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