Science program teaches teens

Teens who attended the library's Dippin' Dots program learned the science behind making ice cream.

Marc Straub of Cool Science visited the Sweetwater County Library last week showing the teens how they can use liquid nitrogen to make ice cream and Dippin' Dots.

First, he started off the program by asking the teens where milk for ice cream comes from. Most of the teens answered cows, however after Straub said any mammal can produce milk teens added goats, cats, dogs and camels to the list. He said around the world people use different kinds of milk, like Americans use cow's milk.

Straub said milk is mostly made of water, but has sugar, proteins and vitamins. It has everything babies need, which is why it has a lot of fat. He asked how the fat is separated from the milk. He said because cream, or the fat, is lighter than water, it rises to the top. The farmer usually takes the cream off and sells it separately because the cream is worth more money. Heavy whipping cream is about 35 percent fat. Straub then asked the teens if they could think of all the foods made out of milk. The list contained, butter, yogurt, cheese, whipping creams, ice cream, sour cream and butter milk.

The teens were then asked which part of the milk they were going to use to make the ice cream out of. They said cream and they were right. He said instead of whipping cream, they were going to use half and half, which is half cream and half milk.

Next, Straub asked the teens how they were going to get the half and half, sugar and vanilla flavoring cold enough to make ice cream. Some of the teens had made ice cream before and suggested ice and salt. Salt lowers the melting point of ice, which makes the ice cream freeze faster. Another said dry ice could be used. Straub said those ideas were all great and would work, but they weren't going to use those.

"We want to make ice cream in three minutes," he said.

He then brought out a blue container filled with liquid nitrogen, which is still a liquid at about 320 degrees below Fahrenheit. When Straub poured the liquid nitrogen into a glass container it began to bubble. He explained to the teens that just because something is boiling doesn't mean it's hot. He said its from a liquid turning into a gas and as it turns into a gas the droplets evaporate causing steam.

One teen wanted to stick his hand into the liquid nitrogen, but Straub said that wasn't a good idea and proceeded to get a hot dog, which would be similar to the makeup on a human finger and put half of it in the liquid nitrogen. After 60 seconds, he pulled it out and smacked the frozen part against the table. It shattered and everyone gasped.

"So we're not going to stick your hand in it," Straub said.

After a few demonstrations of what liquid nitrogen could do, Straub showed the group how they were going to make ice cream. He told them to divide into two lines and as they come through the line, an employee or volunteer would add two or three spoonfuls of liquid nitrogen to the ice cream mixture. The teens would then go to the back of the line and wait to receive more liquid nitrogen. After the third or fourth trip through the line, the ice cream was done.

Students enjoyed the ice cream, but were excited to learn how to make Dippin' Dots. Two lines were formed again and Straub showed them how to take a dropper, fill it with an ice cream mixture and make little drops of it fall into the liquid nitrogen. It froze instantly. The teens watched as the drops hit the liquid nitrogen and froze. He told the teens to wait until the Dippin' Dots warm up a little bit before eating them. He said if the Dippin' Dots stick to one's tongue, wait for them to warm up and then eat them, don't take them off or some of the tongue might come with it. With this last caution in place, the teens were left to making Dippin' Dots, while Straub gave them advice.