
Can you think of any more? Share with your elbow partner!
Chemical ChangesCHEMICAL change: a change that
occurs causing the identity of the substance to change
DOES result in the production of a new substance
CANNOT be reversed by physical means
A chemical change is called a chemical reaction
Can you think of ways I can make chemical changes to a piece of paper?
Burning itPouring acid on itEating it (digestion) – yuck!
Clues to a Chemical Change (Reaction)
As I burn a piece of paper, can you think of up to 6 clues that tell us that a chemical change has taken place?
Clues to a Chemical ChangeIndicators of a chemical change:
1. Production of a gas1. Fizzing, foaming, odor, bubbling
2. Production of energy (heat, light or sound)1. Light given off, feels hot or cold, hear noise(s)
3. Temperature Change1. Be careful with this one!
4. Unexpected Color change1. Be careful with this one!
5. Production of a precipitate (solid)1. Be careful with this one!
6. Production of a New Substance1. Only if the atoms that make it up have been chemically altered!2. The more of clues 1-5 you have, the more likely
Chemical Change Examples
Burning Digesting food Reacting with other substances
• Rusting, • corroding, • decomposing, • tarnishing
Is it Physical or Chemical?
Change Physical Chemical
Melting cheese
Burning wood
Milk souring
Wadding up paper
Bicycle rusting
Indicators of chemical reactionWhat indicators do you observe?2NI3 --- N2 + 3I2
Indicators of chemical reactionWhat indicators do you observe?C12H22O11 + H2SO4 --- 11H20 + 12C
Indicators of chemical reactionWhat indicators do you observe?IO3− + 2H2O2 + CH2(COOH)2 + H+ → ICH(COOH)2 + 2O2 + 3H2O
Indicators of chemical reactionWhat indicators do you observe?
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