Experiments at the Children's Desk - Eggs-periment!

This was probably our grossest (in a good way!) experiment yet--and it didn't turn out exactly like the fabulous blog post we modeled it after, which can be found here. As always, we had a lot of fun and said the word "membrane" a lot that particular week.

The first stage of the experiment went smoothly--we placed two eggs in mason jars filled with vinegar. Our goal was to dissolve the shell of the egg and create semi-permeable membrane. This stage alone makes for an interesting experiment, because when you take the egg out after about 24 hours, you can bounce it! (Just a little, not as high or with as much intensity as a bouncy ball.)

Pictured here is one of our eggs in vinegar. The vinegar contains acetic acid, which breaks apart the solid calcium carbonate crystals that make up the eggshell. The calcium ions float free (calcium ions are atoms that are missing electrons), while the carbonate goes to make carbon dioxide—the bubbles that you see.

24 hours later, most of the eggshell was dissolved. We gently washed off any remaining bits and ended up with two bouncy eggs! Success! Now here's where the eggs-periment didn't go quite as planned...

Next, we put the eggs in two different solutions. The first egg was put into a jar of tap water with a pinch of red food coloring (to differentiate--and see if the membrane would absorb the color). The second jar contained sugar-water. However, we didn't follow a specific recipe to get the results we wanted. We simply made a sugar-water solution instead of measuring out the sugar and water to ensure saturation. That doesn't sound very scientific now, does it?! After searching the web, we found that other people used corn syrup or treacle in order to get the desired results.

 As you can see from the  Science Sparks post that we linked to, the egg in a sugar and water solution should absorb less water than the egg in water. However, we believe that our water was not saturated with enough sugar, and therefore both of our eggs were roughly the same size after a few days in their respective solutions (the weight of the eggs is unknown) because water was able to permeate through the membranes of both eggs at a similar rate.

We also attempted to poke the egg that had been in the water, hoping that water would start streaming from the hole. Perhaps the end of a thumbtack was a poor choice, as this is what we ended up with:

It is probably a good idea to use a thin needle instead!

While this experiment didn't turn out exactly like we planned, it was a lot of fun and comes highly recommended!

Experiments at the Children's Desk - Colorful Celery

This experiment shows how plants absorb water—which usually would not create a change in the color of the plant because water usually has no color. We wanted to see how celery absorbs water by using food coloring!

First, we put the celery stems (called  the petiole) in colorful jars of water. 

Eventually, the petiole and leaves of each stem absorbed some of the color. This is because the celery petiole has tiny tubes that the water travels through. If this celery was still in the ground, its roots would absorb the water from the ground.

The blue food coloring yielded the prettiest result, whereas the yellow gave us the most unnoticeable result (as we predicted since it's such a light color and very similar to the celery leaves). We then decided to combine some colors: we placed the stalk from the yellow jar into the red, and moved the stalk from the red jar into the blue. What do you think we were hoping to achieve?

The stalk that we put in red water after yellow definitely gave us orange--but check out the photo on the right: that's the stalk we moved from red into blue. Instead of just blending, we ended up with leaves of many different colors! We think perhaps this was due to the initial stalk itself--its foliage was slightly withered to begin with.

Experiments at the Children's Desk - Rock Candy!

Last week, we debuted our special Fizz, Boom, Read! Summer Reading display at the CHPL Youth Services Desk. It's been a very sweet week--we moved from gummy bears to rock candy! We started out with this recipe from About.com, and, as always, did it in our own special way.

First, we followed the recipe *almost* exactly how it was presented, using 3 cups of sugar to 1 cup of water. This proved difficult, especially given that we were using a hot plate rather than a traditional pot on a stove. It was difficult to get 3 cups of water to boil because the device is meant to heat water for food and does not go past a certain temperature. We then microwaved the mixture which we believe helped the experiment yield good results the first time around. We hung a string on a popsicle stick over a mason jar (how stylish!) and used a paperclip to weigh it down. Were we to be eating this candy, we probably would not have used a paperclip for safety reasons. The result was great after one day:

We decided to see what would happen if we put a new string in the old mix. We ended up with a jar full of caverns and groups of sugar crystals, but not another string of rock candy. We read that we might be able to re-use a mixture--but we would have to reheat it in order to rearrange the molecules once more. Below you will find an explanation for this issue as well as the basic scientific concepts behind growing sugar crystals.

The basic principle behind growing sugar crystals is to put so much sugar in the water (3 cups sugar to one cup water in our case) to the point where the water can no longer contain all of the sugar molecules. When this happens, the sugar will creep out of the

water, forming crystals.

Q & A

Q. What do you think we did to the water to make the sugar

dissolve?

A. We had to boil the water in order for the sugar to dissolve.

Q. Why do we have to boil the water?

A. When the molecules are heated, they move around more,

making room for more molecules. When the molecules freeze, they slow down and expand, making less room inside a solution for other materials. When making a sugar solution designed to make crystals, we have to completely saturate hot water with sugar until no more can dissolve. This makes it possible for the crystals to grow when the water cools.

Q. Why don’t the jars of sugar-water have lids?

A. This experiment also requires the water to slowly evaporate from the jar to make room for the sugar to form crystals.

(Source)

Another way to ensure a more successful batch of rock candy is to wet and dry the string and rub sugar on it before putting it in your jar/container. The sugar acts as a "seed" and guides the molecules toward it. When we did not boil the water all of the way, we were significantly less successful. We also found that the project was much more manageable when we used 1/3 of the recipe, but be careful using such a small amount of water on the stove--you don't want to ruin your pan/pot!

This project was a LOT of fun, but following directions is really important. We imagine making these with flavors would be absolutely delicious!

                                                

Our most successful batch--this is the result after about 4 days. We were able to dissolve the sugar until the water was clear again because we made a smaller batch. Since the water was fully saturated, perfect crystals formed as we waited patiently!

Experiments at the Children's Desk - Gummy Bear Science

This past week, we've been having a lot of fun in the youth services department. We're conducting experiments in our programs and at our desk now, too! Throughout the summer, we will have a rotating display of different science experiments and projects on display. First, we decided to see what would happen if we let gummy bears soak overnight in four different liquids: water, vinegar, water with baking soda, and saltwater.

We got the idea from the Science for Kids blog. The detailed work of measurement and worksheets would be better suited for an ongoing program, in the classroom, or at home, so we put our own spin on the activity. We lined up the bottles with the different liquids and taped down the normal gummy bears so that our young scientists could look at the differences in size, shape, and texture overtime. Children, parents, and caregivers made observations throughout the day and hypothesized about what might become of the soaking bears. The results were slightly tragic--most of them dissolved after about 24 hours! Our bears were completely immersed in air-tight bottles, which may have made our experiment slightly different from other results found on the web.

The bears in water, salt water, and vinegar all tinted their liquids with their respective colors, whereas the water and baking soda mixture remained quite translucent.

 The only gummy bear that survived was in the salt water, and he was quite inflated and jiggly!