Transcript What is a property?

Reviewing MATTER
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Matter: anything that has mass and takes
up space
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Mass – the amount of matter in something
Volume – the amount of space something
occupies
Which of the following is matter?
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A car?
A box?
You?
What is a property?
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Property: a
characteristic of
a substance that
can be observed
Physical Property
Physical property: a property that can
be observed without changing the
identity of the substance.
Examples:
• melting
• luster
point
• malleability: the
ability to be hammered
into a thin sheet
• ductility: the ability
to be stretched into a
wire
• boiling point
• density
• solubility
• specific
heat
Additional Physical Properties…
EXTENSIVE PROPERTY
Depends on the amount of matter.
Example –
Length, mass,
volume, weight
INTENSIVE PROPERTY
Does not depend on the amount of
matter.
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Example – Color, density,
hardness, ductility,
malleability, odor,
melting/ boiling point
Special Physical Properties
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Melting point: the
temperature at which a
substance changes from a
solid to a liquid at a given
pressure
water = 0oC
Special Physical Properties
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Boiling point: the temperature
at which a substance changes
from a liquid to a gas at a given
pressure
water = 100oC
Density
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Density is the amount of mass per
unit of volume.
Since density is an intensive property,
it can be used to identify a
substance.
Density
The density of water is 1.0g/mL
 If a substance has a density
higher than 1 it will sink in
water, less than 1 it will float in
water.
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Density Calculations
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Calculations:
Density = mass = g/mL = g/cm3
Volume
Units are grams/ml or grams/cm3
where mass is measured in grams and
volume is measured in ml or cm3
Density Calculations
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A cube has a mass of 2.8 g and occupies a
volume of 3.67 ml. Would this object float or
sink in water?
Mass = 2.8 g
Volume = 3.67 mL
D = 2.8g/3.67 mL= 0.76 g/mL
This object would float in water because its
density is less than water (1.0 g/mL).
Chemical Properties
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Chemical property: a property that can
only be observed by changing the
identity of the substance
Examples:
•Flammability: ability to burn
•Ability to rust
•reactivity with vinegar
PHYSICAL & CHEMICAL
CHANGES
Changes in matter
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Change: the act of altering a
substance
In science, we talk of two types of
changes:
physical
chemical
Physical Change
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Physical change: a change that occurs
that does not change the identity or make
up of the substance
 Melting ice (change in state or phase)
 Freezing Kool-aid
 Tearing paper
 Boiling water (same as melting)
Physical Changes
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Physical changes
are changes that
alter the size,
shape, location or
physical state of a
substance but not
its chemical state.
Here’s An Example…
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A physical change in a substance doesn't
change what the substance is.
cutting paper –
 physical change in the shape and size
of the paper.
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It is still paper!!!!!!
So What Does That All Mean?
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If the substance is still the same
substance after it has been
changed…
It’s a Physical Change.
 Example… Boiling water
 Boiling Water becomes
Water vapor
Water = water
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What Other Kinds of Changes
Are Physical?
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Cutting
Tearing
Shredding
Shrinking
Enlarging
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Change in
Phase
Relocating
Dissolving
Rotating
Molding
(shaping)
Under certain conditions, a substance
can change from any one state of matter
another. Changes of state are physical
changes.
Wood cut down into logs is a
physical change
Chemical Changes
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Chemical change: a change that occurs
causing the identity of the substance to
change
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Burning
Digesting food
Reacting with other substances
A chemical change is also called a
chemical reaction
Chemical Changes
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Chemical
changes are
changes that alter
the chemical
make up of the
substance being
changed.
Chemical Changes
If you end up with a chemical
or chemicals that you did not
start with. . .
 It is a chemical change!!!!!!!
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Chemical Changes
A new substance is formed
with new and different
properties.
 A chemical change is not easily
reversed.
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Signs That a Chemical
Change has occurred
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Creation of a gas (bubbles)
Creation or loss of heat
Fire
Rotting
Breaking down (decomposition)
Precipitation (Sour milk clumps)
Cooking
Rusting (oxidation)
The strike of a match is a chemical
change due to the reaction of the
chemicals with oxygen.
Burning woods turns to charcoal and ashes. This is a chemical change.
Is it Physical or Chemical?
Change
Melting cheese
Burning wood
Milk souring
Folding up paper
Bicycle rusting
Physical
Chemical
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Start physical changes challenge Powerpoint
Chemical Reactions are…
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When one or more substances are changed
into new substances.
Reactants- the stuff you start with
Products- what you make
The products will have NEW
PROPERTIES different from the reactants
you started with
Arrow points from the reactants to the
new products
Plants make chlorophyll in the plants leaves.
The color changes in autumn leaves are due, in
part, to the ending of a chemical reaction. The
plants stop making chlorophyll while existing
chlorophyll is breaking down. The brilliant
colors of fall foliage result when green
chlorophyll in leaves breaks down. The colors
of other substances in the leaves become
visible.
The copper-covered Statue of Liberty has stood in upper New York Bay for
more than a 100 years. The green color of the Statue of Liberty comes from
a change to the statues copper metal covering. These changes are a result
from chemical reactions.
Conservation of Mass
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During any chemical reaction, the mass of
the products is always equal to the mass
of the reactants.
All the mass can be accounted for:
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Burning of wood results in products that
appear to have less mass as ashes; where is
the rest?
Law of conservation of mass
Matter changes whenever energy is added or
taken away. In every physical and chemical
change, the total amount of energy stays the
same. This principle is called the Law of
Conservation of Energy.