CBSE Class 9 Science Physical And Chemical Changes Worksheet

CBSE Class 9 Science Worksheet - Physical and Chemical Changes. Students can download these worksheets and practice them. This will help them to get better marks in examinations. Also refer to other worksheets for the same chapter and other subjects too. Use them for better understanding of the subjects.

Reaction of iron with copper sulphate

Experiment No: …5…. Date: ………..

(a) Iron with copper sulphate solution

Objectives: To study the reaction of iron with copper sulphate

Requirements: Iron nails, thread, test tubes, copper sulphate, distilled water, spatula, TT stand, sand paper, etc.

Points to remember:

1. Colour of pure iron is greyish

2. Colour of pure copper is brownish.

3. Aqueous solution of copper sulphate is blue due to the presence of Cu2+ ions and ferrous sulphate is light

green due to the presence of Fe2+ ions.

4. Fe is more reactive than Cu. Due to their difference in reactivity, copper get deposited on iron when

iron is kept in a solution of copper sulphate and metallic iron dissolves in water to form iron sulphate.

5. This is an example of a single displacement reaction.

Procedure:

1. Take 10 ml each of copper sulphate solution in two test tubes and keep on a TT stand.

2. Take two iron nails and clean them using a sand paper to remove any rust.

3. Put one iron nail in one of the test tubes.

4. After 15 minutes, take out the iron nail keep it on a filter paper next to the clean iron nail and compare

them. Compare also the solutions in both the test tubes.

5. Record your observation in the following table.

Nature of the: Observation Inference

Iron nail before the

experiment

Silvery grey in colour and

lustrous Metals are lustrous.

Iron nail after the experiment Brown deposit on the nail

Copper is deposited on the nail due the

displacement reaction that takes place

between Fe & Cu.

Solution before the

experiment

Light blue and

transparent

Copper sulphate solution is peacock blue in

colour

Solution after the experiment Light green and dirty

Due to the chemical reaction, Fe displaces Cu

fromCuSO4 and FeSO4 is formed in the solution.

Dirtiness is due to the rusting of iron.

Conclusions:

Fe displaces Cu from CuSO4 and forms FeSO4 in the solution hence the colour of the solution changes from light

blue to pale green. The displaced copper gets deposited on iron nail. It appears as brown coating on iron nail

Precautions:

1. Iron nail should be clean; otherwise impurity such as rust will cause interference to the expected

reaction.

2. During the experiment the test tube should not be disturbed. (The deposit of copper might fall off)

3. More the time taken better will be the result.

(b) Burning of Magnesium in air

Objectives: To study the burning of Mg in air

Requirements: A strip of Mg ribbon, a pair of tongs, china dish, Bunsen burner, litmus paper, match box etc.

Points to remember:

1. Mg is an active metal.It combines with oxygen to form magnesium oxide.

2. The reaction is an example of direct combination reaction.

3. MgO on dissolving (It is only partially soluble) in water gives a base magnesium hydroxide.

4. Both MgO and Mg(OH)2 turn red litmus blue.

Procedure:

1. Take a clean strip of Mg ribbon and burn it by showing to a Bunsen flame with the help of a pair of

tongs.

2. Collect the white powder that is formed during burning in a china dish.

EXPERIMENT OBSERVATION INFERENCE

Rub the magnesium ribbon with a

sand paper

Silvery grey colour with

lustre

Metals are lustrous

Burn Mg ribbon and note the nature of

the flame and smoke.

It burns with an intensely

bright flame and white

smoke

Mg burns in oxygen to form MgO

Put a small portion of the white

powder on a moist red litmus paper.

Red litmus turns to blue MgO is alkaline/basic. It dissolves in

water to form Mg(OH)2

Conclusions:

1. When Mg burns in air, it combines with oxygen (of air) to form a white powder of magnesium oxide. &

MgO is basic in nature.

Precautions:

1. Mg ribbon should be clean

2. Avoid looking directly at the flame when the Mg ribbon burns as the intensity of the flame may damage

your eye sight.

3. A pair of tongs should be used to hold the Mg ribbon while burning.

4. The white powder formed should not come in contact with your body partsReaction of Zinc with

sulphuric acid

(c) Zinc with Dil.Sulphuric acid

Objectives: To study the chemical reaction between Zn and dil H2SO4 acid.

Points to remember:

1. Zn is an active metal. It has two valance electrons.

2. Hydrogen is less reactive than Zn, so the following reaction takes place when Zn comes in contact with

acid.

3. This reaction is an example of a single displacement .

EXPERIMENT OBSERVATION INFERENCE

Take a small piece of Zn granule in

a test tube and treat it with 3 ml

of dilute sulphuric acid. Wait for

10 minutes.

Slow evolution of a colourless

odourless gas.

Zn displaces H2 gas from HCl and

forms ZnCl2

Zn + H2SO4  Zn SO4 + H2

Precautions:

1. Sulphuric acid should be handled carefully.

2. Use clean Zn granules.

Conclusion:

Zn is more reactive than hydrogen.

(d)Heating of Copper sulphate

Objective : To study the chemical reaction when hydrated copper sulphate is heated.

Apparatus: Test tubes ,bunsen burner ,hydrated copper sulphate,tongs ,spatula etc

Theory : The hydrated copper sulphate loses its water of crystallisation on heating

CuSO4.5H2O CuSO4 + 5H2O

blue white

 It is a reversible chemical reaction

Procedure:

Experiment Observation Inference

Take 1 spatula of hydrated copper

sulphate (blue) in a hard glass

tube gently heat over a Bunsen

flame .

Blue coloured copper sulphate

changes to white

Hydrated copper sulphate loses

water of crystallisation on heating

and becomes anhydrous.

 Use safety goggle while heating..

 Be careful when you handle hot objects.

(e) Reaction between Sodium sulphate &Barium chloride

Objectives: To study the chemical reaction between Sodium sulphate and Barium Chloride.

Requirements: Solutions of Na2SO4 & BaCl2, test tubes etc.

Points to remember:

1. Sodium sulphate contains 2 sodium ions and one sulphate ion.

2. On mixing the solutions a double displacement reactions takes place.

EXPERIMENT OBSERVATION INFERENCE

Take 1 ml of Sodium sulphate

solution in a test tube and add 1

ml of BaCl2 solution to it. Record

the change observed.

A white precipitate is formed The white precipitate formed is

BaSO4

Na2SO4+BaCl2  BaSO4+2NaCl

Questions:

1. What is meant by displacement reaction? (Ans: A stronger element displaces a weaker element

from its compound)

2. Which is more reactive? Copper or iron and why? (Ans: Fe is more reactive as it displaces Cu

from its compounds)

3. Which is more reactive? Copper or iron and why? (Ans: Fe is more reactive as it displaces Cu

from its compounds)

4. Which is more reactive? Copper or iron and why? (Ans: Fe is more reactive as it displaces Cu

from its compounds)

5. What is the colour of copper sulphate solution before the experiment? (Blue/Peacock blue)

6. Which out of the following get coated on iron nail? What is its colour?

(Copper oxide, copper sulphate, copper sulphide, copper metal) [Reddish brown ]

7. Why it is not advised not to look directly at the flame of a burning Mg piece? (Ans: intense

dazzling flame may damage retina)

8. What is the colour of barium chloride solution? What is the colour of barium sulphate

precipitate?

9. What is the colour nature of hydrated copper sulphate?

10. What is the colour of the residue when copper sulphate crystals are heated? .

11. What do you mean by water of crystallisation?

Multiple choice type questions

1 The colour of copper sulphate solution

a) deep blue b) light green c) blue d) light yellow

2 A 10 cm long magnesium ribbon is heated in a Bunsen burner flame till it catches fire.the flame

produced in magnesium ribbon is

a) Yellow b)dazzling white c) brick red d) silvery blue

3 The compound formed when zinc reacts with dil sulphuric acid is

a ) Zinc sulphite b) zinc sulphate c) zinc chloride d)zinc sulphide

4 When solutions of sodium sulphate &barium chloride are mixed ,an insoluble solid settles at the

bottom of the test tube.,its colour

a ) blue b) yellow c) white d)green

5 While heatinng the crystals of copper sulphate the incorrect observation is:

a) blue crystals change to white

b) crackling sound

c) water droplets along the sides of test tube

d) liberates colourless gas

6 Which one of the following is an example of physical change

a ) Burning of magnesium ribbon in air b)Burning of candle

c ) mixing Zinc &dil sulphuric acid d)boiling of water

7 Which one is true about the behaviour of magnesium oxide in presence of water

a) It is basic

b) It is acidic

c) It is amphoteric

d) It is neutral

8 The gas evolved during reaction of zinc with Dil.Sulphuric acid is:

a) a supporter of combustion

b) a potential fuel

c) non – combustible

d) soluble in water

9 What is observed when iron nails are added to copper sulphate solution?

a) the solution becomes pale and eddish brown deposit is seen on the nails.

b) the solution becomes colourless

c) there is no reaction

d) the solution changes to pale green and no change in the iron nails.

10 When magnesium is burnt in air,it produces magnesium oxide that appears to be like: (CCE 2011)

a) wood ash b) chalk powder c) table salt d) powdered sugar

11 When Dil.Sulphuric acid is added to granulated zinc placed in a test tube, the observation made is:

a) the surface of the metal turns shining

b) the reaction mixture turns milky

c) the odour of sulphur is observed

d) the colourless and odourless gas evolves with bubbles.

12 The crystals of copper sulphate turn white on heating due to (CCE 2011)

a) loss of sulphate ions.

b) loss of copper ions.

c) loss of water of crystallisation.

) decomposition of copper sulphate.

Different Physical & Chemical Changes

Reaction of Iron with Copper Sulphate
Experiment No: 5

(a) Iron with copper sulphate solution

Objectives: To study the reaction of iron with copper sulphate

Requirements: Iron nails, thread, test tubes, copper sulphate, distilled water, spatula, TT stand, sand paper, etc.

Points to remember:

1. Colour of pure iron is greyish

2. Colour of pure copper is brownish.

3. Aqueous solution of copper sulphate is blue due to the presence of \( \text{Cu}^{2+} \) ions and ferrous sulphate is light green due to the presence of \( \text{Fe}^{2+} \) ions.

4. Fe is more reactive than Cu. Due to their difference in reactivity, copper get deposited on iron when iron is kept in a solution of copper sulphate and metallic iron dissolves in water to form iron sulphate.

5. This is an example of a single displacement reaction.

Procedure:

1. Take 10 ml each of copper sulphate solution in two test tubes and keep on a TT stand.

2. Take two iron nails and clean them using a sand paper to remove any rust.

3. Put one iron nail in one of the test tubes.

4. After 15 minutes, take out the iron nail keep it on a filter paper next to the clean iron nail and compare them. Compare also the solutions in both the test tubes.

5. Record your observation in the following table.

Conclusions:
Fe displaces Cu from \( \text{CuSO}_4 \) and forms \( \text{FeSO}_4 \) in the solution hence the colour of the solution changes from light blue to pale green. The displaced copper gets deposited on iron nail. It appears as brown coating on iron nail.

Precautions:

1. Iron nail should be clean; otherwise impurity such as rust will cause interference to the expected reaction.

2. During the experiment the test tube should not be disturbed. (The deposit of copper might fall off)

3. More the time taken better will be the result.

(b) Burning of Magnesium in air

Objectives: To study the burning of Mg in air

Requirements: A strip of Mg ribbon, a pair of tongs, china dish, Bunsen burner, litmus paper, match box etc.

Points to remember:

1. Mg is an active metal. It combines with oxygen to form magnesium oxide.

2. The reaction is an example of direct combination reaction.

3. MgO on dissolving (It is only partially soluble) in water gives a base magnesium hydroxide.

4. Both MgO and \( \text{Mg(OH)}_2 \) turn red litmus blue.

Procedure:

1. Take a clean strip of Mg ribbon and burn it by showing to a Bunsen flame with the help of a pair of tongs.

2. Collect the white powder that is formed during burning in a china dish.

Conclusions:
When Mg burns in air, it combines with oxygen (of air) to form a white powder of magnesium oxide, and MgO is basic in nature.

Precautions:

1. Mg ribbon should be clean.

2. Avoid looking directly at the flame when the Mg ribbon burns as the intensity of the flame may damage your eye sight.

3. A pair of tongs should be used to hold the Mg ribbon while burning.

4. The white powder formed should not come in contact with your body parts.

(c) Zinc with Dil.Sulphuric acid

Objectives: To study the chemical reaction between Zn and dil \( \text{H}_2\text{SO}_4 \) acid.

Points to remember:

1. Zn is an active metal. It has two valance electrons.

2. Hydrogen is less reactive than Zn, so the following reaction takes place when Zn comes in contact with acid.

3. This reaction is an example of a single displacement.

Precautions:

1. Sulphuric acid should be handled carefully.

2. Use clean Zn granules.

Conclusion:
Zn is more reactive than hydrogen.

(d) Heating of Copper sulphate

Objective: To study the chemical reaction when hydrated copper sulphate is heated.

Apparatus: Test tubes, bunsen burner, hydrated copper sulphate, tongs, spatula etc.

Theory: The hydrated copper sulphate loses its water of crystallisation on heating.
\( \text{CuSO}_4\cdot5\text{H}_2\text{O} \rightarrow \text{CuSO}_4 + 5\text{H}_2\text{O} \)
(blue) - (white)

• It is a reversible chemical reaction.

Procedure:

• Use safety goggle while heating.
• Be careful when you handle hot objects.

(e) Reaction between Sodium sulphate & Barium chloride

Objectives: To study the chemical reaction between Sodium sulphate and Barium Chloride.

Requirements: Solutions of \( \text{Na}_2\text{SO}_4 \) & \( \text{BaCl}_2 \), test tubes etc.

Points to remember:

1. Sodium sulphate contains 2 sodium ions and one sulphate ion.

2. On mixing the solutions a double displacement reactions takes place.

Questions:

Question 1. What is meant by displacement reaction?
Answer: This type of reaction occurs when a more chemically active element replaces a less active element in its compound.
In simple words: A displacement reaction is when a more powerful chemical pushes out a weaker one to take its place.

Exam Tip: Always specify that reactivity is the driving force of this process. Include a simple general equation like \(A + BC \rightarrow AC + B\) to support your definition.

Question 2. Which is more reactive? Copper or iron and why?
Answer: Iron has a higher reactivity compared to copper because it is capable of displacing copper from its compounds, such as copper sulphate.
In simple words: Iron is more reactive than copper because it easily pushes copper out of copper sulphate to form iron sulphate.

Exam Tip: Remember that iron can displace copper, but copper cannot displace iron from ferrous sulphate.

Question 3. Which is more reactive? Copper or iron and why?
Answer: Iron is more chemically active than copper. We can observe this because iron successfully replaces copper in copper-containing solutions.
In simple words: Iron has more chemical power than copper, which is why it can take copper's place in reactions.

Exam Tip: Mentioning the displacement of copper from copper sulphate is a great practical observation to support your answer.

Question 4. Which is more reactive? Copper or iron and why?
Answer: Out of the two metals, iron is the more reactive one. This is demonstrated when iron displaces copper from copper-bearing salts during a single displacement reaction.
In simple words: Iron is highly reactive compared to copper, which allows it to strip copper of its sulphate group.

Exam Tip: In exams, writing the chemical equation \(Fe(s) + CuSO_4(aq) \rightarrow FeSO_4(aq) + Cu(s)\) perfectly illustrates why iron is more reactive.

Question 5. What is the colour of copper sulphate solution before the experiment?
Answer: Prior to starting the experiment, the copper sulphate solution possesses a distinct blue or peacock blue shade.
In simple words: Before the reaction, the copper sulphate solution has a bright blue color.

Exam Tip: State the color clearly as "blue" or "peacock blue". This color is due to the presence of hydrated \(Cu^{2+}\) ions.

Question 6. Which out of the following get coated on iron nail? What is its colour?
(Copper oxide, copper sulphate, copper sulphide, copper metal)
Answer: The substance that forms a coating on the iron nail is copper metal, which exhibits a reddish-brown color.
In simple words: The iron nail gets covered in pure copper metal, which looks like a reddish-brown layer.

Exam Tip: Make sure to identify "copper metal" (not copper oxide or sulphate) as the deposited substance, and specify "reddish-brown" as its color.

Question 7. Why it is not advised not to look directly at the flame of a burning Mg piece?
Answer: Looking straight at the burning magnesium is highly discouraged because the extremely bright, dazzling light emitted can harm your retina.
In simple words: Burning magnesium produces a blinding white light that can seriously hurt your eyes.

Exam Tip: Use terms like "dazzling white light" and "retinal damage" to explain the hazard clearly.

Question 8. What is the colour of barium chloride solution? What is the colour of barium sulphate precipitate?
Answer: The solution of barium chloride has no color (it is transparent), whereas the resulting barium sulphate precipitate is white.
In simple words: Barium chloride liquid looks like plain water, but the solid barium sulphate that forms is a chalky white color.

Exam Tip: Distinguish clearly between a "solution" (colourless liquid) and a "precipitate" (insoluble white solid).

Question 9. What is the colour nature of hydrated copper sulphate?
Answer: Hydrated copper sulphate is blue in color and possesses a crystalline structure.
In simple words: Hydrated copper sulphate is a bright blue crystal.

Exam Tip: Hydrated salts have a crystalline form because of the water of crystallization locked inside their grid structure.

Question 10. What is the colour of the residue when copper sulphate crystals are heated?
Answer: After heating the copper sulphate crystals, the residue (anhydrous copper sulphate) turns dull white.
In simple words: When you heat the blue crystals, they lose their water and turn into a white powder.

Exam Tip: Explain that the loss of water of crystallization turns the blue hydrated salt into a white anhydrous salt.

Question 11. What do you mean by water of crystallisation?
Answer: Water of crystallization refers to the specific number of water molecules that are chemically bound inside the crystal structure of a salt's single formula unit.
In simple words: Water of crystallization is the set amount of water trapped inside salt crystals that gives them their shape and color.

Exam Tip: Always mention that these water molecules are chemically combined in a fixed ratio, such as 5 molecules of water in \(CuSO_4\cdot5H_2O\).

Multiple choice type questions

Question 1. The colour of copper sulphate solution
(a) deep blue
(b) light green
(c) blue
(d) light yellow
Answer: (c) blue
In simple words: Copper sulphate dissolved in water creates a standard blue solution.

Exam Tip: The blue color of the solution arises from the hydrated copper ions (\(Cu^{2+}\)) present in the water.

Question 2. A 10 cm long magnesium ribbon is heated in a Bunsen burner flame till it catches fire.the flame produced in magnesium ribbon is
(a) Yellow
(b) dazzling white
(c) brick red
(d) silvery blue
Answer: (b) dazzling white
In simple words: Burning magnesium ribbon gives off a brilliant, blinding white light.

Exam Tip: This dazzling white flame is highly characteristic of burning magnesium and is accompanied by the formation of white magnesium oxide powder.

Question 3. The compound formed when zinc reacts with dil sulphuric acid is
(a) Zinc sulphite
(b) zinc sulphate
(c) zinc chloride
(d) zinc sulphide
Answer: (b) zinc sulphate
In simple words: Zinc displaces hydrogen from sulphuric acid to produce zinc sulphate salt and hydrogen gas.

Exam Tip: The chemical equation is \(Zn + H_2SO_4 \rightarrow ZnSO_4 + H_2\). This is a classic single displacement reaction.

Question 4. When solutions of sodium sulphate &barium chloride are mixed ,an insoluble solid settles at the bottom of the test tube.,its colour
(a) blue
(b) yellow
(c) white
(d) green
Answer: (c) white
In simple words: Mixing sodium sulphate and barium chloride forms a solid white precipitate of barium sulphate.

Exam Tip: This is a double displacement reaction, where the white precipitate is barium sulphate (\(BaSO_4\)) and the remaining solution contains sodium chloride (\(NaCl\)).

Question 5. While heatinng the crystals of copper sulphate the incorrect observation is:
(a) blue crystals change to white
(b) crackling sound
(c) water droplets along the sides of test tube
(d) liberates colourless gas
Answer: (d) liberates colourless gas
In simple words: Heating hydrated copper sulphate only drives off water vapor, which condenses on the tube. No gas is actually released.

Exam Tip: Copper sulphate loses its water of crystallization during heating, turning from blue to anhydrous white. This is a reversible physical/chemical transition, not a decomposition that releases a gas.

Question 6. Which one of the following is an example of physical change
(a) Burning of magnesium ribbon in air
(b) Burning of candle
(c) mixing Zinc &dil sulphuric acid
(d) boiling of water
Answer: (d) boiling of water
In simple words: Boiling water is a physical change because it only changes water from a liquid to steam without creating any new chemical substances.

Exam Tip: Physical changes are easily reversible and do not alter the chemical identity of the molecules, unlike chemical changes which produce new substances.

Question 7. Which one is true about the behaviour of magnesium oxide in presence of water
(a) It is basic
(b) It is acidic
(c) It is amphoteric
(d) It is neutral
Answer: (a) It is basic
In simple words: Magnesium oxide reacts with water to form magnesium hydroxide, which is a base and turns red litmus paper blue.

Exam Tip: Metal oxides are generally basic in nature, and they react with water to form basic metal hydroxides.

Question 8. The gas evolved during reaction of zinc with Dil.Sulphuric acid is:
(a) a supporter of combustion
(b) a potential fuel
(c) non – combustible
(d) soluble in water
Answer: (b) a potential fuel
In simple words: The reaction of zinc with acid releases hydrogen gas, which burns readily and is a very efficient fuel.

Exam Tip: Hydrogen gas burns with a popping sound in the presence of a flame, which confirms its highly combustible nature.

Question 9. What is observed when iron nails are added to copper sulphate solution?
(a) the solution becomes pale and eddish brown deposit is seen on the nails.
(b) the solution becomes colourless
(c) there is no reaction
(d) the solution changes to pale green and no change in the iron nails.
Answer: (a) the solution becomes pale and eddish brown deposit is seen on the nails.
In simple words: The blue copper sulphate solution fades to a light green because iron pushes the copper out of the solution, depositing it on the nails as a brown layer.

Exam Tip: This is a displacement reaction where iron, being more reactive, replaces copper to form ferrous sulphate.

Question 10. When magnesium is burnt in air,it produces magnesium oxide that appears to be like: 
(a) wood ash
(b) chalk powder
(c) table salt
(d) powdered sugar
Answer: (a) wood ash
In simple words: Burning magnesium ribbon leaves behind a soft, powdery white residue that looks like wood ash.

Exam Tip: Even though it is pure white magnesium oxide, the texture and appearance of the collected residue is classically compared to wood ash in practical exam questions.

Question 11. When Dil.Sulphuric acid is added to granulated zinc placed in a test tube, the observation made is:
(a) the surface of the metal turns shining
(b) the reaction mixture turns milky
(c) the odour of sulphur is observed
(d) the colourless and odourless gas evolves with bubbles.
Answer: (d) the colourless and odourless gas evolves with bubbles.
In simple words: You will see bubbles of hydrogen gas forming and rising as soon as the zinc starts reacting with the acid.

Exam Tip: Rapid effervescence (bubbling) is the primary visual indicator that a gas is being actively generated during a metal-acid reaction.

Question 12. The crystals of copper sulphate turn white on heating due to 
(a) loss of sulphate ions.
(b) loss of copper ions.
(c) loss of water of crystallisation.
(d) decomposition of copper sulphate.
Answer: (c) loss of water of crystallisation.
In simple words: Copper sulphate crystals lose the water molecules trapped inside them when heated, causing them to lose their blue color and turn white.

Exam Tip: The water molecules inside copper sulphate (\(CuSO_4 \cdot 5H_2O\)) are responsible for its blue color and crystalline shape; removing them makes it anhydrous and white.