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Class 9 Science Chapter 5 Exploring Mixtures and their Separation
Chapter Introduction and Overview
Have you ever wondered how white sugar crystals are obtained from tall green sugarcane plants? Or how
doctors detect diseases like malaria using just a few drops of blood? All of this is possible because of
the science of separating mixtures!
What is a Mixture?
A mixture is formed when two or more substances are combined without any chemical reaction. The
substances in a mixture can be separated by physical methods.
Why Do We Need to Separate Mixtures?
To get pure substances for laboratory experiments
To remove impurities (e.g., purifying water)
For industrial processes like making sugar, petroleum refining
For medical purposes — separating blood components
Environmental applications — treating sewage water
How Can We Classify Mixtures?We Classify Mixtures?
Mixtures are broadly classified into two types based on their uniformity:
Homogeneous Mixture
Uniform composition throughout. You cannot distinguish the individual components. Also called a Solution.
Examples: Sugar in water, salt water, vinegar, aerated drinks (soda), brass alloy
Heterogeneous Mixture
Non-uniform composition. Components are visible and can be distinguished.
Examples: Sand in water, oil and water, muddy water, smoke, fog
The Laser Light Test (Tyndall Effect Test)
When laser light is passed through different mixtures, the results differ:
Mixtures Laser Path Visible? Type Settles
Salt + Water ❌ Not visible Solution (Homogeneous) No
Chalk + Water ✅ Visible (bright) Suspension (Heterogeneous) Yes
Milk + Water ✅ Visible (faint) Colloid No
, NCERT Definition — Homogeneous Mixture:
A mixture that has a uniform composition throughout is called a homogeneous mixture or a solution. A
solution always remains homogeneous.
Comparing Solutions, Suspensions, and Colloids
Property Solution Suspension Colloid
Nature Homogeneous Heterogeneous Appears homogeneous
Particle Size <1 nm >1000 nm 1–1000 nm
Visibility Not visible Visible (naked eye) Not visible (naked eye)
Settles? No Yes (on standing) No
Cannot separate by regular
Filtration Cannot separate Can separate
filter
Tyndall
❌ No ✅ Yes ✅ Yes
Effect
Salt solution, copper sulfate Sand in water, muddy
Examples Milk, blood, fog
solution water
Solutions & Concentration
A solution is a homogeneous mixture of a solute (the substance that dissolves) and a solvent (the
substance that dissolves the solute).
Key Terms:
Solute — the substance dissolved (e.g., sugar, salt).Solvent — the substance that dissolves (e.g.,
water).Concentration— amount of solute in a given amount of solution.
Expressing Concentration — Three Methods
A. Mass by Mass Percentage (% m/m or % w/w)
Tells us how many grams of solute are present in 100 grams of the total solution. Used for solid-in-solid
or solid-in-liquid mixtures (e.g., milk powder, spice mixtures, food labels).
Mass by Mass % = (Mass of Solute / Mass of Solution) × 100
Example: 10 g salt dissolved in 90 g water.
Mass of solution = 10 + 90 = 100 g
% m/m = () × 100 = 10% m/m 10% m/m
B. Mass by Volume Percentage (% m/v or % w/v)
Tells us how many grams of solute are present in 100 mL of solution. Used in medicines and
laboratories (e.g., 5% glucose IV solution, 0.9% saline drip).
(Add : Opp. Sri Dev Suman Park THDC Colony Ranipur, Haridwar)
Mob.no.9852818893view
Class 9 Science Chapter 5 Exploring Mixtures and their Separation
Chapter Introduction and Overview
Have you ever wondered how white sugar crystals are obtained from tall green sugarcane plants? Or how
doctors detect diseases like malaria using just a few drops of blood? All of this is possible because of
the science of separating mixtures!
What is a Mixture?
A mixture is formed when two or more substances are combined without any chemical reaction. The
substances in a mixture can be separated by physical methods.
Why Do We Need to Separate Mixtures?
To get pure substances for laboratory experiments
To remove impurities (e.g., purifying water)
For industrial processes like making sugar, petroleum refining
For medical purposes — separating blood components
Environmental applications — treating sewage water
How Can We Classify Mixtures?We Classify Mixtures?
Mixtures are broadly classified into two types based on their uniformity:
Homogeneous Mixture
Uniform composition throughout. You cannot distinguish the individual components. Also called a Solution.
Examples: Sugar in water, salt water, vinegar, aerated drinks (soda), brass alloy
Heterogeneous Mixture
Non-uniform composition. Components are visible and can be distinguished.
Examples: Sand in water, oil and water, muddy water, smoke, fog
The Laser Light Test (Tyndall Effect Test)
When laser light is passed through different mixtures, the results differ:
Mixtures Laser Path Visible? Type Settles
Salt + Water ❌ Not visible Solution (Homogeneous) No
Chalk + Water ✅ Visible (bright) Suspension (Heterogeneous) Yes
Milk + Water ✅ Visible (faint) Colloid No
, NCERT Definition — Homogeneous Mixture:
A mixture that has a uniform composition throughout is called a homogeneous mixture or a solution. A
solution always remains homogeneous.
Comparing Solutions, Suspensions, and Colloids
Property Solution Suspension Colloid
Nature Homogeneous Heterogeneous Appears homogeneous
Particle Size <1 nm >1000 nm 1–1000 nm
Visibility Not visible Visible (naked eye) Not visible (naked eye)
Settles? No Yes (on standing) No
Cannot separate by regular
Filtration Cannot separate Can separate
filter
Tyndall
❌ No ✅ Yes ✅ Yes
Effect
Salt solution, copper sulfate Sand in water, muddy
Examples Milk, blood, fog
solution water
Solutions & Concentration
A solution is a homogeneous mixture of a solute (the substance that dissolves) and a solvent (the
substance that dissolves the solute).
Key Terms:
Solute — the substance dissolved (e.g., sugar, salt).Solvent — the substance that dissolves (e.g.,
water).Concentration— amount of solute in a given amount of solution.
Expressing Concentration — Three Methods
A. Mass by Mass Percentage (% m/m or % w/w)
Tells us how many grams of solute are present in 100 grams of the total solution. Used for solid-in-solid
or solid-in-liquid mixtures (e.g., milk powder, spice mixtures, food labels).
Mass by Mass % = (Mass of Solute / Mass of Solution) × 100
Example: 10 g salt dissolved in 90 g water.
Mass of solution = 10 + 90 = 100 g
% m/m = () × 100 = 10% m/m 10% m/m
B. Mass by Volume Percentage (% m/v or % w/v)
Tells us how many grams of solute are present in 100 mL of solution. Used in medicines and
laboratories (e.g., 5% glucose IV solution, 0.9% saline drip).
