Matter
Section 3
Section 3: Changes of Matter
Preview
• Key Ideas
• Bellringer
• Physical Changes
• Chemical Changes
• Breaking Down Mixtures and Compounds
Matter
Section 3
Key Ideas
〉Why is getting a haircut an example of a
physical change?
〉Why is baking bread an example of a chemical
change?
〉How can mixtures and compounds be broken
down?
Matter
Section 3
Bellringer
Matter can go through both physical and chemical changes and
can exist as mixtures and compounds. See how matter interacts
when Jordan makes oatmeal bread.
1. To make bread, Jordan must do several things before it is ready to
be baked. For each step, decide whether a physical or a chemical
change occurs, or whether a mixture or compound is formed. Circle
the correct answer.
a. stir flour and dry oatmeal
mixture formed
compound formed
b. heat the water
physical change
chemical change
c. melt the shortening
physical change
chemical change
d. beat the eggs
physical change
chemical change
e. blend molasses with water mixture formed
compound formed
f. bake the bread
physical change
chemical change
Matter
Section 3
Bellringer, continued
2. Jordan accidentally measures sugar instead of flour
and stirs the dry oatmeal with the sugar. Is a mixture
or a compound created? How can the two ingredients
be separated so that the bread is not ruined?
3. The recipe calls for baking powder and water. When
these two ingredients come into contact with each
other, gas is given off. This helps the bread rise. Is
this an example of a physical change or a chemical
change? Explain your answer.
Matter
Section 3
Physical Changes
〉Why is getting a haircut an example of a physical
change?
〉A physical change affects one or more properties of
a substance without changing the identity of the
substance.
• physical change: a change of matter from one form to
another without a change in chemical properties
Matter
Section 3
Physical Changes, continued
• Physical changes do not change
a substance’s identity.
– Examples of physical
changes: cutting, crushing,
reshaping, changing state
• Dissolving is a physical
change.
Matter
Section 3
Chemical Changes
〉Why is baking bread an example of a chemical
change?
〉A chemical change happens when one or more
substances are changed into entirely new
substances that have different properties.
• chemical change: a change that occurs when one or more
substances change into entirely new substances with different
properties
Matter
Chemical Changes
Section 3
Matter
Section 3
Chemical Changes, continued
• Chemical changes happen everywhere.
– Examples of chemical changes: burning, rusting, digesting,
decomposing
• Chemical changes form new substances.
• Chemical changes can be detected.
– Signs include: change of color, change of smell, fizzing,
production of heat, production of sound, production of light
• Chemical changes cannot be reversed by physical changes.
Matter
Section 3
Visual Concept: Comparing Physical and
Chemical Changes
Matter
Section 3
Breaking Down Mixtures and Compounds
〉How can mixtures and compounds be broken down?
〉Mixtures can be separated by physical changes, but
compounds must be broken down by chemical
changes.
Matter
Section 3
Breaking Down Mixtures and Compounds,
continued
• Mixtures can be physically separated.
• Examples of separating a mixture:
– Separating saltwater into its parts by heating it: When the water
evaporates, the salt remains.
– Using a distillation device to heat a mixture whose components
have different boiling points: The component that boils and
evaporates first separates from the mixture.
– Using a centrifuge: The mixture spins rapidly until the
components separate.
Matter
Section 3
Breaking Down Mixtures and Compounds,
continued
• Some compounds can be broken down through chemical
changes.
• Examples of separating a compound:
– When mercury(II) oxide is heated, it breaks down into the
elements mercury and oxygen.
– When a current is passed through melted table salt, the
elements sodium and chlorine are produced.
– When you open a bottle of soda, carbonic acid in the soda
breaks down into carbon dioxide and water.