STEM @ Home presents: Newton's first law of motion: An object in motion tends to stay in motion and an object at rest tends to stay at rest.
You need a butter knife, a table and a stack of coins.
Stack the coins near the edge of the table, within reach of the butter knife. Swipe the butter knife horizontally at the bottom coin. The stack stays upright but the bottom coin goes shooting off. Why?
You exerted an outside force on the bottom coin, putting in motion, while the stack was untouched so it stays at rest. And don't forget about the friction between all of the coins in the stack.

2 cups and toilet paper roll - it's gonna get loud in here!
Cell phone speakers are tiny and tinny but you can make your music sound Bigger and better with this project.
Why?
The sounds from your cell phone are waves spreading out in all directions. When you put your phone inside this speaker the waves bounce around inside the tube and cups so almost all of the sound waves come out the front.  Try crumpling a half of a paper towel and placing loosely inside the end of each tube. This will absorb of the high pitched sounds and make your music sound less tinny.

What happens when you put a marshmallow in the microwave?
It makes a monster one!
Place a marshmallow on a microwave safe plate and set for 30 seconds. Watch closely. After the 30 seconds remove from microwave safely, the plate will be hot.
Why?
Marshmallows contain lots of air pockets. When air heats up and pushes against the soft sugary walls. Air is gas and when gases heat up the molecules they are made of start moving freely at high speeds. This creates the increase of pressure and the the expanding of the marshmallow.

Making a treasure map? An in home scavenger hunt?The easiest invisible ink is lemon juice. All you need is lemon juice, a paint brush (or cotton swab) and white paper. and a heat source to make it legible.
Write a message by dipping the brush in lemon juice and drawing on the white paper. Will you say a secret message, leave a code or make a map? Let it dry. Now your ink is invisible.
To make is visible: preheat the oven to 400 degrees. When it is hot enough put your paper on a cookie sheet and place in the oven. After about half an hour your message will become visible.
Why?
Paper is made from a compound called cellulose, a bunch of molecules bonded together. The citric acid in lemon juice slowly weakens the bonds between these molecules and frees some of them. When the paper is heated these free glucose  molecules react together in a chemical process called Caramelization. This produces new compounds that have a brown color. So it make the ink visible!

Recipe: 1/4 lb of cornstarch, 1 oz of shampoo, warm water, food coloring

Put a few drops of food coloring into a bowl, add the shampoo. Notice how the shampoo flows - that is what scientists call viscosity. Add the cornstarch and mix with spatula. Add warm water a tablespoon at a time and mix after each one.  The water make the starch expand forming a network that holds the water and cornstarch together in a slimy mix. Gradually your mixture will turn into a thick paste.
If you pick it up and knead it in your hand it gets gloopy but if you thump it it gets hard.
Why? Starch molecules are bigger than water molecules so if the mixture can move around it stays liquid - but sudden pressure jams the molecules together so the mixture can't flow because you squeeze out the water molecules.
Keep it in a sealed container if you want to use it later.