Q: If a chemical reaction releases 500 J of energy, how many calories is this?

$$\frac{500}{4.184} \approx 119.5 \text{ cal}$$

Q: A patient receives an IV solution that provides 2000 kJ of energy. How many kilocalories (Cal) is this? ($$1 ext{ cal} = 4.184 ext{ J})$$

$$\frac{2000 \text{ kJ} \times 1000}{4.184 \times 1000} = \frac{2,000,000}{4,184} \approx 478.3 \text{ Cal}$$

Q: A chemical process absorbs 250 cal of energy. How many joules is this?

$$250 \times 4.184 = 1,046 \text{ J}$$

Q: A student burns 500 Cal during exercise. How many joules of energy is this? ($$1 ext{ Cal} = 1 ext{ kcal} = 1000 ext{ cal}; 1 ext{ cal} = 4.184 ext{ J})$$

$$500 \times 1000 \times 4.184 = 2,092,000 \text{ J}$$

Q: Which conversion is correct for energy units?

$$1 \text{ cal} = 4.184 \text{ J}$$

Q: A chemical reaction in a laboratory releases 2.5 kJ of energy. How many calories is this? ($$1 ext{ cal} = 4.184 ext{ J})$$

$$\frac{2,500}{4.184} \approx 597.5 \text{ cal}$$

Question 1

Which of the following is the correct definition of a calorie (cal)?

Accepted Answer

The amount of energy required to raise the temperature of 1 gram of water by 1°C.

Question 2

A nutrition label states that a serving contains 150 Calories. How many joules of energy does this represent? (1 Calorie = 1 kcal; $$1 	ext{ cal} = 4.184 	ext{ J})$$

Accepted Answer

$$150 	imes 1000 	imes 4.184 = 627,600 	ext{ J}$$

Question 3

Which unit is most commonly used to express the energy content in food?

Accepted Answer

kilocalorie (Cal)

Question 4

If a chemical reaction releases 500 J of energy, how many calories is this?

Accepted Answer

$$\frac{500}{4.184} \approx 119.5 	ext{ cal}$$

Question 5

A patient receives an IV solution that provides 2000 kJ of energy. How many kilocalories (Cal) is this? ($$1 	ext{ cal} = 4.184 	ext{ J})$$

Accepted Answer

$$\frac{2000 	ext{ kJ} 	imes 1000}{4.184 	imes 1000} = \frac{2,000,000}{4,184} \approx 478.3 	ext{ Cal}$$

Question 6

Which of the following statements about joules and calories is correct?

Accepted Answer

A joule is a smaller unit of energy than a calorie.

Question 7

A chemical process absorbs 250 cal of energy. How many joules is this?

Accepted Answer

$$250 	imes 4.184 = 1,046 	ext{ J}$$

Question 8

Which of the following best describes the relationship between heat and energy?

Accepted Answer

Heat is a form of energy that is transferred due to a temperature difference.

Question 9

A student burns 500 Cal during exercise. How many joules of energy is this? ($$1 	ext{ Cal} = 1 	ext{ kcal} = 1000 	ext{ cal}; 1 	ext{ cal} = 4.184 	ext{ J})$$

Accepted Answer

$$500 	imes 1000 	imes 4.184 = 2,092,000 	ext{ J}$$

Question 10

Which conversion is correct for energy units?

Accepted Answer

$$1 	ext{ cal} = 4.184 	ext{ J}$$

Question 11

A chemical reaction in a laboratory releases 2.5 kJ of energy. How many calories is this? ($$1 	ext{ cal} = 4.184 	ext{ J})$$

Accepted Answer

$$\frac{2,500}{4.184} \approx 597.5 	ext{ cal}$$

Question 12

Which of the following is NOT a correct unit of energy?

Accepted Answer

gram (g)

Question 13

A nutritionist recommends a daily intake of 8,400 kJ. How many Calories (kcal) is this? ($$1 	ext{ cal} = 4.184 	ext{ J})$$

Accepted Answer

$$\frac{8,400 	imes 1000}{4,184 	imes 1000} = \frac{8,400}{4.184} \approx 2,008 	ext{ Cal}$$

Question 14

Which of the following scenarios best illustrates the concept of heat transfer?

Accepted Answer

A metal spoon becomes warm after being placed in hot soup.

Question 15

A sample absorbs 1,200 cal of heat. How many kilojoules is this? ($$1 	ext{ cal} = 4.184 	ext{ J})$$

Accepted Answer

$$1,200 	imes 4.184 = 5,020.8 	ext{ J}; \frac{5,020.8}{1,000} = 5.02 	ext{ kJ}$$

Question 16

Which of the following is the largest unit of energy?

Accepted Answer

kilocalorie (Cal)

Question 17

A chemical reaction requires 3,500 J of energy. How many kilocalories (Cal) is this? ($$1 	ext{ cal} = 4.184 	ext{ J})$$

Accepted Answer

$$\frac{3,500}{4.184 	imes 1,000} \approx 0.836 	ext{ Cal}$$

Question 18

Which of the following best explains why energy conversions are important in medical settings?

Accepted Answer

They allow accurate calculation of nutritional and metabolic energy requirements.

Question 19

A food item contains 250 Cal. How many kilojoules is this? ($$1 	ext{ Cal} = 1 	ext{ kcal} = 1,000 	ext{ cal}; 1 	ext{ cal} = 4.184 	ext{ J})$$

Accepted Answer

$$250 	imes 1,000 	imes 4.184 = 1,046,000 	ext{ J}; \frac{1,046,000}{1,000} = 1,046 	ext{ kJ}$$

Heat and Energy: Units and Conversions in GOB Chemistry

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