Transcript Chemical Changes

PHYSICAL AND
CHEMICAL CHANGES
Third Year Level
Preciosa V. Cabrera
Ismael Mathay Sr. High School
Objectives:
At the end of the lesson, the students should
be able to:
1. Differentiate physical change from
chemical change.
2. Describe what happens to a
substance that undergoes chemical change.
3. Identify the signs of chemical change
in a reaction.
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
Properties of Matter
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Physical properties:
do not change the chemical nature of matter.
examples: color, smell, freezing point, boiling
point, temperature, density, viscosity
Chemical properties:
change the chemical nature of matter.
examples: heat of combustion, reactivity with
another substance, toxicity, flammability
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
Matter
•anything that has mass and volume
To understand changes in matter,
you need to be able to describe and
classify the sample
• before the change and
• after the change
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
There are two changes in
matter
• Physical change
• Chemical change
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
Physical Changes
• occur when a substance
changes its appearance
without changing its
composition.
• phase change.
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
Phase changes in matter
http://www.clickandlearn.org/images/water_cycle.gif
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
Chemical Changes
http://www.ric.edu/faculty/ptiskus/chemical/
Chemical changes are changes
substances undergo when they
become new or different
substances.
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
Fireworks
The fireworks we
see during New
Year’s Eve are
actually metals such
as magnesium and
copper that change
chemically as they
light up the night
skies with their
fantastic colors.
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
Evidences of Chemical
Change
•
Change in intensive
properties such as
odor, color and taste
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Ismael Mathay Sr. High School
10/16/09
Change in temperature
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
Formation of a solid
substance or precipitate
http://www.ric.edu/faculty/ptiskus/chemical/
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
Production of heat or
light
http://www.ric.edu/faculty/ptiskus/chemical/
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
Production of mechanical
energy
paper
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
Evolution of gas or formation
of bubbles
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Ismael Mathay Sr. High School
10/16/09
Production of electrical
energy
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
Activity
Materials:
pieces of paper
styrofoam
acetone
vinegar
NaHCO3
milk
Preciosa V. Cabrera
test tubes
watch glass
pair of scissors
dropper
match
modeling clay
Ismael Mathay Sr. High School
10/16/09
Procedure
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
2. Mold the modeling clay into different
shapes. Observe.
3. Cut the styrofoam into pieces. Place the cut
styrofoam in the watch glass and add a few
drops of acetone. Observe what happens.
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
4. Put about 10 mL of vinegar in two test
tubes. Add a pinch of sodium bicarbonate
in one test tube and 5 mL of milk in another.
Observe what happens in both test tubes.
5. Enter your observations in the table below.
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
Data and Observation
System
Observation
Physical or
Chemical change
1. Cutting paper
2. Burning paper
3. Molding clay
4. Cutting Styrofoam
5. Styrofoam and
acetone
6. Vinegar and
NaHCO3
7. Vinegar and milk
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
Signs of
Chemical
change
A. Guide questions
1. Can physical and chemical changes
occur in a system at the same time?
2. What is the difference between a
physical change chemical change?
3. What patterns of evidence do you
note in your observations of physical
change? of chemical change?
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
B. Identify the type of change.
Justify your answer.
1. formation of clouds
2.
3.
4.
5.
burning of plastic
corrosion of iron
sublimation of iodine crystals
decaying of food
Preciosa V. Cabrera
Ismael Mathay Sr. High School
10/16/09
Summary of the lesson
Physical
Change
 Original
There is only a

change in phase
substance
can
be recovered

substances
 The
Change
in the
appearance
of the
are
the same
substance
before
and after
the change
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Chemical
Change
 Change
Originalin
the
substanceofcan
properties
the not
be recovered
substance.
The substances
 The substances
are not the same
formed
before are
anddifferent
after
from
the original
the change

substance.
Ismael Mathay Sr. High School
10/16/09