Transcript Physical and Chemical Changes

Physical and
Chemical
Changes
3rd Quarter 2012
Kinetic Theory of Matter
THEORY OF KINETIC
ENERGY
A. ATOMS ARE ALWAYS
MOVING
B. THE MORE ENERGY ADDED
TO THE ATOMS, THE FASTER
& FARTHER APART THEY
MOVE
Physical Changes
Matter is always changing form, size, shape,
color, etc. There are 2 types of changes
that matter undergoes.
PHYSICAL OR CHEMICAL CHANGE
I. Physical Changes: a change of matter
without changing the identity of the
substance. IN OTHER WORDS
– A CHANGE IN STATE
– A CHANGE IN SIZE, SHAPE, MASS
– DOES NOT CHANGE THE CHEMICAL
MAKE UP OF THE MATTER
– YOU HAVE WHAT YOU STARTED
WITH JUST IN A DIFFERENT FORM
Examples of Physical
Changes
- Verbs used to describe physical
changes – grind, dissolve, erode,
rip, tear, break, phase change
(melt, freeze, condense, etc)
Other Physical Change
Examples
• PAPER TORN INTO PIECES
–SUGAR DISSOLVED INTO TEA
–SALT DISSOLVED INTO WATER
–NAILS OR HAIR CUT
Phase Changes are PHYSICAL
PHYSICAL!!!!!
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Types of Phase Changes:
1. Melting
2. Freezing
3. Evaporization
4. Condensation
5. Sublimation
6. Deposition
ALL phase changes are caused by
ADDING or TAKING away energy!!!
• MATTER CHANGES FROM ONE
STATE OF MATTER TO ANOTHER
–WHEN HEAT (ENERGY) IS ADDED
–WHEN HEAT (ENERGY IS TAKEN
AWAY
DRAW THIS DIAGRAM IN YOUR
NOTES!!!!
• CHANGING STATES DOES NOT
CHANGE THE CHEMICAL MAKE UP
OF THE MATTER
• YOU HAVE WHAT YOU STARTED
WITH JUST IN A DIFFERENT
FORM
• ICE  WATER  WATER VAPOR
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H 2O
H 2O
H 2O
• WHEN MOLECULES MOVE FASTER, THEY
PRODUCE MORE FRICTION AND THEREFORE
MORE HEAT. THEY SPREAD FARTHER APART
& EXPAND
• WHEN MOLECULES MOVE SLOWER, THEY
CAUSE LESS FRICTION AND THEREFORE
LESS HEAT & CLOSER TOGETHER &
CONTRACT
Melting
1. MELTING – matter changing FROM A
SOLID TO A LIQUID.
– Energy is added
– When more heat (energy) is added
to matter the particles move faster
till the bonds break.
– Decrease density except ice to
water.
Evaporation/Vaporization
2. EVAPORATION
– Matter changing FROM A LIQUID TO
A GAS AT THE SURFACE
– ENERGY IS ADDED TO SURFACE OF
LIQUID
– THE PARTICLES AT THE SURFACE
MOVE FASTER breaking bonds.
– Decreases density.
• VAPORIZATION- a
general term for any
substance changing to
a gas.
Boiling
3. BOILING
– matter changing FROM A LIQUID TO A GAS
ALL THROUGHOUT THE LIQUID
– ENERGY IS ADDED TO ALL OF LIQUID
– PARTICLES MOVE FASTER ALL THROUGH THE
LIQUID
– SOME PARTICLES MOVE FAST ENOUGH TO
CHANGE TO GAS WHILE THEY ARE IN THE
MIDDLE OF THE LIQUID
– DENSITY DESCREASES
– Water boils at 212 F, 100C.
• EX: pan of liquid on the stove
• VAPORIZATION- a general term
for any substance changing to a gas.
VAPORIZATION!!!
• Remember that vaporization is a
general word for any substance
changing to a gas.
• Boiling, evaporation, and sublimation
are ALL examples of vaporization!!!
Condensation
4. CONDENSATION
– Matter CHANGING FROM A GAS TO A LIQUID
– ENERGY IS REMOVED
• THE PARTICLES MOVE SLOWER
• THE ATTRACTION BETWEEN THE PARTICLES BEGAN
TO PULL THE PARTICLES CLOSER TOGETHER & THE
MATTER TURNS INTO A LIQUID
• DENSTITY INCREASES
• Ex: dew in the lawn, water running down mirror, ring on table
under glass.
• FREEZING
Freezing
– CHANGING FROM A LIQUID TO A SOLID
– ENERGY IS REMOVED
• THE PARTICLES MOVE EVEN SLOWER
• THE ATTRACTION BETWEEN THE PARTICLES
BEGAN TO PULL THE PARTICLES CLOSER
TOGETHER & THE MATTER TURNS INTO A
SOLID
• Increase density.
• Water freezes at 32 F, 0 C
• EX: water to ice, wax or chocolate hardening
SOLIDIFICATION!!!!
• Solidification is a general word for
any substance changing to a solid.
• Freezing and deposition are
examples of SOLIDIFICATION!
Sublimation
• 5. Sublimation: matter changes straight
from a solid to a gas!!!!
• Heat added rapidly
• Molecules speed up and spread out rapidly
• decrease density
• Examples of Sublimation:
dry ice, shrinking ice in a
freezer, air freshener.
Deposition
-Deposition- when matter changes
from a gas directly to a solid.
-Heat is taken away rapidly
-Density increases
-Molecules slow down and get closer
together.
Examples:
Snowflakes,
frost on a wind shield
• WHAT HAS TO HAPPEN FOR
THESE CHANGES OF STATES TO
OCCUR?
Bellringer 2:
1. All phase changes are:
a. physical properties
b. physical changes
c. Chemical properties
d. chemical changes
2. Condensation is:
a. Liquid to gas
b. Gas to solid
c. Solid to gas
d. gas to liquid
Let’s Sing!!!!
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Phase changes are physical, physical…
Melting is physical…. Freezing is physical.
BOYS: Let me see some condensation.
GIRLS: (in high pitch voice) It’s physical.
BOYS: Let me see some sublimation.
GIRLS: (in high pitch voice) It’s physical.
Phase changes are physical, physical…
Boiling is physical… Boiling is physical…
BOYS: Let me see some deposition.
GIRLS: (in high pitch voice) It’s physical
BOYS: Let me see some evaporation.
GIRLS: (in high pitch voice) It’s physical
Chemical Changes
The other way that matter can be
changed is call a CHEMICAL
CHANGE.
occurs
when 2 or more substances
are combined into entirely
new substance with all new
properties. CANNOT
CHANGE IT BACK!!!!!
II. CHEMICAL CHANGE –
Chemical Change Verbs
• Chemical Change Verbs: rusting,
rotting, curdling, burning, cooking,
light sensitivity, digesting,
tarnishing.
Chemical Changes
– SOME SIGNS OF A CHEMICAL CHANGE
• FIZZES OR BUBBLES
• COLOR CHANGE
• HEAT GIVEN OFF
• LIGHT GIVEN OFF
• ODOR
• HEAT REQUIRED FOR REACTION
• NEW SUBSTANCE FORMED
– Precipitate (solid)
– Precipitate (gas bubbles)
• CHEMICAL CHANGE EXAMPLES
–BAKING BREAD – NO LONGER
HAVE FLOUR, EGGS, MILK,
YEAST
–ALKASELTER
–BAKING SODA & VINEGAR
–RUST
–TARNISH