**Statement:**

A petrol is a liquid and it does not mix with water. However, when calcium chloride (CaCl4) is added to petrol, it forms a little liquid layer on top of the water.

**Explanation:**

Petrol is a non-polar liquid, meaning it does not have an electrical charge and does not mix with water, which is a polar liquid. When petrol is added to water, it forms two separate layers with petrol on top and water at the bottom. This is because the intermolecular forces between petrol molecules are stronger than the forces between petrol and water molecules.

**Formation of a little liquid layer with CaCl4:**

When calcium chloride (CaCl4) is added to petrol, it forms a little liquid layer on top of the water. This occurs because calcium chloride is a hygroscopic substance, meaning it has a strong affinity for water and can absorb moisture from the surroundings. When CaCl4 is added to petrol, it absorbs moisture from the air and forms a solution with water, which then separates from the petrol and forms a separate layer.

**Sublimation of naphthalene, camphor, and iodine:**

Naphthalene, camphor, and iodine are substances that undergo sublimation. Sublimation is the process in which a solid directly changes into a gas without passing through the liquid state.

- Naphthalene: Naphthalene is a white solid that sublimes when heated. It directly changes from a solid to a gas when heated, without melting into a liquid. This is because the intermolecular forces between naphthalene molecules are relatively weak, allowing the solid to easily vaporize.

- Camphor: Camphor is also a solid that sublimes when heated. It has a characteristic strong odor and evaporates readily at room temperature. When heated, camphor directly changes from a solid to a gas without going through the liquid state.

- Iodine: Iodine is a dark gray crystalline solid that sublimes when heated. It directly changes into a purple vapor without melting into a liquid. The sublimation point of iodine is relatively low, which allows it to easily undergo sublimation even at room temperature.

**Sublimation of NH4Cl:**

Ammonium chloride (NH4Cl) is a compound that does not undergo sublimation. Instead, it decomposes when heated. The decomposition of NH4Cl results in the release of ammonia gas (NH3) and hydrogen chloride gas (HCl). This process is known as thermal decomposition and is different from sublimation.