Rocks and Minerals - 1 Class 5 Notes Science

Introduction

All land on the earth is made up of soil and rocks. Long ago the ground was mostly solid rock.
The grains that make up rocks are composed of naturally occurring substances called minerals.

Rocks of Different Colours

• All rocks on the earth are made up of minerals. 
• Some rocks contain only one mineral. Others can contain up to six or more minerals. 
• Rocks are of different colours based on the different minerals present in them. 
• Rocks and minerals are called natural resources since they provide us with many metals, non-metals, and fossil fuels.

Rocks

A rock is a solid natural object composed of minerals. Rocks are made up of minerals. Some rocks contain only one mineral while others contain many minerals. Metals are found in the rocks in the form of minerals.

• Rocks are like mixtures of minerals, and each rock has its own special blend of properties like what minerals it has, how big the grains are, and how it feels. 
• We use different systems to group rocks based on their characteristics. In nature, rocks aren't always simple and can have variations in their properties depending on how closely we look at them.

Types of Rocks

1. Igneous Rocks

• Igneous rocks are formed by the cooling and hardening of hot molten rocks. The hot molten rock flows out through a volcano.
• Hot molten rock, when present inside the Earth, is called magma and when it flows on the Earth’s surface, it is called lava.
• Magma or lava cools down and hardens to form igneous rocks. About 95% of the Earth’s crust is made up of igneous rocks. Igneous rocks contain many minerals like mica and feldspar.

Formation of Igneous Rocks 

Types of Igneous Rocks

(i) Granite:It is a very hard rock. It is formed by the slow cooling of magma below the Earth’s surface. It is rich in quartz, feldspar, and mica. It comes in many colours. It is used for making kitchen counters, floors, etc.

(ii) Pumice: It is a light-colour igneous rock. It has many holes which are formed by the gases trapped in the lava at the time of its formation. It is lightweight and can float on water. It is used in polishing the floors. Dentists use powdered pumice for polishing our teeth.

Types of Igneous Rocks

(iii) Obsidian: It is a shiny and smooth igneous rock formed by the quick cooling of lava. It is used for making jewellery. It is also used to make cutting tools.
(iv) Basalt:It is formed by the cooling of lava on the earth’s surface. It is dense and dark. It is used for constructing roads.

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2. Sedimentary Rocks

• Water, wind, rain, and snow break away big rocks. The rock particles so formed are carried away by wind and flowing water into rivers, lakes, and seas.
• These rock particles settle at the bottom of the water bodies and form layers.
• The layers are cemented together by minerals. Repeated deposition of layers presses down the lower layers and then turns them into rocks. Such rocks are called sedimentary rocks.
• Sedimentary rocks are also formed from the shells of sea creatures.
• About 75% of the rocks found on the surface of the Earth are sedimentary rocks.
  
  Formation of Sedimentary Rocks

Types of Sedimentary Rocks

Sedimentary Rocks

3. Metamorphic Rocks

Metamorphic Rocks

Types of Metamorphic Rocks

(i) Marble: It is formed from limestone, a sedimentary rock. It is used for making statues, floors, and slabs.
(ii) Slate: It is formed from shale, a sedimentary rock. Both shale and slate can split into thin layers. It is used for making blackboards and handheld writing boards (slates).

(iii) Gneiss: It is formed from granite. It has light and dark bands. It is used in construction.
(iv) Quartzite: It is formed from sandstone. It is a very hard rock and it is used for making glass and jewellery.

Minerals

All rocks are made up of minerals. Minerals are chemical substances that occur naturally on the Earth. Minerals can be metallic or non-metallic.

Minerals

Types of Minerals

(i) Metallic Minerals

• Metallic minerals contain metals such as gold, iron, aluminium, and copper.
• Such minerals are called ores. Metallic minerals are usually associated with igneous rocks. They are hard and have a shine of their own.
• Gold and silver are commonly used for making jewellery.
• Iron, copper, and aluminium are used for making cooking utensils. Copper is used to make electric wires. Mercury is used for making thermometers.

(ii) Non-metallic Minerals

• Non-metallic minerals are generally associated with sedimentary rocks.
• They are usually not hard and have no shine of their own.
• Graphite, mica, asbestos, potassium, magnesium and feldspar are non-metallic minerals.  
• Precious stones such as diamonds or rubies are also non-metallic.

Fossil Fuels

Fossil fuels are fuels formed by natural processes such as the decomposition of dead and buried organisms.

Coal:

• Coal is a kind of sedimentary rock. Millions of years ago, the Earth was covered with thick swampy forests.
  
  Coal
• When plants died, they fell into the swamps and got buried.
• Due to high temperatures and pressure, these plants get converted into coal.
  
  Formation of coal
• Coal is used as fuel for cooking, for producing electricity, and in steam engines.

Petroleum:

• It is also called crude oil, rock oil, or black gold.
  
  How petroleum is taken out from under the ground
• It is formed from the remains of dead plants and sea animals which got buried under the sea millions of years ago.
• It is mostly used as a fuel in different forms like petrol, diesel, kerosene, and Liquefied Petroleum Gas (LPG). It is also used for dry cleaning.
• Coal and petroleum are not technically considered to be minerals as they are formed from organic matter.
• Besides being used as fuel, coal, and petroleum are used for making important chemicals such as medicines, cosmetics, fertilizers, plastics and many others.

Need for Conservation of Coal and Petroleum

• Coal and petroleum were formed millions of years ago from dead and decaying animals and plants buried in the soil.
• They are very limited resources and once they are finished they cannot be replaced.
• Hence, it is very necessary to conserve these resources by using them carefully.
• Alternative forms of energy like solar energy, water energy, and wind energy should be used.

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Uses of Rocks and Minerals

• Rocks and minerals have various important uses in our daily lives. They serve as the basic materials for constructing things like our homes, schools, roads, and bridges.
• Some rocks provide us with essential fuels, such as coal, petroleum, and uranium. Uranium, a type of mineral, is especially valuable for generating nuclear energy.
• Certain rocks contain metals that are handy for making items we use every day. For example, aluminum and iron from rocks are used to create utensils, while copper is utilized in making electric wires.
• In addition, rocks contribute to the world of jewellery by providing us with gemstones. Well-known gemstones like diamond, ruby, emerald, and sapphire are all minerals extracted from rocks.

What are Minerals?

• If you look closely at a rock with a magnifying glass, you will notice that it consists of tiny pieces known as minerals.
• All rocks are formed from these minerals.
• Minerals are natural substances that can be found on Earth.
• You can think of minerals as the basic parts that make up rocks.
• There are two types of minerals: metallic and non-metallic.

Metallic Minerals 

• Metallic minerals include metals like gold, iron, aluminium, and copper.
• These minerals are referred to as ores.
• The mineral deposits are extracted to obtain the ores, from which the metals are separated.
• Metallic minerals are typically found in igneous rocks.
• They are known for being hard and having a natural shine.

Non-metallic Minerals 

• Non-metallic minerals are mostly found in sedimentary rocks.
• These minerals are typically soft and do not have a shiny appearance.
• Examples of non-metallic minerals include graphite, mica, asbestos, potassium, magnesium, and feldspar.
• This type of mineral is easy to mine and is extracted in large quantities.
• Precious stones, such as diamonds and rubies, are also classified as non-metallic.

What are Fossil Fuels?

• Fossil fuels, such as coal and petroleum, are valuable natural resources found underground and serve as our primary energy sources. 
• As our country has developed since independence, the need for energy has risen significantly. 
• Consequently, the significance of fossil fuels like coal and petroleum as essential energy sources has grown.
• Let's learn about coal and petroleum in detail. 

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Coal

• Coal is a black mineral found in the earth and is an important energy source. It can be used directly or converted into other forms like coal gas and oil.
• Formed about 300 million years ago from dead plants, coal was created when thick forests in swampy areas got buried under sand, clay, and water. Over time, high pressure and temperature transformed these remains into coal.
• In India, coal mines are located in Suhagpur (Madhya Pradesh), Raniganj (West Bengal), Dhanbad (Jharkhand), Neyveli (Tamil Nadu), and Singareni (Andhra Pradesh). The four types of coal are peat, lignite, bituminous, and anthracite.
• Uses of coal:
  1. Fuel: for cooking, generating electricity, powering engines, and in blast furnaces.
  2. Chemicals: used to produce drugs, medicines, nylon, and fertilizers.
  3. Metals: helps extract metals from their ores.

Thus, coal has stored the sun's energy from millions of years ago. When we burn coal as fuel we use this trapped energy of the sun.

Petroleum

• Petroleum is a thick, black liquid found beneath the earth, often referred to as rock oil, black gold, or liquid sunlight. 
• It is believed to have formed from the remains of sea plants and animals buried millions of years ago, where heat and pressure transformed them into petroleum.
• To obtain petroleum, holes are drilled into the earth’s crust, and pipes are sunk to pump it out of oil wells, a process known as mining. In India, petroleum is sourced from places like Ankleshwar and Kalol in Gujarat, Digboi in Assam, and the Bombay High offshore area.
• Uses of petroleum:
  1. Fuel: It is used in various forms such as petrol, diesel, and kerosene, providing half of the world’s energy needs.
  2. Dry Cleaning: Used for cleaning woollen and silk clothes and as lubricating oil.
  3. Paraffin Wax: Extracted from petroleum, it is used to make candles, wax paper, Vaseline, and ointments.
  4. Asphalt: Also derived from petroleum, it is used for road surfaces and in paints.

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Uses of Rocks and Minerals

• Rocks and minerals are important construction materials. 
• Our homes, schools, roads, and bridges are built using rocks and minerals. 
• Rocks are sources of fuels such as coal, petroleum, and uranium. 
• Uranium is a mineral that is used to generate nuclear energy. 
• Rocks also provide us with valuable metals. 
• Aluminium and iron are metals used to make various utensils. 
• Copper is used to produce electric wires. 
• Rocks are also the source of beautiful gemstones. 
• Minerals like diamonds, rubies, emeralds, and sapphires are classified as gemstones. 

Need to Conserve Natural Resources

• Coal and petroleum are natural resources that come from the earth.
• These resources are extremely valuable, but they are also limited.
• If we continue to use them at the current rate, they will run out quickly.
• Burning large amounts of these fuels releases harmful substances, including smoke and poisonous gases.
• This process leads to pollution, which can cause serious health issues.
• To help save coal and petroleum, we should use other types of energy that do not pollute and are available for free.
• The energy from the sun is abundant and will never be depleted.
• Using solar energy does not create pollution.
• Solar energy can be harnessed to cook food using a solar cooker.
• Additionally, solar cells can convert sunlight directly into electricity.