Monday, March 28, 2016

Kitchen Chemistry: Exploring Density with Eggs!


Now that Easter is over, what are we going to do with all of these eggs?!



Easter lends itself to a lot of wonderful traditions with our families. First, we spend time coming up with new and unusual ways of dyeing them, like these silk tie dyed eggs we make every year! But once we're done with the dyeing, the painting, the Easter Egg hunting, and the festivities... what's left? We've got all these eggs lying around, surely we can put them to some use?

We've got a full table of eggcellent egg experiments and demos!

We absolutely can! In this post, we'll explore physics, engineering, and chemistry with Floating Egg Experiment, Dissolving Eggs, An Egg in a Bottle, and we'll conduct our own Egg Races! 

Let's begin by exploring properties of matter through density! Density is simply a measurement of how many atoms are in a molecule, how big those atoms are, and how the molecules are arranged in a material.  A gas is typically less dense than liquid water, as the molecules that make up a gas are spread farther apart, and thus will be "lighter" than liquid water. You'll see this as bubbles rising up to the top of the water. They are less dense than the water, which will sink to the bottom of a glass.

The same can be seen with your eggs! The atoms and molecules that make up the egg, are more dense than the water. So, when you put a raw egg in a glass of water, it will sink to the bottom of the glass.

Using science, can you cause your eggs to float instead of sink?

FLOATING EGGS


Materials Needed:

3 Raw Eggs
3 glasses or wide glass jars
Water
Salt
Sugar

Instructions:
1. Fill all of your jars up halfway with water (making sure it's enough to cover an egg with some room left over.) In the middle, gently place one of your raw eggs in the bottom of the glass. You should see it settle at the bottom of the jar.

2. Ask your kids why the egg is sitting at the bottom of the jar. Why doesn't it float on top? Can you make an egg float on top?

3. In one of your other jars, add some salt! Not just a little, you'll need quite a bit, enough to perhaps fill 1/5 of your jar! Then, put another egg in there. Does it float? I not, add some more salt until it does! What happened? Why does the salt make the egg float?

4. Can you make an egg float with another material? What if you added sugar to your jar? Add the same amount of sugar to your third jar. Place your egg in the water. Does it float? If not, add some more sugar until it does!

What happened?

When you add the salt and sugar to the water, you're causing it to become more dense than the egg, which pushes the egg up to the top! You can see this same principle when you go swimming in the ocean. It's easier to float and easier to swim, because ocean water is more dense than your swimming pool.

Planet floating in water
Image CC: Pete Linforth

Another fun fact about ocean water and density... Let's take a look at the planet Saturn. Saturn is a gas giant, which means it is a GIGANTIC planet! It's so big, that you could fit 736 Earths inside of it! Well, if we could fit Saturn on to one of Earth's oceans, it would actually float! That's because the gasses that make up the planet Saturn, are less dense than the water on the Earth's oceans!


Speaking of density... you can actually change the density of an egg within a couple of minutes and watch a fun chemical reaction at the same time!

DISSOLVING EGG
(NAKED EGG)



This experiment changes the density of a raw egg, right before your eyes! All you need is some time (this usually happens within 30 minutes) and a few kitchen ingredients.

Materials Needed:

White Vinegar
Jar
Raw Egg
Food Coloring (optional

Instructions:

1. Fill your jar about halfway with vinegar. Add some food coloring if desired. When you add your drops of food coloring, pay attention to what happens to the drops! They should sink straight to the bottom, while pooling in a sort of puddle. That's because the food coloring is more dense than the vinegar! After your done admiring the swirls, stir it to mix the color into the vinegar.

2. Carefully place your raw egg in the bottom of your jar.

3. Observe - what do you see happening to the egg shell?

4. Wait approximately 30-60 minutes. Observe and discuss any changes you see on the egg.

5. Place your jar in a refrigerator overnight. As you take it out the next morning, what has happened to the egg? Take it out and carefully examine the surface. Are there any changes to the surface of the egg? Are there any changes in the size of the egg?

What Happened?
You should immediately see some bubbles forming on the egg. This is the result of the acid in the vinegar, reacting to the alkaline calcium carbonate that makes up the egg shell. It begins dissolving the egg, and releasing carbon dioxide bubbles on the shell.

You should see the egg floating towards the top of the jar. This is because the acid has dissolved enough of the egg shell to change the egg's density! You can even see some of the byproducts of the shell as a film on top of the liquid.

As you leave your egg in the jar overnight, you will find that the eggshell has completely dissolved, leaving behind a translucent membrane on the egg! It will also have grown quite a bit larger, as through the process of osmosis (where a solution flows through a semi-permeable membrane to equalize concentrations of the solution), the egg has "absorbed" quite a bit of the vinegar!



NOTE: This demonstration is often referred to as a "bouncy egg" due to its rubbery texture. Don't be fooled, this is not a bounce ball! It will bounce slightly on a surface, however, it's membrane is also fairly stretched due to the amount of vinegar the egg has absorbed. If you would like to test it's elasticity, or bounce factor, I'd definitely recommended doing it outside! It will eventually pop, and it will be a vinegar/egg mess!

Okay, so we've explored some raw egg experiments, but what about all of these hard boiled eggs? After Easter, we usually have a ton of these sitting around, and there are only so many deviled eggs or egg salad sandwiches I'm going to want to eat in the coming days after Easter.

Well, there's yet another experiment where we can explore density, and get some air pressure in while we're at it! For this demonstration, I ask you...

How can we get raw eggs into smaller jars, without touching them, and using only a piece of paper?

EGG IN A BOTTLE


Materials Needed:

Medium Hard Boiled Egg
Glass jar with an opening that is slightly smaller than the egg
Lighter/matches
Index card or piece of card stock
Adult Supervision.

Instructions:

1. Set your egg on top of your jar, making sure it fits securely on the lip (no gaps). We took a hard boiled egg with us to the dollar store to get our jar, so we could make sure it fit.

2. Ask your kids how to get the egg into the jar without touching it, using only a piece of paper! As they brainstorm and try different ideas, talk about how the air inside of the is made of "stuff", atoms and molecules. There is the same amount of stuff inside the jar as there is outside of it.

3. Invite your children to step back and spin around in a circle, with arms open wide. Feel the wind? That's the "stuff" that's in the air! It's also in the jar and it's what is pushing up and down on your egg!

4. Now we're going to get rid of some of that stuff. Ask your kids to step back, as you bring up your lighter and a small piece of paper.

5. Remove the egg from the top of the jar. Light the paper and and drop it to the bottom of the jar, and immediately set the egg back on top.

6. Observe!



What's Happening?


When you lit the piece of paper, it caused the air molecules inside the jar to become excited. The molecules bounced around, expanding in the jar! They pushed the egg out of the way, which allowed some of the gas to escape. Once the air cooled back down, there was more pressure on top of the egg pushing down on it. So, it pushed the egg into the jar!

Finally, now that we've explored physics and chemistry with our eggs, let's finish it all off with a little bit of arts and crafts! You've heard of egg races, where people hold an egg on the spoon and race across the room, hoping the egg doesn't fall and break? Well, we're going to hold our own egg races, with a bit of a twist. We'll be using hard boiled eggs so if they fall, there's no mess!

EASTER EGG RACES!



Materials Needed:

Craft supplies (popsicle sticks, plastic eggs, index cards or cardstock, googly eyes, etc).
Tape
Hot glue gun
Plastic spoons

Instructions: 

1. Tell the kids that they are going to have an egg race across the floor! They need to use their spoon to carry their egg, and they need to build a container to hold the egg in place as they run! They can use any of the craft supplies you have on hand. Their mission is to not drop their egg as they race!

2. Create a start/finish line on your floor with masking tape. Once the kids are finished crafting their egg holders, have them line up at the start line!

3. Now it's time to RACE! First, have the kids to a standard race to the finish line. Then, have them take turns with other kids of races! Make them hop on one foot, make silly faces as sounds, move their eggs up and down as they wiggle across the floor. Make up all kinds of fun ways to race across the floor and test the durability of their egg holders!




There are a lot of wonderful ways to explore science at home. After Easter, when you've got a ton of eggs around in the kitchen, give some of these a try!

As always...

HAPPY EXPLORING!!!

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