Easter Eggs and Acids or Bases
I love spring, it is probably the best season….I know, its not a competition…The blue sky is probably the best blue of the year, and celebrating Easter is always fun for the kids….we’ve got eggs and we’ll hide ‘em. So, what does Easter have to do with chemistry? Pretty much everything, IF all you are referring to is dying Easter eggs. (Chemistry really has nothing to do with Easter) If you have ever been to a science fair, inevitably there are a couple of projects in which the kids soak eggs in different substances to see what happens to the shell. Well, what do a bunch of kids do every Easter? Soak their eggs in stuff to see what happens to the shell. Also, most chemistry courses are covering acids and bases at this time of year so I thought this might be a good time to use Easter eggs as an example to give a little insight into what you are covering in your course.
pH Scale and Logarithms
I’m sure you’ve seen the pH scale before, and that is probably where your instructor started. Did it go something like this……. “Early in the 1900’s a Danish scientist, Soren Sorenson first quantified acids and bases based on the concentration of hydrogen ions in an aqueous solution…….” Did any of that sound familiar? Did any of it make sense? It is a good place to start and credit should be given where credit is due thus “Sorenson” should be a familiar name with respect to the pH scale. He is credited with naming it. “p” stands for power or potential and “H” stands for hydrogen (you know, H, the symbol for hydrogen from the periodic table, and acids have a hydrogen in them) so the scale is based on the power of hydrogen. It is also a logarithmic scale. Remembering, “p is for power”, might help you remember it is based on powers of 10. Even though the scale uses numbers from 0-14, each step is really separated by a power of 10 not just 1 (btw, technically you can also have pH’s beyond this scale since it is all based on a calculation of how many hydrogen ions are in the aqueous solution). Meaning, if you look at the scale, lemon juice is listed with a pH of 2 whereas orange juice is listed with a pH of 3. That means, on this logarithmic scale, that lemon juice is one step more acidic than orange juice and therefore 10x more acidic. (Remember that the lower the number the more acidic and thus the higher the number the more basic. 0 is acidic but 14 is basic). Let’s look as the bases for one more example. Ammonia is considered to have a pH of 11 whereas bleach has a pH of 13. That means that bleach is 2 steps more basic than ammonia and therefore two powers of 10 more basic (two powers of 10 can be rewritten 102 which is 100) making bleach 100x more basic than ammonia.
What is it that makes these substances acidic or basic?
Well, let me tell you……It has to do with the Hydrogen that these acids are made of. Acids will dissolve in water. When they dissolve, their atoms that they are made of, allow the water molecules to spread them apart. They will spread out in certain patterns because they are ionic compounds. For acids, the hydrogen will separate from the rest of the atoms. Depending on how much hydrogen is separated out, determines how acidic a compound is. The way that we determine how much hydrogen is floating around in that water is by measuring its concentration.
And how does one go about measuring the concentration of Hydrogen?
Well, it would be to determine the electrochemical cell potential and use the Nernst equation but who wants to do that? pH meters are easily and inexpensively obtained and have been calibrated (or made just right) to measure that electrochemical cell potential and do the calculation for you. They are quite handy. But there are chemistry teachers out there that have been known to have students calculate the pH from a given value of hydrogen concentration. So, check out the neighboring section for a brief overview of pH calculation. And if that isn’t sufficient, check out my “Ask a Tutor” page and send me an email with the problem you are struggling with.
pH and Eggshells
Now that we have covered a little background information, what does it have to do with eggshells? If you look at the pH scale, it shows that eggs are on the basic side of the scale. If we combine this basic eggshell with a little acid, a reaction will take place and some of the shell will react with the acid. Those little bits of shell that react will turn into something else and dissolve into the solution that the egg is sitting in. That leaves small pits in the shell, which allows for places for the egg dye to penetrate and stay.
This is the point in the post where I’m hoping you are thinking something like,
“How do you know an acid will react with a base?
Why did you choose an acid and not a base for the egg dye?” Well, just so you know, the instructions for the egg dye tells you to use vinegar or lemon juice, which are acids, (check the scale and it will show you they are acids) but I feel like most everyone should know that acids and bases react and therefore we should use an acid to react with the eggshells which are basic. Everyone in the entire world has mixed baking soda and vinegar, right? (well, maybe not everyone but it is close to everyone). Baking soda is a base and vinegar is an acid. When you mix them, they react and you end up with a salt and water. I said “a salt” not “table salt” nor “assault” (ah, chemistry humor). The salt that we end up with when baking soda and vinegar react is sodium acetate. It is referred to as a salt because it is an ionic compound. One other note about this reaction is that it is a type of double displacement (or replacement) reaction. Acid – Base reactions are double displacement reactions.
Isn’t it great to know how the Easter egg dye works?
And if you still haven’t mixed baking soda and vinegar you should try it. Put some in a little plastic egg and close it tightly. Be sure to use smart lab practices for this experiment (that includes eye, clothing and hand protection and maintaining a safe space around the experiment). If you aren’t sure which safe practices you should be using, send me a message or consult a different search engine or even a responsible adult because it’s all fun and games until someone gets hurt. Post in the comments section below how it went.
Disclaimer: I claim no responsibility for any of your actions with regard to this post. If you conduct any experiments with your new information, be sure to use appropriate safety protocol so you aren’t injured in anyway. This post is meant to be informative only.