First Hard Freeze for Our Jars of Water

Back on November 29th we started an experiment on our front porch, with four plastic jars filled with water. At the start of the experiment, the jars looked like this:

Water jar experiment, Day 1, November 29, 2009
Here's what the experiment looked like five days ago, before the temperature hit the freezing mark.

Now, here’s what the experiment looked like on Friday, December 4th, after the air temperature went below freezing, hitting 24 degrees Fahrenheit overnight:

Water jar experiment after a hard freeze, December 4, 2009.
Here's what the water jars looked like after a hard freeze. Three of the five jars had frozen overnight: A, B, and D. Also, we had added a fifth jar: In Jar E, the water that had been BOILED first, then cooled, put in the jar, and sealed with a lid that had NO holes in it. (Thanks to J of Science Museum of Minnesota for suggesting this addition to the experiment.)

Three of the jars had frozen water in them, including the jar with SALTY water. No one predicted that! The two jars that did not freeze were both sealed tight — there were no holes in their lids.

Here’s a closer look at Jar A, which started out as cold, fresh tap water, and was covered by a plastic lid with holes drilled in it:

Jar A (fresh water, started cold, holes in top), Decmber 4, 2009, 24 degreees F
A closer look at Jar A shows intersecting sheets of ice, more densely frozen closer to the top of the jar.

Jar B showed a similar pattern, although the sheets of ice were more horizontal than vertical:

Jar B (fresh water, started warm, holes in top), Decmber 4, 2009, 24 degreees F
Jar B also had sheets of ice, more densely frozen towards the top of the jar -- but the ice sheets were more horizontal than vertical.

Jar D was most surprising. I was expecting the salty water wouldn’t freeze, but the top part of the jar was frozen fairly solid. However, the bottom of the jar was not frozen, but had a bunch of bubbles sticking to the side of the jar:

Jar D (SALTY water, started cold, holes in top), December 4, 2009, 24 degreees F
In Jar D, notice the clear division between frozen water above and unfrozen water below.

So, that leaves us with two mysteries to solve:

  • Why did most of the water in the salty jar freeze?
  • Why did the water in the sealed jars not freeze?

I have some ideas, but I won’t tell you about them yet. However, I will give you one hint about the second mystery. Here’s what the lower part of salty Jar D looked like on December 2, 2009 — three days after the experiment started, but before the temperature dropped below freezing:

Jar D (SALTY water, started cold, holes in top), December 2, 2009, 37 degrees F
Here's what Jar D looked like three days after I had mixed in several handfuls of sidewalk salt, but before the first hard freeze. How can this help us understand why the top of the jar froze, but the bottom did not?

Feel free to tell us your ideas in the comments section (below) or on Facebook.

An Experiment with Freezing Water

The weather forecast says we’re headed into an extended spell of cold weather, with freezing temperatures predicted for the end of the week. So, it’s time to put some water jars on the front porch to see what happens. This year we’re going to be a bit more organized than usual and set up the jars as an experiment. There are reasons we’re setting it up this way, but we’ll let you try to figure out what those reasons are (with a few hints at the end of this post).

First, here’s our experimental setup: Four PLASTIC jars of water set on our front porch rail this afternoon, here in Oak Park, Illinois:

Water Jar Experiment Day 1, November 29, 2009, Oak Park, Illinois
Here are our four experimental jars of water (all made of plastic). Read the descriptions to see how they differ from one another. We started this experiment on November 29, 2009.

Jar A, on the far left, was filled with cold, fresh tap water. It’s lid has holes in it, so air can get in.

Jar B, just left of center, was filled with warm, fresh tap water. It’s lid also has holes in it, so air can get in.

Jar C, just right of center, also was filled with warm, fresh tap water. It’s lid has NO holes in it, so NO air can get in.

Jar D, on the far right, was filled with cold tap water, then a couple of handfuls of rock salt were added — the same kind of salt you may put on your steps or sidewalk when it snows. It’s lid has holes in it, so air can get in.

So, we are experimenting with the following variables:

  • Does the water start out cold or warm?
  • Is the water exposed to the air or not?
  • Is the water fresh or salty?

Why do we want to experiment with those variables? Maybe you can guess if you check out these blog posts from last winter:

And now, here’s the big challenge:

What do you think will happen to each jar once the weather gets really, really cold?

You will need a separate guess — or “hypothesis” — for each jar, A through D. You can list your hypotheses in the comments section, below, or send them to me by e-mail ( or Facebook.

Think hard, and good luck! (Or should I say, “good skill”?)


Note: I revised this post later the same day to make it clear that the jars are made of plastic. (Although it might be fun to try it with glass some day. Fun in a Mythbusters kind of way….)


To find out what happened on December 4th, when the air temperature dropped below freezing, please go here:

Our Pet Water Scorpion and a New Kind of Mosquito Problem

When we dropped Aaron off at his friend’s vacation cottage in Michigan, we brought home a new pet: A Water Scorpion.

Water Scorpions are insects. They look like a cross between a Walking Stick Insect, a Preying Mantis, and a vampire. Their bodies and legs are long and skinny like a Walking Stick, to camouflage them in aquatic vegetation. Their front legs are like Preying Mantis legs, designed to quickly reach out and grab bugs and fish. And they jab their sharp beaks into their prey to suck the juices, like vampires:

A Water Scorpion looks like a cross between a Walking Stick Insect, a Preying Mantis, and a vampire, but it's a kind of insect called a True Bug. The long tail is used to get oxygen from the air while the Water Scorpion hides in underwater plants. Photo by Ethan Gyllenhaal.

Our Water Scorpion lives in a gallon jar, and it’s always hungry. One of its favorite foods is Mosquito larvae. If you’ve been following this blog for a few months, you may remember that we’ve been keeping baby Mosquitoes (called larvae) as pets. (You can see posts about them here and here.) Well, for the last two weeks we’ve been feeding our former pets to our current one. It looks like this — but turn away if you love Mosquito larvae!

The Wtare Scorpion is sucking the juices from one Mosquito larvae while holding its next meal in its Prey Mantis-like front leg. Photo by Ethan Gyllenhaal.
The Water Scorpion is sucking the juices from one Mosquito larvae while holding its next meal with its trap-like front leg. Photo by Ethan Gyllenhaal.

Here’s the problem: Our Water Scorpion eats five or more Mosquito larvae a day, and our Mosquito supply can’t keep up with its appetite! We’ve been using our backyard pools as Mosquito traps. We lure adult Mosquitoes to lay their eggs in the stagnant water, then we capture and raise the newly hatched babies. Fortunately, the hot, wet weather has been good for Mosquitoes. Ethan found about a dozen egg masses this evening, and in a week or so we’ll have another big batch of larvae ready to feed to the Water Scorpion.

Until then, please check any buckets, bird baths, and other water sources in your yard. If you find them filled with wriggling Mosquito larvae, please let us know. We’ll pick them up if you live within five miles of our home in south Oak Park. If you live farther away, you’d better dump the water out, or you’ll soon have a different kind of Mosquito problem in your yard!


To learn more about Water Scorpions, please visit these websites:

Update on Our Pond-water Pets

A week ago we introduced you to our new pet Mosquito larvae and Water Fleas. Since then the larvae have been growing and changing, and we’ve got some new arrivals in our pond water.

Mosquitoes go through life-cycle stages as they grow: First egg, then wriggly larvae, then a make-over pupa stage, and finally a winged adult. (Go here or here to see these stages illustrated.) Last week our Mosquitoes were all larvae. This week, the larvae have grown (some as big as a grain of rice), and some larvae have shed their skins and become curled-up pupae:

The yellow arrow point to a Mosquito pupa, the blue to one of many Mosquito larvae.
The yellow arrow points to a Mosquito pupa, the blue to one of many Mosquito larvae.

Adult Mosquitoes should be appearing soon. (Don’t worry, we won’t turn them loose in the neighborhood!)

The Water Flea jar we showed last week is doing fine — some of the eggs that were inside the Water Fleas’ bodies have even hatched. To see if there were any new creatures in our outdoor pools, we filled a new jar with water from our backyard bug pond. Sure enough, there were two new creatures — both crustaceans, related to crabs and such — along with last week’s Water Fleas.

Ostacods, also called Seed Shrimp, have legs and antenna, but they’re mostly covered by their clam-shaped shells. Copepods are streamlined, with antennae, legs, and a tail-like structure. Many also carry twin egg sacs beside the tail this time of year. As we discussed last week, Water Fleas have large antennae, used as oars:

The green arrow points to an Ostracod, the red arrow to a Copepod (with egg sacs), and the blue arrow to a Water Flea.
The green arrow points to an Ostracod, the red arrow to a Copepod (with egg sacs), and the blue arrow to a Water Flea. (The Water Flea is half the size of the head of a pin.)

To learn more about Ostracods, please go here. To find out more about Copepods, go here or here. To learn more about Water Fleas, go here or here.

We’ll be dipping into our outdoor water every week from now through fall. We’ll post updates as we find new creatures.

Of course, if you’re inadventantly raising mosquitos in your backyard pool or birdbath, now’s the time to do something about it. If you don’t want to keep them as pets in a covered jar, it’s best to dump them on the ground (as food for ants) and start over with new water.


In mid June we added a new pond water pet: A Water Scorpion. We feed it our remaining pet Mosquito larvae.  Go here to read about it.

Our New Pets: Water Fleas and Mosquito Larvae

We’ve been posting lots about birds and some about buds. Now it’s time for a blog post about bugs!

Bugs have long been favorites in our family, at least for me and Ethan. I was a teenage bug collector, and Ethan got interested in bugs as a preschooler. (Visit our Cicada Hunt website to see what our lives were like back then, and go here to find out what Ethan’s bug collections were like when he was young.) We’ve both kept our bug passion burning, even if when it’s partially eclipsed by other interests, like birds.

As noted in this earlier post, we like to keep outdoor water available year ’round for birds and kids to play in. As the weather warms, that water comes to life with bugs and worms that feed on newly grown algae and the winter’s accumulation of dead leaves.

The first water bugs we saw this year were Water Fleas, a crustacean more closely related to lobsters than to insects. They appeared in early April. The biggest Water Flea in this photo is a bit larger than the head of a pin:

Wtaer Flease swim by using their large antennae as oars. The larger one has a bunch of tiny eggs inside its body.
Water Fleas swim using their large antennae as oars. You can see their insides through their transparent skin. The larger Water Flea has a bunch of tiny eggs inside its body. (The white squiggly lines are scratches in the plastic jar that holds the buggy water.)

To learn more about Water Fleas, go here or here. The see a YouTube video of a live Water Flea, go here.

Just this morning we discovered our first Mosquito larvae of the year. Larvae are baby Mosquitoes, which live in water and cannot fly. The biggest larva in this photo is as long as a of grain of rice:

The blue arrows point to the heads of Mosquito larvae.
The blue arrows point to the heads of Mosquito larvae. They stick their tails through the water's surface to get air to breathe.

To learn more about how Mosquitoes grow up, go here or here.

We enjoy our water bugs outdoors as wild visitors to our yard and indoors as-easy-to-care-for pets. We always keep a jar of buggy water on the back window sill, where the afternoon sun fuels the bugs’ algal food:

Here's our jar of pet Mosquito larvae. We use a piece of paper towel to keep grown-up Mosquitoes from escaping through the hole-punctured lid.

It’s better than a lava lamp as a source of meditative concentration, joy, and inspiration (at least for me and Ethan). We put other jars of buggy water on our front porch rail for the neighborhood children to enjoy.

Now that Mosquitoes are back, we’ll have to manage our outdoor water carefully. We empty and refill most pools at least once a week. However, we always keep one pool just for the bugs. When dragonfly nymphs and other underwater predators prowl our bug pool, no Mosquito larvae can survive for long. When there aren’t enough insect predators, we’ll add a few bug-eating fish. Either way, we make sure no Mosquito larvae grow into blood-sucking adults in our back yard.

We have more bug posts coming up, including beetles on the beach and bugs in the soil.


Update added May 13, 2009: To find out what our water pets were like a week later, please go here.


In mid June we added a new pond water pet: A Water Scorpion. We fed it our remaining pet Mosquito larvae.  Go here to read about it.

Raising Nature-loving Kids in an Urbanized Environment

Next Wednesday, April 22, I’ll be putting on an Earth Day event at Wonder Works, a Children’s Museum in Oak Park. I’ll be using this blog to (1) write about and illustrate the principles that I’m using to design this program, (2) show examples of what we wind up doing at Wonder Works, and (3) give readers ideas about what they can do in their own neighborhoods to support the development of nature-loving kids.

In days to come I’ll expound on the history of the No Child Left Inside movement (which I seem to be a part of) and discuss some authors who have helped me develop my ideas (like Richard Louv, David Sobel, and others). For now, I’ll just spell out the most recent version of my own, personal, Principles for Raising Nature-loving Kids in an Urbanized Environment:

1. Appreciate the nature you’ve got. There’s probably a lot more nature in your neighborhood than you realize. Recognize what you’ve got, pay attention to it, appreciate it, incorporate it into your life and into your kids’ play. (This blog provides ideas of what to look for in your neighborhood.)

2. Make your neighborhood a better place for nature-loving kids. Grow a garden, feed the birds, salt your sandbox, keep outdoor containers filled with water all year ’round, give the kids a corner of your yard where they can build a fort or play in the dirt.

3. Bring the outdoors indoors — but do it as a beginning, not as an end in itself. Collect natural things and bring them home, fill the bathtub with snow, raise indoor plants, make sure the kids’ toy box includes sticks and rocks as well as plastic toys, start an aquarium, make home-made play dough when you can’t play in the mud, keep pets — small wild ones and larger domesticated ones. But realize that this is just a beginning — the real goal is to get back outside and experience nature in an outdoor setting.

4. Bring the indoors outdoors. Toy trucks and cars, wooden trains, and plastic dinosaurs are as much fun outdoors as they are inside — and maybe more! Back when my kids were passionately interested in these things, we used to move our play to the front sidewalk or our vest-pocket backyard once the weather turned warm. You can see examples here and here and here. (Oops, maybe skip the last one if you’re not used to having older b0ys around.)

5. Use all the resources available to you — people, print, and electronic. Find informal mentors in your neighborhood, at local organizations (like clubs and museums), or online. Visit your local library frequently and search the Web for more resources. (As your kids grow older and more media savvy, they may take over this role, like my boys did with our family’s birding interest.)

6. Be prepared to travel. The first four principles are about making your home and neighborhood a better place to raise nature-loving kids. If you are successful, they’ll outgrow the nature you can offer close to home. When my kids were young, we visited local parks, museums, zoos, and arboretums. Now we go still go to parks, but we also search out other places, where we make our own natural experiences. (You can see examples here and here.)

7. Understand and support whatever kinds of nature-loving kids you’ve got. Observe how your child interacts with nature, and start from there. Do they lead with their head or their heart? Do they seek adventure or avoid it? What attracts them, what disgusts or frightens them? Knowing these things will help you design a life-in-nature that builds on their interests and strengths.

That’s almost it for now — but I’ll be writing more over the next few weeks (both before and after Earth Day). Feel free to contribute your own thoughts!

For now, just one more thing: A link to a Pioneer Press article about our Earth Day plans for Wonder Works. (Thanks, Myrna!)


Note: Principles 5 and 6 were added on April 20, 2009. Principle 4 was added on August 11, 2009.

Wading Pools in Winter and a New Theory of Dinosaur Extinction

With today’s temperature in the 50s, I urged Aaron and his friend Matt to explore the backyard instead of the icy expanses of Club Penguin. Eventually they agreed, leaving penguins but not ice behind.

Within minutes they called me to the backyard to record a “discovery” they made. I took some photos and wrote a story to go along with them. (The story was inspired by dinosaur books for kids, which I’ve been reading in preparation for a writing project.)

This only happened because we leave out plastic pools filled with water all winter long. That’s one way we make our neighborhood a better place for outdoor play, a place with No Child Left Inside.


Aaron and Matt found a dinosaur disaster in our backyard! An imaginary world of dinosaurs and ice was being destroyed.

What had done this terrible thing to Ethan’s old collection of giant plastic dinosaurs? (Ethan is Aaron’s older brother — he’s loved dinosaurs since he was a little kid.)

Can you help us solve this mystery?
Can you help us solve this mystery?

Matt carefully studied the ice layers searching for clues:

The ice, unfortuantely, held no useful clues to the origin of the disaster.
The ice, unfortunately, held no useful clues to the origin of this disaster.

The team decided to excavate in search of answers. After much digging and clearing of ice, Matt reached into the water with his bare hands. He pulled out a giant rock!

Aaron pulled out a large rock, the cause of the disaster.
Matt pulled out a giant rock, the cause of the disaster.

It was obvious that a flying rock had shattered this icy world. But where did the rock come from? From outer space? From a volcano? Gradually, the true cause of this disaster became apparent, as the rock struck once again:

The evidence was clear -- there were multiple impacts...
The rock struck again -- how did that happen?
There were multiple impacts, in multiple places.
The rock then smashed into another pool.

Aaron and Matt imagined the rock had come from space — that was their Theory of Dinosaur Extinction. Should I believe them?

Do you have a better theory? Who will Ethan agree with?


Thanks to Aaron, who let me tell the story my way, instead of the way it really happened.

With my kids, throwing rocks and smashing ice happen so predictably that they seem almost instinctive. The boys adding characters and plot to the adventure also seemed quite natural. I’ll let evolutionary psychologists explain how these behaviors contributed to our ancestors’ survival on the plains of Africa.

Here’s something that occurred to me — by destroying the ice, the boys found out about the physics of ice, water, and flying rocks. They also learned biology — the smell of dead leaves festering on the bottom of the pools. Smashing things may be the starting point for certain kinds of science, although building things and understanding wholes no doubt have different roots.

And the gender thing: Parents of boys may see more of this than parents of girls, and grown-up boys may better appreciate these images. But if Aaron and Matt’s friend Hannah had been here, she would have been in the thick of it. That’s one reason she’s their friend, and I’m glad they’ve made room for her.

Salty, Super-Cooled, Heat-Sucking Slush — and Homemade Ice Cream

We have a couple of inches of new snow in the neighborhood this morning, so I thought I’d tell you about something “cool” we did with snow. It’s great to do this with new snow, but even if the snow in your yard is already melting or turning gray, that’s fine.

This is as much science as nature, so here’s our research question: What happens when you add salt to snow? The kids in our house that day voted three to one for this hypothesis: “It will get warmer.” Why? “Because salt melts snow.”

Was the majority correct? Let’s do an experiment to find out!

Here’s our experimental apparatus:

We used a large bowl of snow, a bunch of salt, a large metal spoon, and a thermometer left over from Nature and Science Club.
We used a large bowl of snow, a bunch of ice-melting salt, a large metal spoon, and a thermometer left over from Nature and Science Club.

First we took the temperature of the pure snow:

The thermometer reads 0 on the left side (Centigrade) and 32 on the right (Fahrenheit).
The thermometer reads 0 degrees on the left side (Centigrade) and 32 degrees on the right (Fahrenheit).

The snow was at the freezing point of water: 32 degrees Fahrenheit, 0 degrees Centigrade.

Next we mixed a bunch of salt into the snow:

The metal spoon was strong enough to mix the salt and snow without breaking.
The metal spoon was strong enough to mix the salt and snow without breaking.

We stuck the thermometer into the mixture, watched, and waited. Here’s what happened:

The thermometer read _ degrees Centigrade, _ degrees Fahrenheit.
The thermometer read -22.5 degrees Centigrade, -9 degrees Fahrenheit.

Three of four kids were very surprised — the mixture had gotten colder — much colder! Their hypothesis was wrong — but why?

Ethan, who remembered doing this experiment with our old school’s Nature and Science Club, explained it this way: “Because the salt lowers the freezing point of water.” That’s a good start, but remember one more thing: It takes heat to melt snow, and that heat has to come from somewhere. As the salty mixture reached a new balance between liquid and frozen water, heat was sucked out of the mixture,and its temperature dropped. Steve Spangler puts it like this:

When salt is added to the ice (or snow), some of the ice melts because the freezing point is lowered. Always remember that heat must be absorbed by the ice for it to melt. The heat that causes the melting comes from the surroundings.

So, we had this very cold mixture of salty, heat-sucking slush. We couldn’t just let it sit there — we had to put it to use. As Ethan remembered from Nature and Science Club, salty slush is just to thing to suck the heat from a mix of cream and sugar — to make ice cream!

We looked up directions for homemade ice cream on the Web, and kind of followed the ones on Steve Spangler’s website. However, we couldn’t find the vanilla, so we used chocolate sauce instead:

This is what we used to make homemade chocolate ice cream.
This is what we used to make homemade chocolate ice cream.

We mixed the half-and-half, sugar, and chocolate sauce inside a heavy-duty zippered bag:

We mixed the half-and-half, sugar, and chocolate in a zippered bag.
We squeezed and sloshed the bag to make the mix.

Then we put the sealed bag of ice cream mix inside a second zippered bag packed with salty slush. The most important direction was to keep the ice cream mix (half-and-half, sugar, and flavoring) separate from the salty slush:

Make sure the bag of ice cream mix is sealed really tight!
Make sure the bag of ice cream mix is sealed really tight!

And then we held the bag of slush with a really warm glove and carefully shook and jiggled it for 15 minutes.

Make sure that your bare hand never touches the salty slush, and the bag of ice cream mix doesn't leak.
Make sure that your bare hand never touches the salty slush, and the bag of ice cream mix doesn't leak.

When we were done. it looked like this:

It looked good enough to eat -- so we did!
It looked good enough to eat -- so we did!

Everybody had a taste:

Aaron like it!
Aaron liked it! And so did everybody else.

The ice cream was super smooth, because thousands of tiny ice crystals formed as the super-cooled salty slush sucked heat from the mix.

Hurrah! The Ice and Snow Are Back!

We’ve been so immersed in searching for signs of spring that we almost forgot how wonderful winter can be. Then, on our second morning of low teen temperatures, we woke up to this:

Here's what our front-porch jar of water looked like after the second night of temperatures in the low teens.
Here's what our front-porch jar of water looked like after the second night of temperatures in the low teens.

Water is such interesting stuff, and it may be most interesting in early spring, when temperatures fluctuate around the freezing point.That’s why we leave containers of water sitting around outside, like the plastic jar of water on our front porch.

In this case, I think the streaky things are bubbles formed as dissolved air was forced out of the freezing water. The water froze from the outside in, pushing the ever-growing bubbles along as freezing proceeded inwards. There’s even a core of unfrozen water in the center, with air bubblettes accumulating into one big bubble at the top.

With predictions of 4 to 8 inches of snow falling from tonight through Saturday, I’ll have more than enough excuse to post more stories about exploring ice and snow. Maybe we’ll get back to spring late next week.