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LESSON 8 - PHYSICAL AND CHEMICAL CHANGES

VOCABULARY
CHANGE OF STATE, CHEMICAL CHANGE, PHYSICAL CHANGE


DEMONSTRATION:

CHARCOAL ON THE RISE!

PROBLEM: WHAT IS THE DIFFERENCE BETWEEN THE TWO CHANGES IN THE SUGAR. WHY?

HYPOTHESIS:

MATERIALS: 100 ML OF SUGAR CRYSTALS, TWO 100 ML BEAKERS, TWO GLASS STIRRING RODS, GO OUTDOORS OR UNDER A FUME HOOD!

PROCEDURE:

  1. FILL EACH BEAKER HALF FULL OF SUGAR.
  2. ADD ABOUT 40 ML OF WATER TO THE FIRST BEAKER AND THE SAME AMOUNT OF CONCENTRATED SULFURIC ACID TO THE SECOND BEAKER.
  3. STIR AND LET IT STAND.
  4. OBSERVE THE DIFFERENCE BETWEEN THE TWO CHANGES IN THE SUGAR.
  5. ASK: "IN WHICH BEAKER DO THE REACTANTS STILL HAVE THE SAME PROPERTIES?"

OBSERVATION:

CONCLUSION:

  CHARCOAL BUTTTON

DISCUSSION BUTTON

  1. WHAT IS THE DIFFERENCE BETWEEN THE PROCESSES IN BEAKER I AND BEAKER II?
  2. HOW CAN WE RECOGNIZE OR DISTINGUISH BETWEEN A PHYSICAL CHANGE AND A CHEMICAL CHANGE?
  3. IN WHICH OF THE TWO BEAKERS COULD WE GET THE SUGAR BACK AS SUGAR?
  4. WHAT DO YOU THINK HAPPENED IN THE SECOND BEAKER?
  5. WHAT PROPERTY DO YOU THINK CONCENTRATED SULFURIC ACID HAS?
  6. WHAT DO YOU THINK THE BLACK MATERIAL IN BEAKER TWO IS?

CHANGE

THERE ARE TWO TYPES OF CHANGE:

  • PHYSICAL CHANGE
  • CHEMICAL CHANGE

IN A PHYSICAL CHANGE THERE IS ONLY A CHANGE OF STATE. THE NEW SUBSTANCE HAS THE SAME PROPERTIES AS THE OLD ONE. NO NEW SUBSTANCE(S) ARE PRODUCED.

ICE - WATER - STEAM (THEY ARE ALL STILL WATER!) FOR EXAMPLE: ICE MELTING TO WATER OR WATER BOILING.

**IN ALL OF THESE CHANGES, YOU CAN GET THE ORIGINAL MATERIALS BACK!**

A PHYSICAL CHANGE MAY ALSO INVOLVE CHANGING THE SHAPE OF THE SUBSTANCE.

PAPER CUT INTO PIECES IS STILL PAPER, SLOUGHING A FIELD BUT THE FIELD STILL REMAINS AS SOIL, CUTTING WOOD INTO PIECES IS STILL WOOD, AND MOLDING A SCULPTURE IS STILL CEMENT OR MARBLE!

PHYSICAL CHANGE BUTTON

IN A CHEMICAL CHANGE ONE OR MORE NEW SUBSTANCES ARE CREATED. THE NEW SUBSTANCE IS DIFFERENT FROM THE ORIGINAL. IT HAS PROPERTIES THAT ARE DIFFERENT THAN THOSE OF THE STARTING MATERIALS. PLUS, YOU CANNOT GET THE ORIGINAL MATERIALS BACK EASILY.

(THINK ABOUT AN ORDINARY BOX OF MATCHES. A SINGLE MATCH IN A BOX CAN REMAIN UNCHANGED FOREVER. BUT IF SOMEONE WERE TO TAKE THE MATCH AND THEN LIGHT IT...A FLAME LIGHTS UP AND THEN BURNS OUT. WHAT REMAINS WILL HAVE CHANGED FOREVER! THE MATCH CAN NEVER BE LIGHTED AGAIN. THE MATCH HAS UNDERGONE A CHEMICAL REACTION.)TO VIEW A QUICK MOVIE OF A CHEMICAL CHANGE, CLICK THE BUTTON BELOW!

CHEMICAL CHANGE BUTTON

HERE ARE SOME OTHER EXAMPLES OF CHEMICAL REACTIONS:

RAW EGG RAW EGG BECOMES COOKED EGG
COOKED EGG
CAKE BATTER CAKE MIX
BECOMES CAKE
ANGEL FOOD CAKE
NEWSPAPER PAPER BECOMES ASH
ASHES
NEW VEHICLE STEEL BECOMES RUST
OLD, WRECKED AND RUSTED  VEHICLE

 

QUESTION MARK CAN YOU THINK OF OTHER CHEMICAL REACTIONS THAT OCCUR IN EVERYDAY LIFE?

THINK ABOUT THESE CHANGES...

QUESTION MARK WHAT MIGHT BE SOME CLUES THAT WOULD HELP US KNOW WHETHER OR NOT THE CHANGE IS CHEMICAL?

 


ACTIVITY
1). CHEMICAL CHANGE OR PHYSICAL CHANGE?
STATE WHETHER THE FOLLOWING CHANGES ARE CHEMICAL OR PHYSICAL.

  • BOILING WATER
  • TEARING CLOTHES
  • TARNISHING SILVER
  • LIGHTING A MATCH
  • CHEWING A FOOD
  • BREAKING A STICK
  • RUSTING NAIL
  • BURNING GAS IN A STOVE
  • MELTING ICE CREAM
  • SAWING WOOD
  • OXIDIZING FOOD FOR ENERGY
  • STRETCHING A RUBBER BAND

2). FIND THREE EXAMPLES OF CHEMICAL AND PHYSICAL CHANGES IN EVERYDAY LIFE. EXPLAIN WHY EACH OF THESE CHANGES ARE EITHER CHEMICAL OR PHYSICAL.

ACTIVITY

LAB: MELT IT!

PROBLEM: WHICH ICE CUBE WILL MELT THE FASTEST? WHY? A: THE ICE CUBE LEFT ON THE KITCHEN COUNTER. B: THE ICE CUBE LEFT IN A HOT SPOT. C: THE ICE CUBE WITH SALT ON IT. D: THE ICE CUBE CRUSHED GENTLY WITH A HEAVY UTENSIL OR HAMMER.

MATERIALS:
4 ICE CUBES, SAME SIZE
4 SMALL DISHES
SALT
HAMMER OR HEAVY UTENSIL

PROCEDURE:

  1. PUT AN ICE CUBE ON EACH PLATE.
  2. LEAVE ONE ON THE KITCHEN COUNTER.
  3. FIND A HOT SPOT AROUND YOUR LAB OR CLASSROOM. (ON A WINDOWSILL OR NEXT TO A HEATER).
  4. PUT ONE ICE CUBE IN THE HOT SPOT.
  5. POUR SALT ON THE THIRD ICE CUBE.
  6. PUT THIS ICE CUBE ON A TABLE OR COUNTER.
  7. CRUSH THE LAST ICE CUBE GENTLY WITH A HAMMER OR HEAVY UTENSIL AND LEAVE IT ON THE COUNTER.
  8. WAIT A FEW MINUTES. CHECK YOUR ICE CUBES AND SEE WHAT HAPPENED.
  9. WHICH ICE CUBE MELTED THE FASTEST? COMPARE HOW LONG IT TAKES FOR THE ICE CUBES TO MELT.

OBSERVATIONS:

  1. OBSERVE AND RECORD WHAT HAPPENS.
  2. RECORD THE TIME TO THE MINUTE ON YOUR DATA SHEET.
  3. TRANSLATE YOUR COLLECTED DATA INTO A GRAPH.

CONCLUSION:

EXTENSION BUTTON
TO MAKE A CONNECTION TO LITERACY, WRITE A STORY TO EXPLAIN WHAT HAPPENS TO A SNOWMAN WHO SITS FOR TWO HOURS ON A SUNNY DAY! MAKE SURE YOU GO INTO DETAIL FOLLOWING THE STEPS YOU OBSERVED AS THE ICE CUBE MELTED IN THE LAB.

ACTIVITY BUTTON
STATIONS BUTTONUSING THE DATA COLLECTION SHEET PROVIDED, GO THROUGH THE VARIOUS STATIONS AND DETERMINE WHETHER THE CHANGE IS PHYSICAL OR CHEMICAL. MAKE SURE TO INDICATE THE REASONS OR CHARACTERISTICS THAT HELPED YOU TO DECIDED IF IT WAS A CHEMICAL OR PHYSICAL CHANGE.

 

ASSESSMENT/EVALUATION BUTTON

CLASSIFY THE CHANGES LISTED BELOW AS EITHER PHYSICAL OR CHEMICAL, THEN GIVE A REASON FOR YOUR DECISION.

CHANGE/TYPE/REASON PDF: FILL IN THE INFORMATION ABOUT THE TYPE AND THE REASON WHY IT IS A CHEMICAL OR PHYSICAL CHANGE.


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