Testing food samples for carbohydrates, proteins and fats

 

The food sample was tested for carbohydrates, proteins, and fats. The appearance of a blue-black colour with iodine confirmed the presence of starch. A reddish color in milk using milans reagent indicated the presence of proteins. Ethanol emulsion test confirmed the presence of fats.

The experiment successfully identified the major nutrients present in the given food sample using standard food tests. The colour changes and observations confirmed the presence or absence of carbohydrates, proteins, and fats.

Class VIII Activity on building the structure of atom

 

Learners of Class VIII performed activity of making model of structure of atom. Learners have been given five elements on the board. They have to calculate the number of protons, neutrons and electrons in each element with the help of atomic number and mass number. Then they took three different coloured beads or pulses representing electron, proton, neutron. Using compass and pencil they made shells in their activity file. Then they pasted correct counted no. of sub atomic particles. The activity makes them clear about the structure of atom.

Investigating osmosis in potato strips

 

Osmosis is the movement of water molecules from a region of higher water concentration (dilute solution) to a region of lower water concentration (concentrated solution) through a selectively permeable membrane.

Potato cells have partially permeable membranes. Depending on the concentration of the surrounding salt solution, water moves into or out of the potato cells.

Materials Required

• Fresh potato

• cork borer

• Ruler

• Weighing balance

• 5 beakers/test tubes

• Salt (NaCl)

• Water

• Tissue paper

• Labels

Procedure

1. Cut fifteen potato strips of equal length and thickness (e.g., 2 cm )

2. Measure and record the initial length of each strip.

3. Prepare salt solutions of different concentrations:

• 0 g/50 ml
• 1 g/50 ml
• 2g/50 ml
• 3g/50ml
• 4g/50 ml

4. Label the beakers and pour equal volumes of each solution into them.

5. Place three potato strip into each beaker.

6. Leave them for about 20 minutes.

7. Remove the strips, gently blot them dry with tissue paper.

8. Measure and record the final length of each strip.

The experiment demonstrates that osmosis causes water to move across the potato cell membrane depending on the concentration of the surrounding salt solution. Water enters the cells in dilute solutions and leaves the cells in concentrated solutions.

Class VIII Law of conservation of energy through simple pendulum

 

As a part of discussion of Energy, In a simple pendulum with no friction, mechanical energy is conserved.  Total mechanical energy is a combination of kinetic energy and gravitational potential energy.   As the pendulum swings back and forth, there is a constant exchange between kinetic energy and gravitational potential energy. At its starting point, all of the swing’s mechanical energy is potential energy. It has no kinetic energy because it’s not moving.

As the swing moves downward, some of its potential energy changes into kinetic energy.

At its bottommost point, the swing’s kinetic energy is at its maximum because it is moving at its fastest speed. Its potential energy is at a minimum because the swing is at its lowest point.

The learners used the pendulum and observed the rotation of pendulum to get the concept of Energy conservation.