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Chapter 5 – Air Around Us

1. The chart in diagram 1 shows the composition of air in the atmosphere.

Diagram 1

(a) Name the gases P,Q and R and state their percentages in the air. Complete

table 1 .

Gas Name Percentage(%)

P

Q

R

( 3 marks )

(b) Give two similarities between gas P and gas Q.

1.__________________________________________________________________

2.__________________________________________________________________

(2 marks)

(c) i. What can you observe happening when gas R is tested with limewater?

( 1 mark)

ii Give one reason for the observation in (c) i.

(1 mark)

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(d) Fill in the table 1.2 the appropriate test to be used for testing the present of these

gases. (2mark)

Gas Appropriate test

Q

R

Table 1.2 2. Diagram 2 shows the composition of air in atmosphere.

X Y

Diagram 2

( a ) Name the gases V, W, X and Y and state their percentages in the air.

Complete the table 2.1 ( 4 marks )

Table 2.1

( b ) Name another two components of air besides gases V, W, X, and Y ………………………………………………………………………………………. ( 2 marks ) ( c ) What can you observe when gas Y is tested with limewater? …………………………………………………………………………………….. ( 1 mark )

Gas Name Percentage/ % V nitrogen W 21 X 1 Y Carbon dioxide

W

V

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3. Diagram 3 below shows the relationship between respiration and photosynthesis

Diagram 3

( a ) Name the gases R and S

R:………………………… S: …………………………… (2 marks).

( b ) Name a living thing that absorb gas R

..…………………………………………………………………. (1 mark).

( c ) Name 2 living organisms that released gas S

i……………………………… ii …………………………. (2 marks)

( d ) Name a process that release gas S

…………………………………………………………………… . (1 mark)

( e ) State two characteristics of gas R and gas S.

R i: ……………………………………………………………

ii: ……………………………………………………………

S i. :……………………………………………………………

ii:…………………………………………………………….

( 4 marks)

R

S

Photosynthesis Respiration

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4. (a) Complete the table below with the correct answer.

Type of test

Oxygen

Nitrogen

Carbon dioxide

Solubility in sodium hydroxide solution

Not soluble

With hydrogen carbonate indicator

No change in colour

With glowing splint Glowing splint extinguished

(6 marks ) ( b ) Name the test for…..

a. oxygen……………………………………………………

b. carbon dioxide……………………………………………

c. nitrogen …………………………………………………. (3 marks )

( c ) State three characteristics of carbon dioxide that makes it a suitable fire

extinguisher. i ………………………………………………………………. ii ………………………………………………………………. iii ……………………………………………………………….

(3 marks)

( d ) State one use of nitrogen gas. ………………………………………………………………………………(1 mark)

( e ) Inert gases are …………………., ……………………., ……………….

………………………..……………………….., ………………………….

(1 mark )

( f ) State the uses of :

i. argon ……………………………………………………………………

ii. helium …………………………………………………………………… ( 2 marks )

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5. Diagram 5.1 shows the apparatus used in an experiment to study that combustion required oxygen. Candles J, K and L burned under three different conditions.

Diagram 5.1

Table 5.1 below shows the observations obtained at the end of the experiment.

Candle Observation J Continues to burn until the end of the experiment K Burns brightly and goes out after a while L Goes out shortly

Table 5.1

( a ) What inference can you make from the observation on candle

i. J ……………………………………………………………… ii. K ……………………………………………………………… iii. L ………………………………………………………………

(3 mark) ( b ) State a conclusion for the experiment

………………….……………………………………………………………………… (1 mark)

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( c ) Diagram 5.2 below shows a burning charcoal is placed in a gas jar containing oxygen and lime water.

Diagram 5.2

i. What happened to the lime water

……………………………………………………………………………

(1 mark)

ii. Explain your answer in c ( i )

………………………………………………………………………….. (1 mark)

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6. Diagram 6.1 below shows an experiment to investigate the need of oxygen for

combustion. Two same candles labeled M and N are lighted under two gas jars with different volume.

M N

Diagram 6.1

( a ) What is the objective of this experiment?

…………………………………………………………………………………. …………………………………………………………………………………. ( 1 mark )

( b ) What is the hypothesis of this experiment? …………………………………………………………………………………… ( 1 mark ) ( c ) State the variables in this experiment. i. constant variable : ………………………………………………………. ii. manipulated variable : ……………………………………………………. iii responding variable : ……………………………………………………..

( 3 marks )

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Table 6.2 below shows the observations obtained from this experiment.

Candle Observation

M Candle M burns longer than the candle N

N Candle N is extinguished earlier

Table 6.2

( a ) What inferences can you make from the observation of candles?

i. M : ………………………………………………………………………………….

…………………………………………………………………………………

ii N : ................................................................................................................ …………………………………………………………………………………

( 2 marks ) ( b ) What can you conclude from this experiment?

………………………………………………………………………………………. ………………………………………………………………………………………

( 1 mark )

( c ) Predict what will happen if a candle is left burning without the container.

……………………………………………………………………………………. ……………………………………………………………………………………

( 1 mark )

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7. Three sets of apparatus as shown in diagram 7 below are set up and left aside

in a horizontal position for three hours.

Diagram 7

The result of experiment is shown in the table 5.7 below.

Test tube Observation

X Indicator moves inwards towards the boiling tube

Y Indicator moves inwards towards the boiling tube

Z Indicator does not move

Table 7.1

( a ) What inference can you make from the observation on candle?

i X: ………………………………………………………………………………

ii Y : ………………………………………………………………………………

iii Z: …………………………………………………………………………….. ( 3 marks )

( b ) State the function of the cotton soaked with sodium hydroxide solution.

………………………………………………………………………………….

( 1 mark )

( c ) State the conclusion from the observation of the experiment . …………………………………………………………………………………..

( 1 mark )

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8. Diagram 8.1 shows an experiment to study the combustion of charcoal in air. The

gas produced turns lime water to chalky.

Diagram 8.1

( a ) ( i ) Based on Diagram 81, why does the lime water turns to chalky?

……………………………………………………………………………………

( 1 mark)

( ii ) Write a word equation to show the combustion of charcoal. +

( 1 mark )

( iii ) In Table 8.1 , tick ( √ ) examples of substances , that give the same combustion product as charcoal.

Substance Mark with (√ )

Oil

Candle

Coal

( 1 mark )

Carbon dioxide

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( b ) The experiment in Diagram 8.1 is repeated using kerosene as shown below. Colourless liquid droplets formed on the wall of the gas jar.

Diagram 8.2

( i ) The colourless droplets are tested with anhydrous cobalt chloride paper. State the observation. ……………………………………………………………………………………

( 1 mark )

( ii ) What can you conclude about the colourless droplets? ……………………………………………………………………………………

(1 mark )

( iii ) Write a word equation to show the combustion of kerosene.

+ + ( 1 mark)

Liquid droplets

Kerosene Oxygen

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9. Diagram 9.1 shows an experiment of gases.

P

Q

Diagram 9.1

Table 1.1 shows the result of an experiment.

Gas Observation P The burning splinter extinguish. Q The glowing splinter glows brightly.

( a ) ( i ) Based on the result, give a property of each of the following gases based on the following words.

An alkali gas A neutral gas An acidic gas

Gas P : ____________________________________________________________ Gas Q : ____________________________________________________________

( 2 marks)

( ii ) Give an example each of gas P and gas Q. Gas P : ____________________________________________________________ Gas Q : ____________________________________________________________

( 2 marks )

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( b ) Diagram 9.2 shows an experiment to investigate respiration in living things. The result of the experiment is shown in Table 1.2

Diagram 9.2

Boiling Tube Observation of the coloured indicator

R Moves towards the boiling tube

S Moves towards the boiling tube

T Does not move

Table 1.2

( i ) Why is the cotton wool is soaked with sodium hydroxide solution ?

…………………………………………………………………………………

( 1 mark )

( ii ) Why is there no movement of the coloured indicator in boiling tube T ? ………………………………………………………………………………..

( 1 mark ) ( iii ) What is the gas needed by the living things for the respiration ? ……………………………………………………………………………….

( 1 mark )

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10. A group of students carry out an experiment as shown in Diagram 10.1 to

investigate the effect of the size of a container on the length of time a candle to

burns. The stopwatches show the length of time the candles burn.

A B C

__________ second

__________ second

_________ second

Diagram 10

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( a ) State the variables involved in the experiment.

i. Manipulated variable

ii. Responding variable

iii. Constant variable Size of candles (2 marks )

( b ) Record the length of time each candle burns in the table 1.4 below.

Candle Volume of beaker( cm³) Length of time the candle burns ( second )

A 1000 B 500 C 250

(3marks )

( c ) Based on the Table 1.4, complete a bar chart to show the length of time for Candle A burns in the beaker

beaker A B C

The length of time a candle burns

30

25

20

15

10

5

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( d ) Based on the bar chart in ( c ) , what can be said about the length of time a Candle burns ?

………………………………………………………………………………

…………………………………………………………………………….. (2 marks)

( e ) Suggest one inference for your answer in ( d ) ……………………………………………………………………………………..

( 1 mark ) ( f ) A candle is placed in a beaker with a volume of 750 cm ³ . Predict the length of time a candle burns in it. ……………………….. second. [ 1 mark ]

( g ) State the relationship between the volume of the beaker and the length of time a candle burns in it. ……………………………………………………………………………………. …………………………………………………………………………………….

[ 1 mark ]