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Chapter-2. Is Matter around us Pure Science class 9 in english Medium CBSE Notes
CBSE Class 9 Science Notes in English Medium based on latest NCERT syllabus, covering definitions, diagrams, formulas, and exam-oriented explanations.
2. Is Matter around us Pure
Pure Substances
2. Is Matter around us Pure?
(Science-IX)
Introduction:
We have learnt earlier that "The obejct which occupy space and having mass is a matter. "
Pure Substance: A pure substance consists of a single type of particles and all the constituent particles of that substance are the same in their chemical nature.
Element: An element as a basic form of matter that cannot be broken down into simpler substances by chemical reactions. Examples: Iron, gold, silver, carbon, oxygen, nitrogen and sodium etc.
All metals, non-metals and Metelloids come in elements.
Properties of Metals:
(1) These are lustre (shine).
(2) They conduct heat and electricity.
(3) All metals are malleable and ductile.
(4) They are sonorous.
(5) They have silvery-grey or golden-yellow colour.
Properties of Non-metals:
(1) These are not lustrous.
(2) They are poor conductors of heat and electricity.
(3) All metals are not malleable and ductile.
(4) They are not sonorous.
(5) They display a variety of colours.
Metalloids: Some elements have intermediate properties between those of metals and non-metals, they are called metalloids; examples are boron, silicon, germanium etc.
Compounds : A compound is a substance composed of two or more elements, chemically combined with one another in a fixed proportion. Examples: Water, Salt, sugar, Alcohal, carbon dixode etc.
| Name of compounds | Composed substance |
| 1. Water | Two part Hydrogen and one part oxygen |
| 2. Salt | One part sodium and one part chlorine. |
| 3. Carbon-dioxide | One part carbon and two part oxygen |
Note: Above all substances are composed in definite/fixed proportion. These substances cannot be seperated without any chemical process. All components by which they are made are differ to compound.
Mixture: Such substances which are composed of two or more than two elements or compound in indefinite proportion are called mixture.
Examples of mixtures:
Sugar in water,
salt in water,
air,
Mixture of salt and sand.
salt and iron fills
soda water.
Differences between compound and mixture:
| Mixture | Compound |
|
1. Element or compound just mix together to from a mixture. 2. It does not form a new substance. 3. A mixture has a variable composition. 4. It's components can be seperated by physical methods. 5. A mixture shows the properties of the constituents substances. 6. Components have no fixed proportion. |
1. Element react to from new compounds. 2. It is a new sunstance. 3. The composition of each new substance is always fixed. 4. It only can be seperated by chemical process. 5. The new substance has totally different propreties. 6. Components have no fixed proportion. |
Differences between elements and compounds:
| Elements | Compounds |
|
1. Elements contain single kinds of atoms. 2. They can neither be seperated by physical methods of seperating nor chemical methods. 3. They are basic form of matters. |
1. Compounds contains two or more than two kinds of atoms. 2. They can only be seperated by chemical process of seperating. 3. They are mainly made of elements. |
See other sub-topics of this chapter:
2. Types of mixtures and solution