chapter 6
HOT
AND COLD
Why does one Life Saver melt into a bubbling puddle, while another hot Life Saver stays solid? Why does a Smartie melt faster than an Altoid? What kind of candy makes water cold?
In this chapter, you’ll melt Life Savers and shatter taffy. You’ll have races between different kinds of candy to see what melts faster. You’ll turn Skittles into gaping clamshells. You’ll learn how hot and cold change everything!
CAUTION: IT’S HOT!
Think boiling water is hot? Melted candy can be much hotter. To be safe, always have a grown-up help you heat candy in the microwave or the oven. Watch the candy as it melts. If it starts turning brown or black, or starts to smoke, turn off the heat. Use hot pads to pick up hot plates or dishes. Never touch hot candy with your bare fingers (if you want to see how soft it is, poke it with a fork). Never melt a jawbreaker, because it can explode and cause terrible burns.
Time: 5 minutes
Skill Level: Get a grown-up
Some candies turn soft and fluid in the microwave, but which ones?
What you need:
Starburst, Tootsie Rolls, Laffy Taffy, taffy, or other soft candy
Microwave-safe plate
Block of wood
Microwave
What to do:
1 Place the candies in a straight line on one side of your plate. This will be the “starting line.”
2 Set the plate in the microwave with the “start” side on the block of wood so that the plate slants. This will be your race ramp.
3 Microwave for 30 seconds to 1 minute, and watch your heated candy flow down the plate. Which kind wins?
What’s happening:
Most chewy candy turns soft and fluid when it’s heated. How fast this happens depends on many things, including what shape it is, what kind of sugar it’s made from, and how much water it contains. Since softer candy contains more water (it makes the candy soft and chewy), it becomes fluid at a lower temperature than hard candy.
Are these really melting races? Not quite. Melting happens when you heat up a solid (like an ice cube) to change it into a liquid (water). Chewy candy is already a kind of liquid, even if it’s pretty hard. When you heat it up, you’re just making the candy more fluid.
Time: 5 to 10 minutes
Skill Level: Get a grown-up
What’s the difference between a mint Life Saver and a cherry Life Saver? They’re both hard. They’re both sweet. How different could they be? Actually, a mint Life Saver and a fruit-flavored Life Saver are very different. To see one of these differences, just turn on the oven.
What you need:
Oven
1 fruit-flavored Life Saver
1 white mint Life Saver
Aluminum foil–lined
baking sheet
What to do:
1 Preheat the oven to 300°F.
2 Place the two Life Savers on the baking sheet.
3 Heat the Life Savers in the oven for 5 to 10 minutes. What happens?
(Caution: hot! Don’t touch the hot candy.)
What’s happening:
Compare a Legos structure with a basket full of Legos pieces. If you shake them both, which Legos come apart?
Like Legos, the molecules in the mint Life Saver are locked together, forming crystals. You see the same kind of white crystals when you look in your sugar bowl.
The fruit-flavored Life Saver is made from sugar mixed with corn syrup, which contains many different kinds of molecules. These molecules don’t bond together, so they don’t form crystals. Instead, they make a jumble, like the Legos in the basket.
When you heat the Life Savers, the molecules vibrate. Since the molecules in the mint Life Saver are locked into crystals, they hold together. But in the fruit-flavored Life Saver, the unconnected molecules slide apart. The candy becomes softer and more liquid, spreading out into a puddle.
Life Savers melting race: mint vs. cherry.
Time: 5 to 10 minutes
Skill Level: Get a grown-up
They’re both round. They’re both made of sugar. So which one melts first, Smarties or Altoids?
What you need:
Oven
Altoids
Smarties
Aluminum foil–lined baking sheet
What to do:
1 Preheat the oven to 250°F.
2 Place one Altoid and one Smartie on the baking sheet.
3 Put the baking sheet in the oven.
4 After 5 to 10 minutes, check your candy. Which one melted?
What’s happening:
Altoids and Smarties are made of different kinds of sugar. Altoids are made from sucrose (table sugar). Smarties are made from a different kind of sugar, dextrose (also called “glucose”). Dextrose melts at a lower temperature than sucrose, so the Smartie melts first.
Melting race: Smarties vs. Altoids.
Time: 2 to 5 minutes
Skill Level: Get a grown-up
Can you crack Skittles open like clamshells?
What you need:
Skittles
Microwave-safe plate
Microwave
Alternative:
Aluminum foil–lined
baking sheet
Oven
What to do:
1 Place the Skittles on the plate and microwave them for 1 to 2 minutes. (Alternatively, place the Skittles on the baking sheet and melt them in the oven at 350°F for about 5 minutes.)
2 Do the Skittles crack open like clams?
What’s happening:
Since the insides of the Skittles are soft, they contain more water than the outside sugar shells. This means the insides will soften faster when they get hot, spilling out the sides.
Do some of the Skittles open up like clamshells? Perhaps the hot candy on the inside is creating steam, which pushes up the tops of the Skittles.
Melted Skittles clamshells.
Time: 10 to 30 minutes
Skill Level: Get a grown-up
Snap! That’s what happens to your candy cane if you try to bend it. Is there a way to bend candy canes without breaking them?
What you need:
Oven
Aluminum foil
Baking sheet
Candy cane or straight
candy stick
What to do:
1 Preheat the oven to 250°F.
2 Tear off a square of aluminum foil. Fold it in half, then fold again and again to make a rectangular strip about 3 inches wide (wider than the candy cane). Bend this strip into a fun shape, like a zigzag, an S-curve, or a bowl.
3 Place the foil shape on the baking sheet and put the candy cane on the foil shape. Heat in the oven for 5 to 20 minutes. (The melting time will depend on the size of the candy cane.) Check frequently until the candy cane has softened and curved into the shape of the mold.
What’s happening:
When you’re melting an ice cube, you can see it turn to water. An ice cube is a solid, made from molecules locked together as crystals. When it melts, the molecules break apart. The solid becomes a liquid.
The molecules in a candy cane don’t make crystals. Instead, the candy cane contains lots of kinds of molecules jumbled together, like the fruit Life Saver in the Life Savers Melting Race experiment. When it gets warm, it doesn’t turn liquid right away. Instead, it gets softer and softer as the molecules shift around. That’s why you can turn a warm candy cane into a crazy cane.
In fact, your candy cane has already been heated and bent. A candy cane is made from a straight candy stick that’s bent into a cane shape while it’s still warm.
Melted candy canes turn into crazy canes.
Time: 10 to 15 minutes
Skill Level: Get a grown-up
Here’s how you can stretch one brand of candy canes like rubber bands.
What you need:
Oven
Bobs brand candy cane
Aluminum foil–lined
baking sheet
2 pairs of tongs
What to do:
1 Preheat the oven to 250°F.
2 Put the candy cane on the baking sheet and place it
in the oven.
3 Wait about 5 minutes, until
the candy cane is warm
but not yet melting. Remove the pan from the oven.
4 Using the 2 pairs of tongs, pick up the candy cane and break it apart. Does the middle stretch?
What’s happening:
In this type of candy cane, the middle section apparently melts at a lower temperature than the outside. That’s why the outside breaks, but the middle
stretches.
These broken candy canes stretch like rubber bands.
Time: A few hours
Skill Level: Easy
Taffy bends and stretches. Can you shatter it?
What you need:
AirHeads taffies
(do not unwrap them)
Freezer
What to do:
1 Place the AirHeads in the freezer for several hours.
2 Unwrap the AirHeads and
bend them. Did they crack?
What’s happening:
Warm molecules move around. When you bend the taffy, the molecules shift, still holding together. This means you can stretch and bend your taffy.
When you freeze the taffy, the molecules don’t move as much. Instead of shifting when you bend the taffy, they are more likely to simply come apart. Crack! Your taffy shatters.
Warm AirHeads stretch, but frozen AirHeads break.
Time: 5 to 10 minutes
Skill Level: Easy
Can you make water cold without adding ice cubes?
What you need:
3 small bowls
Room-temperature water
6 or more Pixy Stix
Kitchen thermometer (optional)
What to do:
1 Fill 2 of the bowls with ¼ cup of water each.
2 Break open the Pixy Stix and pour the candy powder into the third, empty bowl.
3 Pour the Pixy Stix powder into one bowl of water and stir. Leave the other bowl alone. It will be your “control” (the one that doesn’t change).
4 Touch the water in both bowls. Does the Pixy Stix water feel colder? Compare the temperatures with the kitchen thermometer.
What’s happening:
The sugar powder in the Pixy Stix is made from sugar molecules locked together into crystals. It takes energy to break up those crystals and separate the molecules. This energy comes from the heat in the water. So as the sugar dissolves, absorbing energy from the water, the water gets colder.
Many kinds of sugar absorb energy when they dissolve, making water cool. Even table sugar (sucrose) does this, although it’s hard to detect that change without a thermometer. Dextrose, the kind of sugar in Pixy Stix, absorbs a lot of energy when it dissolves, making the water much cooler. That’s why you can feel the temperature change with your bare fingers.
Pixy Stix candy makes water colder.
more fun
Try this experiment with candy made from dextrose (glucose), mannitol, erythritol, sorbitol, or xylitol. First, crush the candy into small pieces to help it dissolve quickly. Then add it to the water.
An endothermic reaction absorbs heat from its surroundings.
Time: 15 minutes
Skill Level: Get a grown-up
Can you warm up water without using the microwave?
What you need:
3 small bowls
Room-temperature water
6 Jolly Ranchers
2 zip-top plastic bags
Rolling pin or hammer
Kitchen thermometer
What to do:
1 Fill two of the bowls with
¼ cup of water each.
2 Put the Jolly Ranchers in a zip-top bag, zip it closed, then put that bag inside the second zip-top bag. (This will help keep fragments from escaping when you smash the candy.)
3 Smash the candy into very small pieces. If you’re indoors, put the bag on a cutting board and smash the candy with a rolling pin. If you’re outdoors, put the bag on the pavement and smash the candy with a rock or a hammer.
4 Open the bag and pour
the candy into one bowl
of water.
5 Test the temperature in
each bowl of water
with the thermometer.
Is the Jolly Rancher
water a little bit
warmer?
What’s happening:
When sugar crystals dissolve, the molecules must absorb energy to break apart. This makes the water cold (see the Candy Water Cooler experiment).
But Jolly Ranchers aren’t made from sugar crystals. They’re made from sugar and corn syrup, which has many different kinds of molecules. These molecules can’t lock together to make crystals (that would be like trying to combine Legos with Tinkertoys). Instead, the molecules are all jumbled together. So the candy doesn’t need to absorb energy when it dissolves. Instead, it releases energy,
making the water a little bit warmer.
Shattered Jolly Ranchers warm up water.
An exothermic reaction releases heat into its surroundings.
Time: 5 minutes
Skill Level: Get a grown-up
Mint candy tastes “cool” on your tongue. Does it really cool things down?
What you need:
Room-temperature water
4 small bowls
Digital thermometer (must measure increments of 0.1°F)
5 or more starlight mints
12 or more Eclipse mints or other mints made from dextrose, sorbitol, maltitol, erythritol, or xylitol
4 zip-top plastic bags
Cutting board and rolling pin
Peppermint extract (optional)
What to do:
1 Pour ¼ cup water into each bowl. With your thermometer, check that the temperature is the same in each bowl. (If it isn’t, pour all the water together and measure it out again.)
2 Place the starlight mints in a zip-top plastic bag, and put that bag inside a second zip-top bag. Put the Eclipse mints in another set of zip bags.
3 Smash the bagged candy to powder. If indoors, put the bags on a cutting board and smash with a rolling pin or something else hard. If outdoors, put the bags on the pavement and smash with a rock or a hammer.
4 Pour the starlight mints into one bowl of water. Stir and measure the temperature.
5 Pour the Eclipse mints into another bowl of water. Stir and measure the temperature.
6 If testing peppermint extract, pour ¼ teaspoon into a third bowl of water. Stir and measure the temperature.
7 Test the temperature in each bowl again, since the temperatures might change as more candy dissolves. Compare these temperatures with the water in your fourth bowl (your control sample). Did any of your experiments get warmer? Did any get cooler? (You will probably not be able to feel the temperature difference with your fingers.)
What’s happening:
You might think that peppermint candy makes your mouth cooler. But some of it actually makes your mouth a little bit warmer! What’s going on?
In these experiments, it’s not the peppermint changing the water temperature. Instead, it’s what the peppermint is mixed with. The starlight mints contain corn syrup, which releases a little heat when it dissolves in water. The peppermint extract contains alcohol, which also releases a little heat when it mixes with water.
The Eclipse mints, on the other hand, contain maltitol and sorbitol. These two sweeteners absorb heat when they dissolve, so they do make the water cooler. Many other sweeteners also absorb heat when they dissolve (see the Candy Water Cooler experiment). Candy makers sometimes use these sweeteners in mints because they make your mouth feel colder and “mintier.”
So why does peppermint taste “cool?” Scientists think that the menthol in peppermint might trigger the same receptors on your skin that tell your nerves when it’s cold. In other words, the mint feels cold even if it isn’t.
Which mint actually cools water?
