Ch.7.1

Question 1

the layer of air on Earth is called the ___________________.

Answer 1

atmosphere

Question 2

the atmosphere is ___________________ to living things. without air, living things _____________ ______________.

Answer 2

essential, cannot survive`

Question 3

what is air made of?

Answer 3

air is a mixture of gases.

Question 4

what does air consist of? what is the percentage of these gases in air?

Answer 4

nitrogen (78%), oxygen (21%), carbon dioxide (0.03%), noble gases (0.9%), water vapour and small amounts of other gases (0.07%).

Question 5

Noble gases are mainly ___________________. Other examples include ______________ and ______________.

Answer 5

argon, neon, helium

Question 6

The ‘other gases’ in air includes:

Answer 6

methane, ozone, sulphur dioxide and nitrogen oxides etc

Question 7

properties we study when we test for a certain gas:
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-
-
-

Answer 7

what colour is it?
does it have a smell?
does it burn?
can it support burning?
does it react with other chemicals?

Question 8

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Answer 8

it relights a glowing splint

it causes a burning splint to burn more brightly

Question 9

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Answer 9

it turns hydrogencarbonate indicator from red to yellow

it turns limewater from colourless to milky

Question 10

how to test for gases with other chemicals:

—

Answer 10

add a few drops of that chemical to a test tube containing a gas.

Question 11

how to test for water and water vapour?

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Answer 11

both turn dr cobalt chloride paper from blue to pink.

Question 12

how to test for nitrogen and noble gases?

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Answer 12

there are no simple tests.

Answer 13

it is used to keep the cobalt chloride papers dry.

Question 14

why is dry cobalt chloride paper used to test for water?

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Answer 14

it is because a dry cobalt chloride paper shows a colour change when it is in contact with H2O.

Question 15

why are there no simple tests for nitrogen and noble gases?

Answer 15

it is because these gases are very unreactive.

Question 16

how is oxygen used in daily life?
—used to ______________ ______________ with ______________ ______________
—used to ___________ ______________ in a ______________ with a __________ ____________ in ______________, as such _____________________________________________________________________________________.

Answer 16

help patients, breathing difficulties
cut metals, mixture, gas fuel, industry, mixture burns to produce a very high temperature which is high enough for cutting metals

Question 17

how is carbon dioxide used in our daily life?
—used in ________________________________________________________ as it _______________________________ and is _______________________________.
—used on ______________ to __________________________________________________, as ______________ carbon dioxide (___________________) ________________________________________________________.

Answer 17

used in fire extinguishers to put out fires, does not support burning, denser than air
stages, produce a fog effect, solid, dry ice, changes directly to a gas at room temperature.

Question 18

Both oxygen and carbon dioxide are involved in _____________________________________ of living things: including ______________________________________________.

Answer 18

three essential life processes; photosynthesis, respiration, gas exchange

Question 19

how is nitrogen used in our daily lives?
—used to __________________________________________ as it ______________________________________________________.
—______________ nitrogen with a ___________________________________________ is used for ________________________________________________________.

Answer 19

fill some food packages, helps prevent the food from going bad
liquid, temperature below -196°C, storing living cells and tissues

Question 20

how is argon used in our daily life?

—used to ________________________________________.

Answer 20

fill light bulbs

Question 21

how is helium used in our daily life?

—used to __________________________________________.

Answer 21

fill balloons and airships

Question 22

how is neon used in our daily life?

—used to ________________________________.

Answer 22

fill advertising lights