Post on 16-Dec-2015
Physical and Chemical Changes
Qualitative Observations-
Observed using our 5 senses.
Quantitative Observations-Observations using numbers
(counting, measuring)
Physical changes Indicators of a Chemical change
Physical Change
In a physical change,
• you do not get anything new.
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
What is a Physical Change?
• A physical change is a change in which no new substance is formed, but properties may be changed.
What is a Chemical Change?
• A chemical change is a change in which a new ________ with new _________is formed.substance
properties
Take your paper and crumple it.
• Do you have something new?
No, it is still paper although it looks somewhat different.
If shape changes, then you’re observing a _______ change…physical
Physical changes Indicators of a Chemical changes
Change of shape
Take your paper and rip it into 2 pieces.
• Do you have anything new?
No, it is still paper although it looks somewhat different.
If you observe a change in size, then you’re observing
a _______ change…physical
Wet sponge Dry sponge
Physical changes Indicators of a Chemical changes
Change of shape
Change in size
Looking at the ice…..it has melted.
• Do I have anything new?
• No! It is still water. It has just changed its state from a solid to a liquid.
If you observe a change in state, then you’re observing a
________ change…physical
Physical changes Indicators of a Chemical changes
Change of shape
Change in size
Change in state of matter
Measure out a ½ teaspoon of baking soda and put it into a cup.
• Was something new produced?
YES! Bubbles were produced. That indicates a gas was made. The gas is a new substance.
Add 3 pipettes of vinegar.
If you observe bubbling (not due to boiling or shaking), then a
_______change is occurring…chemical
If you observe fizzing, then you will know that a _________ change is
occurring (unless youshook the substance)…
chemical
Physical changes Indicators of a Chemical changes
Change of shape
Change is size
Change in state of matter
Bubbles/fizzing are produced
Rinse out cup and refill 1/3 way with water.
• Was the colored changed? Did you get anything new?
No, you just made the colored water not as dark. You diluted it.
I will pour the cup of water into the cup of colored water.
Physical changes Indicators of a Chemical changes
Change of shape
Change is size
Change in state of matter
Bubbles/fizzing are produced
Diluting
Add a piece of Alka-Seltzer to your cup of water.
Quickly place hand on side of cup for 3 seconds.
• Did you get anything new?
Did you feel any temperature change?
Physical changes Indicators of a Chemical changes
Change of shape
Change is size
Change in state of matter
Bubbles/fizzing are produced
Change in temperature
Diluting
When we burn something…..
• Is a new substance produced?
Yes, soot is produced or ashes.
If you smell burning, then you know that a change is
_________ occurring…chemical
If you SEE burning, then a_________ change is
occurring…chemical
Physical changes Indicators of a Chemical changes
Change of shape
Change is size
Change in state of matter
Bubbles/fizzing are produced
Diluting
Change in temperature
Burning or cooking
Is melting a chemical or physical change?
Physical!
If I add salt to water, can I separate them back into water and salt?
YES! It is a mixture. So physical or chemical change?
Why? When a substance is not changed into a new substance, the change is
only physical.
Physical changes Indicators of a Chemical changes
Change of shape
Change is size
Change in state of matter
Bubbles/fizzing are produced
Diluting
Change in temperature
Burning or cooking
Dissolving
Rusting?
In a chemical reaction,
• old bonds are broken and new bonds are formed.
• A NEW SUBSTANCE IS FORMED.
• Fe and O2 form rust (Fe2O3).
Dirty silver?
Physical changes Indicators of a Chemical changes
Change of shape
Change is size
Change in state of matter
Bubbles/fizzing are produced
Diluting
Change in temperature
Burning or cooking
Rusting/ tarnishing
Dissolving
If you observe that matter is__________, then a
__________change is occurring…chemicaldecaying
Physical changes Indicators of a Chemical changes
Change of shape
Change is size
Change in state of matter
Bubbles/fizzing are produced
Diluting
Change in temperature
Burning or cooking
Rusting/ tarnishing
Odor produced/ decay
Dissolving
Mixing chemicals….
Glow stick
What was observed?
Pour 15–20 mL of copper II sulfate solution into a test tube so it is about ½ full. Add about 10–20 drops of ammonia.
Add about 10–20 drops of hydrogen peroxide.
Physical changes Indicators of a Chemical changes
Change of shape
Change is size
Change in state of matter
Bubbles/fizzing are produced
Diluting
Change in temperature
Burning or cooking
Rusting/ tarnishing
Odor produced/ decay
Dissolving Change of color/ light produced
Physical changes Indicators of a Chemical changes
Change of shape
Change is size
Change in state of matter
Bubbles/fizzing are produced
Diluting
Change in temperature
Burning or cooking
Rusting/ tarnishing
Odor produced/ decay
Dissolving Change of color
Precipitate formed
What was formed was a precipitate.
Precipitate - a solid formed by mixing two or more liquids.
If you observe explosions because of burning, then a ________ change
is occurring…chemical
If you observe cooking, then a _______change is occurring…chemical
If you observe bending (of metal, for example), then a __________change is occurring…
physical
Pulling metal into wires is called _________ductile
If you observe reshaping (into a tube, for example), then a
_______change is occurring…physical
If you observe pounding metal into sheets, then a _________change is
occurring…physical
This is called ______________.malleable
If you observe cutting, then a __________change is
occurring…physical
If you observe melting, then a _______change is
occurring…physical
If you observe rusting, then a ______change is
occurring…Note: Rusting occurswhen some metalsreact with the elementOxygen, which is in the air. For this reason, rusting is also called oxidation.
chemical
If you observe cooling because refrigeration was added, then a _______change is occurring…physical
If you observe warming without the use of fire or a heater, then a
________change is occurring…chemical
If you observe warming with the use of fire or a heater, then a
_______change is occurring…physical
If you observe new matter being made, then a _________change is
occurring…chemical
Indicators of chemical reactions:
• Production of a gas
• Change in color
• New substance produced
• Change in the chemical formulas
• Heat is produced or absorbed
• Odor is produced
Some Examples of Chemical and Physical Changes
Classify each of the following as a
1) physical change or 2) chemical change.
A. ____Burning a candle.
B. ____Ice melting on the street.
C. ____Toasting a marshmallow.
D. ____Cutting a pizza.
E. ____Polishing a silver bowl.
Learning Check
21212
Properties of Matter
observations/changes
observations/changes
State of matter
solid, gas, etc
Density
Hardness
Breaking/ripped
Melting Point
Taste
Diluting
Odor
Physical Chemical
Decaying
Flammability
Tarnishing
Gas produced
Burning
Color change
Temperature change
Precipitate formed