Science Buddies: "Ask an Expert"

Hi...my daughter chose to do this science project. We did the experiment twice, are using high quality digital scales, and the results were the same. The eggs all weighed less after being boiled. Yes, we noticed the bubbles of air all over the egg as they heated. We've figured out that air can enter and leave an egg via its pores. However, we can't figure out why they weigh less. If the egg is losing air and not gaining water during the boiling process, how can they weigh less. Air doesn't have a weight..it's a gas....SOOOO...we can't figure out why the whole experiement relies so much on the weight before and after boiling the eggs, if the experiment was just to see air bubbles then why weigh?? Thanks!!

Hi!
I think that the main answer to your question is the following taken from the project website itself:

If the pores really do allow materials to cross back and forth between the inside of the egg and the outside environment, then the air inside the egg should be replaced by water, and water is heavier than air.

Hope this helps, best of luck!

Thanks for your reply. We get that air/gases can pass through the egg via its pores. Water cannot. My question remains, why do the eggs weigh less?

Just to add to staryl13's response.

It does look as though for some reason the water did not pass through the shell, or your balance or scale is not sensitive enough to measure the change.

Air actually does have weight ! Air has mass, so it weighs something. You can think of air as being similar to water, which is also a fluid. When you dive underwater, all the water on top of you is exerting pressure on you (which is why your ears hurt). It is the same way with air. We are so used to having this pressure on us that we don't know it's there! Just like there are "layers" of water in a pool (each layer supports the layer above it and is also pushed by that layer), there are layers of air in the atmosphere, all exerting forces on each other.

A quick experiment you can do is to take an accurate balance or scale and measure a deflated balloon. Then fill the balloon with air (well...not helium as it would float) and it should weigh more!
http://www.worsleyschool.net/science/fi ... eight.html

Check out these websites for more information:
http://www.weatherquestions.com/How_muc ... _weigh.htm
http://startswithabang.com/?p=672

So, the air in the shell was contributing to the weight. It appears as though the water didn't go into the shell, but the air went out.

You might also check the accuracy and precision of your scale and make sure that you aren't letting the eggs dry too much before weighing them. It is possible that your scale or balance is not sensitive enough to measure the change, and it is just registering as being less.

Just to add to the other experts' advice: Water can evaporate out of an egg through the pores. If you let the boiled eggs air-dry before you weighed them, they may have still been hot enough that a lot of the water evaporated out through the pores. So, I would try the experiment again and just quickly roll them on a paper towel to dry off the outside and then put them on the scale.

i am doing the same experiment for science and found the same results, how much less were your eggs after being boiled? mine was 1.02g.. do you think there would have been a whole gram of air lost?

My daughter and I have done the same experiment with the same results as others. The eggs come out weighing less. We are using a high quality digital scale.

We figured it out!! We let the eggs soak inside of the boiled water until it cooled. The eggs soaked up the water through the pores and increased their weight therefore proving the theory correct.

Hi!
Great! I'm so glad that the experiment worked out well! Feel free to post any more questions if you have any!

My daughter completed this experiment yesterday. One of her eggs weight remained the same after boiling. Two of the others gained a gram and the other two lost a gram. How does one explain the loss in mass?

Hmm...were all the eggs from the same box? the experiment notes that egg age can make a difference.
Were they all equally dry? Additional water could add weight, of course.
Sometimes results are hard to explain, and the best thing is to just come up with some potential explanations to present.

Would it be a good idea to hard boil one egg in a baggie as a control to show water didn't get in when not submerged and the weight didn't change?