Is Matter Around Us Pure Notes with NCERT Solution

Introduction

Matter is defined as anything that occupies space and has mass. It is everywhere around us, from the air we breathe to the water we drink. The substances we encounter daily can be classified as pure or impure. This chapter focuses on understanding the nature of substances and how to differentiate and separate mixtures into their components with NCERT Solution.

Mixture and Its Types

A mixture is a combination of two or more substances that retain their individual properties and can be separated by physical means. Mixtures can be classified into two main types:

Homogeneous Mixture

A homogeneous mixture has a uniform composition throughout. The individual components are not distinguishable. Examples include salt dissolved in water, sugar dissolved in tea, and air (a mixture of gases).

Heterogeneous Mixture

A heterogeneous mixture has a non-uniform composition, where the individual components are distinguishable. Examples include a mixture of sand and iron filings, a salad, and a rock with embedded minerals.

Solution and Its Properties

A solution is a homogeneous mixture composed of a solute dissolved in a solvent. The properties of a solution include:

• Particle Size: The solute particles are very small and cannot be seen with the naked eye.
• Stability: Solutions are stable; the solute does not settle out over time.
• Transparency: Solutions are typically clear and transparent.
• Filtration: The solute particles cannot be separated from the solvent by filtration.
• Example: Saltwater is a common example of a solution, where salt is the solute and water is the solvent.

Concentration of a Solution

The concentration of a solution refers to the amount of solute present in a given quantity of solvent or solution. It can be expressed in various ways:

• Mass Percentage: The mass of solute per 100 grams of solution.
• Volume Percentage: The volume of solute per 100 milliliters of solution.
• Molarity: The number of moles of solute per liter of solution.

Suspension and Its Properties

A suspension is a heterogeneous mixture where the solute particles do not dissolve but remain suspended throughout the solvent. The properties of suspensions include:

• Particle Size: The particles are larger and visible to the naked eye.
• Stability: Suspensions are unstable and the particles settle out on standing.
• Filtration: The particles can be separated by filtration.
• Example: Muddy water is a suspension where soil particles are suspended in water.

Colloidal Solution and Its Properties

A colloidal solution, or colloid, is a mixture where the solute particles are evenly distributed throughout the solvent but are larger than those in a solution and smaller than those in a suspension. Properties of colloids include:

• Particle Size: The particles are not visible to the naked eye but can be seen under a microscope.
• Stability: Colloids are stable and do not separate on standing.
• Transparency: Colloids can be transparent or opaque.
• Tyndall Effect: Colloids scatter light, making a beam of light visible as it passes through.
• Example: Milk is a colloid where fat globules are dispersed in water.

Separation of the Components of Mixtures

Various techniques can be employed to separate the components of mixtures based on their physical properties. These methods include:

Obtaining Coloured Components from Blue/Black Ink

Chromatography is a method used to separate and identify the components of a mixture based on their different rates of movement across a material. In the case of ink, chromatography can separate the different pigments present.

Separation of Cream from Milk

Centrifugation is a technique that uses centrifugal force to separate substances of different densities. When milk is centrifuged, the denser cream separates from the liquid.

Separating Two Immiscible Liquids

A separating funnel is used to separate two immiscible liquids, such as oil and water. The denser liquid can be drained out from the bottom of the funnel.

Separating a Mixture of Salt and Ammonium Chloride

Sublimation is a process where a solid changes directly into gas without passing through the liquid state. Ammonium chloride can be separated from a mixture with salt by heating, as it sublimates, leaving the salt behind.

Separating Dyes in Black Ink

Chromatography can also be used to separate the different dyes present in black ink by allowing the dyes to move at different speeds along a strip of paper.

Separating a Mixture of Two Miscible Liquids

Distillation is used to separate two miscible liquids based on their boiling points. The liquid with the lower boiling point evaporates first and is then condensed back into liquid form. Example: separating alcohol from water.

Obtaining Different Gases from Air

Fractional distillation of liquid air is used to separate its components based on their boiling points. By cooling air to very low temperatures, it can be liquefied and then distilled to obtain gases like nitrogen and oxygen.

Obtaining Pure Copper Sulphate from an Impure Sample

Crystallization is used to purify a compound by dissolving the impure substance in water, allowing it to crystallize out while impurities remain in the solution.

Physical and Chemical Changes

Changes in matter can be classified as physical or chemical:

• Physical Change: A change in which the form or appearance changes, but no new substances are formed. Example: melting of ice, boiling of water.
• Chemical Change: A change in which new substances with different properties are formed. Example: rusting of iron, burning of wood.

Types of Pure Substances

Pure substances have a uniform composition and can be either elements or compounds:

• Elements: Substances that cannot be broken down into simpler substances by chemical means. Example: oxygen (O₂), gold (Au).
• Compounds: Substances composed of two or more elements chemically combined in fixed proportions. Example: water (H₂O), sodium chloride (NaCl).

Difference Between Mixtures and Compounds

• Composition: Mixtures have a variable composition, whereas compounds have a fixed composition.
• Separation: Components of mixtures can be separated by physical methods, while components of compounds can only be separated by chemical methods.
• Properties: In mixtures, the individual components retain their properties, whereas in compounds, the properties are different from those of the constituent elements.
• Formation: Mixtures are formed by physically mixing substances, while compounds are formed by chemical reactions between elements.

NCERT SOLUTION Class 9th Science

Differentiate between Homogeneous and Heterogeneous Mixtures with Examples

Homogeneous Mixture:

• Definition: A homogeneous mixture has a uniform composition and appearance throughout.
• Examples:
  • Salt dissolved in water
  • Sugar dissolved in tea
  • Air (a mixture of gases)

Heterogeneous Mixture:

• Definition: A heterogeneous mixture has a non-uniform composition with distinct phases or layers.
• Examples:
  • A mixture of sand and iron filings
  • Salad
  • Rock with embedded minerals

How are Sol, Solution, and Suspension Different from Each Other?

Sol:

• Definition: A sol is a colloidal suspension of solid particles in a liquid.
• Examples: Paint, blood
• Properties:
  • Particles are not visible to the naked eye
  • Exhibits Tyndall effect
  • Stable and do not settle

Solution:

• Definition: A solution is a homogeneous mixture of two or more substances.
• Examples: Saltwater, sugar water
• Properties:
  • Particles are not visible to the naked eye
  • Does not exhibit Tyndall effect
  • Stable and particles do not settle

Suspension:

• Definition: A suspension is a heterogeneous mixture where solid particles are suspended in a liquid or gas.
• Examples: Muddy water, sand in water
• Properties:
  • Particles are visible to the naked eye
  • May exhibit Tyndall effect
  • Particles settle over time

To Make a Saturated Solution, 36 g of Sodium Chloride is Dissolved in 100 g of Water at 293 K. Find its Concentration at This Temperature.

Calculation:

• Mass of solute (sodium chloride): 36 g
• Mass of solvent (water): 100 g
• Total mass of solution: 136 g

Concentration: Concentration=(Mass of solute/Total mass of solution)×100

Concentration=(36 / 136)×100

Concentration=26.47%

How Will You Separate a Mixture Containing Kerosene and Petrol (Difference in Their Boiling Points is More Than 25ºC), Which are Miscible with Each Other?

Technique: Simple Distillation

Steps:

1. Heat the mixture in a distillation apparatus.
2. The component with the lower boiling point (petrol) will vaporize first.
3. The vapor is then condensed back into liquid form and collected.
4. Continue heating until the second component (kerosene) is left in the distillation flask.

Name the Technique to Separate

(i) Butter from Curd: Centrifugation

(ii) Salt from Sea-water: Evaporation

(iii) Camphor from Salt: Sublimation

What Type of Mixtures are Separated by the Technique of Crystallisation?

Answer: Crystallisation is used to separate solid-solid mixtures, where one solid is more soluble in a solvent than the other. It is also used to purify solids.

Classify the Following as Chemical or Physical Changes:

• Cutting of Trees: Physical Change
• Melting of Butter in a Pan: Physical Change
• Rusting of Almirah: Chemical Change
• Boiling of Water to Form Steam: Physical Change
• Passing of Electric Current through Water and the Water Breaking Down into Hydrogen and Oxygen Gases: Chemical Change
• Dissolving Common Salt in Water: Physical Change
• Making a Fruit Salad with Raw Fruits: Physical Change
• Burning of Paper and Wood: Chemical Change

Try Segregating the Things Around You as Pure Substances or Mixtures.

• Pure Substances: Gold, Oxygen, Water
• Mixtures: Air, Salad, Soil

Which Separation Techniques Will You Apply for the Separation of the Following?

(a) Sodium chloride from its solution in water: Evaporation

(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride: Sublimation

(c) Small pieces of metal in the engine oil of a car: Filtration

(d) Different pigments from an extract of flower petals: Chromatography

(e) Butter from curd: Centrifugation

(f) Oil from water: Separating funnel

(g) Tea leaves from tea: Filtration

(h) Iron pins from sand: Magnetic separation

(i) Wheat grains from husk: Winnowing

(j) Fine mud particles suspended in water: Sedimentation and decantation

Write the Steps You Would Use for Making Tea.

Steps:

1. Boil water in a kettle (solvent).
2. Add tea leaves (solute) to the boiling water.
3. Allow the tea leaves to dissolve in the water, forming a solution.
4. Add sugar and milk, which are soluble in water.
5. Filter the mixture to remove insoluble tea leaves, leaving a filtrate (tea) and residue (tea leaves).

Pragya Tested the Solubility of Three Different Substances at Different Temperatures.

Substance Dissolved in 100 g of Water to Form a Saturated Solution:

• Potassium nitrate:
  • 283 K: 21 g
  • 293 K: 32 g
  • 313 K: 62 g
  • 333 K: 106 g
  • 353 K: 167 g
• Sodium chloride:
  • 283 K: 36 g
  • 293 K: 36 g
  • 313 K: 37 g
  • 333 K: 37 g
  • 353 K: 37 g
• Ammonium chloride:
  • 283 K: 24 g
  • 293 K: 36 g
  • 313 K: 35 g
  • 333 K: 46 g
  • 353 K: 54 g

Questions:

(a) What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313 K?

• Answer: At 313 K, 62 g of potassium nitrate is needed for 100 g of water.
• For 50 g of water: 62​/100×50=31 g

(b) Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the solution to cool at room temperature. What would she observe as the solution cools? Explain.

• Answer: As the solution cools, some of the potassium chloride will crystallize out because its solubility decreases with temperature.

(c) Find the solubility of each salt at 293 K. Which salt has the highest solubility at this temperature?

• Answer:
  • Potassium nitrate: 32 g
  • Sodium chloride: 36 g
  • Ammonium chloride: 37 g
  • Ammonium chloride has the highest solubility at 293 K.

(d) What is the effect of change of temperature on the solubility of a salt?

• Answer: Generally, the solubility of solids in liquids increases with temperature. However, the solubility of gases in liquids decreases with temperature.

Explain the Following Giving Examples:

(a) Saturated Solution:

• Definition: A solution in which no more solute can be dissolved at a given temperature.
• Example: When 36 g of sodium chloride is dissolved in 100 g of water at 293 K, the solution becomes saturated.

(b) Pure Substance:

• Definition: A substance that consists of a single type of particle and has a uniform composition.
• Example: Water (H₂O), gold (Au)

(c) Colloid:

• Definition: A mixture where the solute particles are evenly distributed throughout the solvent, but are larger than those in a solution and smaller than those in a suspension.
• Example: Milk, fog

(d) Suspension:

• Definition: A heterogeneous mixture where solid particles are suspended in a liquid or gas.
• Example: Muddy water, flour in water

Classify Each of the Following as a Homogeneous or Heterogeneous Mixture:

• Soda water: Homogeneous
• Wood: Heterogeneous
• Air: Homogeneous
• Soil: Heterogeneous
• Vinegar: Homogeneous
• Filtered tea: Homogeneous

How Would You Confirm That a Colourless Liquid Given to You is Pure Water?

Answer: By determining its boiling point, pure water boils at 100°C at standard atmospheric pressure. Any deviation suggests impurities.

Which of the Following Materials Fall in the Category of a “Pure Substance”?

• Ice: Pure Substance
• Milk: Mixture
• Iron: Pure Substance
• Hydrochloric acid: Mixture (solution of HCl in water)
• Calcium oxide: Pure Substance
• Mercury: Pure Substance
• Brick: Mixture
• Wood: Mixture
• Air: Mixture

Identify the Solutions Among the Following Mixtures:

• Sea water: Solution
• Air: Solution
• Coal: Mixture
• Soda water: Solution

Which of the Following Will Show “Tyndall Effect”?

• Salt solution: No
• Milk: Yes
• Copper sulphate solution: No
• Starch solution: Yes

Classify the Following into Elements, Compounds and Mixtures:

• Sodium: Element
• Soil: Mixture
• Sugar solution: Mixture
• Silver: Element
• Calcium carbonate: Compound
• Tin: Element
• Silicon: Element
• Coal: Mixture
• Air: Mixture
• Soap: Mixture
• Methane: Compound
• Carbon dioxide: Compound
• Blood: Mixture

Which of the Following are Chemical Changes?

• Growth of a plant: Chemical Change
• Rusting of iron: Chemical Change
• Mixing of iron filings and sand: Physical Change
• Cooking of food: Chemical Change
• Digestion of food: Chemical Change
• Freezing of water: Physical Change
• Burning of a candle: Chemical Change

Take an Earthen Pot (Mutka), Some Pebbles and Sand. Design a Small-Scale Filtration Plant That You Could Use to Clean Muddy Water

Design Steps:

As the water passes through the sand and pebbles, it will get filtered, and cleaner water will collect at the bottom.

Place a layer of pebbles at the bottom of the pot.

Add a layer of sand above the pebbles.

Pour the muddy water into the pot.