CHAPTER 2 IS MATTER AROUND US PURE

What is a Mixture?

Mixtures are constituted by more than one kind of pure form of matter.

Type of mixtures-

Homogeneous Mixture	Heterogeneous Mixture
Composition is uniform throughout	Composition is not uniform
Components are not visible separately	Components are visible separately
Appears as a single phase	Appears as two or more phases
Same properties at every point	Different properties at different points
Particles are evenly mixed	Particles are unevenly mixed
Example: salt solution, sugar in water, air	Example: oil and water, sand in water, soil

✨ One-line trick to remember:

• Homogeneous = “Same everywhere”

Heterogeneous = “Different at different places

What is a Solution?

A solution is a homogeneous mixture of two or more substances.

Alloys: Alloys are mixtures of two or more metals or a metal and a non-metal and cannot be separated into their components by physical methods. But still, an alloy is considered as a mixture because it shows the properties of its constituents and can have variable composition. For example, brass is a mixture of approximately 30% zinc and 70% copper.

Components of solution-

Solute-The component of the solution that is dissolved in the solvent (usually present in lesser quantity) is called the solute.

Solvent-The component of the solution that dissolves the other component in it (usually the component present in larger amount) is called the solvent.

Example-A solution of sugar in water is a solid in liquid solution. In this solution, sugar is the solute and water is the solvent.

Solution of iodine is called tincture of iodine.

Properties of a Solution

1. Homogeneous mixture
   → A solution is a homogeneous mixture, which means it looks same everywhere.

2. Very small particles
   → The particles of solute are very tiny and cannot be seen with naked eyes. diameter 1 nm

3. Particles do not settle down
   → Solute particles do not settle at the bottom even after keeping the solution for a long time.

4. Transparent
   → A solution is transparent, so light can pass through it easily.

5. Cannot be separated by filtration
   → Solute particles are so small that they cannot be separated using filter paper.

6. Stable mixture
   → A solution is stable and does not separate on standing.

 TYPES OF SOLUTIONS-

SATURATED  SOLUTIONS	UNSATURATED SOLUTIONS
Cannot dissolve more solute at a given temperature.	Can dissolve more solute at a temperature
Contain maximum solute	Contain less solute than maximum.
Extra solutes can be settled at the bottom.	Extra solutes dissolves easily.

WHAT IS A SUSPENSION?

Non-homogeneous systems in which solids are dispersed in liquids, are called suspensions. They are heterogenous mixtures.

Properties of a Suspension 

• Suspension is a heterogeneous mixture.

 • The particles of a suspension can be seen by the naked eyes.

• The particles of a suspension scatter a beam of light passing through it and make its path visible.

 • The solute particles settle down when a suspension is left undisturbed, that is, a suspension is unstable

•      They can be separated from the mixture by the process of filtration. 

COLLOIDAL SOLUTION-

What is a Colloidal Solution?

A colloidal solution is a mixture in which very small particles of one substance are spread evenly in another substance, but do not completely dissolve.

Properties of Colloidal Solution (Easy Points)

1. Looks homogeneous but is actually heterogeneous
   → It looks same, but particles are not truly dissolved.

2. Particles are small but visible under microscope
   → We cannot see them with naked eyes.

3. Particles do not settle down
   → They stay mixed for a long time.

4. Shows Tyndall effect
   → It can scatter light (light path becomes visible).

5. Cannot be separated by filtration
   → Filter paper cannot separate the particles.

6. Stable mixture→ Does not separate on standing.

xamples of Colloidal Solution

• Milk

• Fog

• Smoke

• Butter

• Blood

• Starch solution

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Components of a Colloid

• Dispersed phase → Particles present in small amount

• Dispersion medium → Substance in which particles are mixed

📌 Example:
Milk → Fat (dispersed phase) + Water (dispersion medium).

·        How would you confirm that a colorless liquid given to you is pure water?

Ans. If the boiling and freezing points of the given liquid comes out to be  100  degree Celsius and 0 degree Celsius  respectively under one atmosphere pressure, it confirms that the given liquid is pure water.