Author: Maddie Van Beek

This summer has been HOT! When it gets this warm outside, it's time for some frosty treats! Today we're going to make our own homemade ice cream and homemade slushies WITHOUT using a freezer! We'll use the same scientific principles for both activities, so let's get learning!



The History of Ice Cream:

We shared a blog last summer about ice cream, and this gives some great background on the history behind this tasty treat. Check it out here: https://www.discoveryexpresskids.com/blog/cool-down-with-ice-cream



Today, we're going to focus on the science behind homemade ice cream. How do you get the ingredients to freeze without a freezer?



The Science:

Normal water freezes at 32 degrees Fahrenheit. Your goal is to get your ice cream mixture below that temperature so it will freeze. The problem is, just packing ice around the mixture won’t do the trick. Why is that? The ice will begin to melt at room temperature, so while it will definitely cool the mixture down, it won't get it cold enough to freeze the mixture. That leads us to our secret ingredient: salt!


If you add salt (sodium chloride) to ice, it can drastically lower the temperature to almost zero degrees Fahrenheit (0°F)! THAT'S cold enough to quickly begin freezing your ice cream mixture. How does salt do that?!


Take an ice cube out of your freezer and place it on the table. Sprinkle a little salt onto the ice cube and watch carefully. It quickly begins to melt! That's why you see people sprinkling salt on icy roads in the winter--salt lowers the freezing temperature of water. Usually, water freezes at 32 degrees/ice begins to melt at 32 degrees Fahrenheit (32°F). When you add salt to water, it has to be much colder in order to freeze. Thus, ice that would normally remain frozen on a sub-32 degree day begins to melt when you add salt.


It seems strange to melt our ice in order to get our ice cream mixture colder, but remember, even though the salt causes ice to melt, it actually is lowering the overall temperature. The subsequent water is still super cold, it's just liquid instead of solid. So you'll see the salt begin to melt your ice, but it's essentially cooling down your ice cream mixture inside!


Now that you know the science behind our activity, let's get to it!


The Classic: Homemade Ice Cream



YOU WILL NEED:
* Cream
* Vanilla
* Sugar
* Gallon zip-top bag
* Quart zip-top bag
* Ice
* Salt




Here's what to do!
1. Measure 1 cup cream (Half and Half), 2 tablespoons sugar, and 1/2 tsp of vanilla extract into your smaller zip-top bag. Seal it so it is tightly closed!
2. Measure about 6 cups of ice and 1/2 cup salt into your gallon size zip-top bag.
3. Place the small bag of your ice cream mixture into the larger bag of ice and salt.
4. Seal the large zip-top bag and start shaking! Don't throw the bag or shake it too hard--you don't want any leakage!
5. After just a few minutes, you should feel the mixture begin to get firmer. Once it feels like a thick enough consistency, open your large bag and remove the small one.
6. Open your small bag and enjoy! You can carefully dump your ice cream into a dish and top with syrup or sprinkles, or you can just eat it right out of the bag!

Extension:

Use other ingredients to make healthier frosty treats! Try using yogurt instead of cream. Does it take more or less time to freeze? Another great trick is using blended bananas! It gives you a great, creamy texture without all the fat and added sugar.


Banana “Nice” Cream

* 2 ripe bananas
* Ingredients of your choice! (I used mint extract and dark chocolate chips)
* Gallon zip-top bag
* Quart zip-top bag
* Ice
* Salt

Here's what to do!
1. Put two ripe bananas in a food processor or blender, and blend until smooth. Add 1/2 avocado for a creamier texture or some cashews for something more hearty.
2. Add your mix-ins. I picked mint extract and dark chocolate chips, but peanut butter, nuts, or fruit would also be great! You can blend them in, or you can add afterwards.

3. Pour your blended bananas into the quart zip-top bag and seal.

4. Put your ice and salt in the gallon bag, then place the small bag of your ice cream mixture inside. Seal the gallon bag and start shaking! You’ll notice the ice begins to melt pretty quickly!

Within about 5 minutes, my nice cream was ready to eat!

5. Enjoy!

Freezerless Slushy

* YOU WILL NEED:
* Fruit juice
* Gallon Zip-top bag
* Quart Zip-top bag
* Ice
* Salt


Here's what to do!
1. Measure about 1 cup of fruit juice into a quart sized zip-top bag and seal shut.
2. Repeat steps 2-6 from the homemade ice cream activity.
3. Enjoy!

Suggestion:
If you're an athlete or using this recipe for after working out, use an electrolyte sports drink so you have a frosty recovery treat! Even if you’re not working out, it’s super important to stay hydrated in this hot weather. This electrolyte slushy is just more fun :]


Before shaking:

After only 2 minutes of shaking:

After two more minutes:

Ready to eat!

Author: Maddie Van Beek


This week was Independence Day, and we're going to continue the fun with some 4th of July themed science activities! First, we will learn about surface tension and chemical bonds by making fireworks in milk! These fireworks don’t explode, but they do create awesome swirling colors! Let’s get started!


We are going to find out how a simple drop of dish soap can make big changes in milk.
First of all, what is milk made of? Make a list.
.
.
.
You may have listed vitamins, minerals, fats, and protein (all great nutrients for our bodies!) but milk is made up mostly of water. All the other stuff is evenly distributed as a solution held together by weak chemical bonds.

A chemical bond occurs when two or more atoms are attracted together and combine to create something new. Atoms may be attracted to one another for many different reasons, but nearly all bonds form because the final products are more stable than the original reactants. Some bonds are stronger than others. Weaker bonds are more easily broken. Can you think of anything else that might involve chemical bonds? Make a list!


Even the simplest things can be created with chemical bonds, such as water and air! Water is hydrogen bonded with oxygen (H2O), while air is two oxygen molecules bonded together (O2).


Because the chemical bonds in milk are relatively weak, the solution is easily altered. When you add a drop of dish soap, for example, the bonds are broken. Once broken, the molecules of fat and protein move around and bump into each other.

Why does dish soap cause this? Think about trying to wash a greasy plate with no soap. The grease just resists the water, and you can never quite get it clean. If you add dish soap, no problem! The grease comes right off with the suds. Why is this? Dish soap links grease and water together! The hydrophilic (water loving) end of dish soap molecules are attracted to water while the hydrophobic (water fearing) ends bind to the grease. This brings the water and grease together, which allows you to scrub the grease off.

Let’s see this in action!

YOU WILL NEED
* Whole Milk
* Food coloring
* Dish soap
* Cotton swabs
* Dinner Plate (make sure it’s deep enough to hold about 1/4 inch of liquid)
​
Here’s what to do!
1. Carefully pour milk onto the dinner plate until it is about 1/4 inch deep.

2. Add one drop of red food coloring into the center of the milk on the plate. Be careful not to bump the plate!
3. Add one drop of blue food coloring near the first drop.
4. Continue to carefully add a few other drops.

5. Select a cotton swab.
6. PREDICT: What will happen when you touch the cotton swab to the center of the milk?
7. Touch the cotton swab to the center of the milk and record what happens.
8. Select a second cotton swab and squirt a small drop of liquid dish soap onto the end.
9. PREDICT: Now that you have added liquid dish soap, what will happen?
10. Check it out! Touch the cotton swab with dish soap to the center of the milk and hold it there for 15 seconds. How was this different than the first time you touched the plain cotton swab to the milk? Record your observations!
11. Select another cotton swab, add a drop of dish soap to the end, and try it again. What happens when you place the swab at different points in the milk?

Reflect
What exactly did you observe? Why did the dish soap cause the colors in the milk to move?

Extension
How can you make this demonstration an experiment? Instead of just using one kind of milk, try out this activity with different kinds of milk. For example, you could use skim, 1%, and 2%. You could also choose milk alternatives such as almond milk or soy milk. Observe the differences and then compare and analyze your results! You could also try different kinds of soap or sanitizer. Is one more effective than another?


Red, White, and Blue Density Tower

Next, you will be experimenting with liquid density. When you dump more than one liquid together, what do you think happens? If the densities are the same, they will just mix. For example, yellow Gatorade and blue Gatorade would make green. But if the densities are different, you can actually layer liquids to make stripes in a jar! Before we try layering any liquids, you need to know a little bit about density.

Density is the amount of matter in a given space. The density of any given liquid (or solid or gas) is determined by how closely the molecules in that liquid are packed together.

Think about it. Let’s say you put five gummy bears into a Ziploc bag for your little brother and 20 gummy bears into the same size Ziploc bag for yourself. Whose bag of gummy bears is more dense?

A liquid with fewer molecules per unit of volume is less dense than a liquid that has more molecules per unit of volume.

​Which figure is more dense?

If a liquid weighs more than than another liquid with equal volume, the heavier liquid has a higher density. The higher density liquid will sink below lower density liquids. Let’s check out an example that you are probably very familiar with.

Demonstration: Pour 1/4 cup oil and 1/4 cup water into a glass. Which liquid sinks to the bottom (aka, which liquid is more dense?)

What does this tell you about these two liquids?

So you know that water is more dense than oil. Now, let’s try this out with a bunch of
liquids. By using many liquids of varying densities, you can make liquid stripes in a jar!

YOU WILL NEED:
* Jar or clear glass
* Food coloring
* Water
* Olive oil
* Corn Syrup
* Dish soap

Here’s what to do!
​
1. The first liquid that you will add to your jar is the corn syrup. Make sure you pour it straight into the middle of the jar--be careful not to get it on the sides!

5. You’re done! You have your stripes in a jar!

Follow-up Questions:
* How were you able to layer liquids?
* Explain why these liquids didn’t just mix together.
* Were you surprised by your results? Why or why not?
* Draw your density tower and label each layer to record which liquids are more or less dense.
​
Extension: Try this out with different liquids! See if you can discover densities of other common liquids in your home.