Unit 1 Lesson 3 Physical and Chemical Changes
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Discussion: What’s New?
Physical or chemical change?
What is true about the kinds of matter
present before and after a physical
change?
How is matter different?
What substances were formed when the
paper burned?
What is true about the types of matter
present before and after the matter
undergoes a chemical change
What substances were formed when the
paper burned?
Would it be possible to change these types
of matter back into a sheet of paper?
Unit 1 Lesson 3 Physical and Chemical Changes
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Change of Appearance
Physical Changes
• A physical change is a change
that affects one or more physical
properties of a substance.
• The appearance, shape, or size
of a substance may be altered
during a physical change.
• Physical changes, such as
changes in state, do not change
the chemical identity of a
substance.
5) Physical properties of the substance are changed.
7) Yarn was twisted, dyed, and knit to form sweater – it’s still wool.
Unit 1 Lesson 3 Physical and Chemical Changes
Change of Appearance
P38-39
Chemical Changes
• A chemical change is the
process when one or more
substances change into
entirely new substances with
different properties.
• A substance’s identity
changes because the
chemical makeup changes.
• Bonds get rearranged
and/or new bonds form.
• Influenced by temperature: At
higher temperatures, chemical
reactions happen more quickly
8)
A. Flames
B. wood
C. Ashes
8) Burning wood is an
example of a
chemical change in
which wood is
transformed into new
substances, such as
ash and smoke
P38-39
Smart
Activity
9) Raising temp causes
particles in matter to
move more quickly.
Increased motion causes
particles to bump into
each other which
increases the rate of the
chemical reaction
Let’s go to lab
Unit 1 Lesson 3 Physical and Chemical Changes
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Look for the Signs
How can you tell a chemical change has
happened?
• There are several signs that a chemical reaction
has occurred.
• Observing two or more of these signs during a
change means you are likely observing a chemical
change.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 1 Lesson 3 Physical and Chemical Changes
p40 - 41
How can you tell a chemical change has
happened?
• Odors can be produced during a
chemical change.
• Fizzing and foaming may mean
gases are being produced.
• The production of gas is often
evidence of a chemical change.
•Boiling also can produce gas
bubbles, but boiling is a physical
change.
Unit 1 Lesson 3 Physical and Chemical Changes
p40 - 41
How can you tell a chemical change has
happened?
• A precipitate is a solid formed
from liquids.
• The formation of a precipitate can
indicate a chemical change.
• Energy that changes from one
form to another can be evidence
of a chemical change.
• Changes in temperature and
color can be signs of a chemical
change.
Unit 1 Lesson 3 Physical and Chemical Changes
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Conservation Is the Law
What is the law of conservation of mass?
• French chemist Antoine Lavoisier studied chemical
changes in which substances appeared to gain or lose
mass.
• The law of conservation of mass states that in
ordinary chemical and physical changes, mass is not
created or destroyed. It is only transformed into
different substances.
Unit 1 Lesson 3 Physical and Chemical Changes
P42 - 43
What is the law of conservation of mass?
• Physical changes are reversible and follow the law
of conservation of mass.
• Mass is conserved during chemical changes. The
mass of the starting materials is the same as the
mass of the end products.
Chemical Change