Transcript 1.2 Properties and Changes of Matter

1.2 Properties and
Changes of Matter
Objectives:
Distinguish between physical and chemical
properties.
Contrast chemical and physical changes.
Apply the law of conservation of matter to chemical
changes.
Identifying Matter by Its Properties


Physical properties are those that do not change
the composition
They can be quantitative or qualitative.
 Qualitative:


The solid is hard.
The liquid boils at a low temperature.
 Quantitative:
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Ice freezes at 0°C
Iron has a density of 7.86 g/mL
States of Matter

Three common states of matter:
 Solid
 Liquid
 Gas

Fourth less familiar type:
 Plasma:
an ionized gas
Solid

Solid- a substance in which the particles
occupy fixed positions in a well-defined,
three-dimensional arrangement.
 Definite
shape and volume.
 Examples:
Iron
 Ice

Liquid

Liquid - a flowing substance with a
definite volume but an indefinite shape.
 Definite
volume and takes shape of container
 Examples:
Water
 Mercury
 Bromine

Gas

Gas – a flowing, compressible substance
with no definite shape or volume.
 Takes
shape and volume of container
 Examples
Oxygen
 Hydrogen
 Helium

States of Matter
The state in which matter is found
depends on the temperature and pressure.
 When you discuss the physical state of
matter you are discussing the state at
room temperature (20-25°C)h

States of Matter – Disc 2
States of Matter – Disc 2
Physical States

the temperature at which matter changes
from one state to another is closely related
to its physical state
 Water
freezes (and melts) at 0°C
 Salt melts (and freezes) at 804°C
 Oxygen freezes (and melts) at -218°C

The melting points and freezing point are
the same for substances
Volatile

Volatile – describes a substance that
easily change to a gas at room
temperature
 Alcohol
and gasoline are more volatile then
water.
 Naphthalene (mothballs) is a solid that is
volatile.
 You can easily smell alcohol, gasoline and
mothballs because since they are volatile the
molecules are present in the air.
Density
Density- the amount of matter (mass) in a
given unit volume.
 The units for density are usually g/mL

Density

You fill two beakers; one with cotton balls and
one with marbles.
 The
beaker with the marbles is heavier than the one
with the cotton balls, but they both occupy the same
volume (the beaker).
 The marbles have a larger mass than the cotton balls.
 Therefore, the marbles have a larger density than the
cotton balls
Densities of Some Common
Materials
Material
Density, g/mL
Water (4.0°C)
1.000
Ice (0°C)
0.917
Helium (25°C
0.000164
Air (25°C)
0.00119
Aluminum
2.70
Lead
11.34
Gold
19.31
Cork
0.22-0.26
Sugar
1.59
Balsa Wood
0.12
Determining Density

One way you can determine density is by using water
displacing
1.
2.
3.
4.
5.
Weigh you object. (10 g)
Fill a graduated cylinder with water to a particular mark. Such
as, 10mL.
Carefully add you object to the graduated cylinder.
Record the level of the water. ( maybe 15mL)
Next you use the weigh of you object and the level of the water
to determine the density.
a)
Your water level started at 10mL and ended at 15mL.

b)
15mL – 10mL = 5mL
Next you take your mass and divide it by your volume.

10g/5mL = 2 g/mL
Let’s Try It

Determine the density of the objects
provided by your teacher.
The Composition of Pennies
Read over this lab on page 38 & 39 of
your packet.
 Make a flow chart of the procedure for this
lab, using only pictures. We may use this
technique for more complicated labs in the
future.
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It’s a Liquid, It’s a Solid…It’s Slime
Lab is on page 40 of your packet.
 You must wear safety glasses for this lab.
 Please, be very careful with the chemicals.
 You may work in groups of three.
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Chemical Properties and
Changes
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Chemical Properties- can be observed only
when there is a change in the composition of the
substance.
Describes the ability of a substance to react with
another substance or to decompose
Examples:
 Rusting
 Reactivity
Hydrogen Peroxide (H2O2)

Is always stored in brown bottles because
it will break down to hydrogen and oxygen
gas when exposed to light.
Chemical Change
Chemical Change – the change of one or
more substance into other substances.
 Also called a Chemical Reaction

 The
sulfuric acid and the sugar
 If you add vinegar to baking soda
Atoms and Chemical Change
All matter is made up of atoms.
 Any chemical change involves the
rearrangement of atoms.
 When water breaks down it is the
rearrangement of the hydrogen and
oxygen atoms.

Oxygen molecules
Hydrogen molecules
Water molecules
Law of Conservation of Mass
Law of Conservation of Mass – in a
chemical change, matter is neither created
nor destroyed.
 Example: Water molecules

2
H2O  O2 + 2H2
Law of Conservation of Mass
Chemical Reactions and Energy
Chemical changes involve some sort of
energy change.
 Energy – the capacity to do work
 Many reactions give off energy and some
absorb energy.

– gives off heat
 Endothermic - absorbs heat
 Exothermic
Chemistry and Chemical
Reactions

Are all around you and are in everything
that you do.
Properties
Review
1.
2.
3.
Distinguish between a liquid, solid, and a
gas.
Give an example of a physical change
and a chemical change.
What are two substances that would be
considered volatile?