Download Manipulating Matter

10/1/2015
Chemical & Physical Changes
Manipulating Matter
Physical and Chemical Properties
• Physical Properties – property that can be observed or
measured without changing the composition of the
material
• Chemical Properties – property that can only be
observed due to a change in the composition of
matter.
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Notation in Chemistry
∆  change
Pronounced “delta”
EX: ∆T = change in temperature
Physical Changes in Matter
• A physical change occurs when a substance
undergoes a change that does not alter its
chemical composition.
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• Physical changes can be reversible or
irreversible.
• Examples of physical changes:
• Changes of state/phase
• Dissolving
• Cutting, Tearing, Grinding, Reshaping, etc.
H2O & NaCl
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Dissolving a substance
• Both compounds are still in tact.
• Chemical composition was NOT altered.
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H2O & NaCl
Phase Changes
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Chemical Changes in Matter
• Chemical changes occur when a substance
undergoes a change that chemically alters the
composition of that substance.
• After a chemical change, completely new
substances with new properties are formed.
• Examples of Chemical Changes:
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Burning
Scorching
Cooking
Fermenting
Decomposing
• A new single compound is formed with its own new properties and
characteristics. The chemical composition has been altered.
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Basic of Chemical Changes
• In chemistry, we show a chemical change in the form of a chemical
equation.
• The standard form for a chemical equation:
YIELD
Evidence of a Chemical Change (Reaction)
1) Change in Temperature (∆T) *
2) Change in Color *
3) Evolution/Formation of a Gas
(effervescence)
4) Production of Light
5) Production of a Precipitate
* NOT ALWAYS A SIGN OF A CHEMICAL REACTION*
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Law of Conservation
• All chemical changes are governed by a scientific law.
• The law of conservation states, “mass/matter/energy
cannot be created or destroyed during a normal
chemical reaction”.
Combine the two reactants
In-class Assessment
• Determine whether the following are physical (P) or
chemical (C) changes:
A) melting an ice cube
B) burning a wooden log
C) dissolving salt in water
D) fermentation of grapes
E) rusting of iron
F) tearing paper
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