HEAT SOURCES AND FLAMES.

                             

   QUESTIONS

1. Multiple choice.

  Choose the most correct answer.

   (i) The following are laboratory heat sources except.

    A: kerosene burner

    B: Bunsen burner

    C: firewood burner

    D: spirit burner

  (ii) Unburnt region of non-luminous flame is ________ in colour.

  A: colourless

  B: black

  C: yellow

  D: pale blue

  (iii) The following is importance of barrel of the bunsen burner.

   A: to control air that enter the bunsen burner

   B: to mix air with gas fuel

   C: to support the bunsen burner

   D: to adjust air hole

  (iv) The hottest part of non-luminous flame

   A: the outer zone

   B: the tip of outer zone

   C: the tip of middle zone

   D: the tip of inner zone

  (v) Brightness of non-luminous flame is caused by ________

      A: green zone

      B: blue zone

      C: excess unburnt air

      D: glowing carbon particles.

 (vi) Bunsen burner is the best laboratory heat source because it is ______

   A: easy to make any flame with it

   B: easy to handle

   C: free from soot

   D: cheap

 (vii) It is used for lighting

    A: luminous flame

    B: non-luminous flame

    C: charcoal burner

    D: soot less flame

 (viii) Is not found at non-luminous flame

   A: zone of unburnt gas.

   B: blue zone

   C: yellow zone

   D: pale blue zone.

 (ix) The following can not be used to distinguish luminous flame from non-luminous flame.

  A: size of flame

  B: fuel used to produce a flame

  C: colour of the flame

  D: soot production

 (x) The following are not function of electrical burner except ________

   A: lighting

   B: heating

   C: flame testing

2. Matching items.

   Match items in list A with responses in list B.

        List A

 (i) Glowing carbon particles in luminous flame

 (ii) Produced when the air hole of bunsen burner is full opened.

 (iii) It has three zone

 (iv) zones of non-luminous flame

 (v) it is used when an experiment do not need high temperature

 (vi) Can be used if bunsen burner is not available

 (vii) The choice of source of heat

 (viii) zone that burning is complete

 (ix) zone that burning is not complete

 (x) it is large in size.

    List  B

A: non-luminous flame

B: blue/green, pale blue and zone of unburnt gas

C: yellow zone, thin outer zone, colourless or inner zone and blue zone

D: Depends on the degree of the heat produced.

E: the hottest flame.

F: luminous flame

G: is yellow in colour

H: blue zone

I: gas stove

J: charcoal

K: yellow zone

L: candle burner

3. Write T for correct statement and F for incorrect statement.

(i) A non-luminous flame looks similar to candle flame.

(ii) A luminous bunsen burner flame produces less soot than non-luminous flame.

(iii) The dark zone of luminous flame consists of unburnt gas.

(iv) The hottest part of non-luminous flame may be at the top of dark zone.

(v) The yellow colour of luminous flame is formed due to presence of carbon particles.

(vi) A blue bunsen burner flame is formed when the air hole is open.

(vii) A non-luminous flame is hotter than luminous flame.

(viii) The luminous flame produces noise and is soot less.

(ix) Non-luminous flame has four parts.

(x) A yellow bunsen burner flame is obtained when air hole is closed.

4. Explain the meaning of the following.

   (a) flame

   (b) luminous flame

   (c) non-luminous flame

5. The flames that produced by bunsen burner are luminous flame and non-luminous.

 (a) which between these flames is hotter than the other? Why?

 (b) which flame can be easily seen? Why?

 (c) which flame is prefered to be used in the laboratory? Why?

6. Explain the function of the following parts of the bunsen burner

 (a) collar

 (b) air hole

 (c) base

 (d) barrel

7. (a) Differentiate luminous flame from non-luminous flame.

    (b) Outline the similarities between luminous flame and non-luminous flame.

8. Name four substances that burn and produce luminous flame.

9. (a) Mention uses of flames

    (b) Name activities that need non-luminous flame used

10. List four characteristics of

     (i) luminous flame

     (ii) non-luminous flame

11. What is the importance of luminous flame?

12. Which part of the flame is coolest of all? Why?

13. Name four heat sources that can be used in the laboratory.

14. Why the outer zone of the flame is hotter than other parts of the flame?

    ANSWERS.

1. (i)C   (ii)A   (iii)B  (iv)B   (v)D

   (vi)A   (vii)A   (viii)C   (ix)B  (x)B

2. (i) G  (ii)F   (iii)A   (iv) B    (v)L

   (vi)I  (vii) D  (viii)H  (ix)K   (x)F

3. (i) F  (ii)F   (iii)T   (iv)F     (v)T

   (vi)T   (vii)T   (viii)F   (ix)F  (x)T

4. (a) Flame:- is a region of burning gas that produces heat and light.

  Or

      Is a visible gaseous part of fire.

   (b) Luminous flame:- is a flame which formed when burning of fuel is incomplete.

     Incomplete burning caused by insufficient supply of air (oxygen).

   (c) Non-luminous flame:- is a flame which formed when burning of fuel is complete.

     Complete burning caused by sufficient supply of air (oxygen)

5. (a) Non-luminous flame is hotter than luminous flame because formation of the flame involves complete combustion such that more heat is produced but luminous flame formation involved incomplete combustion.

   (b) Luminous flame seen easily because hot bright yellow carbon particles formed due to incomplete burning of fuel. This makes luminous flame to produce light and seen easily.

   (c) Non-luminous flame is most prefered flame in the laboratory because it is hotter and soot free.

6. (a) Collar control the air that enter the bunsen burner.

      This done by adjusting the air hole size.

     (b) Air hole

               Allows air to enter the bunsen burner.

     (c) Base

               It supports the bunsen burner.

     (d) Barrel

             Mix air with gas so as burning to take place on top.

7. (a) Different between Luminous flame and Non

luminous flame

-luminous flame is yellow in colour WHILE non-luminous flame is blue in colour

-luminous flame produces soot WHILE non-luminous flame does not Produce soot

-luminous flame produces less heat WHILE non-luminous flame produces more heat

-luminous flame has a wavy flame WHILE non-luminous flame has a triangular flame

-luminous burns quietly WHILE non-luminous flame burns with a roaring noise

-luminous flame has foul zone WHILE non-luminous flame has three zone.

    (b) Similarities between luminous flame and non-luminous flame.

  -both produce heat

  -both used in heating and cooking.

8. Substances that burn and produce luminous flame.

  -Plastics

  -Candle

  -Paper

  -Firewood

  -Clothes

  -Grass

9. (a) uses of flames.

    -used for heating

   -used for lighting

   -used for testing chemicals(flame test)

   -used for welding.

   -used for cooking.

 (b) activities that need non-luminous flame.

    -welding

   -flame test

   -heating

   -cooking

10. Characteristics of Luminous flame and Non luminous flame.

 (i) Luminous flame

-it is yellow in colour

-Produces soot

-Produces less heat

-Has a wavy flame

-Burns quietly

-has four zone (parts)

 (ii) Non-luminous flame.

 -is blue in colour

- Does not Produces soot

-Produce less more heat

-Has a triangular flame

-Burns with a roaring noise

-has three zone

11. Luminous flame is important because:-

    •it helps to provide heat that used for different activities

     •it helps to provide light during night

12. Inner zone. Because burning does not take place at that zone.

13. -Bunsen burner

       -Spirit burner

      -gas stove

      -kerosene burner (stove)

      -charcoal burner.

      -candle burner

14. Because it receives more air than other parts such that combustion at outer zone is effective, this results to production of more heat than other parts of the flame.particles at a high speed.