Download Properties of Matter PPT

PHYSICAL
PROPERTIES
OF MATTER
REFRESH YOUR
MEMORY:
PRE-LESSON VOCABULARY
• Substance = A substance, in physical science, is not
really a specific object. Rather, it is the material(s) that
make up specific objects. E.g., the plastic in a rubber
ducky.
• Sample = the amount you have of a substance,
measured usually in g or mL.
Here you have three
different substances. You
have a sample of each
substance.
PROPERTIES – WHAT ARE THEY?
• In science, property does not mean
objects that you own.
(Ex., your backpack)
• A property does, however, mean a
characteristic or feature that you
own.
• Properties belong to you and make
you who you are – they’re a part of
your identity!
• Examples: green eyes, light brown
skin tone, born Feb 20, 1988.
PHYSICAL PROPERTIES HELP US TO
IDENTIFY:
• Suppose you are going on a blind date. You don’t
know what the person looks like, but you have a
description of the person’s physical properties .
• You can use physical properties to identify the
person.
• Physical properties of substances work the same
way!
Salt??
– With an unknown substance, if you know
Sugar??
some of its physical properties, you can use
Flour??
the physical properties to figure out what the
Baking Soda??
substance is.
– Physical properties, do NOT depend on
Density = 1.59 g/cm3
sample size. No matter how much or little
sugar you have, the density is always 1.59
g/cm3
7 PHYSICAL
PROPERTIES
YOU NEED
TO KNOW
•
•
•
•
•
•
•
Density
Solubility
Electrical Conductivity
Thermal Conductivity
Magnetism
Boiling Point
Melting Point
DENSITY
• How much matter (mass) is packed into a specific
space (volume).
• Helps us to determine whether substances will float
or sink.
SOLUBILITY
• Solubility = the ability to dissolve within (spread
throughout) another substance (usually liquid) to form
a mixture called a solution.
– If a substance is soluble – it dissolves in water
(Ex., Salt)
– If a substance is insoluble (not soluble) in water – it
does not dissolve (Ex., sand)
Saturated Solution
• Solubility can be measured.
• Terms you need to know:
• Solute = the substance that dissolves (ex. Sugar)
• Solvent = the substance (usually water) that the
solute dissolves in
• Solution = the mixture of solute and solvent
• A solution is “saturated” if no more solute can
dissolve in the solvent, and the solute then settles to
the bottom.
SOLUBILITY HELPS US TO IDENTIFY
SUBSTANCES AND IS INDEPENDENT OF
SAMPLE SIZE
• Whether we have a small
sample of sand, or a large
sample of sand, doesn’t
matter. All sand is insoluble.
ELECTRICAL CONDUCTIVITY
• Electrical conductivity = how well a
substance conducts (moves)
electricity through it.
• Copper, like most metals, is a good
conductor of electricity. Electricity
flows easily through it.
• That’s why most wires that hook up
your TV, computer, etc. are copper.
• Substances like plastic, wood, and
glass are poor conductors of
electricity. Electricity does NOT move
easily through them.
• That’s why copper wires are covered
with plastic – so that you don’t
electrocute yourself!
ELECTRICAL CONDUCTIVITY
• We test electrical conductivity with
simple circuits that include a light
bulb, battery, and wires that connect
to the substance being tested.
• If the substance tested makes the
bulb light up, the substance is a good
conductor of electricity – ex., metals,
salt solution
• If the bulb doesn’t light up, the
substance tested is a poor conductor
of electricity –ex. plastic, sugar
solution
• If the bulb is dim, the substance is a
semi-conductor of electricity.
Sugar Water Solution
Salt Water Solution
ELECTRICAL CONDUCTIVITY
• Electrical conductivity is independent of sample size
• Electrical conductivity helps us to identify substances.
• If we have a white powder that may be salt or sugar,
we can test its conductivity, compare it to what we
know, and figure out the identity.
Sugar?
Salt?
THERMAL CONDUCTIVITY
• How well heat (not
electricity) moves through a
substance
• Why do you cook with
wooden spoons, not metal
spoons?
• Metals heat up and transfer
heat quickly because they
are good thermal
conductors
• Plastics, wood, and glass
slowly heat up because they
are poor conductors of heat
MELTING AND BOILING
POINTS
• Melting point – the temperature (in ºC, ºF,
or K) at which a substance in its solid
state melts into the same substance in a
liquid state.
• Boiling point – the temperature at which a
substance in its liquid state evaporates
into the same substance in its gas state.
Water’s melting point is 0ºC
Gold’s boiling point is 2,970ºC
Gold’s melting point is 1,064ºC
Water’s boiling point is 100ºC
MELTING AND BOILING POINTS
• Like all other physical properties, melting and
boiling points are independent of sample size!
100ºC
Whether the
sample size is
large or small,
water has the
SAME boiling
point
0ºC
Whether the
sample size is
large or small,
water has the
SAME melting
point
100ºC
0ºC
* LIKE ALL OTHER PHYSICAL PROPERTIES,
SINCE BOILING AND MELTING POINTS ARE
INDEPENDENT OF SAMPLE SIZE, THEY NEVER
CHANGE.
* SO THEY CAN BE USED TO IDENTIFY
SUBSTANCES.
Water ?
Alcohol ?
Hydrogen peroxide?
Vinegar?
Boiling Point = 78 ºC
Substance
Boiling Pt.
Water
100ºC
Alcohol
78ºC
Hydrogen
Peroxide
150ºC
Vinegar
118ºC
MAGNETISM
• Magnetism = the
property of being
attracted to a
magnet
• Only nickel, iron,
and cobalt are
magnetic
• SO NOT ALL METALS
ARE MAGNETIC!!!
Iron
Question: So, if Earth
has a magnetic
field… Then what is
the Earth’s core made
of?
Magnetism. No new
substance created.
Density. No
Still iron. . .
new
substance.
Still floats
or sinks…
Thermal conductivity .
Wire doesn’t turn into
a new substance
WHY DO WE CALL PHYSICAL
PROPERTIES PHYSICAL?
Electrical
conductivity
Nothing
new, still
copper.
• There are other types of properties called chemical properties.
When chemical properties are observed, a new substance is
created.
• When physical properties are observed, or tested, they DO NOT
CREATE A NEW SUBSTANCE!!!
Boiling pt. No new
substance created. Still
water, just in the form of
vapor.
Solubility. No new
substance created.
Still salt in the solution
Melting Point. No new
substance created. Still
water, just melted.