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* Color Size Shape Texture 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 change If no: chemical change Was the change awesome to watch? If yes: Probably chemical change If 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 notebook Physical 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