Activities

Activity 1: Action of Saliva on Starch

Aim: To investigate how saliva breaks down starch in food.

Materials:

• Two test tubes, boiled rice, water, and iodine solution.

Procedure:

1. Take boiled rice in test tube A.
2. Take chewed boiled rice (chewed for 30–60 seconds) in test tube B.
3. Add 3–4 mL of water to both.
4. Add 2–3 drops of iodine solution to each and observe the colour change.

Observation:

• Test tube A: Turns blue-black (indicating presence of starch).
• Test tube B: No blue-black colour (starch has been converted to sugar by saliva).

Conclusion: Saliva contains enzymes that begin the process of chemical digestion in the mouth.

---

Activity 2: Model of the Breathing Mechanism

Aim: To demonstrate how the movement of the diaphragm affects the lungs.

Materials:

• Plastic bottle, Y-shaped tube, two balloons, rubber sheet (or large balloon).

Procedure:

1. Remove the bottom of the bottle. Make a hole in the lid.
2. Insert the Y-tube through the lid with balloons attached to the forked ends.
3. Seal the bottom with a rubber sheet.
4. Pull the rubber sheet downwards and then release it upwards.

Observation:

• Pulling down (Inhalation): Balloons inflate.
• Releasing up (Exhalation): Balloons deflate.

Conclusion: The balloons represent the lungs and the rubber sheet represents the diaphragm. Its movement changes the pressure inside the "chest" (bottle), causing air to move in and out.

---

Activity 3: What do we breathe out?

Aim: To prove that exhaled air is rich in carbon dioxide.

Materials:

• Lime water, two test tubes, pichkari/syringe, and a straw.

Procedure:

1. Fill two test tubes (A and B) with equal amounts of fresh lime water.
2. Pass atmospheric air into tube A using a syringe.
3. Exhale air into tube B using a straw.

Observation: The lime water in test tube B turns milky much faster than in test tube A.

Conclusion: Exhaled air contains a higher percentage of carbon dioxide compared to the air we inhale.

---

Activity 4: Researching Animal Breathing Organs

Aim: To explore different structures used for gas exchange in various habitats.

Procedure:

1. Create a table to record the respiratory organs of different animals.
2. Research the following:
   • Fish: Gills (extract O2 from water).
   • Frogs: Lungs (on land) and moist Skin (in water).
   • Earthworms: Moist Skin.
   • Insects: Spiracles/Trachea (air tubes).
   • Birds/Mammals: Lungs.

Conclusion: Animals have adapted specialized structures to suit the gas exchange requirements of their specific environments.