To determine which metal will cool the fastest when dropped into the water, we need to consider the specific heat capacity of each metal. Metals with lower specific heat capacities will cool down faster because they can lose their heat more quickly.
Here are the specific heat capacities of the metals provided:
- Aluminum: 900 J kg⁻¹ K⁻¹
- Copper: 390 J kg⁻¹ K⁻¹
- Brass: 380 J kg⁻¹ K⁻¹
- Silver: 230 J kg⁻¹ K⁻¹
- Platinum: 130 J kg⁻¹ K⁻¹
Among the options given (Aluminum, Copper, Gold (not listed in the given data), and Platinum):
- Platinum (130 J kg⁻¹ K⁻¹) has the lowest specific heat capacity.
Therefore, Platinum will cool the fastest when dropped into the water.
The answer is D (platinum).