Chapter 2: Is Matter Around Us Pure? Long Questions | science Class 9 CBSE

ByteNotes

Chapter 2: Is Matter Around Us Pure? Long Questions | science Class 9 CBSE | ByteNotes.in

Long Answer

Structured explanation

Long Answer

Question 1

Long Form

Q1. Define a mixture. Explain the types of mixtures with suitable examples.

• A mixture is formed when two or more substances are combined physically in any proportion.
• It does not involve any chemical reaction between the constituents.
• Mixtures can be homogeneous or heterogeneous.
• Homogeneous mixtures have uniform composition throughout (e.g., salt in water, air).
• Heterogeneous mixtures have non-uniform composition (e.g., oil and water, soil).
• Constituents of mixtures can be separated by physical methods.
• The properties of mixtures reflect the properties of their components.

ByteNotes

Long Answer

Structured explanation

Long Answer

Question 2

Long Form

Q2. What is a solution? Describe its properties and give examples.

• A solution is a homogeneous mixture of two or more substances.
• It has two main components: solute (smaller quantity) and solvent (larger quantity).
• Examples: sugar in water, soda water, tincture of iodine.
• Particles of a solution are smaller than 1 nm and not visible to the naked eye.
• A solution does not scatter light (no Tyndall effect).
• Solute does not settle down and cannot be separated by filtration.
• Solutions are stable and uniformly mixed at the particle level.

ByteNotes

Long Answer

Structured explanation

Long Answer

Question 3

Long Form

Q3. Explain the concept of concentration of a solution and list three methods to express it.

• Concentration of a solution refers to the amount of solute present in a given amount of solvent or solution.
• It helps differentiate between dilute and concentrated solutions.
• It varies with temperature and nature of solute and solvent.
• (i) Mass by mass percentage = (mass of solute / mass of solution) × 100.
• (ii) Mass by volume percentage = (mass of solute / volume of solution) × 100.
• (iii) Volume by volume percentage = (volume of solute / volume of solution) × 100.
• Example: 40g salt in 320g water gives 11.1% concentration by mass.

ByteNotes

Long Answer

Structured explanation

Long Answer

Question 4

Long Form

Q4. Define suspension. Describe its properties and provide examples.

• A suspension is a heterogeneous mixture where solid particles are dispersed in a liquid.
• The solute particles do not dissolve and are visible to the naked eye.
• Suspension scatters light and the path of the beam becomes visible.
• Particles settle down when left undisturbed.
• It is unstable and can be separated by filtration.
• Example: chalk powder in water, muddy water.
• Suspensions appear cloudy and can block light passage.

ByteNotes

Long Answer

Structured explanation

Long Answer

Question 5

Long Form

Q5. What is a colloidal solution? Describe its properties with examples.

• A colloid is a heterogeneous mixture with particles larger than a solution but smaller than a suspension.
• The dispersed particles are not visible to the naked eye.
• Colloids show Tyndall effect (scattering of light).
• They are stable and do not settle down over time.
• Colloids cannot be separated by filtration but can be separated by centrifugation.
• Examples: milk, fog, shaving cream, butter.
• It has two components: dispersed phase and dispersion medium.

ByteNotes

Long Answer

Structured explanation

Long Answer

Question 6

Long Form

Q6. What is the Tyndall effect? In which mixtures can it be observed?

• Tyndall effect is the scattering of a beam of light by particles in a colloid or suspension.
• It makes the path of light visible through the mixture.
• It occurs due to particle size being large enough to scatter light.
• It can be observed in fog, mist, milk, and forest sunlight.
• Solutions do not show Tyndall effect due to very small particles.
• Tyndall effect helps distinguish colloids from true solutions.
• Example: light passing through dust-filled room or canopy.

ByteNotes

Long Answer

Structured explanation

Long Answer

Question 7

Long Form

Q7. Define saturated, unsaturated, and supersaturated solutions with examples.

• A saturated solution cannot dissolve more solute at a given temperature.
• An unsaturated solution can dissolve more solute at that temperature.
• A supersaturated solution contains more solute than it can normally hold at that temperature.
• Example: 36g of salt in 100g water at 293K forms a saturated solution.
• Cooling a saturated solution may cause excess solute to crystallize.
• Solubility depends on temperature and nature of solute/solvent.
• Supersaturated solutions are unstable and revert to saturated state.

ByteNotes

Long Answer

Structured explanation

Long Answer

Question 8

Long Form

Q8. Differentiate between physical and chemical changes with suitable examples.

• Physical changes do not alter chemical composition (e.g., melting ice, boiling water).
• Chemical changes result in new substances with different properties (e.g., rusting iron).
• Physical changes are usually reversible; chemical changes are not.
• Example: burning of candle involves both changes—wax melting (physical) and combustion (chemical).
• Cutting paper is physical; digestion of food is chemical.
• Physical properties include shape, color, state; chemical properties include reactivity and combustibility.
• Both changes are essential in everyday and industrial processes.

ByteNotes

Long Answer

Structured explanation

Long Answer

Question 9

Long Form

Q9. What are pure substances? Differentiate between elements and compounds.

• Pure substances consist of only one type of particle.
• Elements are basic forms of matter and cannot be broken down chemically.
• Compounds are formed by chemical combination of two or more elements in fixed ratio.
• Elements: oxygen, iron, hydrogen. Compounds: water (H₂O), CO₂.
• Compounds have properties different from their constituent elements.
• Elements are classified into metals, non-metals, and metalloids.
• Compounds can only be separated by chemical methods, not physical.

ByteNotes

Long Answer

Structured explanation

Long Answer

Question 10

Long Form

Q10. Write the properties of metals, non-metals, and metalloids with examples.

• Metals: lustrous, conduct heat/electricity, malleable, ductile, sonorous (e.g., gold, iron, copper).
• Non-metals: dull, poor conductors, brittle, non-sonorous (e.g., carbon, oxygen, bromine).
• Metalloids: show properties of both metals and non-metals (e.g., silicon, boron).
• Metals are generally solid; mercury is liquid at room temperature.
• Non-metals can be solids, liquids, or gases.
• Metalloids are useful in electronics and semiconductors.
• Classification is based on physical and chemical properties.

ByteNotes

Premium Access

Unlock all Long Questions

You are viewing 10 free long questions from this chapter. Upgrade to Premium to unlock the remaining 10 questions.

Upgrade to Premium10 questions locked

Chapter sections

Chapter 2: Is Matter Around Us Pure? | Long Questions

Q1. Define a mixture. Explain the types of mixtures with suitable examples.

Q2. What is a solution? Describe its properties and give examples.

Q3. Explain the concept of concentration of a solution and list three methods to express it.

Q4. Define suspension. Describe its properties and provide examples.

Q5. What is a colloidal solution? Describe its properties with examples.

Q6. What is the Tyndall effect? In which mixtures can it be observed?

Q7. Define saturated, unsaturated, and supersaturated solutions with examples.

Q8. Differentiate between physical and chemical changes with suitable examples.

Q9. What are pure substances? Differentiate between elements and compounds.

Q10. Write the properties of metals, non-metals, and metalloids with examples.

Unlock all Long Questions