(General revision for units 3)
Points of
comparison
Oxygen gas
Carbon dioxide
nitrogen
Percentage in
air:
21 %
0.03 %
78%
Preparation :-
By adding
hydrogen peroxide
to manganese
dioxide
Adding dilute
hydrochloric
acid to calcium
carbonate as a
catalyst
Passing air over
concentrated sodium
or potassium
hydroxide, then hot
copper
Proprieties :
1- Oxygen is a
colorless, tasteless
and odorless gas. It
scarcely dissolves
in water.
1-it is colorless
and odorless.
1-nitrogen is a
colorless, tasteless
and odorless gas.
2-It is heavier
than the air.
3- It does not
2- Oxygen does not
burn and does
burn, but it helps in
not help in
burning.
combustion. So,
3- It has a neutral
it is used for
effect on litmus
extinguishing
paper with its two fires.
colors.
4- The
4- Oxygen is
magnesium
heavier than air as ribbon keeps
it replaces the air. burning and
turns into a
magnesium
oxide (with
white color) and
2- It scarcely
dissolves in water
3- When it combines
with a lighted
magnesium ribbon
composing a white
substance. By adding
a little water, a very
pungent smell
“ammonia” emits
4- can be condensed
to a liquefied state
the carbon (coal)
deposits on the
wall of the
cylinder
Importance
*(uses )
1- Water consists
of oxygen united
with hydrogen
2- Ozone is also
composed of
oxygen(protects
the Earth from
harmful radiation)
A-Refrigeration
on converting it
into a liquid by
pressure and
cooling. Then,
pressure is
relieved
composing dry
ice that we use
in refrigeration.
3- Oxygen gets
compressed in iron
B-extinguishing
cylinders and used
fires.
in: A-Mechanical
ventilation.
C- Used to make
soft drinks.
B- During surgeries.
During diving and
D- used to make
climbing
bread bubbled
mountains.
as yeast which
(Because oxygen
produces carbon
becomes lighter
dioxide by
1- used in filling car
tires.
2- Liquid nitrogen is
used as a treatment
to skin tumors.
3- It contributes in
composing
gunpowder and
ammonium nitrates
included in the
composition of soil
fertilizers.
4-Liquid nitrogen is
used for cooling food
products.
5- It is commercially
used in the
manufacture of
ammonia to produce
when we have rise
above the Earth’s
surface). C-used in
cutting and welding
metals when
combined with
acetylene gas to
produce “oxyacetylene” flame
whose
temperature
reaches 3500oC .
fermentation
when it is
added. Carbon
dioxide gets
expanded due to
the heat making
bread porous
and tasty.
E-contributes in
the
photosynthesis
process.
fertilizers
6-Nitrogen is used in
the tanks of liquified
explosives and during
the manufacture of
electronic devices.
7-Nitrogen is used to
make stainless steel.
8- It is used to store
petroleum and some
flammable materials.
1-Oxygen
- The atmosphere consists of a mixture of gases such as oxygen 21%,
nitrogen 78%, carbon dioxide and other gases 1%.
- The atmosphere contains solid particles such dust and smoke.
- These particles have advantages and disadvantages:
o Disadvantages: these particles are considered air pollutants.
o Advantages: these particles help in condensing water vapor and
turn it into rain or snow.
The importance of the atmosphere:
1-Contains the ozone layer which helps in protecting Earth from harmful
radiation coming from outer space such as the ultraviolet radiation.
2- Adjust the temperature of the earth
Oxygen gas:
1. Produced by plants from the photosynthesis process.
2. One oxygen molecule consists of 2 oxygen atoms.
3. Oxygen composes 1/5 of air volume.
4. Collected by displacing water downward because it rarely dissolves
in water.
5. Colorless, odorless and tasteless.
6. Doesn’t burn but helps in burning.
7. Heavier than air.
Preparation of oxygen:
1- Oxygen is prepared by the dissociation of hydrogen peroxide into oxygen and
water.
2- This dissociation needs the help of a catalyst which is manganese dioxide.
- The catalyst remains without a change in quantity and properties.
- Iron combines with oxygen in the presence of humid to form iron rust.
- Burning iron cleaning wires causes the wires to combine with oxygen forming
iron oxide and resulting increase in weight.
Oxygen
Hydrogen
peroxide
Water
Manganese dioxide
The importance of oxygen:
- Water consists of oxygen united with hydrogen.
- Important for respiration, food combustion and the burning of fuel.
- Ozone consists of oxygen O3.
Uses of oxygen in our life:
Oxygen is compressed in iron cylinders and used in:
1. Mechanical ventilation for patients who suffer from difficulties in breathing.
2. During surgeries.
3. During diving and climbing mountains. Oxygen becomes lighter when we rise
above Earth surface.
4. In cutting and welding metals. By combining oxygen with acetylene a flame of
3500 °C is produced “oxy-acetylene flame”.
2-Carbon Dioxide
- Carbon dioxide molecule consists of 3 atoms: 1 carbon atom and 2 oxygen
atoms.
- The percentage of carbon dioxide in the atmosphere is 0.03%.
Sources of carbon dioxide:
1- The combustion (burning) of organic materials such as wood – coal – fuel.
2- Respiration process (exhalation).
The increase of carbon dioxide percentage causes:
1- The raising of Earth temperature.
2- Suffocation and difficulties in breathing.
Preparation of carbon dioxide in laboratory:
- Add diluted hydrochloric acid to calcium carbonate.
- Bubbles of a gas will be evolved and collected by displacing air upwards.
- The gas is CO2.
- Backing soda and vinegar or lemon also can be used to prepare CO2.
Properties carbon dioxide:
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Colorless and odorless.
Doesn’t burn and doesn’t help in burning.
Heavier than air, so it is collected by displacing air upwards.
Can’t be collected by displacing water because it dissolves easily in water.
A magnesium ribbon keeps burning in a cylinder filled with carbon dioxide
resulting a white substance (magnesium oxide) and a black substance
(carbon) coal
The importance of carbon dioxide:
1- Important for the photosynthesis process.
2- Used in refrigeration by making the dry ice.
3- Is used in extinguishing fires (except magnesium fires) because it doesn’t
help in burning.
4- Is used in making bread by adding yeast which produces CO2 by
fermentation. CO2 cause the bread to be porous and tasty.
5- Is used in making soft drinks.
3-Nitrogen
- The molecule of nitrogen consists of 2 nitrogen atoms.
- Nitrogen is called azote which means lifeless because it doesn’t help in
burning and it is not included in the respiration process.
The existence of nitrogen:
1234-
Nitrogen represents 78% of the atmosphere.
Nitrogen oxides are formed in the atmosphere during lightening.
Nitrogen oxides reach soil with rain water.
Legume plants such as peas, soybeans and clovers produce proteins by the
help of a specific type of bacteria that lives in their roots.
Preparation of nitrogen :-
Properties of nitrogen
1- Nitrogen is colorless, odorless and tasteless.
2- Scarcely dissolves in water.
3- Doesn’t help in burning except with magnesium.
4- Can be condensed to liquefied state.
5- When combined with lightened magnesium it composes a white
substance and by adding water to this substance ammonia pungent
smell is produced.
The importance of nitrogen:
a. Used to fill car tires.
b. Liquefied nitrogen is used to treat skin tumor.
c. Contributes in composing gunpowder.
d. Contributes in making soil fertilizers.
e. Used as inactive element in in tanks of liquefied explosives and during
the manufacturing electrical devices.
f. Small amounts are used to fill some types of lamps.
g. Is used to store petroleum and other flammable materials