Comprehensive Physics and Chemistry Problem Set: Heat Transfer, Electric Circuits, Wave Properties, and Radioactive Decay

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Comprehensive Physics and Chemistry Problem Set: Heat Transfer, ElectricCircuits, Wave Properties, and Radioactive DecayLab Ex.61.How many calories of heat are required to change 1 gram of ice at 0°C to liquid water at0°C?Answer: 80calories.2.How many calories of heat are required to change 1 gram of water at 100°C to 1 gram of steam at100°C?Answer: 540 calories.3.How many calories are needed to melt 50 grams of ice at 0°C and convert it to liquid water at 35°C?Answer:•Heat to melt ice: 50 g × 80 cal/g = 4000 calories.•Heat to raise water from 0°C to 35°C: 50 g × 1 cal/g°C × 35°C = 1750 calories.4000 + 1750 = 5750 calories.4.For the irreversible transition of: 100 g H2O (s,-25°C) → 100 g H2O (v, +120°C) Calculate the totalamount of heat necessary to effect a set of reversible reactions for theses conditions.Answer:•Heat to warm ice from-25°C to 0°C: 100 g × 0.5 cal/g°C × 25°C = 1250 calories.•Heat to melt ice at 0°C: 100 g × 80 cal/g = 8000 calories.•Heat to raise water from 0°C to 100°C: 100 g × 1 cal/g°C × 100°C = 10000 calories.•Heat to vaporize water at 100°C: 100 g × 540 cal/g = 54000 calories.•Heat to raise steam from 100°C to 120°C: 100 g × 0.48 cal/g°C × 20°C = 960 calories.Total = 1250 + 8000 + 10000 + 54000 + 960 = 73,210 calories.5.In a steam radiator, steam at 110°C condenses and the liquid water formed is cooled to 80°C.Howmuch heat per gramof liquid formed, is released in this process?•Heat to condense steam: 1 g × 540 cal/g = 540 calories.

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•Heat to cool water from 110°C to 80°C: 1 g × 1 cal/g°C × 30°C = 30 calories.540 + 30 = 570 calories per gram.6.How much heat is absorbed by a persons hand if 100 grams of liquid water at 100°C is poured on hishand?(Assume the final temperature of the water will be normal body temperature of 37°C)Answer: Heat to cool water from 100°C to 37°C: 100 g × 1 cal/g°C × (100°C-37°C) = 6300 calories.6300 calories.7.How much heat is absorbed by a persons hand if 100 grams of steam at 100°C is first converted toliquid water at 100°C and then cooled to normal body temperature?Answer:•Heat to condense steam: 100 g × 540 cal/g = 54000 calories.•Heat to cool water from 100°C to 37°C: 100 g × 1 cal/g°C × (100°C-37°C) = 6300 calories.54000 + 6300 = 60,300 calories.8.Which causes the more severe burn hot water or steam?Why?Answer:Steamcauses more severe burns because, when steam condenses, it releases the latent heat ofvaporization, which is much higher than the heat released by water alone. Thus, steam transfers moreheat to the skin.Problem Set Eight1.How much heat must be removed from 500 grams of water at 0°C to form ice at 0°C?Answer:2.How much heat is necessary to vaporize 100 grams of water at 100°C to form steam at 100°C?

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Answer:3.A 20.0 kg bag of dirt falls 10.0 m at a construction site.Assuming that all ofthe heat produced isretained by the dirt, how much will its temperature increase?(cdirt = 0.20 cal/g•°C)Answer:4.A 1000 kg car with a speed of 80 km/h brakes to a stop.How many calories of heat are generated bythe brakes as a result?Answer:5.How much heat is needed to cause the following irreversible reaction?200 g of liquid H2O at 50°C is heated to form 200 g of steam at 120°CAnswer:

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6.Calculate the amount of heat needed to increase the temperature of 300 grams of water at 15°C to5°C.Answer:7.How much heat must be added to 100 grams of ice at 0°C to form water at 0°C?Answer:8.How much heat must be removed when 25 grams of steam at 100°C Is condensed to form liquidwater at 100°C?Answer:9.How much heat isabsorbed by pouring 10 grams of 100°C liquid water on a student’s hand.The wateris cooled to body temperature, 37°C.Assume that all of the heat is absorbed by the hand.Answer:

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10.How much heat is absorbed by contacting 10 grams of 100°C steam by a student’s hand.The steamis condensed to liquid and then the liquid is cooled to body temperature, 37°C.Assume that all of theheat is absorbed by the hand.Answer:Lab ex. 71.Access the following web site and follow the directions you find there. It may take several minutes todownload the site so please be patient. http://jersey.uoregon.edu/vlab/Voltage/index.html After youcomplete four different circuits type the data you obtained in the following space.Part 2 Complete thefollowing calculations. Record your work in the space provided below each problem.1.In a simple circuita 6-volt dry cell pushes charge through a single lamp which has a resistance of 3 Ω.According to Ohmslaw the current through the circuit is _____________ Amps.Answer: 2 Amps.2.If a second identical lamp is connected in series, the 6-volt battery must push a charge through a totalresistance of ________ Ω.The current in the circuit is then __________ Amps.Answer: Total resistance = 6 Ω, Current = 1 Amp.

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3.If a third identical lamp is connected in series, the total resistance is now _________Ω.Answer: Total resistance = 9 Ω.4.The current through all three lamps in series is now _________ Amps.The current through eachindividual lamp is__________ Amps.Answer:The current through each individual lamp is the same as the total current (0.67 A).Answer:Total current = 0.67 Amps, Current through each lamp = 0.67 Amps.5.What is the power when a voltage of 120 volts drives a current of 3 amps through a device?Answer:360 Watts.6.What is the current when a 90-W light bulb is connected to 120 V?Answer:0.75 Amps.7.How much current does a 75-W light bulb draw when connected to 120 V?

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Answer:0.625 Amps.8.If part of an electric circuit dissipates energy at 6 W when it draws a current of 3 A, what voltage isimpressed across it?Answer: 2 Volts.9.If a 60 W light bulb at 120 V is left on in your house to prevent burglary, and the power companycharges 10 cents perkilowatt-hour, how much will it cost to leave the bulb on for 30 days?Show yourwork.Answer:$4.32.Problem Set Nine1.An electric current through a wire is 4.0 Coulombs every 3.0 seconds.What is the magnitude of thiscurrent?Answer:1.33 Amps

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2.There is a current of 0.83 Amps through a light bulb in a 120 Volt circuit.What is the resistance of thislight bulb?Answer: 144.58 Ω3.What is the voltage across a 60 Ω with a current of 3.5 amps?Answer: 210 Volts4.An electric motordraws a current of 11.5 A in a 240 V circuit.What is the power of this motor inWatts?Answer:2760 Watts5.A 10.0 Ω light bulb is connected to a 12 V battery.What is the current flowing through the light bulb?Answer:1.2 Amps6.What is the power of the light bulb in question 5 above?

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