Science Buddies: "Ask an Expert"

I have been working with my son a 5th grader on the experiment "how salty does the sea have to bee to float an egg". We have run into obstacles.
We have tried to determine the density of each egg by placing it in the solution and taking the change in water volume once the egg is placed in water to determine the density. Is this appropriate. We do not have a balance to measure the mass and other devices to measure volume.

We are also stomped at the following procedure directions.

We need to conduct the experiment one more time with the dilution with the salt concentration in which the egg first floated. We need to figure out a new serial dilution with smaller steps. For example, you could try diluting the solution by 20 percent with each step. That means with each step, the new concentration should be 80 percent of the original concentration.
What amounts of stock solution and water do you need to use?

I'm not sure how to go about this?
Helplessly lost mom.
Gladys

Are you trying to measure the density of the egg by itself or through the experiment? It can be determined through the experiment by seeing at what concentration of salt the egg first floats. If you do it this way, the displacement doesn't matter. You can measure density using displacement (which finds the volume), but you would have to measure the mass of the egg. From there, the equation for density is equal to mass/volume.

It would actually be easier to do a 25% dilution instead of at 20% dilution. To do this, you would take 3/4 of a cup of the solution you started with (the least concentrated where the egg floated, not the stock solution) and add 1/4 of a cup of water.

Good luck with your project and let me know if you have any more questions!
Katie

Thanks!
G