Science Month Activity Class VII Innovate X

 

Making salt and observing neutralisation reaction

 

Observing Neutralisation

1. Take 10 mL of dilute sodium hydroxide solution in a beaker.
2. Add 2–3 drops of universal indicator.
3. Observe the colour of the solution. It turns pink.
4. Using a dropper, slowly add dilute hydrochloric acid while stirring.
5. Continue adding the acid until the pink colour just disappears.
6. Record the observations.

Result

Sodium chloride salt was prepared by reacting hydrochloric acid with sodium hydroxide.

The experiment demonstrates that an acid reacts with an alkali to form salt and water.

Making Salt

1. Take 20 mL of dilute sulfuric acid in a beaker.
2. Gently warm the acid using a water bath.
3. Add a small amount of black copper(II) oxide.
4. Stir continuously until the black powder begins to dissolve.
5. Continue adding copper oxide until some remains undissolved.
6. Filter the mixture to remove excess copper oxide.
7. Collect the blue copper sulfate solution.
8. Gently heat the filtrate using a water bath to evaporate some water.
9. Allow the concentrated solution to cool.
10. Observe the formation of blue copper sulfate crystals.
11. Observe the formation of sodium chloride crystals as the water evaporates.

Result

Blue crystals of copper sulfate were obtained through a neutralisation reaction between copper(II) oxide and sulfuric acid.

Conclusion

Copper oxide is a basic oxide that reacts with sulfuric acid to produce copper sulfate and water.

Acid + Metal Oxide → Salt + Water

Investigating law of reflection and refraction

 

Experiment A: Investigating Reflection Using a Plane Mirror

Procedure

1. Place a plane mirror vertically on a sheet of white paper.
2. Draw a straight line along the reflecting surface of the mirror.
3. Draw a normal at 90° to the mirror surface.
4. Direct a narrow beam of light towards the mirror at an angle.
5. Mark the paths of the incident and reflected rays.
6. Measure the angle of incidence (i) and angle of reflection (r) using a protractor.
7. Repeat the experiment for different angles of incidence.
8. Record the observations in a table.

Expected Observation

The angle of incidence is equal to the angle of reflection.

Conclusion

The experiment verifies the laws of reflection:

1. The angle of incidence is equal to the angle of reflection.
2. The incident ray, reflected ray and normal lie in the same plane.

Investigating Refraction Using a Rectangular Glass Slab

Procedure

1. Place a rectangular glass slab on a sheet of white paper.
2. Trace its outline using a pencil.
3. Draw a normal at the point where the incident ray enters the glass slab.
4. Direct a narrow beam of light towards the glass slab at an angle.
5. Observe the change in direction of the light ray as it enters the glass.
6. Mark the path of the refracted ray inside the glass and the emergent ray leaving the slab.
7. Measure the angle of incidence and angle of refraction.
8. Repeat the experiment using different angles of incidence.
9. Record the observations in a table.

Expected Observations

• When light travels from air into glass, it bends towards the normal.
• When light travels from glass into air, it bends away from the normal.
• The emergent ray is parallel to the incident ray when the opposite faces of the glass slab are parallel.
• The emergent ray is laterally displaced from the original path.

Conclusion

The experiment demonstrates that light changes direction when it passes from one transparent medium to another because its speed changes.

This phenomenon is known as refraction of light.