Problem 5 - Chemistry and Chemical Reactivity

Question

One food product has an energy content of 170 kcal per serving and another has \(280 \mathrm{kJ}\) per serving. Which food has a greater energy content per serving?

Step-by-Step Solution

Answer

The first food product (170 kcal per serving) has a greater energy content.

Step 1: Understand the Problem

We need to compare the energy content in calories (kcal) of two food products, one with 170 kcal per serving and the other with 280 kJ per serving.

Step 2: Convert Kilojoules to Kilocalories

To compare the energy content directly, we first need to convert the energy content given in kilojoules (kJ) into kilocalories (kcal). Use the conversion factor: 1 kcal = 4.184 kJ. Divide the kilojoules by 4.184 to get kilocalories.\[ \text{Energy in kcal} = \frac{280 \text{ kJ}}{4.184} \approx 66.92 \text{ kcal} \]

Step 3: Compare the Energy Contents

Now, compare the two energy contents: 170 kcal and approximately 66.92 kcal. The food product with 170 kcal clearly has a higher energy content than the one with approximately 66.92 kcal.

Key Concepts

Energy Content Comparison

In the world of nutrition, understanding the energy content of food is crucial. It helps you make informed choices based on your dietary needs. Energy content measures how much energy your body can gain from consuming a particular food. Typically, it's expressed in kilocalories (kcal) or kilojoules (kJ). Here's why comparing energy content is essential:

• If you're watching your weight, you might opt for lower energy foods to help manage your intake.
• For athletes or active individuals, choosing higher energy foods ensures they have enough fuel for activity.

So, when comparing two foods, like in our example with 170 kcal and 280 kJ per serving, converting the units into the same measurement is crucial. Only then can you accurately determine which has the higher energy content.

Kilojoules to Kilocalories Conversion

Understanding how to convert kilojoules to kilocalories is a handy skill. Different countries and products might use one unit over the other, so knowing the conversion can help you better understand food labels. The conversion factor you need is:

• 1 kilocalorie (kcal) equals 4.184 kilojoules (kJ).

To perform the conversion, divide the kilojoule number by 4.184. For instance, if a food item provides 280 kJ per serving, you calculate:\[\text{Energy in kcal} = \frac{280 \text{ kJ}}{4.184} \approx 66.92 \text{ kcal}\]This converted value allows you to easily compare it to another product listed in kilocalories. This step is vital for understanding energy content from different food products.

Calorimetry in Chemistry

Calorimetry is a fascinating field in chemistry that focuses on measuring the amount of heat released or absorbed during a chemical reaction. While it sounds technical, it's the base of understanding energy content in food. Here's how it works:

• A calorimeter, the tool for this process, measures the heat flow during reactions.
• In food, calorimetry results help calculate the calories or energy available.

Why does this matter? Because knowing the energy contributed by food components like carbohydrates, proteins, and fats helps you grasp nutritional content. With accurate calorimetry data, nutritional labels can provide energy content in kcal or kJ, ensuring better dietary decisions.