Embibe Experts Solutions for Chapter: Combustion and Flame, Exercise 1: Exercise

Oxygen is required for burning. But do all substances catch fire? To explain this, the chemistry teacher handed some substances to Tanya and asked her to light a matchstick on those substances.

Tanya has been provided with wood, paper, iron nail, straws, kerosene oil, sand, stone piece, charcoal and glass. Some of these substances could easily catch fire and some are resistant to fire.

Could you help Tanya make the categories of the two different types of substances? What are these substances called? Explain.

Heating value is a very significant property of diesel fuels because it gives the energy content of the fuel. The heating value is expressed as a calorific value. The greater the calorific value the more efficient is the fuel. Calorific value is the heat produced on complete combustion of $1 \mathrm{kg}$ of fuel.

The calorific value of some common fuels are listed below:

Ritvik wants to understand that if he needs to get the same amount of energy from wood as much as he gets from  $1 \mathrm{kg}$ of petrol, does he need to burn $1 \mathrm{kg}$ of wood or he needs to increase its mass? Which fuel listed in the table above has the highest efficiency?

Hydrogen is considered clean fuel because its combustion unlike other fuels does not produce any harmful emissions. These harmful emissions are generally the oxides of non-metals which cause adverse effects on our environment. One such effect is global warming. Global warming is the state of rising the earth's temperature gradually. This temperature rise is due to the increased industrialisation and increased utilisation of automobiles over the last decade.

What does this graph suggest about the increment in earth's temperature by $1.5 °\mathrm{C}$? What is the major pollutant formed by the consumption of fuels that is responsible for global warming?

Write the combustion reaction for hydrogen to justify the fact that it is a clean fuel.

A teacher was explaining the experiments on the concept of 'material burns with or without a flame' in a laboratory. To demonstrate this experiment, the teacher gave a pine wooden cylinder wounded with paper and an aluminium cylinder wounded with paper to a group of students and instructed them to hold both cylinders over a Bunsen flame for ten seconds.

What happens when students hold both cylinders over a Bunsen flame, based on the above understanding? Explain your answer.

Sanju, a student in the eighth grade, attended a magic performance. The magician removes a piece of white solid from water during a magic trick. Immediately, it starts to burn. He has done this performance under highly protective conditions because the released gas is highly toxic. Sanju was perplexed since he knew that in order to burn something, a matchstick or lighter must be used, but in this instance, the magician used neither of them. Can you assist Sanju in determining the material and what we refer to as such substances that burst without apparent cause?

According to the National Snow and Ice Data Center, there is now $10\%$ less permafrost, or permanently frozen ground, in the Northern Hemisphere than there was in the early $1900$s. Rajesh, a student, became quite inquisitive after reading this article. He is curious as to why the earth's ice is melting at such a rapid pace. Can you assist him in determining the reason of the following alteration and the chemicals that contributes towards it?

Student Pavan resides in a major metropolis. He went to his grandmother's place one day. It was situated in a rural location. He observed his grandmother using wood to cook outside. He has never witnessed wood-fired cooking in his family. His meals are usually prepared on LPG stoves. He also noticed smoke being released from wood burning.

Observe the above scenario and answer the following question:

Which was good fuel among LPG and wood? What are the characteristics of an ideal fuel?

Tanush went to his grandmother's house on his holidays. He noticed Grandma heating water in a vessel outside the house, but he also noticed that she was using wood to heat the water. After a while, he came inside and saw his aunt cooking food on a stove, and she had added kerosene oil to the stove before cooking the food. When he returned home, he noticed his mother cooking on the gas stove.

Answer the following question based on your understanding of the above.

How are fuels classified according to their physical state? Please provide two examples of each.