PHYS 104 Chapter 15 homework

Which has more kinetic energy: a molecule in a gram of ice water or a molecule in a gram of steam?

A molecule in a gram of steam has considerably more kinetic energy, as evidenced by its higher temperature

Does substance that cools off quickly have a high or a low specific heat capacity?

A substance that cools quickly has a low specific heat capacity

Northeastern Canada and much of Europe receive about the same amount of sunlight per unit area. Why, then, is Europe generally warmer the winter

Internal energy is carried in the Gulf Stream from tropical waters to the North Atlantic where it warms the otherwise cold climate

Distinguish between a calorie and a joule

One calorie is equivalent to 4.19 joules

If you wish to warm 50 kg of water by 20 C for your bath, show that the amount of heat needed is 1000 kcal (1000 Cal). then show that this is equivalent to about 4200 kJ

Each kg requires 1 kcal for each degree change, so 50 kg needs 50 kcal for each degree change. Twenty degrees means twenty times 50 kcal, which is 1000 kcal. By formula: Q = cm∆T = (1 cal/g⋅°C)(50,000 g)(20°C) = 1000 kcal. We can convert this to joules knowing that 4.19 J = 1 cal. In joules this quantity of heat is 4190 kJ (about 4200 kJ)

the specific heat capacity of steel is 450 J/kgC. Show that the amount of heat needed to raise the temperature of a 10 kg piece of steel from 0C to 100C is 450,000 J. How does this compare with the heat needed to raise the temperature of the same mass of water through the same temperature difference?

Raising the temperature of 10 kg of steel by one degree takes 10kg(450 J/kg ⋅°C) = 4500 J. Raising it through 100 degrees takes 100 times as much, or 450,000 J. By formula, Q = cm∆T = (450 J/kg ⋅°C)(10 kg)(100°C) = 450,000 J. Heating 10 kg of water through the same temperature difference takes 1,000,000 calories, which is [1,000,000 cal(4.18 J/cal)] = 41,800,000 J, nearly ten times that for the piece of steel—another reminder that water has a large specific heat capacity.

Under what conditions can we say that "a thermometer measures its own temperature?"

The necessary condition is thermal equilibrium, for only then will the thermometer and thing being measured have the same temperature

Why does a bimetallic strip bend with changes in temperature?

The strip bends due to its two metals with different rates of thermal expansion

A certain quantity of heat is supplied to both a kilogram of water and a kilogram of iron. Which undergoes the greater change in temperature?

The substance with the smaller specific heat capacity, iron, undergoes the greater change in temperature

What are the temperatures for freezing water on the Celsius and Fahrenheit scales? For boiling water?

Water freezes at 0°C and 32°F, and boils at 100°C and 212°F

Why is the temperature fairly constant for landmasses surrounded by large bodies of water?

Water has a moderating effect, slow to warm and slow to cool

An old method for breaking boulders was to put them in a hot fire and then to douse them with cold water. Why would this fracture the boulders?

When doused, the outer part of the boulders cooled while the insides were still hot. This caused a difference in contraction, which fractured the boulders

Three blocks of metal at the same temperature are placed on a hot stove. their specific heat capacities are listed below. Rank them from greatest to least in how quickly each warms up a. steel 450 J/kgC b. aluminum 910 J/kgC c. copper 390 J/kgC

c, a, b