Question

the juice loses about 15,000 j of energy to the cubes. what is the heat change for the aluminum?
$q_{juice} = -15,000$ j
$q_{al} = ?$ j

• -15,000 j
• -15 j
• +15 j
• +15,000 j

Explanation:

Step1: Recall Energy Transfer Principle

In a closed system (assuming the juice and aluminum cubes are a closed system here), the energy lost by one substance is gained by another. So, the heat lost by the juice ($q_{\text{juice}}$) is equal in magnitude but opposite in sign to the heat gained by the aluminum ($q_{\text{Al}}$).

Step2: Apply the Principle to Given Values

We know $q_{\text{juice}} = - 15000\ \text{J}$ (negative because it loses energy). Then, $q_{\text{Al}}=-q_{\text{juice}}$. Substituting the value of $q_{\text{juice}}$, we get $q_{\text{Al}}=-(- 15000\ \text{J}) = + 15000\ \text{J}$.

Answer:

+15,000 J