At Northeastern University’s Student Chapter of the American Chemical Society (ACS), we start each year off by pairing incoming freshmen in the Chemistry Department with upperclassmen mentors. We welcome our fellow Huskies with a potluck dinner, where everyone can get acquainted with each other and exchange contact information for future events. We then invite everyone back for our first weekly meeting, where we create the perfect liquid nitrogen ice cream.
Here’s how to do it:
Consider safety! Make sure the people making the ice cream wear goggles, gloves, closed-toe shoes, and lab coats. The liquid nitrogen gets very cold, and you’ll need to keep everyone safe. It is important to have a pair of cryogenic gloves when handling the liquid nitrogen, touching the bowl, and stirring; your average laboratory gloves are not enough!
- Ask a professor (or lab technician) for 5 liters of liquid nitrogen in a dewar flask.
- In a large plastic bowl, mix:
- 4 cups heavy cream
- 1.5 cups half-and-half
- 1.75 cups sugar
- 3 teaspoons of vanilla extract for vanilla ice cream, or 0.25 cup chocolate sauce for chocolate ice cream
3. Stir these ingredients together, then slowly add the liquid nitrogen. (We don’t use all 5 L for each batch.)
Tips and tricks: Teamwork is the easiest way to make the ice cream. Having one person pour the liquid nitrogen into the bowl while another constantly stirs the mixture gives the creamiest results. As the ice cream thickens, it becomes more difficult to stir. Be considerate and provide equal bicep-building opportunity by taking turns between pouring and stirring!
Once the ice cream is too hard to stir, remove the spoon and pour a little more nitrogen over the top to allow the ice cream to harden completely. While the last of the nitrogen is boiling off, make sure you have plenty of spoons, bowls, and toppings to satisfy your group. We had Oreos, sprinkles, and M&M’s for people to add as they liked. Our chapter made three batches of ice cream, which was plenty for a meeting of 40 people. By making our ice cream in multiple batches, we were able to make both chocolate and vanilla ice cream and allow several members to contribute.
Scaling up: Ice cream for everyone!
Shopping for all of the materials can sometimes seem overwhelming. It is important to estimate the number of participants you expect and work from there. About 3 gallons of ice cream should feed 60 – 90 people, and about 5 liters of liquid nitrogen makes 3 gallons of ice cream. However, the amount will vary, depending on how creamy or thick of a consistency is desired. If there is a store near you, like Sam’s Club, BJ’s, or Costco, you will be able to buy all the ingredients in bulk. If not, any standard grocery store will work – generic brands work just as well and save your student chapter’s money.
After a tasty (and successful) ice cream social with our ACS chapter, we decided to share what we learned with the other departments at Northeastern University. We contacted the university’s facilities department, booked a space on a major quad in campus, scaled up our synthesis to 40 cups of cream, and provided ice cream for over 200 students and faculty during Welcome Week at the start of the school year. The ice cream went fast, so we bought a little from the store, too. We’re glad we did, as free ice cream goes fast!
Organizing a social of this size takes a little more effort. First of all, we had to publicize the event and let those in charge of facilities know our plan. The dean of the College of Science promoted our event, as did the other science clubs within the College of Science. We advertised through flyers, Facebook events, and simple word of mouth. We also invited students from other departments to participate. Involving students from other departments showed everyone else at the university just how cool chemistry can be.
Hopefully our experience will help your chapter have a liquid nitrogen ice cream social as successful as ours! Feel free to ask questions or leave comments!
Contributions by- Charlie Hoyt, Melissa Page, Bakar Hassan, and Christine Dunne
Just a quick NCW note:
The NCW 2012 Community Event is Do More with Less! You can identify and take action on at least one way to “do more with less” in your local community. Examples could be a recycling drive, a canned food drive, a health fair, park clean-up, or any activity that improves something in your local section’s region. And NCW now has a Facebook fan page! Please like them on Facebook, join the NCW Group on the ACS Network and follow them on Twitter.