Author Topic: This Has Me Stumped (Math Problem) (Read 1246 times)

Radar67 · « **on:** June 09, 2009, 07:33:55 pm »

I am usually pretty good at math, but this one has me pulling my hair out. Would someone please show me how to solve?

How much heat is required to convert 0.3 kilogram of ice at 0°C to water at the same temperature? (in joules)

That zero has me over a barrel, every time I try to solve it ends with multiplying by zero,

isawlogs · « **Reply #1 on:** June 09, 2009, 07:52:16 pm »

convert it to onces and to farenheit .. you will get rid of the zero .

Any more help , just hollar .

Lorax · « **Reply #2 on:** June 09, 2009, 07:54:34 pm »

For a substance undergoing a phase change, just multiply the mass by the latent heat of fusion. For water the latent heat is 80,000 calories per kilogram, or about 335,000 J per kilogram. So in your problem, .3 x 335,000 = 100,500 joules.

Radar67 · « **Reply #3 on:** June 09, 2009, 08:24:42 pm »

Marcel, I should have thought of that. When I figure it that way, it comes out real close to what Lorax said. Thanks guys.

Captain · « **Reply #4 on:** June 09, 2009, 08:34:42 pm »

Lorax beat me to it...

zopi · « **Reply #5 on:** June 09, 2009, 09:36:37 pm »

dunno, but budweiser has a can that will tell you...

sharp edge · « **Reply #6 on:** June 10, 2009, 10:59:13 am »

Isn't it just a 3-1 ratio?

Budweiser- leave in snow bank for 20 min. before phase change.

SE

isawlogs · « **Reply #7 on:** June 10, 2009, 12:43:49 pm »

I dont know why one would want to know , but if he did ever want to share I would be pleased to read why .

Fla._Deadheader · « **Reply #8 on:** June 10, 2009, 05:06:23 pm »

Sure is some very intelligent people on here, EH

Quote

convert it to onces and to farenheit .. you will get rid of the zero . Grin Any more help , just hollar .

Radar67 · « **Reply #9 on:** June 10, 2009, 05:44:07 pm »

I was helping my daughter with her school work, checking her actually, and that was one of 25 problems.

The current subject was "heat" as part of her home school math.

isawlogs · « **Reply #10 on:** June 10, 2009, 07:37:45 pm »

Harrold , I did not know wether he wanted the solution to the problem or if the problem was the zero .. I helped him get rid of the zero .

Now I need add Intelligent to my list of names I have been called.

I am glad that I did not go to that school . $:-\$

Fla._Deadheader · « **Reply #11 on:** June 10, 2009, 08:10:02 pm »

Usted es MUUY LOCO, Marcel

Warbird · « **Reply #12 on:** June 12, 2009, 02:40:43 pm »

Quote from: zopi on June 09, 2009, 09:36:37 pm

dunno, but budweiser has a can that will tell you...

Thanks. I needed a laugh.

ARKANSAWYER · « **Reply #13 on:** June 12, 2009, 07:07:34 pm »

IF you have water at 0°C isn't that ice?

Not much on Metric but I thought water froze at 0°C.

Brucer · « **Reply #14 on:** June 13, 2009, 12:53:53 am »

Quote from: ARKANSAWYER on June 12, 2009, 07:07:34 pm

IF you have water at 0°C isn't that ice? Not much on Metric but I thought water froze at 0°C.

Yep, water freezes at 0°C, and ice melts at 0°C.

Remove heat from water, and the temperature goes down. Keep removing heat and it eventually reaches 0°C (but it's still liquid). Continue to remove heat and it begins to freeze -- but the temperature stops dropping. If you continue to remove heat after all the liquid has frozen, then the temperature starts to drop again.

Same pattern when you thaw ice.

woodmills1 · « **Reply #15 on:** June 13, 2009, 09:19:25 am »

brucer has hit the head on all of his answers on this thread

The whole concept of heat of fusion and heat of vaporization has always fascinated me, as well as many very famous and rich people in history, me neither famous nor rich.

I will attempt a description of what I mean

It takes one calorie of heat to raise the temperature one gram of water by one degree celcius

or

it takes one btu of heat to raise the temperature of one pound of water by one degree fahrenhite

so let us start with a piece of ice at below the freezing temperature

for a one gram block it takes one calorie of heat to make that ice warmer untill the ice hits zero celcius. At zero it doesn't melt instantly, more heat must be added. Actually 80 calories must be added to get the ice to break its molecular bonds and melt to water at zero degrees celcius. this is why ice in coolers works so well. It takes lots of heat to melt ice

for a one pound block of ice it takes one btu to warm it a degree untill it hits 32 degrees then it takes 80 btu's to melt it to 32 degree water

did you ever feel the heat from the steam when you drain your pasta. the steam isn't hotter than the boiling water(unless it is under pressure) it has more heat!!! In fact staeam has 540 times as much heat as boiling water.

The underlying concept that will help you understand the above stories is that heat and temperature are not the same things

james watt knew this..steam engine

some one named westinghouse knew this ...........refrigeration and much more

this concept was very hard to teach to high school students

my favorite demonstration was boiling water in a paper dixie cup using a bunsen burner. the water could extract the heat so fast that the cup did not burn. I still run into ex students(some 40 years old now) who turn to their wives or husbands and say....thats Mr Mills the teacher who boiled water in a paper cup

woodmills1 · « **Reply #16 on:** June 13, 2009, 09:23:48 am »

BTW

the calories in my previous post are calories with a little c and food calories (big C) are a thousand times more heat

isn't science fascinating

Roxie · « **Reply #17 on:** June 13, 2009, 10:02:15 am »

Well, thank you for clarifying that! I was beginning to wonder how the calories in ice cream didn't keep it from melting itself.

DanG · « **Reply #18 on:** June 13, 2009, 12:12:06 pm »

So, how many Calories have I expended when I rent a 12oz beer that is at 33°F, and return it at 98° five minutes later? I got a feeling I've been working a whole lot harder than previously believed.

Gary_C · « **Reply #19 on:** June 13, 2009, 12:24:14 pm »

Well DanG, first you must answer some questions in order to be precise.

How tall are you? Gravity is important you know. And I would need that in both inches and meters.

Do you want the answer in calories with a capital C or small c?

What is the ambient air temperature and were you sweating while consuming that beverage? That should be in celcius and kelvin degrees also.

And the most important question is how many more of those beverages do you have in case someone has to come down there and help you with your answers?

DanG · « **Reply #20 on:** June 13, 2009, 12:47:09 pm »

Ambient temp,90°F. Sitting in shade with a fan blowing on me from the right rear quarter. 8 steps to the rental cooler, 14 to the return tree. Unlimited supply, come on down.

Gary_C · « **Reply #21 on:** June 13, 2009, 12:55:10 pm »

I'll be right there. But I am kind of slow so it might take a while. That 90 degrees F sounds good to me right now. I think it was only in the low 50's this morning.

Jeff · « **Reply #22 on:** June 13, 2009, 01:16:15 pm »

I'll take the low 50's

DanG · « **Reply #23 on:** June 13, 2009, 01:24:34 pm »

Yeah, I was gonna suggest that he bring some of that with him. I recall having longed for warmth just a few months ago, but I could use a dose of cool right about now.

sharp edge · « **Reply #24 on:** June 13, 2009, 01:50:24 pm »

Phase change is a big thing in globle waming, with polar ice caps. But think the oceans in FL. is ging up from DanG. We will have to get busy up north, so we can keep the water even.

SE

woodmills1 · « **Reply #25 on:** June 13, 2009, 07:13:51 pm »

SO

heat is the total amunt of energy of all of the particles in a sample

and temperature is the average amount of enegy of a single particle

the consumed beverage will rapidly warm to the average kinetic energy of the particles it is now stored close to, the passage rate of five minutes seems to be a bit high and would depend on much more than height and weight, more like age and rate of consumption. too bad there isn't a national call for recycled beverage consumption.

olyman · « **Reply #26 on:** June 13, 2009, 08:18:47 pm »

this concept was very hard to teach to high school students

my favorite demonstration was boiling water in a paper dixie cup using a bunsen burner. the water could extract the heat so fast that the cup did not burn. I still run into ex students(some 40 years old now) who turn to their wives or husbands and say....thats Mr Mills the teacher who boiled water in a paper cup
[/quote] ill be jump in a creek. never heard of that before. learn something new every day!!!!!!!!!

Brucer · « **Reply #27 on:** June 13, 2009, 11:12:46 pm »

Quote from: woodmills1 on June 13, 2009, 09:19:25 am

my favorite demonstration was boiling water in a paper dixie cup using a bunsen burner.

I once did it using a paper bag over a campfire. Did it to win a bet

.

woodmills1 · « **Reply #28 on:** June 14, 2009, 07:00:24 am »

I like to throw old christmas trees, one at a time, over the top of a raging bonfire. They kinda levitate a fot or so over the wood and burn like mad

Here is a trick I learned at the adventurers club on pleasure island at disney

take one empty liquor bottle 86 proof or better
warm the bottle with hot water, but don't get water in the bottle
take a plastic coctail straw and put a tooth pick through it a little above the center
put the straw in the mouth of the bottle resting on the tooth pick
drop a match into the bottle and watch the straw take off like a rocket.

Warbird · « **Reply #29 on:** June 14, 2009, 10:20:23 am »

woodmills1, that was a great explanation on the energies involved with state changes. You should write up your thoughts on those observations when considering entropy.

DanG... the truth is, you've been working even harder than you thought. See, you aren't just heating said beverage up to 98 degrees before expelling it. You are also changing part of it into a gaseous form (hence the fan blowing on you from the right rear quarter to dispense the poisonous gas before innocents are harmed).

News:

Author Topic: This Has Me Stumped (Math Problem) (Read 1246 times)