Some Like It Hot: Experiments with Temperature

For the last week of my five-week Sizzling Science workshop for fifth and sixth graders, we explored temperature.

I started out with a brief discussion of hot and cold, asking the kids what they thought happened to the molecules of a substance as it got hot.  They guessed that the heat would make the molecules move around more.  At this point, I had planned to do an experiment where I put drops of red food coloring in three glasses of water (one hot, one warm, and one cold) to show that the dye spread more rapidly through the hot water.  Unfortunately, the water heater didn’t seem to be working, so I wasn’t able to get any hot water.

Instead I pulled out a hand boiler and passed it around.  It’s a cheap toy, but a fun one. In middle school, my friends and I used to have temperature wars with the hand boiler in our classroom.  Each of us would hold one end, and we’d see whose hand was warmer by which side the liquid migrated to (I think that was how we ended up breaking the teacher’s hand boiler, and having to buy a replacement: no easy feat in the days before Amazon).  I explained that the liquid inside the bottom bulb reacts to the heat in your hand, expanding to run through the tube in the middle, and appearing to “boil” in the bulb at the top.  We talked about how traditional thermometers work on this same principle, with the mercury moving up the tube as it gets warm and expands.

Hand Boiler

Hand Boiler

At this point, I brought out a digital thermometer, and explained that these work with a special kind of electronic component called a thermoresistor or thermistor.  At low temperatures, it does not conduct electricity, but as heat is applied, it becomes more and more conductive. A microcontroller inside the thermometer uses the amount of electrical resistance to determine the temperature.  I put the digital thermometer in a glass of water, and then added some rock salt.  The kids watched as the temperature slowly dropped.  We talked about how salt is used to melt ice on the roads, and how we would also be using it to make ice cream.  The milk and sugar in ice cream freezes at a lower temperature than water, so ice alone is not cold enough to make it solidify.  Adding salt to the ice lowers the freezing temperature, causing it to melt, but also to become colder.

I followed up the salt demonstration with another demo where I put calcium chloride in a glass of water.  This time the water heated up several degrees almost instantly.  I explained that calcium chloride is also used to melt ice on roads.

Now it was time to make ice cream in a bag.  I’ve done this activity many times over the years.  It was one of the first library programs I helped with at my first children’s librarian job in Raleigh, NC.  But this was the first time I had used it as a science experiment.

I started by showing the kids all the steps, which are:

  1. Pour 1/2 cup of half-and-half into a small Ziploc bag (I tried to find the yellow-and-blue-make-green kind of bags; but all I could find were the kind with the slider on the top, which unfortunately seem more prone to leaking).
  2. Add 2 tablespoons of sugar and 1/4 teaspoon vanilla to the bag
  3. Seal the bag up tightly, and set it inside a large Ziploc bag
  4. Fill the large bag with ice, followed by several tablespoons of ice cream salt (the recipe calls for 6 tablespoons, but I just eye-balled it)
  5. Shake the bag, or squish the small bag with your hands, for five to ten minutes until the mixture freezes.  The ice cream will be soft, more like a milkshake.

I set up the ingredients on a counter, and had the kids pair up to help each other.  One kid would hold the bag open, while the other poured in the ingredients.  I helped some of them pour the milk and vanilla (the vanilla was especially prone to spilling).  Then they all went to town shaking the bags.  A few of the big bags broke (they don’t make bags like they used to), so we did have some ice and rock salt spills, but thankfully no milk (whew!).  I gave the kids spoons and straws to eat the ice cream. A few complained that the ice cream tasted salty at first, so I ended up suggesting that they rinse the salt water off the outside of the small bag before they ate it.

Large Ziploc Bag with ice and ice cream salt surrounding the smaller bag full of ice cream mixture

Large Ziploc bag with ice and ice cream salt surrounding the smaller bag full of ice cream mixture

That part all went pretty smoothly, except I wish I had thought to bring a dairy alternative.  I had one student who not only could not drink milk, but ended up having a contact allergy just from touching it (that came as a surprise even to her mom).  Luckily, she had some medicine on hand for the hives, but I felt badly about it.  Ice cream needs to have a fairly high fat content to make it creamy rather than icy, and the girl suggested she might try making it with coconut milk, which I thought was a good idea.  I actually tried it at home–substituting the half-and-half with 1/2 cup Silk Brand Coconut Milk, and it turned out really well.  It does taste fairly coconutty, which may not appeal to everyone, but I bet it would work with Almond Milk as well.

Ice Cream made with Coconut Milk

Ice Cream made with Coconut Milk

I had intended to follow-up the ice cream with homemade thermometers, but the ice cream took about 45 minutes of my hour long class.  Instead I showed the kids the thermometer, and a number of them took some portion of the materials home.  I used the thermometer model described by Mike Calhoun on Education.com: http://www.education.com/activity/article/make_a_homemade_thermometer_middle/ because it seemed less messy than the water thermometer on SteveSpanglerScience.com: http://www.stevespanglerscience.com/lab/experiments/water-thermometer-sick-science.  But that night I woke up in the middle of the night worried that someone’s little brother might drink their thermometer, which contained rubbing alcohol, so maybe the water thermometer would have been better.  Both of them are a bit tricky to transport without spilling.

Basically, both thermometers involve sealing a drinking straw inside a water bottle with modeling clay, with the top sticking out.  For Calhoun’s model, you first fill the bottle about a quarter full of equal parts water and rubbing alcohol, and add a few drops of red food coloring. For the water thermometer, you fill the bottle all the way to the top with water, dyed blue with a few drops of food coloring.  In both cases, you mold the modeling clay around the drinking straw at the mouth of the bottle, trying to make an airtight seal, while keeping the straw itself open.  When you put the bottle in hot water, or hold it with your hands, the liquid inside the bottle expands and travels up the straw (the rubbing alcohol reacts more easily to heat, which is why you don’t need to fill the bottle completely).  You can even use another thermometer to gauge the temperature, and then mark that on the side of the straw or on the bottle (with the water thermometer, you can even tape an index card to the portion of the straw that sticks out of the bottle, and mark the temperature on that).

Water thermometer from SteveSpanglerScience.com

Water thermometer from SteveSpanglerScience.com

Homemade Thermometer from Education.com

Homemade Thermometer from Education.com

I was sad to say goodbye to the kids in the class, many of whom I had become quite attached to.  They were a wonderful group, and I’m hoping to see them at future workshops.  I was nervous about offering these science classes at first, but they ended up being the highlight of my summer. I’d love to hear other ideas or activities that have been successful in other classes or libraries, so please share them in the comments.

I Scream, You Scream for Stories about Ice Cream

The ice cream mixture: milk, vanilla and sugar

The ice cream mixture: milk, vanilla and sugar

This week we read books about ice cream, and made ice cream in a bag, something I learned from my very first job as a Children’s Librarian, at the North Regional Library in Raleigh, North Carolina.  I was only there for a few months before my husband got a job that required us to move to the Bay Area, but I learned a lot from my coworkers there, and I’ll always be grateful to them.

I was actually debating about making the ice cream in coffee cans instead of plastic bags, since it would be more environmental, but my kids and I tried it three times at home (yeah, they hated being guinea pigs for this one), and we just couldn’t get it to work.  The stuff in the middle would always be too slushy, and the stuff on the sides so frozen it was hard to scrape off.  So I went back to the original plan. I did collect and wash all the plastic bags at the end.  (Stores in our county no longer give out plastic bags, so I actually hoard them to dispose of my cat litter).

Here’s what we read:

ice-cream-larry-cover

Ice Cream Larry by Daniel Pinkwater; illustrated by Jill Pinkwater (Amazon.com link)

I hadn’t originally planned to read this one, because it’s a longer picture book, but right when storytime started, there was only one 6 year-old and her mom, so I decided to share it with her.  It’s one of a series of books about Larry the polar bear, who lives at the Hotel Larry and serves as the lifeguard for the pool.  In this book, Larry makes the news when he asks a local ice cream shop if he can cool down in their freezer, and then eats 1/8 of a ton of their ice cream.  “I do not feel sick,” he says.  Soon, the owner of the Iceberg Ice Cream company shows up at the hotel to meet with Larry.  He ends up making him the spokesbear for his new line of ice creams, and the company’s new slogan, “I do not feel sick,” becomes a national sensation.  Very silly, but lots of fun to read, and a hit with the kids.

littlepea

Little Pea by Amy Krouse Rosenthal; illustrated by Jen Corace (Amazon.com link)

Other families with younger kids had come in during the first book, so I went with this one next.  It’s not actually an ice cream book, but it tied in with my “Candy Corn for Dinner” song that I sang before I read it.  It’s one of my favorite picture books, about a little pea who dreads having to eat his nightly dinner of candy.  This one always gets laughs from both kids and adults.

icecream

Should I Share My Ice Cream? by Mo Willems (Amazon.com link)

I had to to do this book, which is one of my favorite Elephant and Piggies.  Gerald is just about to enjoy his ice cream cone, when he wonders if he should share it with Piggie instead.  It is a terribly difficult decision, and one that takes him so long that his ice cream melts.  Most of my regular storytime families are familiar with Gerald and Piggie, but there was one new family who had never heard of the series.  I was happy to hear them laughing at the ending.

frogandtoad

Frog and Toad All Year by Arnold Lobel (Amazon.com link)

Occasionally I like to share a chapter from an early reader book like this one, and I was reminded of the “Ice Cream” story in this book when my daughter was listening to the audiobook in the car.  To my surprise, most of the kids had never heard of the Frog and Toad books, which I know are still asked for frequently at the library.  In this story, Toad buys two ice cream cones for himself and Frog to enjoy.  But on his way back to Frog, the ice cream melts, covering his face so he cannot see.  Other animals run from him in alarm, and when he finally gets back to Frog, he looks like a scary monster with two pointy horns.  This one got laughs too.

ninja

Nighttime Ninja by Barbara DaCosta; illustrated by Ed Young (Amazon.com link)

I should have asked ahead of time if the kids knew what a ninja was, because one of them raised the question.  A ninja is stealthily creeping through a house, until he is discovered and unmasked for what he really is: a boy sneaking ice cream from the freezer.  This is a short book that is fun to read aloud because you can build up the suspense in the early pages.

SONGS:

Candy Corn for Dinner

I wrote this song for the storytime, since I couldn’t find many that fit the ice cream theme.  It needs another verse, which I’ll try to add sometime in the future, but the kids seemed to like it.  I’m still too nervous to tell people at storytime when I perform an original song, but it’s a fun challenge to write them.  It’s also not too hard if you know a few chords on the guitar or ukulele, which is all you need for most kids songs anyway.  This one only has three chords: C G7 and F.

C                                                                     G7                   C
My mom and dad put me in charge of our dinner tonight.
C                                                                                G7
They said I could make anything as long as we ate right.
C                                                        G7                   C
I had to serve some vegetables, a salad, and a stew.
C                                                                        G7               C
I thought a while and cooked a bit, and here is my menu.

F                                                     C
We’re having candy corn for dinner
G7                             C
With a side of chocolate stew.
F                               C
A three jelly bean salad,
G7                                                C
And an ice cream sandwich too.

I don’t know why Mom and Dad say cooking’s such a chore,
‘Cause I had such a great time going to the grocery store.
My mom said we were out of milk, so I bought a big milkshake,
And since my dad likes cheese so much, I got him a cheesecake.

We’re having candy corn for dinner
With a side of chocolate stew.
A three jelly bean salad,
And an ice cream sandwich too.

If All the Raindrops

This is an old standby that I use for toddler and baby storytimes too.  (I used to sing it to my daughter at toothbrushing time, and it became kind of a game to brush her teeth while we sang the “Aaahs.”)  I asked the kids to suggest other things they would like the rain to be.  One girl suggested chocolate marshmallows, and her mom suggested margaritas.  Here are the traditional lyrics (click on the triangle for the tune):

 

C
If all the raindrops
G7                           C
Were lemondrops and gumdrops
C                                                 G7
Oh, what a rain that would be!
C                G7                           C                    G7
Standing outside, with my mouth open wide
C                 G7               C                 G7
Ah Ah Ah Ah Ah Ah Ah Ah Ah Ah!
C                                           G7                           C
If all the raindrops were lemondrops and gumdrops,
C                   G7                     C
Oh, what a rain it would be!

If all the snowflakes
Were candy bars and milkshakes…

If all the sunbeams
Were bubblegum and ice cream…

CRAFT: Ice Cream in a Bag

Ice cream mixture sealed in a large bag of ice and rock salt

Ice cream mixture sealed in a large bag of ice and rock salt

The finished product!

The finished product!

I printed out the directions on a half-page handout, in case anyone wanted to take it home.  You can print your own here: ICE CREAM IN A BAG

Before we started, I went over each of the ingredients.  We talked about the vanilla, and I let the kids smell the open bottle.  I showed them the rock salt, and explained that it was important, because without it the ice cream wouldn’t freeze.  (The milk and sugar freeze at a lower temperature than water, but the salt lowers the freezing temperature of water.  When you put it on ice, the ice melts, but it turns into a slushy mixture that is actually colder).

I gave each kid a quart-sized plastic zipper bag (for what it’s worth, the bags I bought from Target claimed to be BPA-free, although I’ve read that the other chemicals plastic companies use aren’t necessarily safer).  I had them hold their bags open, and I poured the 1/2 of whole milk in for them, since it was a large, heavy gallon of milk.  Then I held the bag open for each of them as they scooped in two tablespoons of sugar.  I pour in the 1/2 teaspoon of vanilla extract.  Then I told them to seal their bags tightly, and make sure they were closed (I once had volunteers mix up the ice cream mixture in the bags ahead of time, and they forgot to seal the bags shut.  There were a lot of disappointed kids left holding bags of salty milk).

Once they had their ice cream mixture sealed in the small bags, I gave them each a gallon-sized bag to half-fill with ice.  Then we poured the rock salt in on top of the ice (the recipe calls for 1/2 cup, but I just estimated).  They sealed their ice cream mix into the big bag, and shook the bags while I played some songs on the ukulele.  It takes about 5 minutes for the ice cream to freeze.

Once the ice cream was frozen, I gave out spoons and straws for the kids to each it straight out of the bag.  Some froze more solidly than others, but it has a pretty good flavor that they all seemed to like.

OTHER BOOKS ABOUT ICE CREAM:

I Scream, Ice Cream! a Book of Wordles by Amy Krouse Rosenthal and Serge Bloch (Amazon.com link)

This book’s not actually about ice cream, but I was originally going to read it along with Little Pea, since it references that book at the end.  It’s actually a series of phrases that can mean two different things, depending on how you read them.  For example: “I scream!  Two bucks!” (with a picture of someone running away from two angry deer), sounds just like “Ice cream, two bucks!”  The phrases get increasingly complicated, and it’s fun to try and guess what the alternate meaning will be.

Ice Cream: the Full Scoop by Gail Gibbons (Amazon.com link)

Nice overview of the history of ice cream, and how it is made commercially.  This one was a little long for my group, but would work well for a preschool or elementary school class.

Any other books about ice cream?  I would love some more suggestions.