Science Ch-5

What is combustion?

The process of burning a substance in the presence of air or oxygen with the liberation of heat and light.

Give examples of combustible substances.

Alcohol, petrol, LPG, and nylon fibers.

What are non-combustible substances?

Substances that do not burn in air or oxygen to produce heat and light, such as water, sand, glass, and cement.

Describe rapid combustion.

A type of combustion where a large amount of heat and light are released in a very short span of time.

What is an example of rapid combustion?

Combustion of LPG, which produces heat and light instantly.

Describe explosion.

Explosion is a type of combustion characterized by the sudden release of heat, light, and sound, accompanied by the liberation of a large amount of gas.

What is an example of an explosion?

The bursting of firecrackers is an example of an explosion.

How does spontaneous combustion occur?

Spontaneous combustion is when substances catch fire on their own without the application of heat.

What is an example of an explosion?

The bursting of firecrackers is an example of an explosion.

How does spontaneous combustion occur?

Spontaneous combustion is when substances catch fire on their own without the application of heat.

Define complete combustion.

Complete combustion is a type of combustion that takes place in an adequate amount of air or oxygen, resulting in the formation of carbon dioxide, water, heat, and light.

What happens during incomplete combustion?

Incomplete combustion takes place in an inadequate amount of air or oxygen, resulting in the formation of incomplete products and potentially harmful byproducts.

What is the purpose of water in extinguishing a fire?

Water evaporates, taking away heat from the fire, which cools down the burning material below its ignition temperature.

What is the purpose of water in extinguishing a fire?

Water evaporates, taking away heat from the fire, which cools down the burning material below its ignition temperature.

When should water not be used to extinguish a fire?

Water should not be poured over burning petrol, kerosene, or diesel as these substances are lighter than water and do not mix with it.

Describe the combustion of hydrocarbons.

The combustion of hydrocarbons, such as LPG, petrol, and natural gas, can be of two types: complete combustion and incomplete combustion.

Describe the conditions necessary for combustion to take place.

The presence of a combustible substance, the presence of a supporter of combustion (e.g., oxygen), and the attainment of ignition temperature are the conditions necessary for combustion to take place.

What is the purpose of a carbon dioxide fire extinguisher?

A carbon dioxide fire extinguisher is used to cut off the supply of oxygen and extinguish the fire.

Why should water not be used over electrical fires?

Water conducts electricity and can pose a danger to people trying to extinguish the fire.

Define ignition temperature.

Ignition temperature is the minimum temperature at which a substance starts to burn in the presence of air.

How does a carbon dioxide fire extinguisher work?

A carbon dioxide fire extinguisher contains carbon dioxide gas under high pressure, which settles down and cuts off the supply of oxygen, extinguishing the fire.

What are two common types of fire extinguishers?

Two common types of fire extinguishers are carbon dioxide fire extinguishers and soda-acid fire extinguishers.

Describe the role of water in combustion.

Water forms a layer beneath combustible substances and continues burning, forming carbon monoxide, soot, water, heat, and light.

What is the purpose of using carbon dioxide gas in fire extinguishers?

Carbon dioxide gas is used in fire extinguishers as it is not a supporter of combustion and can extinguish the fire by cutting off the supply of oxygen.

Describe the zone in a candle flame where the wax vapors remain unburned.

The zone where the wax vapors remain unburned is completely dark and emits no light.

What is the substance that burns in addition to the wick in a candle flame?

In addition to the wick, the wax vapors burn in a candle flame.

What happens when a lit match is brought above a blown-out candle wick?

The flame from the match jumps the gap and reignites the wick because the wax vapors rise from the wick.

Define a luminous flame.

A luminous flame is a flame that emits a lot of light and is generally yellow in color.

Describe the appearance of a candle flame when there is insufficient oxygen.

When there is insufficient oxygen, a candle flame appears yellow and is called a luminous flame.

Describe a blue flame.

A blue flame is a non-luminous flame that emits very little light and is observed when there is adequate oxygen available for complete combustion. It leaves behind no residue.

What is the aim of the experiment with a candle and matchbox?

The aim is to prove that when a candle burns, it is the wax vapors that burn and not the liquid wax.

What materials are needed for the experiment?

The materials needed are a candle and a matchbox.

How can you observe the phenomenon of a blue flame?

By ensuring there is adequate oxygen available for complete combustion, a blue flame can be observed, which emits very little light and leaves behind no residue.

Define combustion.

Combustion is a chemical process in which a substance reacts with oxygen to produce heat and light.

Describe the process of combustion in a candle flame.

The heat of the flame vaporizes the molten wax in the wick, and the wax vapors burn in the flame until all the wax is consumed or the candle is extinguished.

What are the three necessary conditions for combustion?

The three necessary conditions for combustion are fuel, oxygen, and heat.

Define spontaneous combustion.

Spontaneous combustion is the process of a substance igniting and burning without an external ignition source.

How are fuels classified based on their physical state?

Fuels can be classified as solid, liquid, or gas based on their physical state.

What are the three zones of a candle flame?

The three zones of a candle flame are the dark zone, the middle zone, and the outer zone.

Describe the three types of fuels mentioned in Table 5.1.

Solid fuels exist in a solid state at room temperature, liquid fuels exist in a liquid state at room temperature, and gaseous fuels exist in a gaseous state at room temperature.

What happens when the wick of a candle is pinched?

Pinching the wick stops the absorption of liquid wax, cutting off the flame's fuel supply and extinguishing it.

What are some examples of solid fuels?

Wood, charcoal, cow dung cakes, agricultural waste, coke, and coal are examples of solid fuels.

How can carbon dioxide production be proven when burning candle wax?

By conducting an experiment using a candle, glass jar, aluminium foil, and lime water solution.

What factors determine the choice of fuel for domestic or industrial use?

The choice of fuel depends on its cost, efficiency, availability, and the extent of pollution it causes.

Describe the calorific value of a fuel.

The calorific value of a fuel is the amount of heat produced in kilojoules when one gram of the fuel is completely burned.

What happens when lime water reacts with carbon dioxide gas?

Lime water turns cloudy when it reacts with carbon dioxide gas.

Define fuel efficiency.

Fuel efficiency is the proportion of energy produced by a machine that cannot be converted into useful work.

Do wood and firecrackers exhibit rapid combustion?

No, wood is not a non-combustible substance and firecrackers do exhibit rapid combustion.

How is the calorific value of a fuel related to its heat production?

The higher the calorific value of a fuel, the more heat it produces when burned.

Describe an inexhaustible resource.

An inexhaustible resource is a resource that has a limitless supply, such as sunlight and natural air.

What is the calorific value of wood pellets?

The calorific value of wood pellets is 17 kJ/g.

Define an exhaustible resource.

An exhaustible resource is a resource that is limited and can be depleted over time, such as fossil fuels, forests, and wildlife.

How is coal mainly used?

Coal is mainly used for power generation and heating.

Describe the characteristics of an ideal fuel.

An ideal fuel should have a high calorific value and a low ignition temperature, but well above room temperature.

Describe the process of coal formation.

Trees and plants in swampy areas died and their remains got buried in the soil, forming layers of sediments over time.

What is the carbon content of lignite?

Lignite has a carbon content of around 60-70%.

Define coke.

Coke is a fuel manufactured from coal, with a moderate rate of combustion and controlled heat release.

How is hydrogen as a fuel different from other fuels?

Hydrogen is highly inflammable and has the highest calorific value.

What are the characteristics of an ideal fuel?

An ideal fuel should have a high calorific value, be easily available, safe to handle and transport, and not cause pollution on burning.

What is peat?

Peat is a dark brown material formed from buried plant material in low-oxygen conditions.

Describe the use of lignite.

Lignite is mainly used for power generation.

What are the difficulties associated with hydrogen as a fuel?

Hydrogen has difficulties in transport, storage, and handling, making it suitable for specific applications only.

What are the difficulties associated with hydrogen as a fuel?

Hydrogen has difficulties in transport, storage, and handling, making it suitable for specific applications only.

Describe the formation process of fossil fuels.

Fossil fuels are formed from the buried remains of plants and animals over a period of millions of years.

What are some examples of fossil fuels?

Coal, petroleum, and natural gas are examples of fossil fuels.

What are the advantages of using methane and LPG as fuels?

Methane and LPG have high calorific values, burn smokelessly, do not cause pollution, and are easily transported.

What are the advantages of using methane and LPG as fuels?

Methane and LPG have high calorific values, burn smokelessly, do not cause pollution, and are easily transported.

What are the disadvantages of using petrol and diesel as fuels?

The limited availability of petrol and diesel is a disadvantage, as well as the release of harmful gases into the atmosphere during combustion.

Describe the process of obtaining useful materials from coal.

Coal is processed further to obtain useful materials such as coke, coal tar, high and coal temperature gas.

What is coke and how is it produced?

Coke is a hard, dry fuel produced by heating bituminous coal. It has a high carbon content and is used as a fuel and in steel manufacture.

What is coal tar and how is it obtained?

Coal tar is a black, opaque fluid obtained as a by-product of the process of manufacturing coke.

What are the uses of coal gas?

Coal gas is used in anti-dandruff shampoos, ointments, soaps, perfumes, and in the manufacturing of coke.

What is the temperature range for obtaining petroleum gas?

Petroleum gas is obtained at temperatures below 40°C and is used as a domestic fuel in its liquified form, LPG.

What is the main temp its obatained at petrol and how is it used?

Petrol is mainly used as a fuel in automobiles, dry cleaning, and various chemicals. It is obtained at temperatures between 40-170°C.

How was petroleum and natural gas formed?

Petroleum and natural gas were formed from the remains of tiny marine organisms that died millions of years ago.

What is the temperature range for obtaining diesel?

Diesel is obtained at temperatures between 250-350°C and is used as a fuel in heavy motor vehicles and generators.

What is the main temp obtained at fuel oil and where is it used?

Fuel oil is obtained at temperatures between 350-400°C and is used for power stations and ships.

Describe the process of petroleum and natural gas formation.

Tiny marine organisms died and settled on the ocean floor. Over time, this layer was covered by sediments. The pressure and heat transformed these remains into petroleum and natural gas.

What are the main uses of natural gas?

It is used for the generation of electricity, as a domestic fuel transported via gas pipelines, and as a fuel in automobiles (CNG).

Define refining in the context of petroleum oil.

Refining is the process of separating petroleum oil into useful substances.

What are the main products obtained from petroleum refining?

The main products obtained from petroleum refining are lubricating oil, paraffin wax, boiler fuel, and asphalt.

What are the main products obtained from petroleum refining?

The main products obtained from petroleum refining are lubricating oil, paraffin wax, boiler fuel, and asphalt.

How is compressed natural gas (CNG) more environmentally friendly than petrol or diesel?

Compressed natural gas (CNG) is more environmentally friendly than petrol or diesel because it produces fewer emissions when burned.

Describe the extraction process of petroleum and natural gas.

Petroleum and natural gas are extracted by drilling through impermeable rocks.

What are the limitations of fossil fuels?

The two main limitations of fossil fuels are their limited availability and their contribution to environmental pollution.

Name some uses of natural gas.

Natural gas is used for electricity generation, as a domestic fuel, in the production of ammonia, to produce hydrogen, and in the manufacture of steel, glass, plastics, and other products.

Describe the process of fractional distillation of petroleum.

Petroleum is heated to temperatures above 400 oC and introduced into a fractionating column. As the vapours rise inside the column, they cool and condense at different heights, forming different products that are collected in different trays.

What is the main purpose of fractional distillation of petroleum?

The main purpose is to separate petroleum into different products with different boiling points.

Define fossil fuels.

Fossil fuels are limited availability energy sources that take millions of years to form and are derived from the remains of ancient plants and animals.

How does the use of fossil fuels contribute to air pollution?

The combustion of fossil fuels releases pollutants, including carbon dioxide, into the atmosphere.

What are the main products obtained through fractional distillation of petroleum?

The main products obtained are petrol, methanol, and petroleum gas.