Important Points: Is matter around us Pure? | Science Class 9 PDF Download

Matter

Matter is anything that occupies space and has mass.

Pure Substances

• Pure substances consist of elements with the same chemical properties.
• A substance that cannot be separated into other types of matter by any physical process is pure.

Mixture

• A mixture is a substance in which two or more elements or compounds are simply mixed together in any proportion.
• Examples include air, which is a mixture of oxygen, nitrogen, carbon dioxide, and water vapor.

Types of Mixture:

Mixture is categorized into two types:

• Homogeneous Mixture: These mixtures have no visible boundaries of separation between their constituents. Example: Sugar in water.

• Heterogeneous Mixture: These mixtures have visible boundaries of separation between their constituents. Example: Mixture of sugar and sand.

Solution

A solution is a homogeneous mixture of two or more substances. It has a solvent and a solute. Solvent dissolves the solute.

Properties of a Solution

• A solution is a homogeneous mixture.
• Solution particles are tiny and not visible to the naked eye.
• The path of light is not visible through a solution, and solution particles do not scatter light.
• Solution particles cannot be separated by filtration.

Concentration

• Concentration refers to the amount of a substance in a defined space or as the ratio of solute in a solution to the solvent or the total solution.
• Two methods for finding concentration are mass by mass percentage and mass by volume percentage.

Saturated and Unsaturated Solutions

A saturated solution is one where no more solute can be dissolved at a given temperature. An unsaturated solution can dissolve more solute at the same temperature.

Solubility

Solubility is the amount of solute present in the saturated solution at a given temperature.

Suspension

• Suspension is a heterogeneous mixture in which solute particles do not mix with the solvent.
• Particles tend to settle down and can be separated using filtration.

Colloidal Solution (Colloid)

• A colloid is a uniform solution of two or more substances where the particles are relatively small.
• Colloids scatter light and produce the Tyndall effect.
• Colloids are stable and cannot be separated by filtration.

Tyndall Effect

When light passes through a colloid, the particles scatter the light, making the path of light visible.

Methods of Separation of Mixtures

• Evaporation: Used to separate components with different boiling points.
• Centrifugation: Separates substances based on density when a mixture is rotated rapidly.
• Separating Funnel: Separates immiscible liquids.
• Sublimation: Separates substances where one sublimes (directly converts to gas from solid).
• Chromatography: Separates colored components using an adsorbent.
• Distillation: Separates miscible liquids with different boiling points.
• Crystallization: Dissolves a substance, then crystallizes one component.

Physical Properties

Properties like rigidity, color, fluidity, boiling point, melting point, density, and hardness are observable and known as physical properties.

Physical Change

A change in the physical properties of a substance, such as a change of state (e.g., solid to liquid), without affecting its chemical nature.

Chemical Change (Chemical Reaction)

A change in a substance's chemical properties, involving alteration of its chemical composition.

Elements

The simplest form of matter that cannot be broken down into other elements by chemical reactions.

Categorized as metals, non-metals, and metalloids.

• Metals: Lustrous, conduct heat and electricity, have varied colors, can be hammered into thin sheets (malleability), can be converted into wires (ductility), and produce a ringing sound when hit (sonorous).
• Non-Metals: Do not conduct heat and electricity, are not sonorous, lustrous, or ductile, and have varied colors.
• Metalloids: Show properties of both metals and non-metals.

Compounds

Substances that consist of two or more substances chemically combined in fixed proportions. They have properties different from their constituents.

Mixtures vs. Compounds

Mixtures involve physically mixing substances with no fixed proportions, while compounds involve chemically combining substances in fixed proportions.