These comprehensive RBSE Class 9 Science Notes Chapter 2 Is Matter Around Us Pure will give a brief overview of all the concepts.
RBSE Class 9 Science Chapter 2 Notes Is Matter Around Us Pure
→ Matter: Matter can be classified into two types on the basis of their chemical nature:
(a) Substance (b) Mixture
→ Substance : A substance is a matter which has a specific composition and specific properties. Every pure element or compound is a substance.
A pure substance consists of a single type of particles i.e. all the constituent particles are same in their chemical nature.
On the basis of chemical composition, substances are classified i.e. element and compound.
→ Element is a pure substance that cannot be broken down into any simpler chemical substances by any physical or ordinary chemical means.
For example- Carbon, oxygen, nitrogen, hydrogen, gold, etc. It cannot be further divided into two or more substances. Elements may be classified as metals, non-metals and metalloids based on their properties.
→ Compound is a pure substance made up of two or more substances mixed chemically in a fixed ratio. In a compound properties of individual constituent is absent. For example – Water.
→ Mixture : When two or more substances are mixed together in any ratio in such a way that they do not undergo any chemical change is called a mixture. For example – Brass is a mixture of copper and zinc.
- In a mixture, properties of its constituents remain the same. A mixture contains more than one pure substances.
- It can be further divided into two types of mixture : Homogeneous and Heterogenous mixture.
→ Homogeneous Mixture : A mixture in which all the constituents are mixed in uniform composition is called homogeneous mixture. For example – Tap-water, vegetable-oil used in cooking, mouthwash, etc.
→ Heterogeneous Mixture : A mixture in which all the constituents are not mixed in uniform composition is called heterogeneous mixture. For example – Gun powder, brass, steel, bronze (alloys).
→ Solution : A homogeneous mixture of two or more substances is called a solution. A solution can have either a solid or a liquid or a gas dissolved in it but the mixture should have homogeneity of particles.
→ Components of a Solution : A solution have two components – solvent and solute.
(a) Solvent: The component of the solution that dissolves the other component in it (usually the component present in larger amount) is called solvent.
(b) Solute : The component of the solution that is dissolved in the solvent (usually present in lesser quantity) is called the solute.
Example : A solution of sugar in water; here, sugar is the solute and water is the solvent.
Types of Solution :
→ Saturated Solution : A solution in which the maximum amount of solute concentration has been dissolved at certain temperature.
→ Unsaturated Solution : An unsaturated solution is a chemical solution in which the solute concentration is lower than its equilibrium solubility.
→ Concentration of a Solution : The relative amount of solute and solvent present in a given quantity of the solution is known as the concentration of a solution.
→ In a solution, the ratio of the solute and solvent can vary. It can be known as dilute, concentrated or saturated solution depending upon the amount of solute present in a solution.
→ Solubility of a Solute : The amount of solute (in gram), which dissolve in 100 g of solvent, at a given temperature, is called solubility of the solute at that particular temperature.
→ Suspensions : A suspension is a heterogeneous mixture in which the small particles of a solid are dispersed in a liquid without dissolving in it.
→ The particles can have settle down at the bottom and can be filtered out, because their size is big enough to filter. These suspended particles can be seen through naked eyes. Example : Mixture of chalk – water, muddy water, etc.
→ Colloids : A colloid system is a heterogeneous solution in which the particle size is very fine such that neither dissolves nor settles down in a solvent.
→ Colloidal solutions are not transparent, but translucent in nature.
→ The particles of a colloidal solution scatter light, i.e. when strong beam of light is passed through the colloidal solution.
→ Brownian Movement of Colloids : The colloidal particles move at randomly in zig-zag motion in all directions. This type of erratic, zig-zag motion of colloidal particles in dispersion medium is called Brownian movement.
→ Tyndall effect : When the strong beam of light is passed through a true solution, the path of light become visible; this phenomenon is called Tyndall effect.
→ Coagulation: If the charge on colloidal particles is decreased then colloidal particles come closer and form large particles which settle down as precipitate, it is known as coagulation or precipitation.
→ Separating the Components of Mixture: Heterogeneous mixtures can be separated by simple physical methods to get their constituent particles.
- Magnetic Separation
- Using separating funnel
- Fractional Distillation.
→ Physical and Chemical Changes : Matter undergoes two types of changes as physical change and chemical change.
|Physical Change||Chemical Change|
|1. Physical change is a change in which physical appearance of substance can change but its composition remains the same.||Chemical change is a change when a new substance with new property and composition formed.|
|3. No new substances are formed.||New substances are formed.|
|4. Change in physical properties of the substance.
Example – Tearing of paper, freezing of water, cutting of trees, etc.
|Change in chemical properties of the substance.
Example – Burning of paper, rusting of iron, formation of curd from milk, etc.