Warm-Up

• Please sit down quickly and quietly.

• Please copy down the schedule in your Raven Book.

• Next, answer this Warm-Up Question on your yellow sheet:– Explain what you think is a physical property.

Name five physical properties of your desk.

Physical vs. Chemical Changes

Goal: How do you tell the difference between chemical and physical

changes?

Physical Change*• A change in any object’s physical

properties

• any change in an object’s:

- mass - color

- weight - shape

- volume - hardness

- density - texture

Physical Changes*

Changes in Density, Mass or Volume D = M/V

Physical Changes*

Creating mixtures that can be separated out - mixtures can be reversed.

Physical Changes*

Changes in Phase of Matter

Example of a Physical Change:

A Melting Icicle

• physical properties = characteristics of a substance that can be observed without changing the identity of the substance.

ex.) wood is still wood whether it is shaped into a baseball bat or used to build the walls of your house – or if it’s still in the shape of a tree!

ex.) water is still water whether it is in the form of ice, liquid water, or water vapor. It’s still H2O!

Review: Other Physical Properties*

ColorSize

ShapeTexture

Magnetism

Chemical Changes*

• Chemical Changes occur when atoms react with other atoms to form chemical bonds.

• When atoms are bonded together they make a molecule.

Chemical Changes*

• When a chemical reaction happens the new molecules are a new substance or compound.

• A + B AB

Chemical Change

> changes that substances undergo when they turn into other substances

> Also called a “Chemical Reaction”

ex.) as coal burns, O2 (in the air) combines chemically with C (the substance that makes up most of the coal) and forms a completely new substance = CO2

- C and O2 have changed chemically! They

no longer exist in their original forms!

- Written out: C + O2 = CO2

Evidence of Chemical Changes, Reactions or Bonding

• Energy being taken in or given off (heat, coolness, light)

Evidence of Chemical Changes, Reactions or Bonding

• Gas or Bubbles

Evidence of Chemical Changes, Reactions or Bonding

• Color or Texture Change

Evidence of Chemical Changes, Reactions or Bonding

• Color and Texture Change that is not easily reversed

Evidence of Chemical Changes, Reactions or Bonding

• Forming of a Precipitate (adding to solutions and a solid is formed)

How to decide type of change

• Ask yourself: Can I easily turn substance back to the way it was?

If yes: physical changeIf no: chemical change

• Was the change awesome to watch? If yes: Probably chemical changeIf no: Probably physical change

• Did the name of the new substance change?If yes: Probably chemical If no: Probably physical

Examples of Chemical Change*

–The rusting of iron

–The baking of bread

–Burning of a match

–Fireworks

Example of a Chemical Change: The Electrolysis of Water

(H2O)

The Chemical Identity of Water ( H2O ) is changed into the elements Hydrogen ( H2 ) and Oxygen ( O2 )

Homework: Complete in notebookPhysical or chemical change with explanation

Sugar water

Frying an egg

Whipping egg whites

Melting of dry ice

Burning gasoline

Boiling water

Breaking glass

Souring milk

Sun tanning

Boiling coffee

Copy the chart below for the lab tomorrow (you need 10 rows)

Station Substances combined

Observations Physical or Chemical Change

1

2

3

4

5

6

7

8

9

10

Station # 1• Step 1 – measure 1 gram of baking soda and

put it into the 100 ml beaker• Step 2 – measure 1 mL of vinegar• Step 3 – pour the 1 mL of vinegar into beaker

with baking soda• Step 4 – observe what happens and record

observations and inference about whether you think it is a physical or chemical change

• Step 5 – clean up & rinse out the beaker and graduated cylinder in the sink

Station # 2• Step 1 – take a sheet of paper and drop it on to

the ground – how many seconds does it take to hit the ground?

• Step 2 – now crumple up the paper into a ball.• Step 3 – drop the paper ball from the same

height you dropped the flat paper – how many seconds does it take for the crumpled ball to hit the ground?

• Step 4 – observe what happens and record observations and inference about whether you think it is a physical or chemical change

• Step 5 – clean up

Station # 3• Step 1 – take a tarnished penny and try to clean

it with soap and water…does it work?• Step 2 – now try to clean it with a few drops of

lemon juice…does it work? • Step 3 – rinse and dry the penny and try to clean

it with water and salt…does it work?• Step 4 – now use a a few drops of lemon juice

and a dash or two of salt to try to clean the penny

• Step 5 – observe what happens and record observations and inference about whether you think it is a physical or chemical change

• Step 6 – clean up, rinse and dry the penny and put the penny in the plastic container on the counter

Station # 4• Step 1 – take a the 100 mL beaker and fill it with

water from the sink. • Step 2 – take one spoon full of table sugar and

put it in the beaker with water.• Step 3 – stir the sugar in the solution until

dissolved. • Step 4 – observe what happens and record

observations and inference about whether you think it is a physical or chemical change

• Step 5 – clean up & rinse out the beaker

Station # 5

• Step 1 – put 50 ml of water into the beaker• Step 2 – drop 2 – 3 drops of food coloring

into the water (one drop at a time) and watch

• Step 3 –observe what happens and record observations and inference about whether you think it is a physical or chemical change

• Step 4 – clean up & rinse out the beaker

Station # 6• Step 1 – measure out 10 mL of milk and pour

into beaker• Step 2 – in a different graduated cylinder

measure out 2 mL of vinegar and pour into the beaker with milk

• Step 3 – stir the milk and vinegar together • Step 4 – observe what happens and record

observations and inference about whether you think it is a physical or chemical change

• Step 5 – clean up & rinse out the beaker and graduated cylinder in the sink