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2. Is Matter around us Pure

Chapter Review

Chapter-Review:  

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• The substance are the same in their chemical nature and consists of a single type of particles are called pure substance.
• Mixture: A mixture is a combination of two or more substances which show the properties of each of the substance combined. E.g: A mixture of iron powder and sulphur show the properties of both sulphur and iron.
• The concentration of a solution is the amount of solute present
  per unit volume or per unit mass of the solution/solvent.
• There are two types of mixture. (i) Homogenous Mixture (ii) Heterogenous Mixture. 
• Mixture having uniform composition are called homogeneous mixture.
• Those mixture that do not have uniform composition are called heterogeneous mixture.
• Type of solution: (i) Colloidal Solution (ii) Concentration Solution (iii) Suspention.
• Alloys are homogeneous mixtures of metals and cannot be separated into their components by physical methods.
• Air is a homogeneous mixture of a number of gases. Its two main constituents are: oxygen (21%) and nitrogen (78%). The other gases are present in very small quantities.
• A solution of iodine in alcohol known as ‘tincture of iodine’.
• If the amount of solute contained in a solution is less than the saturation level, it is called an unsaturated solution.
• Mercury is the only metal that is liquid at room temperature.
• Some elements have intermediate properties between those of
  metals and non-metals, they are called metalloids. Examples:- Boron,
  silicon, germanium etc.
• Elements, gallium and cesium become liquid at a temperature
  slightly above room temperature (303 K).
• Crystallisation is a process that separates a pure solid in the
  form of its crystals from a solution. Crystallisation technique is better than simple evaporation technique.
• A dye is a mixture of two or more colours. The coloured component that is more soluble in water, rises faster and in this way the colours get separated.This process of separation of components of a mixture is known as chromatography.

2. Is Matter around us Pure

Text-book Questions

In Text Questions

Page No: 15

Q1. What is meant by a pure substance?

Solution: A pure substance consists of single type of particles that is all the constituent particles of a pure substance have same chemical nature. 

Q2. List the points of differences between homogeneous and heterogeneous mixtures.

Solution: The difference between between homogeneous and heterogeneous mixtures:

Homogeneous mixtures	Heterogeneous mixtures
1. Homogeneous mixtures have uniform composition.	1. Heterogeneous mixtures have non uniform composition.
2. It has no visible boundaries of separation between its constituents.	2. It has visible boundaries of separation between its constituents.

Page No: 18

Q1. Differentiate between homogeneous and heterogeneous mixtures with examples.

Solution: 

A homogeneous mixture is a mixture having a uniform composition throughout the mixture. For example, mixtures of salt in water, sugar in water, copper sulphate in water, iodine in alcohol, alloy, and air have uniform compositions throughout the mixtures.

On the other hand, a heterogeneous mixture is a mixture having a non-uniform composition throughout the mixture. For example, composition of mixtures of sodium chloride and iron fillings, salt and sulphur, oil and water, chalk powder in water, wheat flour in water, milk and water are not uniform throughout the mixtures.

Q2. How are sol, solution and suspension different from each other?

Answer: 

Sol	Solution	Suspension
They are heterogeneous in nature.	They are homogeneous in nature.	They are heterogeneous in nature.
They scatter a beam of light and hence show Tyndall effect.	They do not scatter a beam of light and hence do not show Tyndall effect.	They do not scatter a beam of light and hence do not show Tyndall effect.
They are quite stable.	Examples of solution are: salt in water, sugar in water.	Examples of suspension are: sand in water, dusty air

Q3. 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.

Solution:

Mass of solute (sodium chloride) = 36 g (Given)

Mass of solvent (water) = 100 g (Given)

Then, mass of solution = Mass of solute + Mass of solvent

= (36 + 100) g

= 136 g

PAGE NO 24.

Q1. How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25°C), which are miscible with each other?
Solution:
Kerosene and petrol are miscible liquids also the difference between their boiling point is more than 25 ºC so they can be separated by the method of distillation.

In this method, the mixture of kerosene and petrol is taken in a distillation flask with a thermometer fitted in it. We also need a beaker, a water condenser, and a Bunsen burner. The apparatus is arranged as shown in the above figure. Then, the mixture is heated slowly. The thermometer should be watched simultaneously. Kerosene will vaporize and condense in the water condenser. The condensed kerosene is collected from the condenser outlet, whereas petrol is left behind in the distillation flask.

Q2. Name the technique to separate
(i) butter from curd.

Sol: By Centrifugation.

(ii) salt from sea-water.

Sol:  By Evaporation.

(iii) camphor from salt

 Sol: By Sublimation.

Q3. What type of mixtures is separated by the technique of crystallization?

Solution:

The crystallisation method is used to purify solids.

Q1. 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 water breaking down into hydrogen and oxygen gas.
 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.

Page No: 28
Excercise

Q1. Which separation techniques will you apply for the separation of the following?

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

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

(c) Small pieces of metal in the engine oil of a car.
Solution:  Filtration or Centrifugation or decantation.

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

(e) Butter from curd.
 Solution: Centrifugation.

(f) Oil from water.
Solution:  Using separating funnel.

(g) Tea leaves from tea.
Solution:  Filtration.

(h) Iron pins from sand.
Solution:  Magnetic separation.

(i) Wheat grains from husk.
Solution:  Winnowing.

(j) Fine mud particles suspended in water.
Solution:  Centrifugation.

Q2. Write the steps you would use for making tea. Use the words: solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.

Solution:

First, water is taken as a solvent in a saucer pan. This water (solvent) is allowed to boil. During heating, milk and tea leaves are added to the solvent as solutes. They form a solution. Then, the solution is poured through a strainer. The insoluble part of the solution remains on the strainer asresidue. Sugar is added tothe filtrate, which dissolves in the filtrate. The resulting solution is the required tea.

Q3. Pragya tested the solubility of three different substances at different temperatures and collected the data as given below( results are given in the following table, as grams of substance dissolved in 100 grams of water to form a saturated solution).

(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?

(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.

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

(d)  What is the effect of change of temperature on the solubility of a salt? 
Solution: 
(a) Since 62 g of potassium nitrate is dissolved in 100g of water to prepare a saturated solution at 313 K, 31 g of potassium nitrate should be dissolved in 50 g of water to prepare a saturated solution at 313 K.

(b) The amount of potassium chloride that should be dissolved in water to make a saturated solution increases with temperature. Thus, as the solution cools some of the potassium chloride will precipitate out of the solution.

(c) The solubility of the salts at 293 K are:

Potassium nitrate – 32 g
Sodium chloride – 36 g
Potassium chloride – 35 g
Ammonium chloride – 37 g

Ammonium chloride has the highest solubility at 293 K.

(d) The solubility of a salt increases with temperature.

Q4. Explain the following giving examples:

(a) Saturated solution

(b) Pure substance

(c) Colloid

(d) Suspension

Solution:

(a) Solution in which no more solute can be dissolved at a particular temperature is known as saturated solution. For example in aqueous solution of sugar no more sugar can be dissolved at room temperature.

(b) A pure substance is a substance consisting of a single type of particles i.e., all constituent particles of the substance have the same chemical properties. For example water, sugar, salt etc.

(c) A colloid is a heterogeneous mixture whose particles are not as small as solution but they are so small that cannot be seen by naked eye. When a beam of light is passed through a colloid then the path of the light becomes visible. For example milk, smoke etc.

(d) A suspension is a heterogeneous mixture in which solids are dispersed in liquids. The solute particles in suspension do not dissolve but remain suspended throughout the medium. For example Paints, Muddy water chalk water mixtures etc.

Q5. Classify each of the following as a homogeneous or heterogeneous mixture.
Soda water, wood, air, soil, vinegar, filtered tea:

Solution:

Homogeneous mixtures: Soda water, air, vinegar

Heterogeneous mixtures: Wood, soil, filtered tea

Q6. How would you confirm that a colourless liquid given to you is pure water?

Solution:

Take a sample of colourless liquid and put on stove if it starts boiling exactly at 100 ºC then it is pure water. Any other colourless liquid such as vinegar always have different boiling point. Also observe carefully that after some time whole liquid will convert into vapour without leaving any residue.

Q7. Which of the following materials fall in the category of a "pure substance"?

(a) Ice

(b) Milk

(c) Iron

(d) Hydrochloric Acid

(e) Calcium oxide

(f) Mercury

(g) Brick

(h) Wood

(i) Air
Solution:
The following materials fall in the category of a "pure substance":

(a) Ice

(c) Iron

(d) Hydrochloric acid

(e) Calcium oxide

(f) Mercury

Q8. Identify the solutions among the following mixtures:

(a) Soil
(b) Sea water
(c) Air
(d) Coal
(e) Soda water

Solution:

The following mixtures are solutions:
(b) Sea water
(c) Air
(e) Soda water

Q9. Which of the following will show the "Tyndall effect"?

(a) Salt solution
(b) Milk
(c) Copper sulphate solution
(d) Starch solution

Solution:

Tyndall effect is shown by colloidal solution. Here milk and starch solution are colloids therefore milk and starch solution will show Tyndall effect.

Q10. Classify the following into elements, compounds and mixtures:

(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

Solution:

Elements: Sodium, Silver, Tin and Silicon.

Compounds: Calcium carbonate, Methane and carbon dioxide.

Mixtures: Soil, Sugar, Coal, Air, Soap and Blood.

Q11. Which of the following are chemical changes?

(a) Growth of a plant
(b) Rusting of iron
(c) Mixing of iron fillings and sand
(d) Cooking of food
(e) Digestion of food
(f) Freezing of water
(g) Burning of candle

Solution:

The following changes are chemical changes:
(a) Growth of a plant
(b) Rusting of iron
(d) Cooking of food
(e) Digestion of food

(g) Burning of candle

 

2. Is Matter around us Pure

Additional -Questions

Additional -Questions

Que: - What is solution?

Ans: - A solution is a homogeneous mixture of two or more substances. Ex. – lemonade and soda water etc.

Que:- What  is mixture ?

Ans:- A mixture is a combination of two or more substances which show the properties of each of the substance combined. A mixture of iron powder and sulphur show the properties of both sulphur and iron.

Que: - write the type of mixture? Difined them ?

Ans: -

1. Homogenous mixture – Mixture having uniform composition are called homogeneous mixture.
2. Heterogeneous mixture - – those mixture that do not have uniform composition are called heterogeneous mixture

Que: - Write the type of solution?

Ans: -  There are three type :-

1. Colloidal solution
2. Concentration solution
3. Suspension

Que: - What is suspension?

Ans: - suspension is a heterogeneous mixture which solids are dispersed in liquids are called suspension.

Que: - What is solute?

Ans: - The component of the solution that is dissolved in the solvent (usually present in lesser quantity) is called

the solute.

Que: - Write the properties of a solution?

Ans:- Properties of a solution

1. A solution is a homogeneous mixture.
2. The particles of a solution are smaller than 1 nm.
3. They cannot be seen by naked eyes.
4. They do not scatter a beam of light passing through the solution.
5. The path of light is not visible in a solution.
6. The solute particles cannot be separated from the mixture by the process of filtration.

Que : - Write the properties of suspension.

Ans: - The properties of suspension.

1. Suspension is a heterogeneous mixture.
2. The particles of a suspension can be seen by the naked eye.
3. The particles of a suspension scatter a beam of light passing through it and make its path visible.
4. They can be separated from the mixture by the process of filtration.

Que:-  Write the properties of a colloid ?

Ans: -  The properties of a colloid

1. A colloid is a heterogeneous mixture.
2. The size of particles of a colloid is too small to be individually seen by naked eyes.
3. Colloids are big enough to scatter a beam of light passing through it and make its path visible.
4. They do not settle down when left undisturbed, that is, a colloid is quite stable.

Que : - What is solubility?

Ans:- The amount of the solute present in the saturated solution at this temperature is called its solubility.

Que:  - Write the type of solution? Define them ?

Ans: -

1. Saturated solution –  When no more solute can be dissolved in a solution at a given temperature, it is called a saturated solution.
2. Unsaturated solution – The amount of solute contained in a solution is less than the saturation level, it is called an unsaturated solution.

Que: - What is solvent ?

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

Que: What is decantation?

Ans:      The process of separating a solid from a liquid by pouring out the liquid is known as decantation.

Que:- What is dilute ?

Ans:- Depending upon the amount of solute present in a solution, it can be called a dilute.

Que: - How can we separate cream from milk?

Ans: - By the centrifugation.

Que; - What is chromatography?

Ans: - This process of separation of components of a mixture is known as chromatography.

Que: - What is chemical change ?

Ans:- Chemical change brings change in the chemical properties of matter and we get new substances. A chemical change is also called a chemical reaction.

Que:- How can we separate mixture of two imscible liquid?

Ans:-By distillation.

Que:- How can we separate a mixture of salt and ammonium chcoride?

Ans:- By susblimation

Que:-What is crystallization?

Ans:- Crystallisation is a process that separates a pure solid in the form of its crystals from a solution.

Que:- Write the difference between  a pure substance and a mixture?

Ans: -

Pure substance:

(i) All elements and compounds are pure substance.

(ii) particles are same chemical nature.

Example : H₂, O₂, Fe, CO₂, H₂O, NaCl etc.

Mixture:

(i) Mixing two or more than elements and compund in not any fix ratio is mixture.

(ii) particles are not same chemical nature. 

Example: Soda water, mixture of sand and iron fills, air etc.

Que:-What are the types of pure substance?

Ans; -  There are two types :-

1. Element
2. Compound

Que: What is element?

Ans: An element is a pure substances of matter. Which can’t be broken down into simpler substances by chemical method.

Ex. -  copper, Iron, Alumunium, Oxygen, nitrogen etc.

Que: Write the types of element and define them ?

Ans:  Element can be normally divided into metal non-metal and metalloids.

1. Metal:-

2. Non metal -

3. Metalloids:- some elements have intermediate properties between those of metals and non-metals they are called metalloids examples: are boron, silicon germanium etc.

Que: Write the properties of metal and non-metal? 

 Ans: Metals usually show some or all of the following properties:

 metal-

• They have a lustre (shine).

• They have silvery-grey or golden-yellow colour.

• They conduct heat and electricity.

• They are ductile (can be drawn into wires).

• They are malleable (can be hammered into thin sheets).

• They are sonorous (make a ringingsound when hit).

  Non metal:-

 Non-metals usually show some or all of the following properties:

• They display a variety of colours.

• They are poor conductors of heat and electricity.

• They are not lustrous, sonorous or malleable.

Que- What is compound?

Ans- A compound is a substance composed of two or more elements, chemically combined with one another in a fixed proportion.

2. Is Matter around us Pure

Additional -Questions 2

Additional-Questions:

Que- Write the difference between mixture and compound?

Mixture	Compound
(i)  Element or compound just mix together to from a mixture and no new compound is formed. (ii)  A mixture has a variable composition. (iii)  A mixture shows the properties of the constituents substances. (iv)  The constituents can be separated farily easily by physical methods.	(i)  Element react to from new compounds. (ii)  The composition of each new substance is always fixed. (iii)  The new substance has totally different propreties. (iv)  The constituents can be separated only by chemical or electrochemical rections.

Que: Write the various methods of separation.

Ans:

1. Evaporation
2. Chromatography.
3. Centrifugation.
4. Sublimation.
5. Filtration.
6. Crystallisation.
7. Distillation.
8. Magnetic separation.
9. Separating Funnel.
10. Winnowing
11. Decantation.
12. Sedimentation.   

Que- What type of mixtures are separated by the technique of crystallisation?

Ans:(i) Salt from sea water.

        (ii)  Alum (Phitkari) from impure sample.

Que: -Which separation techniques will you apply for the separation of the following?

a. Sodium chloride from its solution in water.

Ans: Evaporation .

b. Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.

Ans: Sublimation.

c. Small pieces of metal in the engine oil of a car.

Ans: Filtration.

d. Different pigments from an extract of flower petals.

Ans: Chromatography.

e. Butter from curd.

Ans: Centrifugation.

f. Oil from water.

Ans: Separation funnel. 

g. Tea leaves from tea.

Ans: Filtration.

h. Iron pins from sand.

Ans: Magnetic Separation.

i.  Wheat grains from husk.

Ans: Winnowing.

j. Fine mud particles suspended in water.

Ans: Decantation.

 Que; - Differentiate between homogeneous and heterogeneous mixtures with examples.?

Ans: - Homogeneous - Mixture having uniform composition are called homogeneous mixture. Ex. Mixture of sat in water and mixture of alcohol in water.

Heterogeneous – those mixture that do not have uniform composition are called heterogeneous mixture.ex. mixture of salt and sugar ,Mixture of sand and salt. 

Que: - how can we separate a mixture two immiscle liquid?

Ans:- By Separating Funnel.

​Que:- What is distillation ?

Ans:- Distillation is a method to separate a mixture of liquid components into individual liquid components at various boiling points.

Que-1 What is a Mixture?

Ans-Mixture consist of more than one kind of pure form of matter,know as a substance of mixture.

Que-2 What type of matters around us?

Ans-There are two types of matter around us:(i)PURE SUBSTANCE (ii)IMPURE SUBSTANCE.

Que-3 What is pure substance?

Ans-Thoes substance which contains particles of only one kind is called a pure substance.ex-carbon, chlorine,iron,copper and all the elements and compounds are pure substances.

Que-4 What is impure substance (mixture)?

Ans-Thoes substance which contains particles of different kinds is called an impure substance.(atoms and molecules)a mixture contains two or more pure substances mixed together ex-salt solution,sugar solution,milk,sea-water and all the mixtures are impure substances.

Que-5 What type of mixtures?

Ans-There are two type of mixtures:(i)Homogeneous mixture(ii)Heterogeneous mixture.

Que-6 What is Homogeneous mixture?

Ans-Thoes mixtures in which the substances are completely mixed together and are indistinguishable from one another, are called homogeneous mixtures.ex-Copper sulphate solution,sugar solution,salt solution etc.

Que7: What is Heterogeneous mixtures?

Ans-Thoes mixtures in which the substances remain seprate and one substance is spread throughout  the other substance as small particles,droplets or bubbles,are called heterogeneous mixtures.ex-Chalk and water solution,sugar and sand solution ect.

Que-8 List the points of differences between homogeneous and heterogeneous mixtures?

Ans-

Homogeneous mixtures:Mixtures having uniform composition are called homogeneous mixtures.For ex-mixture of salt in water,mixture of sugar in water and mixture of alcohol in water.

Heterogeneous mixtures:Mixture having non uniform composition are called heterogeneous mixtures.For ex-mixture of salt and sugar,mixture of sand and salt.

Que-9 How many classes all the matter can divided?

Ans-All the matter can divided into three general classes:(i)ELEMENT (ii)COMPOUNDS (iii)MIXTURES.

Que-10 What is malleability?

Ans-The property which allows the metals to be beaten into thin sheets is called malleability.

Que-11 What is ductility?

Ans-The property which allows the metals to be drawn into thin sheets is called ductility.

Que-12 What is elements?

Ans-An element is a substance which is made up of only one kind of atoms.For ex-copper and iron.

Que-13 How many groups the elements are divided?

Ans-All the elements can be divided into three groups:(i)Metals (ii)Non-metals (iii)Metalloids

Que-14 Define the metals and write its properties?

Ans-A metal is an element that is malleable and ductile,and good conducts of electricity.

Properties of metals:

(i)Metals are Malleable

(ii)Metals are Ductile

(iii)Metals are good conductors of heat and electricity.

(iv) Metals are Lustrous(or shiny),and can be polished

(v) Metals are generally hard

(vi) Metals are usually strong.they have high tensile strength.

Que-15 Define the non-metals and write its properties?

Ans-A non-metals is an element that is neither malleable nor ductile,and does not conduct electricity.

Properties of non-metals:

(i)Non-metals are not malleable,Non-metals are brittle

(ii)Non-metals are not ductile

(iii)Non-metals are bad conductors of heat and electricity (iv)Non-metals are Not lustrous(Not Shiny).They are dull in appearance(v)Non-metals are Generally Soft(vi)Non-metals are Not Strong.They Have Low Tensile strength

Que-16 What is metalloids?

Ans-The elements which show some properties of metals and some otjer properties of non-metals are called metalloids.ex-Boron,Silicon,Germanium etc.

Que-17 How would you confirm that a colourless liquid given to you is pure water?

Ans-The colourless liquid has fixed boiling point 100®C freezing point 0®C then it is pure water.

Que-18 Classify each of the following as a homogeneous and heterogeneous mixture:Soda water,air,wood,soil,vinegar,fitered tea?

Ans-Homogeneous mixture:Soda water,vinegar and filtered tea.Heterogeneous mixture:Wood,air and soil.

Que-19 What did you mean by mixture?

Ans- A mixture is a substance which consists of two or more elements or compounds not chemically combined together.All the solution are mixtures.

Que-20 What is compounds?

Ans-A compounds is a substance made up of two or more elements chemically combined in a fixed proportion by mass.ex-Ammonia,Carbon dioxide,steam,ice,calcium carbonate etc.

Que-21 What is alloys?

Ans-Alloys are homogeneous mixtures of metals and cannot be separated into their components by physical methods an alloy is considered a mixture.

Que-22 What is solutions?

Ans-A solution is a homogeneous mixture of two or more substance.ex-Salt solution,Sugar solution,vinegar,metal and alloys.

Que-23 What is suspensions?

Ans-A suspension is a heterogeneous mixture in which the small particles of a solid are spread throughout a liquid without dissolving in it.ex-Sand particles suspended in water,and flour in water.

Que-24 What is colloids?

Ans-A colloids is a kind of solution in which the size of solute particles is intermediate between those in ture solutions and those in suspensions.ex-Soap solution,Starch solution,Milk,Ink,Blood,Jelly ect.

Que-25 What is tyndall effect?

Ans-The scattering of light by colloidal particles is known as Tyndall effect.

Que-26 What is solvent?

Ans-The liquid in which solute is dissolved is known as solvent.ex-copper sulphate etc.

Que-27 What is solute?

Ans The substance which is dissolved in a liquid to make a solution is called solute.ex-salt solution etc.

Que-28 Write the classification of colloids?

Ans-(i)sol,(ii)solid sol,(iii)aerosol,(iv)emulsion,(v)foam,(vi)solid foam,(vii)gel

Que-29 What is concentration of a solution?

Ans-The concentration of a solution is the amount of solute present in a given quantity of the solution.the concentration of a solution is defined as the mass of solute in grams present in 100 gram of the solution.

Que-30 How many types of solutions?

Ans-There are two types of solution are:(i) SATURATED solution (ii) UNSATURATED solution.

Que-31What is saturated solution?

Ans-A solution in which no more solute can be dissolved at that temperature,is called a saturated solution.ex-an aqueous salt solution.

Que-32 What is unsaturated solution?

Ans-A solution in which more quantity of solute can be dissolved without raising its temprature,is called an unsaturated solution.

Que-33What is solubility?

Ans-The maximum amount of a solute which can be dissolved in 100 grams of a solvent at a specified temperature is known as the solubility of that solute in that solvent (at that temperature).

Que-34 Which sepration techniques will you apply for the separation of the following?

(i)sodium chloride from its soltion on water.(ii)Ammonium chloride from a mixture comtaining sodium chloride and ammonium chloride.