Chhattisgarh State Board Class 8 Science Chapter 6 Carbon Exercise Multiple Choice, Fill in the Blanks, Questions and Answers here.
Choose the correct answer
1.) Graphite is not used-
a) As lubricant
b) In electrode
c) In pencil lead
d) In cutting instruments
Ans- d) in cutting instruments
2.) Carbon dioxide converts blue litmus into red, thus it is an-
a) Acidic oxide
b) Alkaline oxide
c) Neutral oxide
d) None of these
Ans-a) acidic oxide
3.) Carbon allotrope with 60 atom is –
4.) Dry ice is
a) Solid CO2
b) Liquid CO2
c) Gaseous CO2
d) Solid CO
Ans- a) soild CO2
5.) The hardest substance in nature is
Ans- c) diamond
6.) Which zone of the flame has the highest temperature?
a) Inner dark zone
b) Shining and bright middle zone
c) Light blue zone
d) Unlighted zone
Ans- light blue zone (outer zone )
7.) Allotropy is a characteristic of
d) All of the above
2.) Fill in the blanks
2.) Because of its softness—– is used in pencil lead.
3.) —– is the hardest allotropic from of carbon
4.) Carbon dioxide is a ——, ——- gas
Say whether the following statements are correct or wrong. Correct the wrong statement.
1.) Both graphite and diamond have the same element , carbon in it.
Ans-true, but graphite and diamond shows different properties.
2.) Diamond is a good conductor of electricity.
Ans-false, diamond is a bad conductor of electricity.
3.) The light blue zone in flame is in the middle of the flame.
Ans-false. The lightly blue zone is the outer most part of the zone.
4.) Combustion doesn’t take place in the outer zone of the flame.
Ans-true. Combustion is almost complete in the outer most zone.
5.) Carbon dioxide is of alkaline nature.
Ans-false, carbon dioxide alkaline in nature.
4.) Match the following
- Lamp black and charcoal-carbon allotrope
- Made of 60 carbon atoms- Fullerene
- Hardest substance- diamond
- Dry ice-solid carbon dioxide
Answer the following question
1.) What do you understand by allotropy? What are the different allotropes of carbon? Write two uses of each?
Ans-different forms of an element having different physical properties but the same chemical properties are called allotropes, and the property of an element having different forms is called allotropy. Carbon has different allotropes like fullerene, diamond and graphite .
Uses of diamond- 1) It is used the hardest substance so it is used for cutting of glass and instruments.
2) it is used in ornaments.
Uses of graphite- 1) it is used in making pencil lead.
2) it is used as a conductor of electricity and electrode in dry cell.
2.) How will you differentiate between graphite and diamond?
|It is the hardest substance||It is not hard as diamond it is soft.|
|It is used for cutting glass||It is not used for cutting glass.|
|It appears shiny and used in ornaments.||It is grey in clour and used in electrodes in dry cell and also used for electricity.|
3.) What is fullerene? What are its main uses?
Ans- Fullerene is the allotrope of carbon. It having 60 carbon atoms in their structure joined to each other. Fullerene having C-70 , C-90, C120 carbon atoms are also discovered. The main uses of fullernece in future for manufacturing of super conductors ,semicondusctors, lubricants, catalyst and electric wires. C-60 containg substances may also be used in the prevention and care of AIDS.
4.) What is dry ice? What are its important uses?
Ans- when carbon dioxides is cooled it solidifies and this solid carbon dioxide is called dry ice. The important uses of dry ice as a coolant.
5.) What are the main parts of candle flame? Explain with a diagram.
Ans-there are three different zones are shown in candle flame.
1) The inner most zone- the inner most part is the darkest it is the coldest part of the flame. In this zone there is the hot vapour of the combustible substance(wax). In this area there is not combustion because there is no oxygen.
2) The middle zone- the middle portion is the shining , bright zone. In this zone the fuel partly burns and forms carbon particles which shines when hot
3) The outer most zone- the outer most part is slightly blue in clour . in this area the oxygen of the atmosphere mixes properly with the fuel and there is almost complete combustion. This is hottest zone. Its max temperature is 1800 degree celcius.
6.) Give the reasons
a) Diamond is used in ornaments.
Ans- Diamond is used in the ornaments because of its luster is a precious stone and it appears very shiny also it is most attractive therefore it is used in ornaments.
b) Diamond is used in cutting instruments.
Ans- diamond is the hardest substances so it is used the cutting of glass and instruments used in drilling hard stone. Therefore it used for cutting glass or instruments.
c) Graphite is used as lubricant
Ans- graphite is the allotrope of carbon and shows the property for friction therefore it is used as lubricants.
d) Graphite is used in electrodes.
Ans- Graphite is the allotrope of carbon and it is good conductor of electricity therefore it is used as electrodes in dry cell.
e) Petrol is not used in cooking stoves
Ans- petrol is not used in cooking stoves because petrol has lower ignition temperature than kerosene. Petrol vapourizes easily and catches fire quickely. therefore it is not used as cooking fuel for stoves.
7.) The clour of flame in Fatima’s gas stove is blue and Rajesh’s is yellow. Who will cook fast and why?
Ans- Fatima’s gas stove flame is blue and Rajesh’s stove flame is yellow so as we know about the three layers of flame the outer most layer of flame i.e blue flame is most hot because in this area of the atmosphere mixes properly with the fuel and there is almost complete combustion. Therefore this zone is most hot than other two zones ,so Fatima’s cook fast than Rajesh. Because Fatima’s gas stove is on blue flame so she cook fast.
8.) Why doesn’t charcoal burn with flames?
Ans-charcoal doesn’t burn with the flames because only those solids or liquid which on heating produce vaporus burn with a flame and coal do not vaporizes therefore charcoal doesn’t burn with flames.