Question

Rice boils in about 10 minutes at sea level. What happens to the boiling time at mountains?

• A. Time increases due to lower boiling point
• B. Time decreases
• C. No change
• D. Cannot be predicted

Hint:

Remember the relationship: Higher Altitude (implies) Lower Atmospheric Pressure (implies) Lower Boiling Point (implies) Longer Cooking Time. This is why pressure cookers are very useful at high altitudes. They create an artificially high-pressure environment inside the pot, which raises the boiling point of water above 100°C and allows food to cook much faster.

Answer 1

The Correct Option is A

Step 1: Understanding the Question: The question asks how the time required to cook rice by boiling changes when moving from sea level to a high altitude, like a mountain.

Step 2: Key Formula or Approach: This question relates atmospheric pressure, altitude, and the boiling point of water. 1. Atmospheric pressure decreases as altitude increases. 2. The boiling point of a liquid is the temperature at which its vapor pressure equals the surrounding atmospheric pressure. 3. Cooking is a chemical process that is temperature-dependent. Higher temperatures lead to faster cooking.

Step 3: Detailed Explanation:
• At Sea Level: The atmospheric pressure is approximately 1 atm (101.3 kPa). Water boils at 100°C (212°F). Rice cooks at this temperature.
• At Mountains (High Altitude): The column of air above is shorter, so the atmospheric pressure is significantly lower. For example, at 2000 meters (approx. 6500 feet), the pressure is lower, and water boils at about 93°C.
• Effect on Cooking: Cooking food, such as boiling rice, involves chemical processes like the gelatinization of starch. These processes are driven by heat. Since the water on the mountain is boiling at a lower temperature (e.g., 93°C instead of 100°C), the rice is being cooked at a lower temperature.
• Conclusion: Because the cooking temperature is lower, the chemical reactions proceed more slowly. Therefore, it will take a longer time to cook the rice to the desired level of tenderness. The reason the time increases is directly linked to the fact that the boiling point of water is lower at high altitudes.

Step 4: Final Answer: At mountains, the atmospheric pressure is lower, which causes water to boil at a temperature below 100°C. Since the cooking temperature is lower, the time required to boil the rice increases.