Heat — Important Questions

Land heats up faster, hot air rises, and cool sea air moves in to replace it

Step 1: During the day, the sun heats the land faster than the sea. Step 2: The hot air above the land becomes less dense and rises upward. Step 3: This creates a low-pressure area above the land. Step 4: Cool air from over the sea (which is at higher pressure) moves towards the land to fill this low-pressure area. Step 5: This movement of cool air from sea to land is called sea breeze. This is a real-life example of convection in nature.

Radiation can travel through vacuum as electromagnetic waves

Step 1: Radiation is the transfer of heat in the form of electromagnetic waves. Step 2: Electromagnetic waves do not need any medium to travel — they can pass through a vacuum. Step 3: This is how heat from the Sun reaches the Earth, even through the vacuum of space. Step 4: Radiation travels at the speed of light, which is much faster than sound. Step 5: Like all heat transfer, radiation flows from hotter to cooler objects. This makes radiation unique compared to conduction and convection, which both need matter.

310.15 K

Step 1: The formula to convert Celsius to Kelvin is: K = C + 273.15. Step 2: Substitute the given value: K = 37 + 273.15. Step 3: K = 310.15 K. Step 4: 373.15 K is the boiling point of water (100°C), not 37°C. Step 5: Always remember that Kelvin temperature is always higher than the Celsius temperature by 273.15 units. This formula is very important and is used in many scientific calculations.

210,000 J

Step 1: Use the formula Q = m × C × ΔT. Step 2: Identify values: m = 1 kg, C = 4200 J/kg·K, ΔT = 70 - 20 = 50°C (or 50 K). Step 3: Substitute: Q = 1 × 4200 × 50. Step 4: Q = 210,000 J or 2.1 × 10⁵ J. Option 84,000 J is wrong (uses ΔT = 20 incorrectly). Option 4,200 J is only the heat for 1°C rise. Option 294,000 J uses ΔT = 70 without subtracting the initial temperature.