Q51. Why some substances burn with a flame while as some burn without a flame?
Q52. 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.
Q53. List conditions under which combustion can take place.
What are the conditions necessary for combustion to take place?
Q54. When the clothes of a person catch fire the person is covered with a blanket to extinguish fire. Can you guess why?
Why is a person whose clothes have caught fire wrapped in a thick blanket?
Why do we cover a burning person in the blanket as a first aid?
What should be done if the clothes of a person catch fire accidentally? Why?
Q55. What does a fire brigade do when it arrives at a place where a building is on fire?
When a fire brigade arrives at a place where a building is on fire, what does it do?
Q56. 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?
Q57. Can the process of rusting be called combustion? Discuss.
Q58. State any three characteristics of an ideal fuel.
What are the characteristics of an ideal fuel?
What is an ideal fuel?
Q59. What is acid rain? How is acid rain harmful?
What are the causes and effects of acid rain?
Q60. If a can full of kerosene catches fire, what is the simplest way to put off this fire?
Q61. What is explosive combustion? Give one example.