Science Buddies: "Ask an Expert"

I'm trying to find out why different frozen liquids melt quicker than other liquids. They were all frozen at the same time and taken out of the freezer to a 67 degree temperature. The liquids are as follows and melted in this order, ice cream,cranberry juice,shampoo,water,beer gatorade,milk,oj,sierra mist soda,coffee,serria mist light, pantene conditioner. Ice cream took 57 minutes and the conditioner took 2 hrs and 45 minutes. We have the ingredients in all the liquids, however, it was difficult to find out the exact percentage of ingredient in each. Can someone help or direct me to find the answer to my science project.

It sounds like you did a very involved project, but you may be testing a few too many variables. Having so many different products with so many different ingredients will make it difficult to prove out a hypothesis. What is your hypothesis? You might want to rethink it and then test a few items that will prove it out more simply.

Maybe consider testing three liquids like milk, water and soda. Or maybe even carbonated water versus tap water. That should help remove the problems you are currently facing.

If you absolutely need to track down the ingredients, you might do some searches on google and others. I checked and nothing popped out right away.

dmcc wrote:I'm trying to find out why different frozen liquids melt quicker than other liquids. They were all frozen at the same time and taken out of the freezer to a 67 degree temperature. The liquids are as follows and melted in this order, ice cream,cranberry juice,shampoo,water,beer gatorade,milk,oj,sierra mist soda,coffee,serria mist light, pantene conditioner. Ice cream took 57 minutes and the conditioner took 2 hrs and 45 minutes. We have the ingredients in all the liquids, however, it was difficult to find out the exact percentage of ingredient in each. Can someone help or direct me to find the answer to my science project.

Hi, dmcc!

I assume that you used equivalent volumes of each liquid. If this is the case, I think there are probably two main causes:

1) Different masses or densities. The rate at which a substance changes temperature is related to its mass. If 1 fluid ounce of ice cream is less dense than a fluid ounce of coffee, the ice cream will change temperatre more quickly.

2) Differences in melting points. If substance A melts at 32 degrees and substance B melts at 34 degrees, assuming they have equivalent mass, substance A will melt first. Melting points can be heavily influenced by the constituents that make up a liquid.

I suggest that you do some investigation around these two issues and consider how they might affect your results when applied together. You may find that one or the other is dominant.

I hope this helps!

I want to add to Brians comments. In addition to differences in mass and melting temperature, one also has to worry about differences in "heat of fusion" and in thermal conductivity. One thing you might do is to put a thermometer in the liquid when the solid is partially melted. that should give you a measure of the melting temperature. You also might want to look up the effect of dissolved material on the melting point of ice.

One way to salvage an experiment that didn't come out quite right is to write a report that shows or analyzes what was wrong with the experimental design. The most important thing I look for in judging science fair entries is whether the student learned anything from the experiment.

Also, were all of these substances in identical containers? With identical surface areas for thermal conductivity? I can envision a plastic shampoo container, a glass beer bottle, a paper ice cream container, etc.

A 1 pound block of ice and 1 pound of ice cubes melt at very different rates. The only difference between the two is the surface area exposed to the ambient temperature.

Heat transfer is somewhat complicated. Usually a college course in mechanical or chemical engineering. But the basic concepts are very easy to understand.

When you stand in front of a fan, the movement of air cools you. That is convection.

When the Sun's rays beat down on you at the beach and warm you up - that's radiation.

When you touch a cold object and your hand gets cold - that's conduction.

There's a brief article about heat transfer, with a number of links on wikipedia:

http://en.wikipedia.org/wiki/Heat_transfer

Keep as many variables constant as possible, and the data will start to make more sense to you. Basically, you have an experiment that sounds simple on the surface, but is deceptively difficult ( I think this is often the case with good science fair experiments.) Eliminate as many confounding variables as you can, and things will become much more clear.

I did use all the same volumes and containers (an ice cube tray). Therefore, it sounds like mass and melting point are the keys. How do I find the different masses for liquids the liquids I used such as water, beer, milk, etc? Also, how do I find the different melting points for those same liquids?

Mass is easy. Take a scale, weigh identical volumes of each liquid, and you have their mass and by extension density.

Paulsdecarli's post about measuring the temperature of the liquid when the solid is partially melted is a very good one (they don't call them experts for nothing). I don't know if you can just look up the melting points of all of those substances. Probably just easier to measure them.

Here's a link to a lab experiment showing how to calculate the melting temperature of a substance. You really don't need to be this accurate, but the bleep is sound:

http://www.geocities.com/CapeCanaveral/ ... -C-14.html