Lesson 1:
The states of matter
Matter
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Anything that has mass and takes up space.
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There are three physical states: solid, liquid and gas.
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Every pure substance has its own melting and boiling
point. This is a distinguishing property for this substance.
Sublimation
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A volatile liquid is one which evaporates easily and hs a
relatively low boiling point.
Ethanol (b.p. 78 C) is a more volatile liquid than water (b.p.
100 C).
Lesson 2:
Pure substances and purity
Pure substances
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A pure substance consists of only one
substance.
There is nothing else in it; it has no
contaminating impurities.
We can use melting and boiling points to
test the purity of a substance.
MP and BP can also be used to check the
identity of an unknown substance.
MP can be measured using and
electrically heated melting point apparatus.
The effect of impurities
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Seawater is impure water. It contains salt and other
minerals. Seawater freezes well below the the freezing
point of water (0 oC) and boils at a temperature above the
boiling point of water (100 oC)
The presence of an impurity in a substance:
lowers the melting point
raises the boiling point
of the substance.
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Why do you think salt is sprinkled to the roads in
snowy days?
Measuring melting point in laboratory
A powdered solid
is put in a narrow
melting-point
tube so that it can
be heated easily.
Heating curves
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Naphthalene melts at
precisely 80 C. Notice that,
while the solid is melting, the
temperature stops rising.
Generally, the heating curve
for a pure solid stops rising at
its melting point.
The heating curve of a wax,
which is a mixture of
substances, shows the solid
wax melting over a range of
temperatures.
Heating curve of ice
Cooling curves
Important ❗️
When a pure solid is melted, or a pure liquid is
boiled, the temperature stays constant until the
process is complete. The same is true in reverse
when a gas condense or a liquid freezes.
Purity is very important in pharmacy.
Lesson 3:
Types of mixtures
Mixtures
Homogeneous
Heterogeneous
Solutions
Suspensions
Solid in liquid : Salty water
Liquid in liquid : alcohol+water
Gas in liquid : fizzy drinks
Gas in gas : air
Chalk + Water
Sand + Water
Emulsions
Oil + Water
Solutions
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They seem as one phase.
For example salty water
looks like pure water.
Solutions have two parts.
Solute : the substance that is
dissolved in another
substance (minor part)
Solvent : the substance that
dissolves the other
substance (major part)
Solution : Solvent + solute
Miscible and immiscible
liquids
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Alcohol and water are miscible in each other. They can be
dissolved in each other and they form a solution
(homogeneous mixture).
Oil and water are immiscible liquids. One can not dissolve
the other. So they form an emulsion which heterogeneous.
We can see two layers.
Suspensions
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If a solid is not soluble in a liquid, the solid is dispersed as
large lumps in the liquid. So a cloudy substance will form.
You can see different phases.
For example : chalk is not soluble in water. The large
lumps are suspended in water.
Fizzy drinks
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Carbon dioxide is
dissolved in water under
high pressure.
Lesson 4
Separating and purifying
substances
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The most useful separation method for a particular mixture
depends on:
The type of mixture, and
Which substance in the mixture we are most interested in.
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Separation depends on the physical differences of the
substances in the mixture.
Separating insoluble solids from liquids
(suspension)
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If the particles of solid are
large enough, we can use
a process called decanting.
Once the solid has settled
to the bottom, the liquid
can be carefully poured off.
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A more generally useful
method is for separating
solids from liquids is
filtration.
Separating immiscible liquids (emulsions)
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Mixtures of two immiscible liquids can be separated if the
mixture is placed in a separating funnel and allowed to stand.