Given below are the Class 9 Science CBSE Extra Questions Is Matter around us pure .It has three and five questions to practice and excel in examination
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3-Marks Questions
Question 1. A solution contains 40 g of common salt in 320 g of water. Calculate the concentration in terms of mass by mass percentage of the
solution.
Solution
Mass of solute (salt) = 40 g
Mass of solvent (water) = 320 g
We know,
Mass of solution = Mass of solute + Mass of solvent
= 40 g + 320 g
= 360 g
$\text{mass by mass percentage}= \frac {40}{360} \times 100 = 11.1%$
Question 2.Define solubility. How does solubility. How does solubility of a solid in water change with temperature?
Solution
Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a solution of the solute in the solvent.
For many solids dissolved in liquid water, the solubility increases with temperature. The increase in kinetic energy that comes with higher temperatures allows the solvent molecules to more effectively break apart the solute molecules that are held together by intermolecular attractions.
Question 3.Two students A and B were given 10 ml of water in a bowl and a plate respectively. They were told to observe the rate of evaporation. Name the student whose water evaporates faster and explain its reason.
Solution
Student B water will evaporates faster as it has bigger surface area
Question 4.Why the inter-conversion of states of matter is considered as a physical change? Give three reasons to justify your answer.
Question 5.(a) Name the separation technique you would follow to separate
(i) Dyes from black ink.
(ii) A mixture of salt and ammonium chloride
(iii) Cream from milk
(iv) Sodium chloride from its solution in water
(b) State the principle used in separating a mixture of two immiscible liquids.
Solution
a) i)chromatography
ii)sublimation
iii)centrifugation
iv) evaporation
Question 6.How many litres of 15% (mass/ volume) sugar solution would it take to get 75 g of sugar?
Solution
We want a liquid which has 15% sugar as it's concentration.
Let the volume be x
Now Concentration% = Mass of the solute/Volume of the solution
15% =75/x
x=500ml =.5 l
Question 7.During an experiment the students were asked to prepare a 10 % (Mass/ Mass) solution of sugar in water. Ramesh dissolved 10 g of sugar in 100 g of water while Sarika prepared it by dissolving 10 g of sugar in water to make 100 g of the solution.
a)Are the two solutions of the same concentration?
b)Compare the mass % of the two solutions.
Solution
1. No both the solution have different concentration.
2. In case of Ramesh it is 10 gram of solute in total 110 g solution ( 10 g sugar + 100 g water)
So concentration in mass % = 10 / 110 x 100 = 9.09 %
But in case of Sarika ?it is 10 gram of solute in total 100 g solution ( 10 g sugar + 90 g water)
So concentration in mass % = 10 / 100 x 100 = 10 %
The solution prepared by Ramesh contains less amount of solute than Sarika.
Question 8.Calculate the mass of sodium sulphate required to prepare its 20% (mass percent) solution in 100 g of water.
Solution
Let mass of sodium sulphate required be x grams.
Given that the mass of water is 100 g.
20 = [x/(x + 100)] * 100
x = 25
Thus, 25g of sodium sulphate is required.
Question 9.Give an example for each of following:
a)Solid -liquid homogeneous mixture
b)Gas- gas homogeneous mixture
c)Liquid -liquid heterogeneous misture
Solution
a) salt in water
b) Air
c) Water and oil
Question 10.Distinguish between homogeneous and heterogeneous mixtures. Classify the following mixtures as homogeneous and heterogeneous:
(i) Tincture of iodine (ii) Smaoke
(iii) Brass(iv) Sugar solution
Question 11.A teacher told three students A, B and C to prepare 25% solution (mass by volume) of KOH. Student A dissolved 25 g of KOH in 100 g of water, student B dissolved 25 g of KOH in 100 mL of water and student C dissolved 25 g KOH in water and made the volume 100 mL. Which one of them has made required 25% solution? Give your answer with reason.
Solution
Student C
Mass of solute = 25g
Mass of solution = 100 m
concentration % = (25/100)100
=25%
Therefore Student C has made 25% of solution(mass by volume)
Question 12.Calculate the mass of water and mass of glucose required to make 250 g of 40% solution of glucose.
Solution
We know that
Mass percent = mass of solute / mass of solution
Here mass of solution = 250g
Mass of solute = x
Mass percent = 40
Hence 40 % = x/ 250
x = 100g
Hence amount of solute needed to make 250g of 40 % solution of is 100 g
Therefore Mass of Solute = 250g - 100g =150g
Question 13.‘Colloidal solution appears to be homogeneous but actually it is heterogeneous.’ Give justification for this statement.
Question 14.When a fine beam of light enters a room through a small hole, Tyndall effect is observed. Why does this happen? Give one more example where this effect can be observed.
Question 15.With the help of a flow diagram, show the process of obtaining different gases from air. if the boiling point of oxygen, argon and nitrogen are 183° C, - 186° C and - 196° C respectively, which gas gets liquefied first as the air is cooled?
Solution
Since Oxygen has the highest boiling point,it get get liquiefied first as the air is cooled
Question 16.Differentiate between miscible and immiscible liquids. Give an example of each.
Question 17.Write the role of following in water purification system:
(a) Sedimentation Tank(b) Loading tank(c) Chlorination tank
Question 18.Crystallization is better technique than simple evaporation technique. Justify this statement by giving two reasons.
Question 19.(i) Name a technique to separate a mixture of two or more miscible liquids for which difference in boiling points is less than 25 K.
(ii) Describe the structure of the column used in the above technique. Why is it used?
Question 20.When do we use the process of centrifugation? State the principle involved in this process. List its any two applications in our daily life.
Question 21.A mixture contains two liquids A and B, which differ in tyheir boiling points by 20 K. suggest a suitable process to separate them. Draw a neat labeled diagram to explain this process.
Question 22.Define distillation. What type of mixture can be separated by distillation?
Question 23.What is the principle of separating funnel technique? How it is useful in extraction of iron from its ore?
Question 24.List three differences between a physical change and a chemical change.
Solution
Physical Change
|
Chemical Change
|
- The chemical composition of a substance does not change.
- Change is only in the state of matter and not in the chemical identity
|
- The chemical composition of a substance changes.
- Change is in chemical identity, but may or may not be in the state of matter.
|
- Most changes are reversible
|
- Most changes are irreversible.
|
- No new substances are formed. For example,
Ice → Water → Steam
|
- New substances are formed.For example,
methane → carbon dioxide and water (on heating)
|
Question 25.Differentiate between, an element and a compound (any two points) with one example each.
Solution
Question 26.(i) Name the compound formed on heating a mixture of iron filings and sulphur.
(ii) If dilute HCI is added to above compound then name the gas evolved and write down its two properties.
Solution
i. Iron Sulphide(FeS)
ii. $FeS + 2HCL \rightarrow FeCl_2 + H_2S$
Question 27.State any three differences between a mixture and a compound.
Solution
Question 28.How will you separate a mixture of common salt, camphor and iron filings .Describe the process.
5-Marks Questions
Question 1.Write your observation when the following processes take place:
a. An aqueous solution of sugar is heated till it gets dried up.
b. A saturated solution of KCL at 60° C is allowed to cool at room temperature.
c. A mixture of iron filings and sulphur powder is heated strongly.
d. A bean of light is passed through colloidal solution.
e. Dilute HCI is added to mixture of iron filings and sulphur powder.
Solution
a. When an aqueous solution of sugar is heated to dryness, the sugar will be left behind in the container after the vaporization of water.
b. we would observe crystals of potassium chloride being formed in the liquid solution
c. Iron Sulphide(FeS) will be formed
d. The light is scattered and it is called tyndall effect
e. It will separate S and Fe, to form $H_2S$ gas and iron chloride($FeCl_2$)
Question 2.what is chromatography? How will you separate the components of black ink using chromatography? Write any two applications of chromatography.
Question 3.(a) You are given a mixture of sand, water and mustard oil. How will you separate the components of this mixture? Explain it with the help of different separation methods involved in it.
(b) Give flow diagram showing the process of obtaining gases from air.
Question 4.
A.Which of the following are chemical changes and physical change?
(i) Decaying of wood
(ii) Sawing of wood
(iii) Burning of wood
(iv) Hammering of a nail into a piece of wood
B.We know that Tincture of iodine has antiseptic properties. This solution is made by dissolving
(a) iodine in alcohol
(b) iodine in vaseline
(c) iodine in $H_20$
(d) iodine in $KI$
Solution
A. Chemical change : (i) and (iii)
Physical change: (ii) and (iv)
B. (d)
Question 5.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) =36g
Mass of solvent (water) =100g
Mass of solution = Mass of Solute + Mass of solvent
= 36g +100g = 136g
$Conc \; % = \frac {36}{136} \times 100 =26.47%$
Question 6.Give two examples from daily life where Tyndall effect is observed.
Question 7.Identify homogeneous and heterogeneous mixtures among the following:
Air, salt solution, kerosene in water, muddy water, soil, soda water
Question 8.Three students A, B and C prepared mixtures using chalk powder, common salt and milk respectively in water. Whose mixture:
a)Would not leave residue on filter paper after filtration?
b)Would show Tyndall effect?
c)Would give transparent/ clear solution?
d)Would settle down at the bottom when left undisturbed?
e)Could be filtered by filter paper?
Solution
a) Mixture done by B will not leave any residue as salt solution is a true solution.
b) Tyndall effect will be shown by milk solution of C. It's a colloidal solution. So it shows tyndall effect.
c) Salt solution will obviously be the clear solution. So, again its B.
d) Chalk powder mixture of A will settle down when left undisturbed as the particles are too heavy to resist gravity.
e) Again, Chalk powder of A can be filtered by filter paper. Although, it is possible to filter milk solution of C also, if sufficiently micro-porous filter is used.
Question 9.Based on the following characteristics distinguish in tabular form the behavior of true solution, suspension and colloidal solution:
(i) Appearance(ii) Visibility(iii) Filterability
(iv) Tyndall effect(v) stability(vi) Particle size
OR
List any three properties on the basis of which a colloidal solution can be recognized.
Question 10.How will you separate a mixture of red and blue inks? Name the technique used. Draw a labeled diagram and explain it.
Question 11.Explain the term fractional distillation. Draw a labeled diagram for carrying out the process of fractional distillation.
Question 12.Show diagrammatically how water is purified in the water works system and list the processes involved.
Solution
Question 13.(i) What is meant by crystallization? How is impure copper sulphate purified by the process?
(ii) Differentiate between simple distillation and fractional distillation.
Solution
Crystallization is the process of slow precipitation of solid crystals of a substance from a concentrated homogeneous solution. It is basically a separation method in which a substance is transferred from the liquid (i.e. solution) phase to the solid state. The substance is thus obtained in pure crystalline form and has no impurity. It is used by chemists for the purification of solid substances.
Simple Distillation is the process of distillation used to seperate two substance when the boiling point difference is more than 250 C. No fractionating column is used.
fractional distillation is the process of distillation used to seperate two substance when the boiling point difference is less than 250 C.Fractionating column used to separate substance
Question 14.Identify the physical and chemical changes from the following:
(i) Heating the mixture of iron and sulphur
(ii) Ripening of fruits
(iii) Dissolution of salt in water(iv) Rusting of iron – chair
(v) Making egg omelets
Solution
i) Chemical change
ii) Chemical change
iii) Physical change
iv) Chemical change
v) Chemical change
Question 15.(a) Compare metals and non - metals based on their physical properties. (any four points)
(b) What are metalloids? Give two examples.
(c) Identify metals from the following: Boron, sodium, mercury, carbon.
Solution
a.
b. Elements which show some properties of metals and some other properties of nonmetals are called metalloids. Boron and Silicon
c. Sodium and Mercury
Crossword Puzzle
Across
1. hydrogen ______ is a color gas with a smell of rotten eggs
5. The major components in solution
6. Melting point and boiling point are _______ properties
7. Two elements are liquid at room temperature are mercury and _______
Down
2. In colliads ,The particles are called the ______ phase and the medium in which they are distributed is called the dispersion medium.
3. amount of solute present per unit volume or mass of the solution or solvent
4. denser particles are forced to the bottom and the lighter particles stay at the top when spun rapidly
Solution
1. sulphide
2. dispersed
3. concentration
4.centrifugation
5. solvent
6. physical
7. bromine
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