Subject Experts Solutions for Chapter: Combustion and Flame, Exercise 3: TOUGH NUT

Wood, on burning, produces a bright flame initially and glows later, while LPG continues to burn with a flame. Can you explain why?

Shyam noticed that his gas stove is beginning to give out yellow flames. What does it mean?

Rohan wants to know why gas burners do not use wicks. Can you explain?

Tania and Manjeet are good friends and classmates in class 8. One day, Manjeet invited Tania for spending some time with her. After having a heavy lunch, both of them were relaxing when they saw smoke coming through the door into Manjeet's bedroom. Manjeet immediately woke Tania who opened the door and looked outside. She saw fire coming out of a wooden cupboard. She could also see electric sparks in the dangling electric wires. They looked inside the room and found two buckets of sand kept for making sandcastles, one large size bottle of industrial cleaner, and buckets filled with water in the bathroom. Manjeet immediately called the fire brigade and then started thinking about what could be done immediately. Which of the three items can be used dousing fire? State two methods to control fire. Fireman sometime risk lives to protect others because there is no greater love than to lay down one's life for protecting others. Do you agree? why?

Everybody in the family knows that Rekha has a passion for bikes and cars. She likes to collect information related to bikes  i.e., speed, performance, looks, warranty, service etc. On her birthday, Rekha's father decided to surprise her by taking her to a motor exhibition. Rekha was overjoyed and thanked her father for giving her this opportunity. At the exhibition she could see the latest bikes and cars. She saw some breakthrough vehicles using hydrogen as fuel and some which were powered by solar energy. Her father told her that these vehicles were currently experimental in nature and will produce zero pollution. At other counters, Rekha saw the latest luxury vehicles. She checked and found that these luxury vehicles were consuming too much fuel. Some of them were consuming two to three times the fuel consumed by normal vehicles. These made her sad as she has been reading about the harm caused by the fuels in chapter 6 of her science textbook. Why was Rekha sad? Suggest three ways in which Rekha can reduce the harm caused to the environment by burning fuels.