Which of these materials will heat up faster and why?

[mrchopsy]

Hello,

I am doing a high school EEI to investigate the impact that the material of a cup has on the temperature of water inside the cup when left outside in the sun.
The cups I am using are:

Glass
Steel
Plastic
Paper

Theoretically, if I poured the same amount of water into each of the cups (assuming the size and shape of the cups were identical) and left them out in the hot sun (approx 30 degrees Celcius) for an hour, which of the cups will have the hottest water temperature and why?

Thank you!
p.s. this is my first post so I'm not sure if I've posted this in the right forum

 

[berkeman]

Welcome to the PF.

I've moved your thread to the Homework Help forums. All schoolwork-type questions go here in the HH forums.

We require that you show us your work so far before we can offer any tutorial help. What material properties will influence the answers? What do you think the answers are, and why?

 

[berkeman]

Also, you did not specify the color of the cups. Why would that matter?

 

[anorlunda]

Welcome to PF.

Do you know the colors of the cups? A black one will absorb sunlight faster than a white one, sometimes a transparent one faster still.

For example, camp showers like the one below are transparent on the front and black on the back to heat water as fast as possible.

 

[sophiecentaur]

Welcome to PF.

Do you know the colors of the cups? A black one will absorb sunlight faster than a white one, sometimes a transparent one faster still.

For example, camp showers like the one below are transparent on the front and black on the back to heat water as fast as possible.

View attachment 223496

20 litres will run out half way through rinsing off the soap. I've been there!

 

[Funestis]

Hello,

I am doing a high school EEI to investigate the impact that the material of a cup has on the temperature of water inside the cup when left outside in the sun.
The cups I am using are:

Glass
Steel
Plastic
Paper

Theoretically, if I poured the same amount of water into each of the cups (assuming the size and shape of the cups were identical) and left them out in the hot sun (approx 30 degrees Celcius) for an hour, which of the cups will have the hottest water temperature and why?

Thank you!
p.s. this is my first post so I'm not sure if I've posted this in the right forum

There are three main methods of heat transfer - conduction, convection, and radiation. If you don't already know the difference between them, you can look them up to get an idea of how they work. Then think about which ones will be applicable to your experiment, and why. Are there any environmental factors that might also be at work?

Good luck!

 

[haruspex]

when left outside in the sun.

How long for? Open or covered? The thread title refers to the rate of heating, but in your post you wrote:

temperature of water inside the cup

So which is it, the rate of increase or the temperature reached?

the hot sun (approx 30 degrees Celcius)

That sounds like the ambient temperature. A suitably designed hotbox (a car for instance) can get a lot hotter.

sometimes a transparent one faster still.

Not if transparent both sides, surely? Something has to absorb the rays.

 

[sophiecentaur]

Something has to absorb the rays.

Yes. The black back face of the container. (A misunderstanding, I think) The transparent front bit will absorb and radiate less (none) and the backing can transfer more heat to the water and only a little to the surroundings. An outer insulating sheet behind the back would help further.

 

[berkeman]

20 litres will run out half way through rinsing off the soap. I've been there!

What do you expect? Silverbacks have a lot of fur!

 

[mrchopsy]

Hello, thank you for the replys and apologies for my late reply.

I believe the thermal conductivity of the materials, as well as the colour of the materials will be the main factors that influence how quickly the water heats up inside of the cups.

In my hypothesis I stated that steel will heat up the quickest because it has the highest thermal conductivity, k.

I actually did the test, and it turned out that the water inside the glass (transparent) cup heated up fastest.

Now my question is, why would this be the case? The thermal conductivity of steel is approximately 30 to 40 times greater than that of glass. I don't expect direct answers, but it would be great if someone could help to steer me in the right direction, since I have tried to discover why through research, but have not been able to find anything to help.

Thank you

 

[anorlunda]

You're learning some good physics here. Apparently, it is the sunlight absorbed by the object that is more important than thermal conductivity. What are the factors that affect sunlight absorption/reflection/transparency?

Completely transparent things neither absorb nor reflect, but what about water? Is the ocean warmed by sunlight?

 

[mrchopsy]

You're learning some good physics here. Apparently, it is the sunlight absorbed by the object that is more important than thermal conductivity. What are the factors that affect sunlight absorption/reflection/transparency?

Completely transparent things neither absorb nor reflect, but what about water? Is the ocean warmed by sunlight?

But if the glass is transparent, meaning that it doesn't absorb or reflect, then why would the water in the glass be heating up faster? And yes, the ocean is warmed by sunlight isn't it? hence why it evaporates, but I'm sure some of the sunlight is also reflected rather than absorbed.

 

[mrchopsy]

I'm so confused about the results and am not able to find much help online

 

[mrchopsy]

ahhh, the glass cup was a lot thicker than the others, could this possibly be the reason why the glass cup heated up the fastest?

 

[kuruman]

As @anorlunda pointed out, the color of the cup is relevant as a control parameter. What if you took three identical paper cups, painted one black, one white and wrapped tin foil around the third? You can repeat with the other materials and study the effect that the color has for a given material and the effect that material has for a given color.

 

[anorlunda]

But if the glass is transparent, meaning that it doesn't absorb or reflect, then why would the water in the glass be heating up faster? And yes, the ocean is warmed by sunlight isn't it?

I'm surprised you don't see the connection. Why shouldn't the sunlight heat the water in the glass like it heats the ocean? The opaque cup materials kept the water in the shade, and as you know it feels cooler in the shade.

This curve may help explain. IR stands for infrared. Most heat in sunlight is in the infrared part of the spectrum.

Edit: Strange, you must click on that figure to see it full size.

 

[haruspex]

steel will heat up the quickest because it has the highest thermal conductivity, k.

But steel is also quite reflective.

glass (transparent) cup heated up fastest.

Sunlight is not just visible light. The infrared will be important too.
Water is opaque to IR. Some glasses block more IR than others; maybe the glass you used is fairly transparent to it.