Download Physical Changes

Chemistry
is the science
that investigates
and explains the
structure and
properties of
matter.
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Chapter 1 Matter
key Terms
matter, mass
Properties, qualitative, quantitative
substance, compound, element, chemical symbol
heterogeneous & homogeneous mixture, solution
Solute, solvent, aqueous solution, alloy
physical property, physical change
phase, distillation
chemical property, chemical change/reaction
law of conservation of matter
Endothermic, exothermic
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Matter
Matter is anything that has
mass and occupies space.
Mass is the measure of the amount
of matter that an object contains.
(The quantity of matter can be
measured by determining the
amount of matter.)
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Observations of the composition of matter
are based on a macroscopic view
(large enough to be seen)
The world of atoms is
submicroscopic
(too small to be seen under the microscope)
The trick is to deduct
the submicroscopic world from
macroscopic observations
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Elements and Compounds
•Elements are made from one type of atoms
•Compounds are made from more than one type of
atoms. Compounds can be separated into simpler
substances only by chemical means.
•Properties of a compound are different from those of
the elements composing it.
•Elements are always present in the same ratio in a given
compound.
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Classify the following as element or compound
water
 gold
 diamond
ammonia mercury  carbon dioxide
Name the chemical symbol for
Carbon
 Oxygen
 Hydrogen
Sodium
Chlorine
 Nitrogen
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Mixtures
•A mixture is a combination of two or more
substances that can be separated by physical
methods.
•Heterogeneous mixtures are not uniform in
composition.
•Homogeneous mixtures, also called solutions,
have uniform properties throughout and may be
gases, liquids, or solids.
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Classify the following mixtures as either
homogeneous or heterogeneous
motor oil
 clear nail polish
 granite
 glass
 air
 chocolate-chip ice cream
 brass (blend of copper and zinc)
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Examples of homogeneous mixtures
• Alloys are solid solutions (homogenous
mixtures) that contain different metals (brass,
steel, bronze etc.).
•Aqueous solution is a homogeneous mixture
where water is the solvent.
•Example sugar water:
•Sugar is the solute
•Water is the solvent
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Mixture, compound or element?
 motor oil
 sugar
 salad dressing
 chlorine
 air
 salt water
 diamond
 glass
 hydrogen peroxide
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Chemical Reactions
Chemical Change changes
composition of a substance.
the
chemical
Chemical Property is the ability of a substance
to undergo a chemical reaction
Example: iron + sulfur  iron sulfide
iron + oxygen  rust
Name chemical and physical properties of iron
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Physical Property of a substance can be
observed or measured without changing the
substance’s composition.
•Examples: color, odor, hardness, boiling point,
melting point, solubility, density...
•Physical Changes is a change of matter without
changing chemical composition
•Examples: boiling, freezing, evaporating,
breaking, splitting, cutting, crushing...
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Distillation
Examples of methods
to separate mixtures
•Filtering
•Evaporating
•Distilling
•chromatography
•...
Physical methods
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Example
Sugar water
Mixture
Physical
methods
Compound
separated
by
Example
water (H2O)
Chemical
methods
into
Example
Substances
water and sugar
Elements
Example
oxygen, hydrogen
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Qualitative or Quantitative
“The water is hot”
“The temperature is
54C (129F)”
descriptive,
nonnumerical form
definite form
number + unit
qualitative
quantitative*
Qualitative
Quantitative
L = letter (words)
n = numbers
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Exothermic and Endothermic
All chemical reactions involve some sort of
energy change.
Chemical reactions that give off heat energy
are called exothermic (exo = out)
ex. dynamite
Chemical reactions that absorb heat energy
are called endothermic (endo = into)
Ex: cooking; you need to heat up the food for it
to be cooked, photosynthesis needs sunlight 17
•In a chemical change (chemical reaction),
reactants are converted to products.
•Conservation of matter: Mass is conserved
in any physical or chemical change. The sum
of masses of all reactants is equal to the sum
of masses of all products.
Example
iron + oxygen  rust
112 g + ? g
 160 g
Assign reactants and products,
how much oxygen reacted with iron?
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