Transcript Physical and Chemical Changes

CHANGING MATTER
PHYSICAL & CHEMICAL CHANGES
LESSON GOALS AND OBJECTIVES
I CAN
• EXPLAIN WHAT PHYSICAL CHANGES ARE AND HOW
MATTER CAN CHANGE FROM ONE STATE TO ANOTHER.
• EXPLAIN HOW CHEMICAL CHANGES CAN CAUSE SOME
KINDS OF MATTER TO BECOME NEW MATTER.
• DISTINGUISH BETWEEN A PHYSICAL AND CHEMICAL
CHANGE.
REVIEWING MATTER
• MATTER IS EVERYWHERE.
• MATTER IS ANYTHING WITH VOLUME AND MASS.
• HOW WE IDENTIFY MATTER: PROPERTIES
• MATTER HAS PROPERTIES
• TWO BASIC TYPES OF PROPERTIES THAT WE CAN
ASSOCIATE WITH MATTER.
• PHYSICAL PROPERTIES
• CHEMICAL PROPERTIES
PHYSICAL PROPERTIES
• ANYTHING THAT CAN BE OBSERVED WITHOUT CHANGING THE
IDENTITY OF THE SUBSTANCE. (TENDS TO BE MEASURABLE.)
•
•
•
•
melting point
boiling point
electrical conductivity
color
•
•
•
•
density
thermal conductivity
ductility
malleability
CHEMICAL PROPERTIES
• THE WAY A SUBSTANCE MAY CHANGE OR REACT TO FORM NEW SUBSTANCES
• heat of combustion
• reactivity with water
• pH
• Oxidation
• Flammability
• Reactivity to other
chemicals
CHANGING MATTER
•MATTER IS CONSTANTLY EXPERIENCING
BOTH CHEMICAL AND PHYSICAL CHANGES.
•MATTER CAN BE CHANGED TWO WAYS
•PHYSICALLY
•CHEMICALLY
PHYSICAL CHANGES
•
A PHYSICAL CHANGE IS A CHANGE IN A SUBSTANCE THAT DOES NOT CHANGE THE
IDENTITY OF THE SUBSTANCE.
•
NO NEW SUBSTANCES ARE FORMED.
•
CHANGE IN THE FORM OF A SUBSTANCE, NOT IN ITS CHEMICAL COMPOSITION.
•
SUBSTANCE MAY SEEM DIFFERENT, BUT THE WAY THE ATOMS LINK UP IS THE SAME.
•
A PHYSICAL CHANGE ALTERS THE FORM OF A SUBSTANCE, BUT DOES NOT CHANGE IT
TO ANOTHER SUBSTANCE.
•
PHYSICAL CHANGES ARE THOSE CHANGES THAT DO NOT RESULT IN THE PRODUCTION OF
A NEW SUBSTANCE. IF YOU MELT A BLOCK OF ICE, YOU STILL HAVE H2O AT THE END OF
THE CHANGE.
PHYSICAL CHANGE – EXAMPLES
CHANGE IN SIZE OR
SHAPE
•
•
•
•
MASS
VOLUME
DENSITY
WEIGHT
DILUTIONS
DISSOLVING
MAKING A MIXTURE
• 2 OR MORE TYPES OF MATTER
(SUBSTANCES) MIXED TOGETHER
• NOT IN SPECIFIC AMOUNTS
• CAN BE SEPARATED PHYSICALLY
PHYSICAL CHANGE – EXAMPLES
• CHANGE IN PHASE
•
IN ALL THREE PHASES, WATER
MOLECULES ARE STILL INTACT.
•
MOTIONS OF MOLECULES AND
THE DISTANCES BETWEEN THEM
CHANGE.
• MELTING (SOLID TO LIQUID)
• BOILING (LIQUID TO GAS)
• VAPORATION (LIQUID TO GAS)
• CONDENSATION (GAS TO LIQUID)
• FREEZING (LIQUID TO SOLID)
• SUBLIMATION (SOLID TO GAS)
• DEPOSITION (GAS TO SOLID)
PHYSICAL CHANGE
• PHYSICAL CHANGES MIGHT BE CAUSED BY:
• GRINDING
• CUTTING
• CRUSHING
• BENDING
• BREAKING
• HEATING/COOLING (CHANGE IN PHASE)
• SQUISHING
PHYSICAL CHANGE
• EVIDENCE THAT A PHYSICAL CHANGE HAS OCCURRED
MIGHT INCLUDE:
• CHANGE IN SHAPE
• CHANGE IN FORM
• CHANGE IN SIZE
• CHANGE IN PHASE (THIS IS ALWAYS A PHYSICAL CHANGE!)
• PHYSICAL CHANGES ARE USUALLY REVERSIBLE
• IF YOU REMEMBER, ICE IS WATER IN THE SOLID STATE.
• WHEN YOU DROP THE ICE CUBE INTO THE LIQUID, IT
BEGINS TO MELT BECAUSE THE TEMPERATURE IS HIGHER
THAN THAT OF THE ICE CUBE.
• IT'S LIKE PUTTING A SNOWMAN ON YOUR FRONT LAWN
IN JULY.
• THE ICE CUBE BECOMES LIQUID WATER.
• THIS IS AN EXAMPLE OF A PHYSICAL CHANGE.
• THE SOLID WATER TURNED TO LIQUID WATER.
PHYSICAL CHANGE
SPECIAL TYPES OF PHYSICAL CHANGES
WHERE ANY OBJECT CHANGES STATE,
SUCH AS WHEN WATER FREEZES OR
EVAPORATES, ARE SOMETIMES CALLED
CHANGE OF STATE OPERATIONS.
MORE EXAMPLES OF PHYSICAL CHANGES
• CHANGE IN SIZE, SHAPE, OR COLOR
• PENCIL SHAVINGS
• TORN PAPER
• CRUSHED ICE
• SUGAR DISSOLVED IN WATER
• PAINTING A WALL
CAN YOU THINK OF WAYS THAT YOU CAN
PHYSICALLY CHANGE A SHEET OF PAPER?
• CUTTING
• TEARING
• SHREDDING
• FOLDING
• PAINTING
• WRITING ON
• GLUING
PHYSICAL CHANGE
• WHAT COULD
YOU DO TO THESE
ITEMS TO CAUSE A
PHYSICAL CHANGE
TO OCCUR?
PHYSICAL AND
CHEMICAL CHANGES
HOW TO TELL THE
DIFFERENCE
IF YOU BREAK A BOTTLE, YOU STILL
HAVE GLASS. PAINTING YOUR NAILS
WILL NOT STOP THEM FROM BEING
FINGERNAILS. SOME COMMON
EXAMPLES OF PHYSICAL CHANGES ARE:
MELTING, FREEZING, CONDENSING,
BREAKING, CRUSHING, CUTTING, AND
BENDING.
SOME, BUT NOT ALL PHYSICAL CHANGES
CAN BE REVERSED. YOU COULD
REFREEZE THE WATER INTO ICE, BUT YOU
CANNOT PUT YOUR HAIR BACK
TOGETHER IF YOU DON’T LIKE YOUR
HAIRCUT!
CONCEPT CHECK
1. WHICH OF THE FOLLOWING ARE PHYSICAL
PROPERTIES?
a) LIQUID AT ROOM TEMPERATURE
b) REACTS WITH METALS TO FORM H2 GAS
c) ACIDS AND BASES COMBINE TO FORM WATER
AND A ‘SALT’
d) BOILS AT 145 DEGREES CELSIUS
CHEMICAL PROPERTIES
Remember?
Chemical properties can ONLY be
observed AS the substances are changing
into different substances.
CHEMICAL CHANGES
• CHEMICAL CHANGES DO ALTER THE IDENTITY OF
A SUBSTANCE
• IN OTHER WORDS, A CHEMICAL CHANGE IS
WHEN SOMETHING CHANGES INTO AN ENTIRELY
DIFFERENT SUBSTANCE
• THE COMPOSITION OF THE SUBSTANCE
CHANGES.
• THE SUBSTANCES PRESENT AT THE BEGINNING
OF THE CHANGE ARE NOT PRESENT AT THE
END
• NEW SUBSTANCES ARE FORMED.
• THE CHANGE CANNOT BE “UNDONE.”
CHEMICAL CHANGE
• CHEMICAL CHANGES
OCCUR WHEN A
CHEMICAL REACTION
CAUSES BONDS
BETWEEN ATOMS TO
BREAK OR TO FORM.
CHEMICAL CHANGES
• ATOMS ARE RE-ARRANGED,
NOT CREATED OR DESTROYED
EXAMPLES OF CHEMICAL CHANGES
• WHEN YOU BURN A LOG IN A FIREPLACE, YOU ARE
CARRYING OUT A CHEMICAL REACTION THAT RELEASES
CARBON. WHEN YOU LIGHT YOUR BUNSEN BURNER IN LAB,
YOU ARE CARRYING OUT A CHEMICAL REACTION THAT
PRODUCES WATER AND CARBON DIOXIDE.
REACTIVITY
HOW READILY (EASILY) A SUBSTANCE COMBINES
CHEMICALLY WITH OTHER SUBSTANCES.
REACTIONS WITH
ACID
REACTIONS WITH
OXYGEN
REACTIONS WITH
ELECTRICITY
VINEGAR + BAKING
SODA = RELEASE OF
CARBON DIOXIDE GAS
OXIDATION
SILVER PLATING
IRON + OXYGEN = RUST
Reactions between
Substances
Sodium + chloride = salt
Silver + sulfur in the air =
tarnish
REACTS WITH ACIDS
There were a few horror movies made in the 70s, 80s, and 90s and even this decade
starring these guys:
Besides many gross events, one of the things the people in the movie quickly realize is
that if you cut or damage one of these aliens, it bled a concentrated acid that would
“melt” or “corrode” anything it came into contact with. Nasty.
WHAT’S THE
POINT OF
THIS?
DEBUNKING THE MYTH
Well, I think those movies have perpetuated a myth common to many people
that acids are all super-harmful, extremely dangerous, eat-through-anything
chemicals. Really? Here’s some examples of acidic compounds:
So…not ALL acids are
instant-death, huh.
Now, some of those acids can be pretty powerful substances. The next time you lose a tooth or
eat a chicken wing, soak that bone in coke for a few days and observe it…no wonder dentists
don’t like soda. Acids (and their opposites…bases) are just reactive chemicals that behave in
certain ways. Here are some common bases:
IS THERE A POINT TO THIS?
Well, yeah. Acids and bases are just a few of MANY kinds of chemicals that can
react with each other. When chemicals react, they rearrange their atoms & molecules
to produce new substances. New substances! Chemical change!
You’re familiar with baking soda and vinegar, right?
They combine…
They react and make a
new substance (CO2 gas)
And we
all know
that gas
under
high
pressure
can be
fun…or
deadly.
FLAMMABILITY: A MATERIAL’S
ABILITY TO BURN IN THE
PRESENCE OF OXYGEN
OTHER EXAMPLES
• WOOD BURNING
• METAL RUSTING
• FOOD DIGESTING
• GASOLINE BURNING
• CAKE BAKING
• RESPIRATION
• PHOTOSYNTHESIS
• DECOMPOSITION
• POLYMERIZATION
ELECTROLYSIS OF WATER
Copyright © Cengage Learning. All rights
reserved
ELECTROLYSIS OF WATER
•
WATER DECOMPOSES TO HYDROGEN AND OXYGEN
GASES.
Copyright © Cengage Learning. All rights
reserved
COMMON ERRORS
• ICE MELTING, WATER FREEZING, WATER
EVAPORATING, AND STEAM CONDENSING ARE ALL
EXAMPLES OF A STATE CHANGE.
• THESE ARE PHYSICAL CHANGES, NOT CHEMICAL.
• DILUTING A SOLUTION IS A PHYSICAL CHANGE, EVEN IF
THE COLOR BECOMES MORE FAINT.
CONCEPT CHECK
HOW MANY OF THE FOLLOWING ARE EXAMPLES OF A
CHEMICAL CHANGE?
1)
2)
3)
4)
PULVERIZING (CRUSHING) ROCK SALT
BURNING OF WOOD
DISSOLVING OF SUGAR IN WATER
MELTING A POPSICLE ON A WARM SUMMER DAY
CONCEPT CHECK
CLASSIFY EACH OF THE FOLLOWING AS A PHYSICAL OR CHEMICAL
CHANGE.
 SUGAR FERMENTING TO FORM ETHYL ALCOHOL
CHEMICAL
 IRON METAL MELTING
PHYSICAL
 IRON COMBINING WITH OXYGEN TO FORM RUST
CHEMICAL
Copyright © Cengage Learning. All rights
reserved
HOW DO WE KNOW IF A CHEMICAL CHANGE HAS OCCURRED?
Possible Indicators of a Chemical Change
Energy Release
(a change in
temperature heats up
or cools down/light)
ex: match burns,
cold packs cool
Forms bubbles or
Permanent
odor released
gas
unexpected color
new gases
ex: vinegar + baking change
ex: baking
ex: burning
bread creates
soda  CO2
wood changes its
color
Irreversibility
difficult to reverse
ex: can’t turn a
cookie back into
dough
Production of a gas
ex: vinegar and
baking soda
produces CO2
Formation of a
precipitate
ex: vinegar and milk
forms curds (cheese)
Light is produced
and/or sound is
given off
Ex: fireworks
Change in
temperature
ex: water and baking
soda feels cool
ex: hydrogen
peroxide and yeast
feels hot
Change in color
ex: pH indicator
going from colorless
to color
NOT an ex: food
coloring in water
CHEMICAL CHANGE INDICATORS
• EVIDENCE OF A CHEMICAL REACTION
• DIFFICULT OR IMPOSSIBLE TO REVERSE
• FORMATION OF GAS
• FORMATION OF PRECIPITATE
• CHANGE IN COLOR
• CHANGE IN ENERGY
ABSORBS HEAT ENERGY
(GETS COLD)
• EXOTHERMIC RELEASES HEAT ENERGY
(GETS HOT)
Evidence of Chemical Change
ENERGY RELEASE
A chemical reaction often releases forms of energy such as light and
heat.
Glow sticks work when a capsule of
phenyl oxalate is broken (by you) and it mixes
with hydrogen peroxide. This releases
energy that causes a colored dye to glow with
light.
When you burn something, the fuel is
reacting with oxygen in the air to produce
fire–a combination of heat AND light.
FORMS BUBBLES OR GAS
Well, back to vinegar and baking soda…the huge release of gas is
a good sign that a new substance (the gas, duh) has been produced.
Hydrochloric acid creates hydrogen gas
when reacting with zinc metal.
COLOR
A permanent, unexpected change in color often lets you know that a
substance has been chemically, not physically, changed into a new
substance.
mmm…the perfect cookies
Whoa!  The total change in color
to “char black” is a chemical change.
ODORS
Yes. Here’s another one…imagine what this:
•odor released
ex: baking bread creates
new gases
Perfectly good
cookies.
RUINED.
…smells like. Probably not the
way it smelled 10 minutes before
being pulled out of the oven.
ONE LAST ONE…
What do the previous four indicators of chemical change have in
common?
They let you know
that a chemical change
has happened?
Well, yeah, no kidding.
BESIDES that?
ALL HARD TO REVERSE!
Yeah! Imagine trying to stuff the heat and light back into a burning
candle.
Uh huh…ouch.
Or imagine trying to get burned cookies to go back to
being brown. Or take it another step. Try to get a
nicely baked cookie to “unbake” and turn into cookie
dough.
gee…how?
IRREVERSIBILITY
•difficult to reverse
ex: can’t turn a cookie back into dough
Chemical Changes
THE OTHER KIND OF CHANGE
So…the other kind of changes tend to:
a. Not release heat or light
b. Not release gas or bubbles
c. Not change the color of something permanently
d. Not release new odors
e. Be somewhat reversible
You can cut, mash, smash, stretch, flatten, divide, shave, freeze, thaw
cookie dough and it’s STILL cookie dough. Those kinds of changes
haven’t made new substances.
Let’s see you put this all together. A ____ change happens when no new substance is
made. The opposite kind of change, a ____ change, DOES create a new substance.
PRACTICE, PRACTICE, PRACTICE
I CAN DISTINGUISH BETWEEN A
PHYSICAL AND CHEMICAL
CHANGE.
WHAT KIND OF CHANGE IS IT IF
SOMEONE...
•TEARS UP PAPER?
•PHYSICAL CHANGE
•MIXES SALT AND
WATER?
•PHYSICAL CHANGE
WHAT KIND OF CHANGE IS IT IF
SOMEONE...
•BURNS PAPER?
•CHEMICAL CHANGE
•EVAPORATES SALT
WATER?
•PHYSICAL CHANGE
WHAT KIND OF CHANGE IS IT IF
SOMEONE...
•MIXES VINEGAR
AND BAKING SODA?
•CHEMICAL CHANGE
QUIZ TIME!
• WHICH LIFE CYCLE IS MOST
SIMILAR TO A CHEMICAL
CHANGE?
• WHY?
Grasshopper =
Eggnymphadult
Butterfly =
egglarvapupaadult
QUIZ TIME!
• WHAT TYPE OF CHANGE
IS MOST LIKELY
OCCURRING HERE?
• HOW DO YOU KNOW?
QUIZ TIME!
• WHAT TYPE OF
CHANGE IS MOST
LIKELY OCCURRING
HERE?
• HOW DO YOU
KNOW?
QUIZ TIME
• WHAT TYPE OF
CHANGE IS MOST
LIKELY OCCURRING
HERE?
• HOW DO YOU
KNOW?
PHYSICAL OR CHEMICAL
CHANGE?
• WATER EVAPORATES
FROM THE OCEAN.
PHYSICAL OR CHEMICAL
CHANGE?
• THE YOLK OF AN EGG,
WHICH CONTAINS
SULFUR, CAUSES
TARNISH TO FORM ON
SILVER.
PHYSICAL OR CHEMICAL
CHANGE?
• THE ICE ON A LAKE
MELTS TO BECOME
WATER IN THE LAKE.
PHYSICAL OR CHEMICAL
CHANGE?
• CHARCOAL IN A FIRE
TURNS TO ASH AFTER
SEVERAL HOURS.
PHYSICAL OR CHEMICAL
CHANGE?
• A PENCIL IS
SHARPENED IN A
PENCIL SHARPENER,
LEAVING BEHIND
SHAVINGS.
PHYSICAL OR CHEMICAL
CHANGE?
• A BATTERY MAKES
ELECTRICITY TO TURN
ON A FLASHLIGHT.
PHYSICAL OR CHEMICAL
CHANGE?
• A BICYCLE RUSTS WHEN LEFT IN THE
RAIN.
PHYSICAL OR CHEMICAL
CHANGE?
• A SHIRT IS
ACCIDENTALLY TORN
IN THE WASHING
MACHINE.
PHYSICAL OR CHEMICAL
CHANGE?
• A LOG IS SPLIT IN TWO
BY AN AXE.
CHEMICAL OR PHYSICAL CHANGE?
• CUTTING
PAPER?
• PHYSICAL
CHEMICAL OR PHYSICAL CHANGE?
• ICE MELTING?
• PHYSICAL
CHEMICAL OR PHYSICAL CHANGE?
• BREAD
TOASTING?
• CHEMICAL
CHEMICAL OR PHYSICAL CHANGE?
• ROCKET FUEL
BURNING?
• CHEMICAL
CHEMICAL OR PHYSICAL CHANGE?
• SAWING WOOD?
• PHYSICAL
CHEMICAL OR PHYSICAL CHANGE?
• METAL
RUSTING?
• CHEMICAL
CHEMICAL OR PHYSICAL CHANGE?
•DISAPPEARING
PUDDLE?
•PHYSICAL
CHEMICAL OR PHYSICAL CHANGE?
• CANDLE
BURNING?
• CHEMICAL
CHEMICAL OR PHYSICAL CHANGE?
• DRY ICE?
• PHYSICAL
PHYSICAL OR CHEMICAL CHANGE?
•PAINTING WOOD
•PHYSICAL
Physical or Chemical Change?
• Burning Paper
• CHEMICAL
Physical or Chemical Change?
• Digestion of food
• CHEMICAL
Physical or Chemical Change?
• Sugar dissolving in
water
• PHYSICAL
Physical or Chemical Change?
• Iron turning red when
heated
• PHYSICAL
Physical or Chemical Change?
• Evaporation
• PHYSICAL
Physical or Chemical Change?
• A pond freezing in
winter
• PHYSICAL
Physical or Chemical Change?
• Melting ice
• PHYSICAL
Physical or Chemical Change?
• Cutting wire
• PHYSICAL
Physical or Chemical Change?
• Painting fingernails
• PHYSICAL
Physical or Chemical Change?
• Cutting fabric
• PHYSICAL
Physical or Chemical Change?
• Baking muffins
• CHEMICAL
Physical or Chemical Change?
• Shattering glass
• PHYSICAL
Physical or Chemical Change?
• Decomposition of old
leaves
• CHEMICAL
Physical or Chemical Change?
• Wrinkling a shirt
• PHYSICAL
Physical or Chemical Change?
• An old nail rusting
• CHEMICAL
CONCEPT CHECK
• SUBSTANCE A IS A YELLOW LIQUID AND SUBSTANCE B IS
A BLUE LIQUID. THE TWO ARE MIXED AND FORM A
GREEN LIQUID AND A WHITE SOLID.
• WHAT EVIDENCE SUGGESTS A CHEMICAL CHANGE
OCCURRED?
• WHAT OTHER THINGS COULD YOU LOOK FOR TO
DETERMINE IF THERE WAS A CHEMICAL CHANGE?
STOP & THINK
- WHICH SHOWS PHYSICAL CHANGE AND WHICH
SHOWS CHEMICAL CHANGE?
• LINK TO CHANGE ANIMATION #1
• LINK TO CHANGE ANIMATION #2
PHYSICAL AND CHEMICAL
CHANGES
QUIZ
Number your paper (1-10)
1. A. PHYSICAL CHANGE
B. CHEMICAL CHANGE
Rusting nails
2. A. PHYSICAL CHANGE
B. CHEMICAL CHANGE
Effervescent tablet
3. A. PHYSICAL CHANGE
B. CHEMICAL CHANGE
Cut paper
4. A. PHYSICAL CHANGE
B. CHEMICAL CHANGE
Vinegar and Baking soda
5. A. PHYSICAL CHANGE
B. CHEMICAL CHANGE
Salt and water
6. A. PHYSICAL CHANGE
B. CHEMICAL CHANGE
Broken glass
7. A. PHYSICAL CHANGE
B. CHEMICAL CHANGE
Burning wood
8. A. PHYSICAL CHANGE
B. CHEMICAL CHANGE
Ice melting
9. A. Physical Change
B. Chemical Change
Removing iron filings from a mixture
10. A. Physical Change
B. Chemical Change
Boiling water
1.
CHECK YOUR PAPER AND PLACE IN
NOTEBOOK
B - CHEMICAL
2. B - CHEMICAL
3. A - PHYSICAL
4. B - CHEMICAL
5. A - PHYSICAL
6. A - PHYSICAL
7. B - CHEMICAL
8. A - PHYSICAL
9. A - PHYSICAL
10. A - PHYSICAL