1. NCERT Solutions - Science , Class 8
1. Crop Production and Management
2. Microorganisms: Friend and Foe
3. Synthetic Fibres and Plastic
4. Materials: Metals and Non-Metals
5. Coal and Petroleum
6. Combustion and Flame
7. Conservation of Plants and Animals
8. Cell — Structure and Functions
9. Reproduction in Animals
10. Reaching the Age of Adolescence
11. Force and Pressure
14. Chemical Effects and Electric Current
15. Some Natural Phenomena
17. Stars and the Solar System
18. Pollution of Air and Water
Q1) List conditions under which combustion can take place.
Q2) Fill in the blanks.
(a) Burning of wood and coal causes _____________ of air.
(b) A liquid fuel, used in homes is _______________.
(c) Fuel must be heated to its ___________ ___________ before it starts burning.
(d) Fire produced by oil cannot be controlled by ____________ .
Q3) Explain how the use of CNG in automobiles has reduced pollution in our cities.
Q4) Compare LPG and wood as fuels.
Q5) Give reasons.
(a) Water is not used to control fires involving electrical equipment.
(b) LPG is a better domestic fuel than wood.
(c) Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not.
Q6) Make a labelled diagram of a candle flame.
Q7) Name the unit in which the calorific value of a fuel is expressed.
Q8) Explain how CO_2 is able to control fires.
Q9) It is difficult to burn a heap of green leaves but dry leaves catch fire easily. Explain.
Q10) Which zone of a flame does a goldsmith use for melting gold and silver and why?
Q11) In an experiment 4.5 kg of a fuel was completely burnt. The heat produced was measured to be 180,000 kJ. Calculate the calorific value of the fuel.
Q12) Can the process of rusting be called combustion? Discuss.
Q13) Abida and Ramesh were doing an experiment in which water was to be heated in a beaker. Abida kept the beaker near the wick in the yellow part of the candle flame. Ramesh kept the beaker in the outermost part of the flame. Whose water will get heated in a shorter time?
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NCERT Solutions - Science , Class 8
Crop Production and Management
Microorganisms: Friend and Foe
Synthetic Fibres and Plastic
Materials: Metals and Non-Metals
Coal and Petroleum
Combustion and Flame
Conservation of Plants and Animals
Cell — Structure and Functions
Reproduction in Animals
Reaching the Age of Adolescence
Force and Pressure
Chemical Effects and Electric Current
Some Natural Phenomena
Stars and the Solar System
Pollution of Air and Water
Race To Space
Terms & Policies