Maharashtra State Board Class 7 Science Natural Resources Notes / Textbook Exercises and Extra Question and Answers.
Class 7 Science Natural Resources Notes
Types of Natural Resources:
- Natural resources are substances obtained from nature that satisfy various daily needs.
- They include soil, stones, minerals, air, water, plants, and animals.
- Resources in the Earth’s crust comprise minerals, ores, mineral oil, rocks, water, and elements.
Minerals and Ores:
- Minerals are formed through natural environmental processes and can be obtained by mining.
- Metals are often found in the form of compounds within minerals. Minerals rich in metals are called ores.
- Examples of important minerals and ores include iron ore, manganese, bauxite, copper, and mica.
- Fuels are substances used to generate energy and can be in solid, liquid, or gaseous states.
- Coal, a fossil fuel formed from ancient buried forests, is classified into various types, with anthracite being the highest grade.
- Coal is a significant source of energy used in thermal power plants, boilers, engines, cooking, and industrial processes.
- The increasing demand for fossil fuels, such as mineral oil and coal, is depleting limited reserves, leading to an energy crisis.
- Alternative fuels like hydrogen, biofuels, methanol, ethanol, and wood alcohol are being explored to address this issue.
- Forests cover a substantial portion of the Earth’s land and serve as natural habitats for plants, animals, and microbes.
- Forests perform protective and productive functions and are crucial for ecological balance.
- Oceans offer a potential source of energy, including power generation from sea waves, tides, and currents.
- Seawater, the seabed, and beneath the seabed hold vast reserves of minerals like tin, chromium, phosphates, copper, zinc, and more.
- The sea is a source of gems, conches, shells, pearls, mineral oil, and natural gas.
Metals are extracted and purified from their ores, with impurities like sand and soil in ore referred to as “gangue.”
Minerals are formed from magma, lava from volcanic eruptions, and evaporation processes, cooling into solid crystals.
Temperature and pressure changes can transform minerals from one form to another.
Some living organisms produce inorganic minerals, like conches and shells, for protection.
Gemstones like diamond, ruby, sapphire, emerald, jade, and zircon are highly valuable and in demand.
Common salt deposits, called rock salt, are used in food and medicine.
The Indian School of Mines, Dhanbad, founded in 1926, has become an Indian Institute of Technology.
The Oil and Natural Gas Corporation (ONGC) is the largest oil and gas research and production company in India.
ONGC produces a significant percentage of India’s crude oil and natural gas, exploring many underground oil reserves.
Mineral oil, also known as petroleum or crude oil, is a liquid fuel formed from decomposed organic substances buried underground.
Natural gas is a fossil fuel primarily composed of methane and can be transported as compressed natural gas (CNG) or liquefied natural gas (LNG).
CNG is easy to ignite, leaves no solid waste after combustion, produces minimal carbon dioxide and water, and can be easily transported and controlled.
Fossils are preserved remains of organisms in rocks, offering evidence of past life.
Petroleum gas is obtained during crude petroleum refining and stored as liquefied petroleum gas (LPG).
LPG is mainly composed of propane and butane and is odorized for leak detection.
Write answers to the following questions in your own words.
(a) What is meant by fossil fuel ? What are their types ?
Over millions of years, heat and pressure convert organic materials into fossil fuels. There are three main types of fossil fuels: coal , petroleum and natural gas.
(b) Make a list of the components we obtain from mineral oil.
Components Obtained from Mineral Oil: