Q5.16
The nail is an excellent conductor, and transports heat directly to the interior of the potato. Without the nail, the potato center warms slowly as heat gradually is conducted from the exterior to the center.
Q5.25
Water would only be a little less effective in fighting fires. Most of the heat that water absorbs in firefighting goes to boiling 100 degree C water to steam, not warming room temperature water to the boiling point. Thus water would still be more than 80% as effective in fighting fires.
However, the water in your engine never boils, as long as everything is working correctly. It stays as liquid water. Therefore, the lowering of the specific heat capacity to one-fifth of normal would make it tremendously less effective in cooling your engine. It could remove only one-fifth the heat for the same temperature rise.
P5.10
P5.11
P5.13
P5.16
