Basic Science JSS 3 Parts of the Eyes

1a. Define Chemical Formula (2 marks)

A chemical formula is a symbolic way of showing the elements in a substance and the number of atoms of each element.
Example: H₂O (water), CO₂ (carbon dioxide).

1b. Mention the main subatomic particles of an atom (3 marks)

The main subatomic particles are:

1. Protons (p⁺) – positively charged, found in the nucleus.
2. Neutrons (n⁰) – neutral (no charge), found in the nucleus.
3. Electrons (e⁻) – negatively charged, orbit around the nucleus.

1c. Explain a Chemical Reaction and a Catalyst (4 marks)

Chemical Reaction:
A chemical reaction is a process in which substances (reactants) change to form new substances (products). Bonds are broken and formed.
Example:
2H₂ + O₂ → 2H₂O

Catalyst:
A catalyst is a substance that speeds up a chemical reaction without being used up in the reaction.
Example: Enzymes in digestion, manganese dioxide (MnO₂) in the decomposition of hydrogen peroxide.

2a. State the Law of Conservation of Mass (4 marks)

The Law of Conservation of Mass states:
“Mass cannot be created or destroyed in a chemical reaction; the total mass of reactants equals the total mass of products.”

2b. Mention the divisions of the brain (3 marks)

The brain is divided into:

1. Forebrain – responsible for thinking, memory, and voluntary actions.
2. Midbrain – controls vision, hearing, and motor movements.
3. Hindbrain – controls balance, coordination, and vital functions like breathing.

2c. Mention any three parts of the eye (3 marks)

1. Cornea – transparent layer at the front of the eye.
2. Lens – focuses light onto the retina.
3. Retina – contains cells that detect light and send signals to the brain.

3a. Draw a well-labelled diagram of the eye (marks vary)

Labels to include:

• Cornea
• Iris
• Pupil
• Lens
• Retina
• Optic Nerve
• Ciliary Body
• Sclera
• Aqueous Humor

(For Word/Notebook, a neat circular diagram with arrows pointing to each part is ideal.)

3b. Describe the parts of the eye (brief description)

1. Cornea – protects the eye and helps focus light.
2. Iris – the colored part, controls the size of the pupil.
3. Pupil – black circular opening that allows light in.
4. Lens – transparent structure that focuses light on the retina.
5. Retina – layer at the back of the eye with light-sensitive cells (rods and cones).
6. Optic Nerve – transmits visual information from the retina to the brain.
7. Ciliary Body – helps the lens change shape for focusing.
8. Sclera – tough outer layer that protects the eye.
9. Aqueous Humor – fluid between the cornea and lens, nourishes the eye.