Is Matter Around us Pure Class 9 NCERT Solutions, “Is Matter around Us Pure” provide comprehensive and detailed answers to the exercise questions given in the chapter. The solutions cover even the smallest details, which will help students in clearing all their doubts. NCERT Solutions are extremely beneficial for CBSE students as it covers the entire syllabus and emphasizes fundamental concepts to assist students in grasping the basics.
Is Matter Around us Pure Class 9 NCERT Solutions
Q. What is meant by a substance?
Answer – A pure substance is composed of only one kind of particles or molecules, and it cannot be separated into simpler substances by physical means.
Q. Provide examples of how homogeneous and heterogeneous mixes differ from one another.
Answer – Differences between homogeneous and heterogeneous mixtures are –
| Homogeneous Mixtures | Heterogeneous Mixtures |
|---|---|
| Uniform composition throughout | Non-uniform composition |
| Only one phase | More than one phase |
| No visible boundaries of separation | Visible boundaries of separation |
| Examples: saltwater, sugar water, air | Examples: sand and sugar mixture, oil and water mixture, mixture of rocks and soil |
Q. Provide examples to distinguish between homogeneous and heterogeneous mixtures.
Answer – Differences between homogeneous and heterogeneous mixtures examples are –
| Homogeneous Mixtures | Heterogeneous Mixtures |
|---|---|
| Uniform composition throughout | Non-uniform composition |
| Only one phase | More than one phase |
| No visible boundaries of separation | Visible boundaries of separation |
| Examples: saltwater, sugar water, air | Examples: sand and sugar mixture, oil and water mixture, mixture of rocks and soil |
Is Matter Around us Pure Class 9 NCERT Solutions
Q. What differences occur between a sol, solution, and suspension?
Answer –
| Property | Sol | Solution | Suspension |
|---|---|---|---|
| Type of mixture | Colloid | Homogeneous | Heterogeneous |
| Particle size | <1 nm | Tiny | Large |
| Appearance | Translucent | Transparent | Cloudy or opaque |
| Settling of particles | Do not settle out | Do not settle out | Settle out over time |
| Example | Paints, inks, and blood | Sugar in water | Mud in water |
Q. 36 g of sodium chloride are dissolved in 100 g of water at 293 K to create a saturated solution. Find its concentration at this temperature.
Answer –
The mass of sodium chloride (NaCl) in the solution is 36 grams.
The mass of water (H2O) in the solution is 100 grams.
The total mass of the solution is 136 grams.
The concentration of the solution is calculated using the formula: concentration = (mass of solute / mass of solution) x 100.
Plugging in the values, we get: concentration = (36 g / 136 g) x 100 = 26.47%.
This means that for every 100 grams of the solution, 26.47 grams of it is sodium chloride.
Q. How can a mixture of kerosene and gasoline, which are miscible with one another and have boiling points that differ by more than 25°C, be separated?
Answer –
- To separate a mixture of kerosene and petrol, we can use fractional distillation.
- The mixture is heated and vaporized, and the components with lower boiling points (petrol) will condense first and are collected.
- The higher boiling point component (kerosene) remains in the flask.
- The temperature is increased gradually, and the process is repeated until both components are fully separated.
- The collected fractions are further purified to remove any impurities.
Is Matter Around us Pure Class 9 NCERT Solutions
Q. Identify the process for separating
(i) butter from curd,
(ii) salt from sea-water,
(iii) camphor from salt.
Answer –
(i) Churning or spinning are two terms used to describe the process of separating butter from curd.
(ii) Evaporation or distillation is the process used to extract salt from seawater.
(iii) “Sublimation” is the process used to extract camphor from salt.
Q. What kinds of mixes are separated using the crystallisation process?
Answer – A solid solute is frequently separated from a liquid solution using the crystallisation method. This method is usually used to separate mixtures of a solute that is more soluble at higher temperatures and less soluble at lower temperatures and is dissolved in a liquid. Slowly chilling the solution causes the solute to begin to crystallise out of the solution. The resulting crystals can then be filtered or centrifuged to remove them from the liquid.
Q. Indicate whether the following changes are chemical or physical:
• cutting of trees,
• melting of butter in a pan,
• rusting of almirah,
• boiling of water to form steam,
• when water is sent through an electric current, the water decomposes into gases such as hydrogen and oxygen,
• dissolving common salt in water,
• making a fruit salad with raw fruits, and
• burning of paper and wood.
Answer –
| Physical Change | Chemical Change |
|---|---|
| Cutting of trees Melting of butter in a pan Boiling of water to form steam Dissolving common salt in water Making a fruit salad with raw fruits | Rusting of almirah Passing of electric current through water and the water breaking down into hydrogen and oxygen gases Burning of paper and wood |
Is Matter Around us Pure Class 9 NCERT Solutions
Q. Try classifying the objects in your environment as either pure substances or mixes.
Answer –
| Pure Substances | Mixtures |
|---|---|
| Distilled water in a bottle | Coffee in a mug (contains water and coffee grounds) |
| Table salt in a shaker | Milk in the refrigerator (contains water, fats, proteins, lactose, etc.) |
| Refined sugar in a jar | Air in the room (contains nitrogen, oxygen, carbon dioxide, etc.) |
| Iron nail on my desk | Hand sanitizer (contains alcohol, water, glycerin, etc.) |
| Copper wire on my desk | Soap solution in a dispenser (contains soap, water, fragrance, etc.) |
| Oxygen gas in a cylinder |
Is Matter Around us Pure Class 9 NCERT Solutions
Q. What methods of separation will you use to separate the following?
(a) Sodium chloride from its water-based solution.
(b) Sodium chloride and ammonium chloride combined to produce ammonium chloride.
(c) Small metal fragments in a car’s engine oil.
(d) Different pigments from an extract of flower petals.
(e) Butter from curd.
(f) Oil from water.
(g) Tea leaves from tea.
(h) Iron pins from sand.
(i) Wheat grains from husk.
(j) Fine mud particles suspended in water.
Answer –
(a) Sodium chloride from its solution in water – Crystallisation
(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 – Filtration
Q. Put down the procedures you would follow to make tea. Employ the terms filter, residue, soluble, insoluble, solvent, and solution.
Answer – Here are the steps for making tea using the given words:
- Take a solvent, which is usually water, in a container and heat it.
- Add the solute, which is tea leaves, into the solvent and let it dissolve. Tea leaves are soluble in hot water.
- Stir the mixture to help the solute dissolve completely in the solvent.
- Allow the mixture to boil for a few minutes.
- Turn off the heat and let the mixture settle down for a minute.
- Pour the mixture through a filter into a cup. The liquid that passes through the filter is called the filtrate, which is the solution of tea and water.
- Discard the residue, which is the insoluble part of tea leaves left behind in the filter.
- Add sugar or milk to the filtrate according to taste preference.
Is Matter Around us Pure Class 9 NCERT Solutions
Q. Pragya examined the solubility of three distinct compounds at various temperatures and gathered the information listed below (results are given in the following table, as grammes of substance dissolved in 100 grammes of water to form a saturated solution).
(a) How much potassium nitrate would be required to create 50 grammes of saturated potassium nitrate solution in 313 K of water?
(b) Pragya prepares a saturated potassium chloride solution in water at a temperature of 353 K and allows the solution to cool to ambient temperature. When the solution cooled, what would she notice? Explain.
(c) Determine each salt’s solubility at 293 K. At this temperature, which salt is more soluble?
(d) How does a salt’s solubility alter when the temperature changes?
Answer –
(a) To make a saturated solution of potassium nitrate in 100 g of water at 313 K, 62 g of potassium nitrate is required. If we want to make a saturated solution in 50 g of water, we can use the formula: required amount = (given amount of solute/given amount of solvent) x required amount of solvent. Using this formula, we can find that 31 g of potassium nitrate is required.
(b) The solubility of potassium chloride in water decreases as the temperature decreases. At a certain temperature, called the saturation point, no more potassium chloride can dissolve in the water. If the saturated solution loses heat, the solubility of potassium chloride decreases even more, causing crystals to form.
(c) Solubility is a measure of how much solute can dissolve in a given amount of solvent at a specific temperature. From the given data, we can see that ammonium chloride has the highest solubility at 293K compared to potassium nitrate, sodium chloride, and potassium chloride.
(d) The solubility of a salt in water is dependent on temperature, with solubility generally increasing as temperature increases. When a salt solution reaches its saturation point at a specific temperature, increasing the temperature of the solution can cause more salt to dissolve. Conversely, decreasing the temperature can cause the salt to precipitate out of solution.
Is Matter Around us Pure Class 9 NCERT Solutions
Q. Provide examples to the following and explain.
(a) saturated solution
(b) pure substance
(c) colloid
(d) suspension
Answer –
(a) A saturated solution is a solution that has dissolved the maximum amount of solute possible at a particular temperature and pressure. Further addition of solute will not dissolve in the solution. For example, when we dissolve table salt in water and keep adding it until it stops dissolving, we obtain a saturated solution.
(b) A pure substance is a type of matter that has a fixed chemical composition and distinct physical properties. It cannot be separated into simpler substances by physical or chemical means. Examples of pure substances include elements like gold, silver, and carbon, and compounds like water, table salt, and sugar.
(c) A colloid is a type of mixture in which the particles of one substance are uniformly dispersed throughout another substance, but are not dissolved in it. The size of the particles is intermediate between those of a solution and those of a suspension. Examples of colloids include milk, blood, and fog.
(d) A suspension is a type of mixture in which small particles of a solid are dispersed throughout a liquid or gas, but are not dissolved in it. The particles are typically large enough to be seen with the naked eye and will eventually settle down when the mixture is left undisturbed. Examples of suspensions include muddy water, sand in water, and dust in air.
Is Matter Around us Pure Class 9 NCERT Solutions
Q. Indicate if the following mixtures are homogenous or heterogeneous for each. wood, soil, soda water, air, vinegar, and filtered tea.
Answer –
- Soda water: homogeneous mixture
- Wood: heterogeneous mixture
- Air: homogeneous mixture
- Soil: heterogeneous mixture
- Vinegar: homogeneous mixture
- Filtered tea: homogeneous mixture
Q. How would you know whether a given colourless liquid was actually pure water?
Answer – Boiling is a simple test that can determine the purity of a colorless liquid. Pure water has a boiling point of 100°C, so if a substance reaches this temperature, it is considered pure. Impurities in the liquid can cause the boiling point to be either higher or lower than 100°C, indicating the presence of other compounds. The strength of intermolecular forces between molecules in a liquid is what determines its boiling point, and the presence of impurities can influence these forces. As a result, the boiling point of a liquid will vary from pure water’s boiling point if other compounds are present.
Is Matter Around us Pure Class 9 NCERT Solutions
Q. Which of the following substances is considered a “pure substance”?
(a) Ice
(b) Milk
(c) Iron
(d) Hydrochloric acid
(e) Calcium oxide
(f) Mercury
(g) Brick
(h) Wood
(i) Air.
Answer – The materials that fall in the category of a “pure substance” are:
(a) Ice
(c) Iron
(d) Hydrochloric acid
(e) Calcium oxide
(f) Mercury
These materials are pure substances because they consist of only one type of molecule or atom.
Is Matter Around us Pure Class 9 NCERT Solutions
Q. Pick out the answers from the following mixtures.
(a) Soil
(b) Sea water
(c) Air
(d) Coal
(e) Soda water.
Answer – The solutions among the following mixtures are:
(b) Sea water – a mixture of salt and water
(e) Soda water – a mixture of carbon dioxide, water, and sugar/sweeteners, etc.
Is Matter Around us Pure Class 9 NCERT Solutions
Q. Which of the following exhibits the Tyndall effect?
(a) Salt solution
(b) Milk
(c) Copper sulphate solution
(d) Starch solution.
Answer –
(b) Milk and
(d) Starch solution will show Tyndall effect as they are colloids. The particles in colloids are large enough to scatter light, and this scattering of light is known as the Tyndall effect. Salt solution and copper sulphate solution are true solutions, which have particles that are too small to scatter light, and hence do not exhibit the Tyndall effect.
Is Matter Around us Pure Class 9 NCERT Solutions
Q. Sort the items listed below into elements, compounds, and mixes.
(a) Sodium
(b) Soil
(c) Sugar solution
(d) Silver
(e) Calcium carbonate
(f) Tin
(g) Silicon
(h) Coal
(i) Air
(j) Soap
(k) Methane
(l) Carbon dioxide
(m) Blood
Answer –
| Category | Examples |
|---|---|
| Elements | Sodium, Silver, Tin, Silicon |
| Compounds | Calcium carbonate, Soap, Methane, Carbon dioxide |
| Mixtures | Soil, Sugar solution, Coal, Air, Blood |
Is Matter Around us Pure Class 9 NCERT Solutions
Q. Which of the following changes are chemical?
(a) Growth of a plant
(b) Rusting of iron
(c) Mixing of iron filings and sand
(d) Cooking of food
(e) Digestion of food
(f) Freezing of water
(g) Burning of a candle.
Answer –
| S. No. | Process | Chemical Change? |
|---|---|---|
| 1 | Growth of a plant | Yes |
| 2 | Rusting of iron | Yes |
| 3 | Mixing of iron filings and sand | No |
| 4 | Cooking of food | Yes |
| 5 | Digestion of food | Yes |
| 6 | Freezing of water | No |
| 7 | Burning of a candle | Yes |