Transcript 3.2 * Physical and Chemical Properties and Changes

Matter
Chapter 2
The Basics of Matter
• Matter – is anything that has mass and takes
up space – it is the “stuff” of which the
universe is composed
– Extensive properties – depend on the amount of
matter in a sample
• Mass, Volume
• Energy, molarity (dilute or concentrated)
– Intensive properties – depends on the type of
matter in a sample, not the amount of matter
• Density, freezing pt., boiling pt., absorbency, elasticity
The States of Matter
State
Definition
Examples
Solid
Rigid; has a fixed
shape and volume
Ice cube, diamond,
iron bar
Liquid
Has a definite
Gasoline, water,
volume but takes
alcohol, blood
the shape of its
container
Has no fixed volume Air, helium, oxygen
or shape; takes the
shape and volume
of its container
Gas
Physical Properties
• Things you can tell about a substance just by
looking at it
• You don’t need to alter the composition of the
substance to determine these
• Examples:
– Color
– Odor
– Volume
- density
- melting point
- boiling point
MIXTURES AND PURE SUBSTANCES
PURE SUBSTANCES
• Always have the same composition
• Pure substances are either elements or
compounds
• Examples:
– Pure water (not lake/ocean water)
– Copper
– Zinc
– rubbing alcohol
MIXTURES
• A substance with variable composition
• Made up of multiple pure substances
• Examples:
– Air
– Wood
– Coffee
– Cookie dough
Two Types of Mixtures
• Homogeneous mixture – looks the same
throughout – can’t see different parts
– Ex: Kool-Aid, sugar cookie dough
• Heterogeneous mixture – can see the
different parts
– Ex: chocolate chip cookie dough, sand and water
solution
Practice
State whether each of the following is a pure
substance, a homogeneous mixture, or a
heterogeneous mixture.
- Maple syrup
- The oxygen and helium in a scuba tank
- Oil and vinegar salad dressing
- Common salt (sodium chloride – NaCl)
Practice
State whether each of the following is a pure
substance, a homogeneous mixture, or a
heterogeneous mixture.
- Maple syrup
HOMOGENEOUS MIXTURE
- The oxygen and helium in a scuba tank
HOMOGENEOUS MIXTURE
- Oil and vinegar salad dressing
HETEROGENEOUS MIXTURE
- Common salt (sodium chloride – NaCl)
PURE SUBSTANCE
SEPARATION OF MIXTURES
Distillation
• Boil the liquid off of a
solution and leaves the
other components behind
Laboratory display of distillation: 1: A
heating device 2: Still pot 3: Still
head 4: Thermometer/Boiling point
temperature 5: Condenser 6:
Cooling water in 7: Cooling water
out 8: Distillate/receiving flask 9:
Vacuum/gas inlet 10: Still receiver
11: Heat control 12: Stirrer speed
control 13: Stirrer/heat plate 14:
Heating (Oil/sand) bath 15: Stirring
means e.g.(shown), anti-bumping
granules or mechanical stirrer 16:
Cooling bath.
Filtration
• Separates a liquid from
the solid
• The liquid passes
through the filter paper,
but the solid particles
are trapped
Summary – Breaking Down Matter
MATTER
HOMOGENEOUS
MIXTURES
HETEROGENEOUS
MIXTURES
Physical methods
PURE SUBSTANCES
ELEMENTS
COMPOUNDS
Chemical
methods
ELEMENTS AND COMPOUNDS
ELEMENTS
• Fundamental substances that cannot be
broken down into other substances by
chemical means
• Found on the Periodic Table of Elements (if it’s
not on the chart, it’s not an element)
• Examples:
– Aluminum
– Oxygen
– Hydrogen
COMPOUNDS
• Compounds are combinations of different
elements.
• They can be broken down into their constituent
elements by chemical changes.
• A compound always has the same composition
(i.e., the same combination of elements).
• Examples:
– Water (H2O)
– Carbon Dioxide (CO2)
Element or Compound?
• Hydrogen peroxide (H2O2)
• Mercury (Hg)
• Vanadium (V)
• Sodium chloride (NaCl)
Element or Compound?
• Hydrogen peroxide (H2O2)
– compound
• Mercury (Hg)
– element
• Vanadium (V)
– element
• Sodium chloride (NaCl)
– compound
CHEMICAL AND PHYSICAL
PROPERTIES
Physical Properties
• Things you can tell about a substance just by
looking at it
• You don’t need to alter the composition of the
substance to determine these
• Examples:
– Color
– Odor
– Volume
- density
- melting point
- boiling point
Chemical Properties
• These refer to the ability of a substance to
form new substances (i.e., its reactivity)
• Examples:
– propane burns in the air
– Baking soda fizzes if mixed with vinegar
– A marshmallow gets black when toasted too long
in a campfire
– Hydrogen and oxygen react violently
Chemical or Physical?
•
•
•
•
•
The boiling point of a certain alcohol is 78°C.
Diamond is very hard.
Sugar ferments to form alcohol.
Gallium metal melts in your hand.
Platinum does not react with oxygen at room
temperature.
• Your paper is white.
Chemical or Physical?
•
•
•
•
•
The boiling point of a certain alcohol is 78°C.
Diamond is very hard.
Sugar ferments to form alcohol.
Gallium metal melts in your hand.
Platinum does not react with oxygen at room
temperature.
• Your paper is white.
Green is physical. White is chemical.
CHEMICAL AND PHYSICAL
CHANGES
Physical Changes
• Physical changes do not affect the
composition of the substance.
• Examples:
– State changes (solid liquidgas)
•
•
•
•
Melting
Evaporating
Freezing
etc
– Breaking a substance into smaller pieces
Chemical Changes
• Chemical changes involve a change in the
composition of the substance.
• Examples:
– Burning something
– Reacting two substances to make something new
– Running an electric current through water to
decompose water into hydrogen and oxygen
Some practice…
Chemical or Physical?
•
•
•
•
•
Iron metal is melted.
Iron combines with oxygen to form rust.
A piece of wood is burned in a fireplace.
A rock is broken into small pieces.
A log of wood is chopped up with an axe into
smaller pieces of wood.
• Water evaporates to become water vapor.
Some practice…
Chemical or Physical?
•
•
•
•
•
Iron metal is melted.
Iron combines with oxygen to form rust.
A piece of wood is burned in a fireplace.
A rock is broken into small pieces.
A log of wood is chopped up with an axe into
smaller pieces of wood.
• Water evaporates to become water vapor.
Green is physical. White is chemical.
Recognizing a Chemical Change
• Formation of a precipitate
– A solid that forms and settles out of a liquid mixture
• Change in color
– Some reactions result in a change from one color to
another
• Production of a gas
– Bubbles must be a new substance
– Results of physical change are not new substances (ex:
boiling)
• Transfer of energy
– Burning something gives off energy in the form of heat and
light
Law of Conservation of Mass
“During any chemical reaction, the mass of the
products is always equal to the mass of the
reactants.”