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Is Matter Around Us Pure Class 9 Science Notes Chapter 1
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INTRODUCATION-
Matter can be defined as anything that occupies space and has mass. The substances that make up matter can be classified as pure substances or mixtures. A pure substance consists of only one type of particle, whereas a mixture contains two or more substances physically combined.
MIXTURE AND ITS TYPES-
A mixture is a combination of two or more substances that are not chemically combined. Mixtures can be :
Homogeneous Mixtures: Is has a uniform composition throughout, such as saltwater or air.
Heterogeneous Mixtures: This composition is not uniform, and different components can be seen, such as a mixture of sand and iron filings.
SOLUTION AND ITS PROPERTIES-
A solution is a homogeneous mixture of two or more substances. The substance that dissolves is called the solute, and the medium in which it dissolves is called the solvent.
Properties of a solution:
Homogeneous in nature
Particles are very small and do not scatter light
Stable and do not settle on standing
Cannot be separated by filtration
Concentration of a Solution
The concentration of a solution can be defined as the amount of solute dissolved in a given quantity of solvent. It can be expressed in various ways:
Mass percentage = (Mass of solute / Mass of solution) × 100
Volume percentage = (Volume of solute / Volume of solution) × 100
Molarity (M) = Moles of solute / Volume of solution in liters
Suspension and Its Properties
A suspension can be defined as the heterogeneous mixture in which the solute particles do not dissolve but remain suspended.
Properties of a suspension:
Heterogeneous in nature
Particles are large and visible by eyes
Particles scatter light (Tyndall effect)
Unstable, particles settle down over time
Can be separated by filtration process.
Colloidal Solution and Its Properties
A colloidal solution can be defined as a mixture where the solute particles are larger than in a solution but smaller than in a suspension.
Properties of a colloidal solution:
Heterogeneous mixture
Particles do not settle over time
Particles scatter light (Tyndall effect)
Cannot be separated by filtration but can be separated by centrifugation
SEPARATION OF COMPONENTS OF MIXTURES-
The Mixtures can be separated using different techniques based on their properties.
Obtaining Colored Components from Blue/Black Ink
The Ink is a mixture of different dyes. Paper chromatography is used to separate its components by allowing the solvent to carry different dyes at different rates.
Separation of Cream from Milk
Cream can be separated from milk using the process of centrifugation, where the denser liquid (milk) settles at the bottom, and the less dense cream floats.
Separating Two Immiscible Liquids
Liquids like oil and water can be separated using a separating funnel, which allows the denser liquid to be drained first.
Separating a Mixture of Salt and Ammonium Chloride
Ammonium chloride sublimes on heating and can be separated from salt using the sublimation process.
Separating Dyes in Black Ink
Chromatography helps separate different dyes in black ink, as different dyes travel at different speeds along the chromatography paper.
Separating a Mixture of Two Miscible Liquids
Distillation is used to separate liquids with different boiling points, such as ethanol and water.
Obtaining Different Gases from Air
Fractional distillation is used to separate gases in air by cooling it to very low temperatures to liquefy and separate them based on boiling points.
Obtaining Pure Copper Sulphate from an Impure Sample
Crystallization helps purify impure copper sulphate by dissolving it in hot water, filtering the solution, and allowing it to cool to form pure crystals.
PHYSICAL AND CHEMICAL CHANGES-
Physical Change: The change in the physical properties of a substance without altering its composition is known as Physical Change., e.g., melting of ice, boiling of water.
Chemical Change: The change in which a new substance is formed with different properties is known as Chemical Change., e.g., rusting of iron, burning of paper.
TYPES OF PURE SUBSTANCES-
Elements: The substances made up of only one type of atom is called Elements, e.g., gold, oxygen.
Compounds: The Substances formed by chemical combinations of two or more elements is called Compounds. e.g., water (H₂O), carbon dioxide (CO₂).
Difference Between Mixtures and Compounds
| FEATURE | MIXTURE | COMPOUNDS |
|---|---|---|
| Definition | A combination of two or more substances that are physically mixed but not chemically combined. |
A substance formed when two or more elements chemically bond in fixed proportions. |
| Composition | Components can vary in proportion. | Fixed proportion of elements. |
| Properties | Retains the properties of its components. | Has new properties different from its constituent elements. |
| Separation | It Can be separated by physical methods (e.g., filtration, evaporation, magnetism). |
It Can only be separated by chemical methods (e.g., electrolysis, chemical reactions). |
| Examples | Air (a mixture of gases), sand and salt, saltwater. | Water (H₂O), carbon dioxide (CO₂), sodium chloride (NaCl). |
| Energy Change | No chemical reaction, so no significant energy change. | Formation involves energy changes (heat absorption or release). |
