Does hand-washing really get rid of germs? Yes! Scrubbing your hands with soap and water for the length of time it takes you to recite the ABC’s will get rid of the majority of harmful microbes on your hands.
Here’s a video on how to make Petri plates for a hand-washing experiment, where you touch labeled sections of the plates with your fingertips before washing, after washing with water alone, and after scrubbing with soap or hand sanitizer. You can also use the plates to swab and grow microbes from around your house or school!
Find the recipe for Petri Plates in my book Kitchen Science Lab for Kids, or click here for a link to the recipe on my original blog post, where you can also read more about the science!
Under the right conditions, purified water can get much colder than 32 degrees before it freezes into a solid. This “supercooled” water will instantly freeze when it touches an ice crystal.
You don’t need a special lab to make supercooled water. In fact, you can make it in your own freezer!
1. Place three 12 oz bottles of water (caps loosened and re-tightened) in the freezer. Two should be filled with purified water and one with tap water.
2. Wait 2 hours and then check them every 5 minutes. When the tap water is frozen, gently remove the other two bottles from the freezer. (Tap water freezes first, because it contains some impurities that help ice crystals form more easily.)
3. Carefully open one bottle of purified water and pour it onto a few ice cubes on a plate. The supercooled water from the bottle will instantly crystallize into ice when it hits the cubes, making slush. Try it with the second bottle. There may be some freezing time variation between freezers, so you may have to experiment to find the perfect amount of time it takes your freezer to supercool water!
You can do the same thing by putting bottled water in a cooler full of ice, salt, and water. Salt lowers the melting temperature of ice, which makes the salty ice water cold enough to freeze bottles of liquid. Try the same experiment using soda to make a slushy! (From Outdoor Science Lab for Kids-Quarry Books 2014)
Have you ever wondered why putting chemicals like salt on a road makes the ice melt?
To see how NaCl (table salt) melts ice by lowers the melting temperature of water, you’ll need an ice cube, a glass of water, and a piece of kitchen twine or string about 6 inches long and salt.
What to do:
Drop an ice cube in a glass of ice water. Try to pick the ice cube up without your fingers by simply placing the string on it and pulling up. Impossible, right?
Now, dip the string in water, lay it across the ice cube and sprinkle a generous amount of salt over the string/ice cube. Wait about a minute and try again to lift the cube using only the string. What happens?
It may seem like magic, but it’s only science. Here’s a video from my KidScience app where I demonstrate the experiment.
Salt lowers the temperature at which ice can melt and water can freeze. Usually, ice melts and water freezes at 32 degrees Farenheit, but if you add salt to it, ice will melt at a lower (colder) temperature.
The salt helps the ice surrounding the string start to melt, and it takes heat from the surrounding water, which then re-freezes around the string.
Different chemicals change the freezing point of water differently. Salt can thaw ice at 15 degrees F, but at 0 degrees F, it won’t do anything. Other de-icing chemicals they add to roads can work at much colder temperatures (down to 20 degrees below zero.) If it’s cold enough, even chemicals won’t melt the ice.
Pressure can also make ice melt at colder temperatures. This is why ice skates glide on rinks. The pressure is constantly melting the ice a where the blade presses down on it so the blade glides on a thin layer of water!
It’s fun to track the weather, and you can create some cool meteorology instruments using stuff you have around the house. Here’s a great post by NOAA (The National Oceanic and Atmospheric Association) on how to make your own weather station.
It’s also fun and easy to do this cool convection current experiment, using warm and cold water to explore how air moves in Earth’s atmosphere.
To see how cold fronts move under warm fronts, you’ll need ice cube trays, water, blue and red food coloring and a clear container.
- Add water to an ice cube tray and add a few drops of blue food coloring to the water in each cube space. Freeze.
- Fill a clear container with room temperature water.
- Place one or two blue ice cube or two at one end of the container, and a few drops of red food coloring at the other end.
- Observe what happens.
The Science Behind the Fun:
Cold water(blue) is more dense than warm water and forces warmer water (red) to move up and over it.
This is similar to the way warm air is forced up when it collides with masses of cold air in the atmosphere. Warm air carries energy, and when there’s lots of moisture in the air, these collisions often result in thunderstorms.
(Adapted from Kitchen Science Lab for Kids)
Grab an extra bag of cranberries this Thankgiving! Kids can use it to reveal invisible messages they write with baking soda and water.
-around 2 cups of cranberries
-small paintbrush, Q-tip, or lollipop stick
Safety tips and Hints:
Boiling the berries should be done by an adult. Keep the lid on the pan, since the air pockets that make cranberries float can also make them explode. Kids can take over once the juice is cool.
When playing with cranberry juice, aprons or old clothes are a good idea, since it stains!
Step 1. Cut a cranberry in half and observe the air pockets that make it float.
Step 2. Boil the cranberries in about three cups of water for 15 to 20 minutes, covered. Listen for popping sounds as the air in the cranberries heats up and they explode.
Step 3. Crush the cooked berries and push the liquid through a sieve or colander to collect the concentrated cranberry juice.
Step 4. Allow the juice to cool and pour it into a casserole dish or cake pan big enough to hold a piece of paper. If your cranberry juice seems thick and syrupy, add a little water, so that it’s thin enough to soak into paper!
Step 5. Test the paper you want to use by cutting a small piece and soaking it in the cranberry juice. If it stays pink, it will work, but if it turns blue or gray, try some other paper.
Step 6. Add a few teaspoons of baking soda to 1/3 cup of warm water and stir well. Don’t worry if you can still see some baking soda.
Step 7. Using a Q-tip, paintbrush, or a homemade writing tool, use the baking soda solution as ink to write a message on your paper. It may take a little practice, so don’t get frustrated.
Step 8. Let your message air dry, or speed things up with a blow dryer.
Step 9. To reveal your message, place your paper in the cranberry juice and see what happens!
*What other natural acid/base indicators could you use to do this experiment? What else could you use as ink.
The Science Behind the Fun:
Cranberries contain pigments called anthocyanins (an-tho-SY-a-nins,) which give them their bright color. In nature, these pigments attract birds and other animals to fruit. This is important because animals eat the berries and spread plants seeds from one place to another.
These pigments, called flavanoids, change color when they come in contact with acids and bases. Cranberry juice is very acidic, and the pigment is pink in acids, but when you add it to a base, it turns purple or blue.
Baking soda is a base, so your baking soda message will turn blue when it comes into contact with the pigments in the cranberry juice. Eventually, when enough cranberry juice soaks into the paper, it will dilute the baking soda, turning the pigment back to red and your message will disappear!
There are over 300 kinds of anthocyanins which are found in many fruits and vegetables including blueberries, red cabbage, grapes and blueberries. Scientists believe they may have many health benefits.
We supersized the foaming slime experiment from Outdoor Science Lab for Kids to make a giant foaming slime volcano. And it was awesome!
This bloody candy experiment takes a few weeks , but is worth the wait! If you start today, you’ll have gorgeously gruesome rock candy, dripping with sugary fake blood, in time for Halloween.
This experiment requires adult supervision for boiling and handling the hot sugar syrup. Once it’s cooled down, kids can take over.
To make 12-15 sticks, you’ll need the following:
-2 and 1/2 cups white granulated sugar
– 1 cup water
-cake pop sticks or wooden skewers
-red food coloring
- Dip one end of cake-pop sticks or wooden skewers in water and then roll them in granulated white sugar. The sugar should cover 2-3 inches of the stick. Let them dry completely. These are the seeds for the sugar crystal growth.
- Boil 2 cups water and 5 cups sugar until sugar is dissolved as much as possible. It should look like syrup. Once it cools, this syrup is your supersaturated sugar solution.
- Let syrup sit until it is no longer hot and pour into a large glass jar or deep bowl.
- When syrup is completely cool, set the sugary end of the sugar-seeded cake pops or skewers into the syrup, evenly spaced in the jar. Cover loosely with plastic wrap and let them sit for about a week. Gently move the sticks around occasionally, so they don’t stick to each other and the crystals in the bottom of the glass. If the glass container gets too full of crystals, pour the syrup into a new container and move your stick into the cleaner syrup to grow more crystals.
- When the rock candy is done, pull them from the syrup and let them dry. Save the syrup.
- To serve, pour a few cm of your sugar syrup into the bottom of a pretty glass and add a few drops of red food coloring. You can even add a little flavoring to the syrup (like cherry extract.) Stir.
- Put your rock candy, handle side up, into the glass. Be sure to give your guests napkins, so they don’t drip “blood” all over the house!
How do Crystal Grow?
Like bricks in a wall, crystals are solids formed by a network of repeating patterns of molecules. Instead of the mortar that holds brick together, the atoms and molecules are connected by atomic bonds.
Crystals that share the same chemical composition can be big or small, but the molecules always come together to form the same shape. Table sugar, or sucrose, is made up of a molecule composed of two sugars, glucose and fructose. Crystals formed by sucrose are hexagonal (six-sided) prisms, slanted at the ends.
The crystals on your rock candy sticks grow from the “seeds” of the sugar you rolled on the stick before you put them in the syrup.
If you got any sour gummy worms for Halloween, they’re probably coated with sweet-sour powder made from citric acid and sugar crystals. Using the same science used to make rock candy, you can use sour gummy worms to crystallize sugar syrup and make an”icy worm pond.” It’s even more fun to add sugar cubes to your pond! After a few days, you can chip your worms out of the “ice” to see how they taste. I created this experiment for Imperial Sugar and Dixie Crystals. Check it out on their website (click here) for directions and to learn more about the science behind the fun!
If you don’t have sour worms, try coating other (non-chocolate) candy with sugar by dipping it in water, rolling it in sugar and letting it dry before you add it to your pond. It would be fun to do this experiment with Swedish fish, or lifesavers!
Can you make up an experiment using Halloween Candy? Comment on this post with the experiment you created and you could win a copy of Kitchen Science Lab for Kids*!
*Winner will be chosen at random.
My book, “Kitchen Science Lab for Kids,”is finally out, and over Labor Day weekend, I traveled to Dragon Con in Atlanta to talk about it and do science with the kids at the convention. At the convention, I got to meet lots of fantastic scientists, science writers, science entertainers and science enthusiasts. One of them was the amazing Paul Zaloom, of “Beakman’s World.” I checked out his “Beakman Live” show and learned some awesome new experiments.
I tried one of them out this morning. Check it out, and then try it out! All you need is a playing card, a glass and some water. The science explanation is in the video.
Be sure to catch some episodes of Beakman’s World online!
What happens when food coloring molecules move, or DIFFUSE through gelatin, the substance that makes jello jiggle?
This creative science experiment that my kids and I invented lets you play with floatation physics by sprinkling glitter on melted gelatin, watch colorful dyes diffuse to create patterns and then use cookie cutters to punch out sticky window decorations. Water will evaporate from the gelatin, leaving you with paper-thin “stained glass” shapes.
You can watch us making them on Kare11 Sunrise News by clicking here.
-plain, unflavored gelatin from the grocery store or Target
–a drinking straw
*You can use the recipe below for two pans around 8×12 inches, or use large, rimmed cookie sheets for your gelatin. For a single pan, cut the recipe in half.
Step 1. Add 6 packs of plain, unflavored gelatin (1 oz or 28 gm) to 4 cups of boiling water. Stir well until all the gelatin has dissolved and remove bubbles with a spoon.
Step 2. Allow gelatin to cool to a kid-safe temperature. Pour the liquid gelatin into two large pans so it’s around 1-1.5 cm deep. It doesn’t have to be exact.
Step 5. In the pan with no glitter, use a straw to create holes in the gelatin, a few cm apart, scattered across the surface. It works best to poke a straw straight into the gelatin, but not all the way to the bottom. Spin the straw and remove it. Then, use a toothpick or skewer to pull out the gelatin plug you’ve created. This will leave a perfect hole for the food coloring. Very young children may need help.
Step 6. Add a drop of food coloring to each hole in the gelatin.
Step 7. Let the gelatin pans sit for 24 hours. Every so often, use a ruler to measure the circle of food coloring molecules as they diffuse (move) into the gelatin around them (read about diffusion at the bottom of this post.) How many cm per hour is the color diffusing? Do some colors diffuse faster than others? If you put one pan in the refrigerator and an identical one at room temperature, does the food coloring diffuse at the same rate?
Step 8. When the food coloring has made colorful circles in the gelatin, use cookie cutters to cut shapes from both pans of gelatin (glitter and food coloring), carefully remove them from the pan with a spatula or your fingers, and use them to decorate a window. (Ask a parent first, since some glitter may find its way to the floor!) Don’t get frustrated if they break, since you can stick them back together on the window.
Step 9. Observe your window jellies each day to see what happens when the water evaporates from the gelatin.
When they’re dry, peel them off the window. Are they thinner than when you started? Why? Can you re-hydrate them by soaking the dried shapes in water?
The Science Behind the Fun:
Imagine half a box filled with red balls and the other half filled with yellow ones. If you set the box on something that vibrates, the balls will move around randomly, until the red and yellow balls are evenly mixed up.
Scientists call this process, when molecules move from areas of high concentration, where there are lots of other similar molecules, to areas of low concentration, where there are fewer similar molecules DIFFUSION. When the molecules are evenly spread throughout the space, it is called EQUILIBRIUM.
Lots of things can affect how fast molecules diffuse, including temperature. When molecules are heated up, they vibrate faster and move around faster, which helps them reach equilibrium more quickly than they would if it were cold. Diffusion takes place in gases like air, liquids like water, and even solids (semiconductors for computers are made by diffusing elements into one another.)
Think about the way pollutants move from one place to another through air, water and even soil. Or consider how bacteria are able to take up the substances they need to thrive. Your body has to transfer oxygen, carbon dioxide and water by processes involving diffusion as well.
Why does glitter float on gelatin? An object’s density and it’s shape help determine its buoyancy, or whether it will float or sink. Density is an object’s mass (loosely defined as its weight) divided by its volume (how much space it takes up.) A famous scientist named Archimedes discovered that any floating object displaces its own weight of fluid. Boats have to be designed in shapes that will displace, or push, at least as much water as they weigh in order to float.
For example, a 100 pound block of metal won’t move much water out of the way, and sinks fast since it’s denser than water. However , a 100 pound block of metal reshaped into a boat pushes more water out of the way and will float if you design it well!
What is the shape of your glitter? Does it float or sink in the gelatin?
Here’s a video I made for KidScience app that demonstrates how to make window gellies
Credit: My 11 YO daughter came up with the brilliant idea to stick this experiment on windows. I was just going to dry out the gelatin shapes to make ornaments. Kids are often way more creative than adults!