Today, we're going to use our Christmas candy to learn about phase changes!
Why do things melt?
Melting is actually a scientific process called a "phase transition." There are three different physical phases of matter: solid, liquid, and gas.
Every item you see around you is made up of molecules. Molecules are the building blocks of everything! However, the structures that molecules form are not necessarily permanent; they can undergo physical or chemical changes. Let’s explore this:
Grab a handful of gumdrops and make a square. Pack them as closely together as possible in neat lines. This is what the molecules in a solid phase object look like. The molecules are in a nice, tight order, and can hardly move. If a solid is heated, the molecules start to shift.
The next phase is liquid. Move the gumdrops a little further apart from one another. They might not be in straight lines, but they are still fairly close together. Liquids can move and shift and change shape, but the molecules still sort of stay together. Picture an ice cube left out in the sun. After a short amount of time, the ice begins to melt. Ice melts at 32 degrees Fahrenheit, but every substance melts at a different temperature. The point at which a solid changes to a liquid is called the melting point. Even rocks can melt if they are heated to a high enough temperature!
Heat a liquid even more, and the phase changes from liquid to a gas. Move your gumdrops even further apart from each other. They don't need to be in any sort of pattern at all. When a substance is in the gas phase, the molecules can spread apart and fill a whole room! For example, when water is heated, it evaporates into the air! What's another gas you can think of?
Now you know the three physical phases: solids, liquids, and gases. Heat causes a phase change from solid to liquid, or from liquid to gas. Every substance has a different melting point, the point at which a solid changes to a liquid. Why do some objects not melt at all?
Some substances, when heated, will combust (burn) before they ever melt. Instead of staying solid until they reach their melting points, they react with oxygen and burn instead. This reaction is a chemical change. For example, if you burn a piece of paper, it changes form from paper to ashes. This chemical change is irreversible; you cannot change ashes back to paper.
Make a list of items you think would melt, like a plastic toy, and a list of items you think would burn, like a piece of paper.
Items that melt, like ice melts into water, are undergoing physical phase changes.
Items that burn, like paper or wood, are undergoing a chemical change.
Now, let's start our experiment!
YOU WILL NEED:
A variety of Christmas candy
-Paper and pencil
Here's what to do!
1. Make a list of the Christmas candy you have.
2. Next to the name of the candy, draw an X if you think it will melt. Draw a circle if you don't think it will melt.
3. Now, number the items from 1-4 based on which you think will melt first to last (1 is fastest, 4 is slowest).
4. Place the saucepan on the stove, and turn the heat to medium-low.
5. Place the unwrapped candy cane in the center of the saucepan.
6. Time how long it takes for the candy cane to start melting. Record what you find.
7. Carefully rinse out your saucepan with cool water, and wipe clean.
8. Place the saucepan on the stove, and repeat the process with the Oreo, the chocolate, and the gumdrops.
9. Compare your results to your guesses.
10. So, which item has the lowest melting point? Which one has the highest melting point?
The Oreo was the same from 0-10 minutes. The frosting softened, but the cookie remained unchanged.
1. Preheat the oven to 400 degrees Fahrenheit.
2. Cover a baking sheet with tin foil.
3. Place a cookie cutter on the tin foil.
4. Fill the cookie cutter with gumdrops. Be as creative with your design as you wish, but make sure to pack them tightly so there isn’t any space in between the gumdrops.
7. Repeat with crushed candy cane or hard candy for a stained glass look! For the candy cane, reduce the temperature to 350 degrees, and it should only take 7 minutes to melt (check every minute after 5 minutes). It is difficult to remove the
design from the cookie cutter once it solidifies, so don’t worry if it breaks. It still looks like cool stained glass! (You could also try lining the inside of the cookie cutter with tin foil to make it easier to remove the shape.)