1.Examination of Animal and Plant Cells Using a Light Microscope

Aim

• Examine animal and plant cells using a light microscope.

• Produce labeled scientific diagrams based on observations.

Equipment

• Light microscope

• Microscope slide

• Cover slip

• Onion

• Forceps

• Mounted needle

• 0.1% methylene blue solution

• Iodine solution

• Cotton wool bud

• Scalpel

Method for Onion Cells (Plant Cells)

1. Preparation of the Slide:

   • Peel an epidermal layer from an onion using forceps.

   • Mount the tissue on a microscope slide with a drop of water using a pipette. Ensure the tissue lies flat.

2. Staining:

   • Add 2 drops of iodine solution to stain the cells.

3. Placing the Cover Slip:

   • Place the cover slip by positioning one edge on the slide first, then slowly lower the other side using a mounted needle to avoid air bubbles.

4. Microscopic Examination:

   • View the slide using a low power objective (10X).

   • Switch to a high power objective (40X) to identify cell structures.

5. Drawing:

   • Draw a labelled diagram of the observed cells, including:

     • Cytoplasm

     • Cell membrane

     • Nucleus

     • Cell wall

Method for Cheek Cells (Animal Cells)

1. Preparation of the Slide:

   • Place a drop of methylene blue on a glass slide.

   • Rub the inside of your cheek with a cotton bud.

   • Wipe the cotton bud in the methylene blue on the glass slide.

   • Dispose of the cotton bud in a beaker of disinfectant.

2. Placing the Cover Slip:

   • Place the cover slip by positioning one edge on the slide first, then slowly lower the other side using a mounted needle to avoid air bubbles.

3. Microscopic Examination:

   • View the slide using a low power objective (10X).

   • Switch to a high power objective (40X) to identify cell structures.

4. Drawing:

   • Draw a labelled diagram of the observed cells, including:

     • Cytoplasm

     • Cell membrane

     • Nucleus

Key Points

• Iodine Solution: Used to stain plant cells (onion cells) to make cell structures more visible.

• Methylene Blue Solution: Used to stain animal cells (cheek cells) to enhance visibility of cell structures.

• Cover Slip Technique: Essential to avoid air bubbles that can obscure the view of cells.

• Objective Lenses: Start with low power (10X) for general observation, then switch to high power (40X) for detailed examination.

• Labeled Drawings: Include all visible and identifiable structures based on staining and magnification.

General Tips

• Handle the microscope carefully to avoid damaging the lenses.

• Use fresh stains and slides to ensure clear visibility of cells.

• Ensure accurate positioning of the cover slip to prevent the formation of air bubbles, which can interfere with observations.

2. Energy Content of Food

Aim:

• Measure the energy content of food samples by heating and recording the change in water temperature.

Equipment

• 25 cm³ measuring cylinder

• Boiling tube

• Stand + clamp

• Mounted needle

• Thermometer

• Bunsen burner

• Heat-proof mat

• Sample of food

• Electronic balance

Method

1. Preparation:

   • Measure 20 cm³ of water using the measuring cylinder and pour it into the boiling tube.

   • Clamp the boiling tube at an angle for better heat exposure.

2. Initial Measurement:

   • Record the initial temperature of the water with the thermometer.

3. Weighing and Fixing:

   • Weigh the food sample using an electronic balance.

   • Fix the sample onto a mounted needle for combustion.

4. Combustion:

   • Light the food sample using a Bunsen flame and immediately hold it under the boiling tube to heat the water.

   • If the flame goes out, relight it and continue heating until the sample no longer lights.

5. Final Measurement:

   • Record the final temperature of the water once the food sample is fully combusted and the flame goes out.

6. Repeat:

   • Repeat the process for different food samples to gather multiple data sets.

7. Calculations:

   • Calculate the temperature rise in the water.

   • Calculate the energy value of the food sample using the formula: Energy (J)=mass of water (g)×4.2 (J K−1g−1)×temperature change (°C)mass of food sample (g)

Safety Precautions

• Avoid contact with burning food, dripping fat, and the Bunsen flame.

• Handle hot equipment and water with care.

• Wear eye protection and tie back long hair.

• Ensure good ventilation to avoid inhaling fumes.

• Avoid using nuts to prevent allergic reactions.

Controlled Variables

• Volume of water: Consistent at 20 cm³ for all tests.

• Angle of tilting: Fixed angle for the boiling tube for uniform heat exposure.

Sources of Error

• Heat loss to surroundings can reduce the accuracy of temperature measurement.

• Incomplete combustion of the food sample can lead to underestimation of the energy content.

General Tips

• Accurate Measurement: Use precise measurements for water volume and temperature.

• Monitor Combustion: Ensure complete combustion of the food sample for accurate energy content calculation.

• Minimize Heat Loss: Conduct the experiment quickly and in a controlled environment to reduce heat loss to the surroundings.

Note:

This method provides an estimation of the energy content of food, but results may vary due to environmental factors and experimental conditions.

3. Enzymes: Investigation into the Effect of Temperature on Enzyme Action

Aim

• Investigate how temperature affects the activity of amylase, an enzyme that catalyzes the breakdown of starch into maltose.

Equipment

• Test tubes

• Test tube rack

• Water baths (electrical or Bunsen burners and beakers)

• Spotting tiles

• 5 cm³ measuring cylinder

• Syringes or 10 cm³ measuring cylinders

• Glass rod

• Stopwatch

• Starch solution

• 10% amylase solution

• Iodine solution

• Thermometer

Method

1. Preparation:

   • Label each well on a spotting tile with times (e.g., 0, 1, 2, etc.) and add a drop of iodine solution to each well.

2. Temperature Setup:

   • Prepare water baths at various temperatures: 20°C, 30°C, 40°C, 50°C, and 60°C.

3. Equilibration:

   • Transfer 3 cm³ of amylase solution into a labelled test tube and place it in the water bath.

   • Transfer 3 cm³ of starch solution into another labelled test tube and place it in the same water bath.

   • Allow a few minutes for the solutions to reach the water bath temperature.

4. Reaction Initiation:

   • Mix the amylase and starch solutions together in one of the test tubes and start the timer immediately.

   • Use a glass rod to transfer a drop of the mixture to the well labelled ‘0’ on the tile.

5. Testing:

   • Repeat step 4 every minute, using the glass rod to transfer a drop to the corresponding well on the tile.

   • Rinse the glass rod between each transfer to avoid contamination.

6. Observation:

   • Continue testing until the iodine solution remains brown and does not turn blue-black, indicating that the starch has been fully broken down.

7. Recording:

   • Record the time taken for the iodine solution to remain brown in a table for each temperature.

8. Rate Calculation:

   • Calculate the rate of enzyme reaction using the formula: Rate of reaction=1/time taken for iodine to remain brown

   • Repetition: Repeat steps 2-8 for each temperature (20°C, 30°C, 40°C, 50°C, and 60°C).

9. Graphing:

• Plot a graph of the rate of enzyme reaction against temperature.

4. Photosynthesis: Investigation into the Effect of Light on the Rate of Photosynthesis

Aim

• Investigate how light affects the rate of photosynthesis by measuring the production rate of oxygen bubbles in pondweed (Elodea).

Equipment

• 250 cm³ beaker

• Boiling tube

• Freshly cut 10 cm piece of pondweed (Elodea)

• Light source (lamp)

• Meter ruler

• Test tube rack

• Stopwatch

• Sodium hydrogen carbonate powder

• Glass rod

• Stand and clamp

• Filter funnel

• Plasticine

Method

1. Setup:

   • Place the freshly cut pondweed in a 250 cm³ beaker with 200 cm³ of water, ensuring the cut end is at the top.

   • Gently push the pondweed down with a glass rod to position it properly.

2. Add Sodium Hydrogen Carbonate:

   • Add a spatula of sodium hydrogen carbonate powder to the beaker to provide a source of carbon dioxide.

3. Position the Filter Funnel:

   • Invert a filter funnel over the pondweed, ensuring it is securely in place with plasticine to prevent movement.

4. Set Up Boiling Tube:

   • Fill a boiling tube completely with water and place it over the narrow end of the funnel underwater.

   • Secure the boiling tube in place using a stand and clamp.

5. Position Light Source:

   • Place a light source (lamp) 5 cm away from the pondweed, using a meter ruler to measure the distance accurately.

6. Measure Oxygen Production:

   • Start the stopwatch and count the number of oxygen bubbles produced in one minute.

7. Record Data:

   • Record the number of bubbles produced in a table. Perform three trials for accuracy.

8. Repeat at Different Distances:

   • Move the lamp to a new distance (10 cm, 15 cm, 20 cm, 25 cm, 30 cm) from the pondweed.

   • Repeat steps 1-7 for each new distance.

9. Graphing:

   • Plot a graph with the rate of photosynthesis (number of bubbles per minute) on the y-axis and the distance from the light source on the x-axis.

5.Transpiration: Investigation into Factors Affecting Transpiration

Aim

• Investigate how different environmental factors affect the rate of transpiration in plants.

Equipment

• Potometer

• Leafy shoot

• Plastic bag

• Fan

• Water bath

• Lamp

• Vaseline

• Beaker of water

Method

1. Set Up Potometer:

   • Immerse the potometer in a beaker of water.

   • Cut the leafy shoot underwater to prevent air bubbles from entering the vascular tissues and insert it into the potometer. Ensure the leaves remain above the water.

2. Seal Gaps:

   • Use vaseline to seal any gaps in the potometer underwater, ensuring it is airtight.

3. Prepare Leafy Shoot:

   • Dab the leaves gently to remove excess water if present.

4. Set Up Environmental Factors:

   • Temperature: Control using a temperature-controlled room or immerse the potometer in a thermostatically controlled water bath.

   • Humidity: Wrap the shoot in a plastic bag.

   • Wind Speed: Set up a fan at various speeds.

   • Light Intensity: Position a lamp at different distances from the shoot.

   • Surface Area: Remove leaves one by one to vary the surface area.

5. Form Air Bubble:

   • Remove the capillary tube from the water to allow an air bubble to form, then return it to the beaker.

6. Start Experiment:

   • Wait for the air bubble to reach the start of the scale and start timing.

7. Measure Transpiration:

   • Leave the apparatus for 30 minutes.

   • Record the final position of the air bubble and calculate the distance moved.

8. Calculate Water Absorption:

   • Calculate the volume of water absorbed by the plant during the period.

9. Repeat Measurements:

   • Repeat steps 1-9 two more times and calculate a mean value.

10. Change Factors:

    • Repeat steps 1-10, altering the factor being investigated at fixed intervals.

11. Graph Results:

    • Plot a graph with the environmental factor on the x-axis and the mean water loss per minute on the y-axis