Science Exploration Notes Class 9 English Medium 2026-27

Science Exploration Chapter 5. Exploring Mixtures and their Separation

CBSE Notes New Syllabus: Class 9

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Chapter 5. Exploring Mixtures and their Separation

This section explains solutions, solute, solvent, concentration of solutions and solubility. These concepts help us understand how substances dissolve in one another and how the amount of dissolved substance affects the properties of a solution.

9. Solution

A solution is the most common type of homogeneous mixture. In a solution, one substance dissolves completely in another, producing a uniform mixture in which the individual components cannot be seen separately.

Definition

A solution is a homogeneous mixture formed when one or more solutes dissolve completely in a solvent.

Characteristics of a Solution

• Homogeneous Mixture – Uniform composition throughout.
• Transparent – Components cannot be seen separately.
• Stable Mixture – Particles do not settle on standing.
• Cannot be Separated by Ordinary Filtration – Solute particles pass through filter paper.

Examples

• Salt Solution
• Sugar Solution
• Vinegar
• Soft Drinks

10. Components of a Solution

Every solution is made up of two main components—a solute and a solvent.

Solute

The substance that dissolves in another substance is called the solute. It is usually present in a smaller amount.

Examples

• Salt in salt solution.
• Sugar in sugar solution.
• Carbon dioxide in soft drinks.

Solvent

The substance that dissolves the solute is called the solvent. It is generally present in a larger amount.

Examples

• Water in salt solution.
• Water in sugar solution.
• Alcohol in tincture iodine.

11. Difference Between Solute and Solvent

12. Concentration of a Solution

The amount of solute dissolved in a given amount of solvent or solution is called the concentration of the solution. It tells us whether a solution is dilute or concentrated.

Definition

Concentration is the amount of solute present in a given quantity of solvent or solution.

Types of Solutions Based on Concentration

• Dilute Solution – Contains a small amount of solute.
• Concentrated Solution – Contains a large amount of solute.

Methods of Expressing Concentration

• Percentage by Mass (% m/m) – Mass of solute in 100 g of solution.
• Percentage by Volume (% v/v) – Volume of solute in 100 mL of solution.
• Mass by Volume (% m/v) – Mass of solute in 100 mL of solution.

13. Solubility

Different substances dissolve in different amounts in the same solvent. The maximum amount that dissolves at a particular temperature is known as solubility.

Definition

Solubility is the maximum amount of solute that can dissolve in a given amount of solvent at a specified temperature.

Factors Affecting Solubility

• Nature of Solute – Different substances have different solubilities.
• Nature of Solvent – Solubility depends on the solvent used.
• Temperature – The solubility of most solids increases with temperature.
• Pressure – Mainly affects the solubility of gases.

14. Saturated and Unsaturated Solutions

Saturated Solution

A saturated solution contains the maximum amount of solute that can dissolve at a given temperature.

Characteristics

• Cannot dissolve more solute.
• Extra solute remains undissolved.
• Exists at a particular temperature.

Unsaturated Solution

An unsaturated solution contains less solute than its maximum dissolving capacity and can dissolve more solute.

Characteristics

• Can dissolve additional solute.
• Contains less than the maximum possible amount of solute.

15. Difference Between Saturated and Unsaturated Solutions

16. Everyday Applications of Solutions

• ORS Solution – Used to prevent dehydration.
• Soft Drinks – Carbon dioxide dissolved in water.
• Medicines – Many syrups are solutions.
• Seawater – A natural solution containing dissolved salts.
• Lemon Water – Sugar and lemon juice dissolved in water.

ATP Education Tip

Remember these important concepts: Solution = Solute + Solvent, Dilute solution contains less solute, Concentrated solution contains more solute, and a saturated solution cannot dissolve any more solute at a given temperature. These concepts are frequently asked in CBSE objective, competency-based and case-study questions.