How salty does the sea have to be for an egg to float ?

[lonique]

I'm doing a project on determining what salt concentration will float an egg. I got the idea from this site actually. However, I am a bit confused about some things.

What is:
-absolute concentration or
-relative concentration ?

Wait, what is concentration ?

Help me please.

[donnahardy2]

Hi Ionique,

Floating eggs is a density project; dissolving salt in water increases its density, so eggs will float when the density of the salt water is greater than the egg.

Since this is a science fair project, you should refer to the salt as sodium chloride; since I'm sure you used table salt.

Next, you should calculate the concentration of salt in moles per liter, if you have the information to do this. NaCl has a molecular weight of 58.5 grams per mole. If you convert the volume of water you used to liters you can use the following formula to determine the molar concentration:

grams NaCl/liter x mole/58.5 grams = moles/l

This is the absolute concentration of salt in your sample. Relative concentration is when you compare results with two different concentrations of salt.

Concentration can also be calculated using percent concentration (grams/100 ml), but moles per liter is preferred by chemists.

I assume you have had chemistry, but do let me know if you need more explanation.

Donna Hardy

[wbhdjhhmh]

Hello. I am conducting the same experiment. The procedure instructs to plot the densities of all five eggs on a chart. I am confused. First of all, which density is it asking for? If I take an egg that has a mass of 57 grams, according to wiki answers, then submerge it in 100 ml of tap water and it sinks to the bottom, the new volume of the water has risen to 175ml, therefore the egg has a volume of 75ml. I then calculate the eggs density at 57g/75ml to get .76g per cm3. Now if water is 1g per cm3, how can the egg sink since .76g is less than 1g? I think I'm missing something here.
What would be the correct procedure for measuring the densities of all five eggs?

Thanks for any help!

[MelissaB]

Hi,

You need to measure the actual mass of your eggs. Egg mass can vary quite a lot, and if you are using larger or smaller eggs this could really throw off your calculations. You should therefore measure each egg's mass and each egg's volume--those measurements will allow you to calculate a density estimate for each of the five eggs. You should also repeat the volume measurements on each egg. Those seem a little large to me--are you using a graduated cylinder to measure the change in volume, or something less accurate, like a beaker? That could also cause problems.

[wbhdjhhmh]

I am using a standard measuring cup, so it would be slightly difficult to get an accurate volume reading, since it is labeled in 25 ml increments. What do you suggest I use?

Thanks!

[donnahardy2]

Hi,

You are perceptive to realize that something is wrong with your measurements. You need a graduated cylinder or some other container with smaller than 25 ml increments to more accurately measure the change in volume. Water has a density of 1, so if the egg sinks in the water, the actual density of the egg has to be greater than 1. Can you repeat this experiment at school where you should have access to an accurate balance and volumetric measuring device? If not, then measure the density of all 5 eggs as carefully as you can using the same procedure. If the eggs sink in water, and your calculated density is less than 1, then you can include a discussion on your conclusion section about possible sources of error in your experiment.

I hope this helps.

Donna Hardy

[deleted-291984]

I have already conducted this experiment, but I need a few questions answered. This is a summer assignment of mine, performing an experiment, and I have to write a proposal sheet. Some things I need for it is the variables: Independent, Dependent, and Controlled. I know what they all are, but I can't seem to figure out what they are based on the experiment's format. I also have to write out my hypothesis, which I also understand completely. It must be in the "If...then..." format, but since I can't figure out the variables or how much salt is actually in cup 1, where the egg floats, I can't really do any of this. I hope there is some way that my question can be answered.

[deleted-2131]

Hi Lexus Hills,

I'm responding to your questions on your other topic thread. We ask that you keep all of your posts on a single thread to help us Experts help you more effectively.