Question

b. suppose a snack bar is burned in a calorimeter and heats 2,000 g water by 20 °c. how much heat energy was released? (hint: use the specific heat equation.) give your answer in both joules and calories.

Explanation:

Step1: Recall specific - heat formula

The specific - heat formula is $Q = mc\Delta T$, where $Q$ is the heat energy, $m$ is the mass of the substance, $c$ is the specific - heat capacity, and $\Delta T$ is the change in temperature. For water, $c_{water}=4.184\ J/g^{\circ}C$ and $1\ calorie = 4.184\ J$.

Step2: Calculate heat energy in joules

Given $m = 2000\ g$, $c = 4.184\ J/g^{\circ}C$, and $\Delta T=20^{\circ}C$.
$Q = mc\Delta T=2000\ g\times4.184\ J/g^{\circ}C\times20^{\circ}C = 167360\ J$.

Step3: Convert heat energy to calories

Since $1\ calorie = 4.184\ J$, then the heat energy in calories is $Q_{calories}=\frac{167360\ J}{4.184\ J/calorie}=40000\ calories$.

Answer:

The heat energy released is $167360\ J$ and $40000\ calories$.