Chapter 3: Rocks and Minerals
Descriptive Questions
- Q: How is coal formed?
- A: Millions of years ago when the plants in the marshy forests died they got buried inside the earth. Due to extreme heat and pressure, these materials decayed and converted into coal.
- Q: What are ores?
- A: Rocks containing minerals are used to obtain metals and known as ores. For ex – bauxite and hematite.
- Q: What is rock?
- A: Rocks are made up of one or more naturally occurring substances called minerals. On the basis of their formation, rocks are classified into three types: Igneous Rocks (granite, basalt, obsidian, pumice), Sedimentary rocks (sandstone, shale, conglomerate, limestone), and Metamorphic rocks (marble, slate, gneiss, quartzite).
- Q: What is a mineral?
- A: Minerals are naturally occurring chemical substances that are present in the rocks. They may be present in simple or complex form in rocks. They are natural resources of the earth and can be categorized into metallic (hematite, bauxite) and non-metallic minerals (calcite, gypsum).
- Q: How are igneous, metamorphic and sedimentary rocks formed?
- A: Igneous rocks are formed by the cooling of lava on the surface of the earth. Sedimentary rocks are formed when weathered rocks are carried by wind and water to water bodies, sink to the bottom to form layers, and are cemented together. Metamorphic rocks are formed when igneous and sedimentary rocks change due to high pressure and heat under the earth’s surface.
- Q: Write two uses of granite, slate, marble and quartz.
- A: Granite is used to make statues, buildings, flooring, kitchen tops, and in paving roads. Slate is used in making slates, black boards and building roofs. Marble is commonly used for making statues and buildings (e.g., The Taj Mahal). Quartz is used in making glass.
- Q: Write five Point about conservation of coal and petroleum.
- A: Use public transport or carpools to travel.
- Use air conditioners or heaters only when required.
- Use alternative sources of energy like solar energy.
- Use energy saving LED bulbs over regular incandescent bulbs.
- Use pressure cookers for cooking purposes to save LPG or kerosene.
Objective Questions
- Match the following:
- Core ————-> Innermost layer of the earth;
- Mine ————–> Obtained from rocks;
- Metals ———–> Obtained from ores;
- Gemstone ———> Used to make jewellery;
- Coal ————->Used as fuel.
- Answer in one word:
- It is used for making lubricants: Petroleum
- Paraffin wax is obtained from it: Petroleum
- It is used in the blast furnace of steel industries: Coal
- These minerals do not contain metals in them: Non metallic minerals
- This type of rock is made up of calcite: Limestone
- Fill in the blanks:
- Pumice rock is used by the dentist.
- Limestone is made of a mineral known as calcite.
- Marble is formed from metamorphosed sedimentary rocks.
- Shale is made up of fine grains of clay and mud.
- True or False:
- Fossil fuels are minerals: True
- Granite is used in cutting tools: False
- Igneous rocks are called fiery rocks: True
- Basalt is made of calcite mineral: False