Students can rely on these Class 8 Science Notes Chapter 8 Nature of Matter Elements Compounds and Mixtures Class 8 Notes for complete exam preparation.
Class 8 Science Chapter 8 Nature of Matter Elements Compounds and Mixtures Notes
Class 8 Science Curiosity Chapter 8 Notes
Class 8 Science Chapter 8 Notes – Nature of Matter Elements Compounds and Mixtures Notes Class 8
→ Matter Anything that occupies space and has mass.
→ Mixture A combination of two or more substances that are physically mixed and can be separated by physical means.
→ Components of a Mixture The individual substances that make up a mixture.
→ Non-uniform Mixture A mixture where the components are not evenly distributed.
→ Uniform Mixture A mixture where the components are evenly distributed.
→ Alloy A uniform mixture of metals or a metal and a non-metal designed for better properties (e.g. strength, corrosion resistance).
→ Pure substance A substance made of only one kind of particle that cannot be separated by physical means.
→ Element A pure substance made of only one kind of atom; cannot be broken down further by chemical means.
→ Metal Elements that are hard, shiny, malleable, ductile and good conductors of heat and electricity.
→ Non-metal Elements that are brittle, dull, and poor conductors (except graphite).
→ Metalloid Elements having properties of both metals and non-metals.
→ Compound A pure substance formed by chemically combining two or more elements in a fixed ratio.
→ Minerals Naturally occurring substances in rocks and soil, which may be elements or compounds.
→ How many types of particles make up a pure substance?
→ Name one element and one compound.
→ What type of element is silicon-metal or non-metal?
→ Name any two mixtures used in construction.
→ Name two minerals that are compounds.
→ From which mineral is talcum powder made?
Matter
Matter is composed of tiny particles called atoms, which combine in various ways to form elements, compounds and mixture. Matter can be systematically classified based on its composition and properties.
What Are Mixtures?
A mixture is formed when two or more substances are physically mixed together in any proportion without undergoing any chemical change. Each component in a mixture retains its original properties. Examples: sugar solution, salt solution, etc.
Components of a Mixture
The individual substances that are mixed to form a mixture are called components of the mixture.
Characteristics of a Mixture
- Components do not react chemically.
- Components retain their individual properties.
- Can be separated by physical methods.
Types of Mixtures
Mixtures are of two types based on how well the components are mixed:
- Non-Uniform Mixtures : In these mixtures, the components are not uniformly mixed. The different parts are visible to the naked eye.
Examples Sprout salad, soil, mixture of sand and iron filings. - Uniform Mixtures : In these mixtures, the components are evenly distributed and cannot be seen separately with naked eye.
Examples Sugar dissolved in water, salt solution, air.
Classification of Pure Substances
Pure substances can be classified into the following
substances can be classified into the following
1. Elements
- Elements are substances that are made of only one kind of atom. They cannot be broken down into simpler substances by chemical means. They are the building blocks of kll matter.
Example Hydrogen, oxygen, gold, silver, carbon. - Each element is made of only one type of atom. These atoms can combine to form molecules. For example, Molecule of Hydrogen (H2): Two hydrogen atoms.
- Elements are broadly classified into metals, non-metals and metalloids based on their physical and chemical properties.
- Metals are elements that are generally hard, lustrous, malleable, ductile, and good conductors of heat and electricity. Examples: Iron (Fe), gold (Au), silver (Ag), aluminium (Al), copper (Cu), magnesium (Mg), etc.
- Non-metals are elements that are usually brittle, dull, and poor conductors of heat and electricity (except graphite). Examples: Carbon (C), Sulphur (S),
Hydrogen (H), Oxygen (O), Nitrogen (N), etc. - Metalloids are elements that have properties of both metals and non-metals. They behave like metals in some conditions and like non-metals in others. Examples: Silicon (Si), boron (B), arsenic (As), antimony (Sb), etc.
- There are 118 known elements.
11 elements exist as gases at room temperature (e.g. oxygen, nitrogen). Only two elements are liquid at room temperature: Mercury (metal) and bromine (non-metal). Gallium and caesium melt just above room temperature (~30°C).
2. Compounds
- A compound is a pure substance made by chemically combining two or more elements in a fixed ratio.
- For example, water (H2O) is a compound made of hydrogen and oxygen in a fixed ratio of 2:1.
- The properties of a compound are different from its elements. Example: Hydrogen is a fuel, oxygen supports combustion, but water extinguishes fire.
- The constituent elements of a compound cannot be separated by any physical method. They are chemically bonded.
- Appearance, gas tests and magnet tests help differentiate mixtures from compounds.
Uses of Elements, Compounds and Mixtures
- The air we breathe is a mixture of gases like oxygen, nitrogen, and carbon dioxide.
- Water which is essential for life, is a compound made of hydrogen and oxygen.
- Elements like iron and aluminium are used to make bridges, buildings and vehicles.
- Materials like wood, steel and concrete are all mixtures used in construction.
- Understanding elements and compounds helps in:
- Making medicines and vaccines
- Improving fertilisers, thus boosting crop production for a growing population.
- Developing stronger materials like alloys (e.g. stainless steel)
Graphene aerogel is a modern wonder material made from carbon. It is the lightest material known. It is highly porous and can absorb large amounts of liquids, making it useful in cleaning oil spills from water and land. It is also used in energy-saving devices and building coatings due to its special properties.
What Are Minerals?
- Minerals are natural substances found in rocks and soil. Most rocks are mixtures of minerals.
- Native minerals: Found as pure elements like gold, silver and copper.
- Most minerals are compounds made of more than one element. Examples: Quartz, calcite, mica, pyroxene, olivine, talc etc.
- Minerals are used in making cement (from calcite, quartz, alumina), Talcum powder (from talc), etc.
Dhokra art is a traditional tribal craft from Bihar and Odisha that uses metal casting. A wax model is made and coated with clay to form a mould. Then, molten brass or bronze is poured in. After cooling, it forms beautiful metal figures. This art shows how elements, mixtures and compounds are used in creative ways.