Class 10 Science Notes Chapter 1 (Chapter 1) – Lab Manual (English) Book

Detailed Notes with MCQs of the practical aspects covered in the initial experiments of your Class 10 Science Lab Manual. These experiments are fundamental for understanding chemical reactions and the nature of substances, and questions based on these often appear in various government exams.

Chapter 1: Chemical Reactions and Properties of Substances (Based on Initial Lab Manual Experiments)

This section covers key experiments typically performed at the beginning of the Class 10 curriculum, focusing on observing chemical changes, identifying reaction types, and determining the pH of various substances.

Experiment 1: Observing the Action of Water on Quicklime (Calcium Oxide)

• Aim: To observe the reaction between quicklime (CaO) and water and identify the type of reaction.
• Materials: Quicklime (Calcium Oxide), Water, Beaker, Dropper, Glass Rod, Touch.
• Procedure: Take a small amount of quicklime in a beaker. Slowly add water to it using a dropper. Stir gently. Carefully touch the outside of the beaker.
• Observations:
  • A hissing sound is produced.
  • The mixture starts to "boil" and steam may be produced.
  • The beaker becomes hot.
  • A white suspension called slaked lime (Calcium Hydroxide, Ca(OH)₂) is formed.
• Inference: Quicklime reacts vigorously with water to form slaked lime. Since heat is released, it is an exothermic reaction. It is also a combination reaction as two substances (CaO and H₂O) combine to form a single substance (Ca(OH)₂).
• Chemical Equation: CaO(s) + H₂O(l) → Ca(OH)₂(aq) + Heat
• Precautions: Add water slowly. Avoid touching the mixture directly as it is hot.

Experiment 2: Observing the Action of Heat on Ferrous Sulphate Crystals

• Aim: To study the decomposition reaction of ferrous sulphate.
• Materials: Ferrous sulphate crystals (FeSO₄·7H₂O), Boiling tube, Bunsen burner, Test tube holder.
• Procedure: Take a small amount of green ferrous sulphate crystals in a dry boiling tube. Heat the boiling tube gently over a Bunsen burner, observing any changes. Note the smell of any gas evolved (waft gently towards your nose).
• Observations:
  • The green colour of the crystals first changes to white (due to loss of water of crystallization).
  • On further heating, the white anhydrous ferrous sulphate decomposes to form a reddish-brown solid (Ferric Oxide, Fe₂O₃).
  • A colourless gas with the pungent smell of burning sulphur is evolved (mixture of SO₂ and SO₃).
• Inference: Ferrous sulphate decomposes upon heating. Since one substance breaks down into multiple simpler substances using heat, this is a thermal decomposition reaction.
• Chemical Equation:
  • FeSO₄·7H₂O(s) (Green) --Heat--> FeSO₄(s) (White) + 7H₂O(g)
  • 2FeSO₄(s) (White) --Strong Heat--> Fe₂O₃(s) (Reddish-brown) + SO₂(g) + SO₃(g)
• Precautions: Point the mouth of the boiling tube away from yourself and others. Do not inhale the gases directly; waft them gently. Use a test tube holder.

Experiment 3: Observing the Reaction between Iron Nails and Copper Sulphate Solution

• Aim: To study the displacement reaction between iron and copper sulphate solution.
• Materials: Copper sulphate solution (CuSO₄), Iron nails, Test tubes, Sandpaper, Thread.
• Procedure: Prepare a blue copper sulphate solution in a test tube. Clean two iron nails with sandpaper. Tie one nail with a thread and immerse it in the copper sulphate solution for about 15-20 minutes. Keep the other nail aside for comparison. Observe the changes in the colour of the solution and the iron nail.
• Observations:
  • The blue colour of the copper sulphate solution fades and gradually turns light green.
  • A reddish-brown coating (of copper metal) deposits on the surface of the iron nail immersed in the solution.
• Inference: Iron is more reactive than copper. It displaces copper from the copper sulphate solution, forming iron(II) sulphate (light green) and copper metal (reddish-brown). This is a displacement reaction.
• Chemical Equation: Fe(s) + CuSO₄(aq) (Blue) → FeSO₄(aq) (Light Green) + Cu(s) (Reddish-brown)
• Precautions: Clean the iron nails properly before the experiment.

Experiment 4: Observing the Reaction between Sodium Sulphate and Barium Chloride Solutions

• Aim: To study the double displacement reaction between sodium sulphate (Na₂SO₄) and barium chloride (BaCl₂).
• Materials: Sodium sulphate solution, Barium chloride solution, Test tubes.
• Procedure: Take a small amount of sodium sulphate solution in one test tube and barium chloride solution in another. Mix the two solutions.
• Observations:
  • A white, insoluble substance (precipitate) is formed immediately.
• Inference: Sodium sulphate reacts with barium chloride through an exchange of ions (Na⁺ with Ba²⁺, SO₄²⁻ with Cl⁻) to form a white precipitate of Barium Sulphate (BaSO₄) and Sodium Chloride (NaCl) which remains dissolved in the solution. Since there is an exchange of ions and a precipitate is formed, this is a double displacement reaction (specifically, a precipitation reaction).
• Chemical Equation: Na₂SO₄(aq) + BaCl₂(aq) → BaSO₄(s) (White Precipitate) + 2NaCl(aq)
• Precautions: Use clean test tubes.

Experiment 5: Determining the pH of Various Substances using pH Paper/Universal Indicator

• Aim: To find the approximate pH value of given samples (dilute HCl, dilute NaOH, dilute ethanoic acid, lemon juice, water, dilute sodium bicarbonate solution) using pH paper or universal indicator solution.
• Materials: pH paper strips or Universal Indicator solution, Dropper, White tile/Test tubes, Given samples.
• Procedure:
  • Using pH paper: Place a drop of the sample solution on a strip of pH paper using a clean dropper. Compare the colour developed on the pH paper with the standard pH colour chart provided.
  • Using Universal Indicator: Add a few drops of universal indicator solution to a small amount of the sample in a test tube. Observe the colour change and compare it with the pH colour chart.
• Observations (Typical Approximate pH values and Nature):
  • Dilute HCl: pH 1-2 (Red/Orange) - Strongly Acidic
  • Dilute NaOH: pH 13-14 (Dark Blue/Violet) - Strongly Basic
  • Dilute Ethanoic Acid (CH₃COOH): pH 3-4 (Orange/Yellow) - Weakly Acidic
  • Lemon Juice: pH 2-3 (Orange/Red) - Acidic
  • Water (Distilled): pH 7 (Green) - Neutral
  • Dilute Sodium Bicarbonate (NaHCO₃) solution: pH 8-9 (Greenish-Blue) - Weakly Basic
• Inference: pH paper/Universal Indicator changes colour depending on the hydrogen ion (H⁺) concentration of the solution, allowing us to determine if a substance is acidic (pH < 7), neutral (pH = 7), or basic (pH > 7).
• Precautions: Use a clean dropper for each sample. Do not dip the pH paper directly into the solution bottle. Compare colours immediately.

Multiple Choice Questions (MCQs)

1. When water is added to a lump of quicklime in a beaker, what observation(s) would you make?
   a) The beaker becomes cold and a clear solution is formed.
   b) A hissing sound is heard and the beaker becomes hot.
   c) No change is observed.
   d) A blue precipitate is formed.
   Answer: b) A hissing sound is heard and the beaker becomes hot.

2. A student heats ferrous sulphate crystals in a dry boiling tube. The colour change observed in the solid residue upon strong heating is:
   a) Green to White
   b) White to Yellow
   c) Green to Reddish-brown
   d) Green to Black
   Answer: c) Green to Reddish-brown (Initial change is green to white, but strong heating leads to reddish-brown Fe₂O₃)

3. The gas(es) evolved during the thermal decomposition of ferrous sulphate have a characteristic smell of:
   a) Rotten eggs
   b) Burning sulphur
   c) Ammonia
   d) Chlorine
   Answer: b) Burning sulphur (Due to SO₂ and SO₃)

4. When an iron nail is placed in a blue copper sulphate solution, the solution turns light green after some time. This happens because:
   a) Iron displaces copper from the solution.
   b) Copper displaces iron from the nail.
   c) A double displacement reaction occurs.
   d) The iron nail dissolves completely.
   Answer: a) Iron displaces copper from the solution.

5. Mixing aqueous solutions of barium chloride and sodium sulphate results in the formation of:
   a) A yellow precipitate
   b) A clear solution
   c) A white precipitate
   d) Evolution of a gas
   Answer: c) A white precipitate (Barium Sulphate)

6. The reaction BaCl₂(aq) + Na₂SO₄(aq) → BaSO₄(s) + 2NaCl(aq) is an example of a:
   a) Combination reaction
   b) Decomposition reaction
   c) Displacement reaction
   d) Double displacement reaction
   Answer: d) Double displacement reaction

7. A student tests a sample solution with universal indicator solution, and it turns dark blue. The sample solution is likely:
   a) Dilute Hydrochloric Acid
   b) Distilled Water
   c) Dilute Sodium Hydroxide solution
   d) Lemon Juice
   Answer: c) Dilute Sodium Hydroxide solution (Strongly basic)

8. Which of the following substances would turn pH paper yellowish-orange?
   a) Dilute NaOH solution
   b) Distilled Water
   c) Dilute Ethanoic Acid solution
   d) Dilute Sodium Bicarbonate solution
   Answer: c) Dilute Ethanoic Acid solution (Weakly acidic, pH around 3-4)

9. A safety precaution while performing the experiment of heating ferrous sulphate is:
   a) To add water to the crystals before heating.
   b) To point the mouth of the boiling tube towards yourself.
   c) To smell the evolved gas directly by bringing the tube close to the nose.
   d) To use a test tube holder and point the tube away from everyone.
   Answer: d) To use a test tube holder and point the tube away from everyone.

10. What type of reaction is primarily demonstrated when quicklime reacts with water?
    a) Decomposition and Endothermic
    b) Combination and Exothermic
    c) Displacement and Exothermic
    d) Double Displacement and Endothermic
    Answer: b) Combination and Exothermic

Make sure you understand the observations, inferences, and the balanced chemical equations for each of these experiments thoroughly. Good luck with your preparation!