91Ó°ÊÓ

When you skate on ice, a thin liquid film forms under the skate; why?

At higher elevations, as in mountains, air pressure is lower; how does that affect the cooking of food?

Can a vapor exist below the triple point temperature?

Ice cubes can disappear and food can dry out (freezer burn) in the freezer. What happens to the ice?

Locate the state of \(\mathrm{R}-410 \mathrm{~A}\) at \(500 \mathrm{kPa},-10^{\circ} \mathrm{C}\). Indicate in both the \(P-v\) and \(T-v\) diagrams the location of the nearest states listed in Table B. 4 .

How does a constant- \(\nu\) process for an ideal gas appear in a \(P-T\) diagram?

Give the missing property of \(P-v-T\) and \(x\) for water at a. \(10 \mathrm{MPa}, 0.003 \mathrm{~m}^{3} / \mathrm{kg}\) b. \(1 \mathrm{MPa}, 190^{\circ} \mathrm{C}\) c. \(200^{\circ} \mathrm{C}, 0.1 \mathrm{~m}^{3} / \mathrm{kg}\) d. \(10 \mathrm{kPa}, 10^{\circ} \mathrm{C}\)

A constant pressure piston/cylinder has water at \(1000 \mathrm{kPa}\) with a quality of \(25 \%\). Its temperature is lowered \(20^{\circ} \mathrm{C}\). What is the new quality and specific volume?

Saturated vapor \(\mathrm{R}-410 \mathrm{~A}\) at \(60^{\circ} \mathrm{C}\) has its pressure decreased to increase the volume by \(10 \%\) while keeping the temperature constant. To what pressure should it be expanded?

A pressure cooker has the lid screwed on tight. A small opening with \(A=5 \mathrm{~mm}^{2}\) is covered with a petcock that can be lifted to let steam escape. How much mass should the petcock have to allow boiling at \(120^{\circ} \mathrm{C}\) with an outside atmosphere at \(101.3 \mathrm{kPa}\) ?