Question

How many calories are there in 1 joule ?

• A. 0.23
• B. 0.19
• C. 0.21
• D. 0.25

Hint:

Remember the approximate relationship: 1 calorie = 4.2 joules. This is easy to remember and useful for quick estimations in exams. From this, 1 joule = 1/4.2 ≈ 0.24 calories.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Joules (J) and calories (cal) are both units of energy. The question asks for the conversion factor from joules to calories.

Step 2: Key Formula or Approach:
The standard conversion factor between calories and joules is:
\[ 1 \text{ calorie} \approx 4.184 \text{ joules} \] To find how many calories are in 1 joule, we need to calculate the reciprocal of this value.

Step 3: Detailed Explanation:
\[ 1 \text{ joule} = \frac{1}{4.184} \text{ calories} \] \[ 1 \text{ joule} \approx 0.2389 \text{ calories} \] Rounding this value to two decimal places gives 0.24. However, looking at the options, 0.23 is the closest available answer. The exact value depends on the definition of the calorie being used (e.g., thermochemical calorie vs. 15\(^\circ\)C calorie), but they are all very close to this value. The common approximation used is \(1 \text{ J} \approx 0.24 \text{ cal}\) or sometimes rounded to 0.23.

Step 4: Final Answer:
Based on the standard conversion, 1 joule is approximately 0.239 calories. The closest option is 0.23.