[b] About how many joules of heat energy does it take to cook a pound of pasta? Use reasonable estimates of pasta cooking methods as well as the heat capacity of water. (It might be useful to know that the mass of a pound of pasta is about 0.45 kg, and that cooked pasta has twice the mass of uncooked pasta because it has absorbed its mass in water. Or it might not.)

[b] About how many joules of heat energy does it take to cook a pound of pasta? Use reasonable estimates of pasta cooking methods as well as the heat capacity of water. (It might be useful to know that the mass of a pound of pasta is about 0.45 kg, and that cooked pasta has twice the mass of uncooked pasta because it has absorbed its mass in water. Or it might not.)

University Physics Volume 2

18th Edition

ISBN:9781938168161

Author:OpenStax

Publisher:OpenStax

Chapter3: The First Law Of Thermodynamics

Section: Chapter Questions

Problem 66P: One of a dilute diatomic gas occupying a volume of 10.00 L expands against a constant pressure of...

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One of a dilute diatomic gas occupying a volume of 10.00 L expands against a constant pressure of 2.000 atm when it is slowly heated. If the temperature of the gas rises by 10.00 K and 400.0 J of heat are added in the process, what is its final volume?
In an air conditioner, 12.65 MJ of heat transfer occurs from a cold environment in 1.00 h. (a) What mass of ice melting would involve the same heat transfer? (b) How many hours of operation would be equivalent to melting 900 kg ofice? (c) If ice costs 20 cents per kg, do you think the air conditioner could be operated more cheaply than by simply using ice? Describe in detail how you evaluate the relative costs.
If the air temperature isthe same as the temperature of your skin (about 30°C), your body cannotget rid of heat by transferring it to the air. In that case, it gets ridof the heat by evaporating water (sweat). During bicycling, a typical70 kg person’s body produces energy at a rate of about 500 W due tometabolism, 80% of which is converted to heat. (a) How many kilogramsof water must the person’s body evaporate in an hour to get ridof this heat? The heat of vaporization of water at body temperature is2.42 * 10^6 J/kg. (b) The evaporated water must, of course, be replenished,or the person will dehydrate. How many 750 mL bottles of watermust the bicyclist drink per hour to replenish the lost water? (Recall thatthe mass of a liter of water is 1.0 kg.)
Suppose 8.50 x 10° J of energy are transferred to 1.79 kg of ice at 0°C. The latent heat of fusion and specific heat of water are L; = 3.33 x 10° J/kg and c = 4186 (kg · °C) HINT (a) Calculate the energy (in J) required to melt all the ice into liquid water. (Enter your answer to at least three significant figures.) (b) How much energy (in J) remains to raise the temperature of the liquid water? (Enter your answer to at least three significant figures.) (c) Determine the final temperature of the liquid water in Celsius. °C
Calculate how many kg an 80 kg person who replaces 30 minutes/day will lose in a yearin front of the TV for 30 minutes of brisk walking. Use the following data: Expensecalories during the walk (5 km/h) = 0.063 kcal/kg/minute. Calorie expenditure watching TV = 0.028kcal/kg/min. 1 kg of weight lost is equivalent to about 7000 kcal.
Digestingfat produces 9.3 food calories per gram of fat, and typically 80%of this energy goes to heat when metabolized. (One food calorie is1000 calories and therefore equals 4186 J.) The body then movesall this heat to the surface by a combination of thermal conductivityand motion of the blood. The internal temperature of the body(where digestion occurs) is normally 37C, and the surface is usuallyabout 30C. By how much do the digestion and metabolism of a2.50 g pat of butter change your body’s entropy? Does it increase ordecrease?
(a) If the heat capacity of an electric jug is 500 J °c1, how much heat energy does it absorb when heating 1.5 L of water, specific heat 4200 J kg1 0c1, from 20°C to 95°C?
The human body, while at rest, produces heat energy at a rate of about 117 W. How much sweat (in g) must evaporate every minute from their skin to carry away this excess energy? (Note: according to your book, the latent heat of vaporization of water at body temperature is 2.43 * 106 J/kg).
A gasoline engine has a power output of 200 kW. (Note that 1 Watt = 1 Joule/s). Its thermal efficiency is 32%. (a) How much heat must be supplied per second? (b) How much heat is discarded by the engine per second?
(a) The specific heat of copper is 92.5 Jkg-1°C¯1. A copper with mass of 250 g was heated to 100 °C. Ah Beng makes a conclusion that the copper now contains 2312500 J of heat. Point out the mistakes in this conclusion and correct them.
Heat of combustion of gasoline is 50 MJ/kg. What mass of the gasoline is needed to release 10 MJ of heat? /Give the answer in [g] /
How much energy is required to change 2 kg of ice cube to steam. (Specific heat of water = 4200 J kg-1 °C1, latent heat of fusion = 334 kJ kg', latent heat of vaporization = 2260 KJ kgʻ*) (6.03 MJ)