Explain the following observations: (A) Lightening is seen before thunder. (B) A boy holding a metal rod in fire feels heat in palm. (C) Clinical thermometer breaks when measuring boiling water temp.

Q1d. Explain the following observation:

(A) Lightening is seen before the thunder is heard.
Light travels at an extremely high speed ($3 \times 10^8 \text{ m/s}$), while sound travels much slower (approximately $343 \text{ m/s}$ in air). Therefore, the light from a lightning strike reaches our eyes almost instantaneously, but the sound (thunder) takes a noticeable amount of time to travel the same distance to our ears.

(B) A boy holding a long metal rod with one end in fire feels a burning sensation in the palm.
Metals are excellent thermal conductors. When one end of the metal rod is heated in the fire, the heat energy is efficiently transferred along the rod by conduction from the hotter end to the cooler end (the boy's palm). This transfer of thermal energy causes the burning sensation.

(C) A clinical thermometer breaks when used to measure the temperature of boiling water.
A clinical thermometer is specifically designed to measure human body temperature, typically having a narrow range of about $35^\circ C$ to $42^\circ C$. Boiling water is at $100^\circ C$. When exposed to such a high temperature, the liquid inside the thermometer (usually mercury or alcohol) expands excessively beyond the thermometer's calibrated range, causing the glass tube to shatter due to the immense pressure.

Q1e. Name the two methods of making magnets.

• Stroking method
• Electrical method (Electromagnetism)

Q3a. Name the planting material used in the propagation of each of the following crops:

(i) Plantain: Suckers

(ii) Banana: Suckers

(iii) Yam: Setts (or tubers)

(iv) Cassava: Stem cuttings

Q3b.

(i) In a laboratory experiment, a student was required to prepare 500 cm³ of 0.1 M solution of glucose (C₆H₁₂O₆). Calculate mass of the glucose the boy need. [C=12, H=1, O=16]