1.5 Phase Changes

Explain why a cup of water (or soda) with ice cubes stays at $0 ° \text{C},$ even on a hot summer day.

Why does snow often remain even when daytime temperatures are higher than the freezing temperature?

A pressure cooker contains water and steam in equilibrium at a pressure greater than atmospheric pressure. How does this greater pressure increase cooking speed?

Can carbon dioxide be liquefied at room temperature ($20 ° \text{C}$)? If so, how? If not, why not? (See the phase diagram in the preceding problem.)

Heat transfer can cause temperature and phase changes. What else can cause these changes?

What is the temperature of ice right after it is formed by freezing water?

What effect does condensation on a glass of ice water have on the rate at which the ice melts? Will the condensation speed up the melting process or slow it down?

In winter, it is often warmer in San Francisco than in Sacramento, 150 km inland. In summer, it is nearly always hotter in Sacramento. Explain how the bodies of water surrounding San Francisco moderate its extreme temperatures.

In a physics classroom demonstration, an instructor inflates a balloon by mouth and then cools it in liquid nitrogen. When cold, the shrunken balloon has a small amount of light blue liquid in it, as well as some snow-like crystals. As it warms up, the liquid boils, and part of the crystals sublime, with some crystals lingering for a while and then producing a liquid. Identify the blue liquid and…

A bag containing $0 ° \text{C}$ ice is much more effective in absorbing energy than one containing the same amount of $0 ° \text{C}$ water. (a) How much heat transfer is necessary to raise the temperature of 0.800 kg of water from $0 ° \text{C}$ to $30.0 ° \text{C}$? (b) How much heat transfer is required to first melt 0.800 kg of $0 ° \text{C}$ ice and then raise its temperature to $30.0 ° \text{C}$? (c) Explain how your answer supports the contention that the ice is more effect…

Condensation on a glass of ice water causes the ice to melt faster than it would otherwise. If 8.00 g of vapor condense on a glass containing both water and 200 g of ice, how many grams of the ice will melt as a result? Assume no other heat transfer occurs. Use $L_{v}$ for water at $37 ° \text{C}$ as a better approximation than $L_{v}$ for water at $100 ° \text{C}$.)

On a certain dry sunny day, a swimming pool’s temperature would rise by $1.50 ° \text{C}$ if not for evaporation. What fraction of the water must evaporate to carry away precisely enough energy to keep the temperature constant?

In 1986, an enormous iceberg broke away from the Ross Ice Shelf in Antarctica. It was an approximately rectangular prism 160 km long, 40.0 km wide, and 250 m thick. (a) What is the mass of this iceberg, given that the density of ice is $917 \text{kg}/\text{m}^{3}$? (b) How much heat transfer (in joules) is needed to melt it? (c) How many years would it take sunlight alone to melt ice this thick, if the ice absorbs an averag…

(a) It is difficult to extinguish a fire on a crude oil tanker, because each liter of crude oil releases $2.80 \times 10^{7} \text{J}$ of energy when burned. To illustrate this difficulty, calculate the number of liters of water that must be expended to absorb the energy released by burning 1.00 L of crude oil, if the water’s temperature rises from $20.0 ° \text{C}$ to $100 ° \text{C}$, it boils, and the resulting steam’s temperature rises to $300 ° \text{C}$ at constan…

To help prevent frost damage, 4.00 kg of water at $0 ° \text{C}$ is sprayed onto a fruit tree. (a) How much heat transfer occurs as the water freezes? (b) How much would the temperature of the 200-kg tree decrease if this amount of heat transferred from the tree? Take the specific heat to be $3.35 \text{kJ}/\text{kg} \cdot ° \text{C}$, and assume that no phase change occurs in the tree.

A 0.0500-kg ice cube at $−30.0 ° \text{C}$ is placed in 0.400 kg of $35.0 - ° \text{C}$ water in a very well-insulated container. What is the final temperature?

Indigenous people sometimes cook in watertight baskets by placing hot rocks into water to bring it to a boil. What mass of $500 - ° \text{C}$ granite must be placed in 4.00 kg of $15.0 - ° \text{C}$ water to bring its temperature to $100 ° \text{C}$, if 0.0250 kg of water escapes as vapor from the initial sizzle? You may neglect the effects of the surroundings.