(bright sound) - Mmm, sponge candy.

A delicate get crunchy toffee confection covered in chocolate.

This delectable treat is known around the world for its distinct texture.

Variations come with and without chocolate.

Honeycomb from Australia.

Sponge toffee from Canada.

Sea foam from the Pacific Northwest.

Fairy food from Chicago.

Hokey pokey from New Zealand.

And cinder toffee from the UK.

But here in Buffalo, New York, we call it "sponge candy," and we can't get enough of the stuff.

While the precise origin of sponge candy remains unknown, we know confectioners like Fowler's in western New York have been making sponge candy for over a century.

There's a lot of Buffa-love for this toffee treat, so much so that the city declared September 21st National Sponge Candy Day.

And sponge candy is quite possibly the sweetest way to explore chemistry.

(slide whistle) (whimsical music) Take a look under the chocolate exterior.

This candy is filled with tiny bubbles.

Like most toffees, you start by boiling sugar, but by adding a special ingredient or two, you set off a chemical reaction, and this chemical reaction gives off the gas that blows those bubbles.

But what is a chemical reaction?

We have to start by thinking about matter, the stuff that makes everything.

Matter refers to anything that has mass and takes up space.

You and I are made of matter, and so are books, desks, your pet dog, even the air.

- Und this is ein atom, joined together -- - All matter is made up of tiny particles called atoms.

When atoms are joined together, they create a molecule.

As of 2020, there are 118 different types of atoms.

We call these types "elements," and you may have heard of some of them before, like helium, oxygen, or carbon.

Sometimes matter can change, and there are two types of changes: physical and chemical.

In a physical change, the matter changes state.

There are many different states of matter, but we usually focus on these three: solid, liquid, and gas.

When a physical change happens, it doesn't change the atoms or molecules, and those changes are usually reversible.

What happens when you melt some ice?

You get water.

Now, imagine taking that water and putting it into the freezer.

It'll go back to ice.

(rewind record scratch) It doesn't change the molecules, so it's a physical change.

Chemical changes do change the molecules.

For example, take this classic chemical reaction, baking soda and vinegar.

Everyone's seen the volcano trick.

We start off with a powder, sodium bicarbonate, and a liquid, acetic acid.

When they combine, they create something new, a gas, carbon dioxide, and a brand new substance called sodium acetate.

But how do I turn the carbon dioxide and the sodium acetate back into vinegar and baking soda?

I can't 'cause it's a chemical change.

When we cook or digest food, it undergoes chemical changes too.

Once a raw egg is cooked, you can't make it raw again.

Chemical changes aren't reversible.

(buzzer buzzing) Did you know that baking soda will break down and produce bubbles if you add enough heat?

It's called "thermal decomposition," and it's the secret to making sponge candy.

So let's head to the kitchen and make a batch!

(eyes blinking) (inquisitive music) To make sponge candy, there are a couple of chemical reactions that have to happen.

First.

We have to turn sugar into toffee.

So for this experiment...

Recipe, I'm going to combine two cups of sugar, a half cup of corn syrup... Oh, look at that, so sticky.

And a third cup of water.

So I'm just going to mix that up.

Oh, look at that; oh, wonderful.

Okay, so finishing that up.

(spatula tapping) We're also going to have to put a candy thermometer.

You need a candy thermometer for this.

So I'm just going to tuck it right in to that mixture.

Then we're going to line a square baking dish with some parchment paper.

I've already greased the sides.

You need to do that.

Keep a tablespoon of baking soda handy because we're going to need to mix it really quickly to maximize that spongy goodness.

Just like professional candy makers, we're going to heat this mixture over medium heat.

Yes, heat.

Chemical changes can be caused or helped along by heat.

And this mixture will get hot.

We'll be heating it up to 300 degrees Fahrenheit, or 150 Celsius.

It may not look like it now, but there's a lot going on in this sugar mixture.

The sugar, or sucrose, molecule is a disaccharide, which means it's made up of two molecules stuck together.

These two monosaccharides are glucose and fructose.

When you heat the sucrose molecule to the right temperature, it breaks apart and forms caramel.

And this process is called caramelization.

We can see these changes as the sugar turns from white to yellow and then brown.

We can thank caramelization for the wonderful flavor of our sponge candy.

By raising the temperature of the liquid, you can force more sugar to dissolve and create a super saturated liquid.

As a super saturated sucrose liquid cools, the sugar molecules will try to crystallize back into solid molecules.

This is where we can interfere and prevent crystallization from happening with our baking soda.

All right, now that our mixture has reached 300 degrees, prepare yourselves.

It's time for some kitchen science.

Now it's time to add the magical ingredient, baking soda.

(paper crinkling) (whisk scraping) (liquid plopping) Whoa, look at this!

It happened!

So what's happening here?

When the baking soda, also known as sodium bicarbonate, is mixed into the hot sugar, another chemical reaction occurs.

The baking soda breaks up, or decomposes, into sodium carbonate, water, and carbon dioxide.

The water vapor and carbon dioxide gases get trapped in the sugary mixture, leaving behind these bubbles.

And now we wait.

Let the sponge candy cool off and don't touch it for about two hours.

(cheerful waiting music) After that, take the candy out of the dish and smash it into smaller pieces.

Some people like to dip it in chocolate, but I think it tastes great on its own.

Keep in mind though, when you eat candy, another unfortunate chemical reaction happens between the sugars and your teeth, so remember to brush them.

(bright waltz music) We saw how heat can be used to create a chemical reaction when we made sponge candy.

But if you're interested in learning more about chemical reactions, check out our Compact Science viewer challenge!

We have a fun experiment that you can try at home to see what happens when baking soda, a base, is combined with an acid.

Get all the instructions on our website and be sure to share back your results in the comments.

I'm Sarajane Gomlak-Green, and you've been watching "Compact Science."

Until next time, stay curious.

(upbeat music) - [Narrator] "Compact Science" is funded by the Joy Family Foundation.

- Mmm, sponge candy, a delicate yet crunchy... Bleh.

Coffee, coffee.

Now it's time to add the magical ingredient, baking soda.

Baking soda?

Baking soda.

Eugh, who wants some of this?

I love cooking, it's great, okay.