create a model in response to the prompts in the quiz below. Be sure to apply a model from this class and include the relevant diagram(s) for that model. And don't forget to use the Claim, Evidence, Reasoning framework to present your solution.

 

Phenomenon: Making hot chocolate with a chocolate bar

 

Part 1: Heating the milk

 

Since it's been so chilly out, you're in the mood for some hot chocolate. You take your biggest mug and fill it with 0.4 kg of milk from the 4˚C refrigerator. Then, you put the mug into your 1000 Watt microwave and heat it for two minutes. (Assume the microwave is perfectly efficient in heating the milk.)

 

Big Question: What is the temperature of the milk when you remove it from the microwave assuming it stays in the liquid phase? 

 

Use what you've learned in PHYS 2A so far to analyze the hot chocolate.

 

1. Include Temperature vs Energy and Energy Interaction diagrams as evidence in your response. Consider how many of each diagram(s) you need to fully model the process(es).
2. Use your diagrams to construct an equation that can be used to precisely answer the big question.
3. Make a clear claim that answers the question and provide detailed reasoning that connects your evidence to that claim.

 

Reminder: Use the Claim, Evidence, Reasoning framework to present your solutions. This means using a model from class including relevant, complete diagram(s) and explicitly writing out your reasoning.

 

Part 2: Adding the Chocolate Bar

 

You quickly pour the hot milk into a travel mug, making it thermally insulated. The milk is at the temperature you previously calculated. If you were not able to get a final value, choose a temperature that makes sense in this problem and clearly state it as an assumption.  Then you add two squares of a room temperature (20˚C ) chocolate bar, with a total mass of 40 grams (0.04 kg).  You stir it up until all the chocolate melts.

 

Big Question: What is the final temperature of the hot chocolate/milk mixture at thermal equilibrium? 

 

Use what you've learned in PHYS 2A so far to analyze the hot chocolate/milk mixture.

 

1. Include Temperature vs Energy and Energy Interaction diagrams as evidence in your response. Consider how many of each diagram(s) you need to fully model the process(es).
2. Use your diagrams to construct an equation that can be used to precisely answer the big question.
3. Make a clear claim that answers the question and provide detailed reasoning that connects your evidence to that claim.

 

Maybe useful information: 

 

TBP, H2O = 100˚C	Cp,Solid milk = 1.97 kJ/(kg˚C)	Hp,melting chocolate = 15 kJ/(kg)
TMP, H2O = 0˚C	Cp liquid milk = 3.89 kJ/(kg˚C)	Hp,melting  milk = 330 kJ/(kg)
TMP, chocolate = 34˚C	Cp solid chocolate = 1.80 kJ/(kg˚C)
	Cp,liquid chocolate = 1.60 kJ/(kg˚C)
[Watt] = [Joule/s]	[kiloWatt] = [kiloJoule/s]
∆Ethermal = m Cp ∆T	∆Ephase = ∆m Hp
Q = ∑∆E	P = Q/∆t  or  P = ∑∆E/∆t

Answer rating: 100% (QA)

Part 1 Heating the Milk Claim The temperature of the milk when removed from the microwave and assumi... View the full answer