## [anyqs] Hurricane Irene Edition

So I made this short video:

… because a week earlier I read this awesome hurricane preparation tip:

If an evacuation is required, one should freeze a nice, clear, full, pint-sized glass of water into solid ice and put a penny on the top of the ice in the freezer. Given that power outages can vary from block to block for varying lengths of time, and that power can be restored before one can return home, it is very possible to arrive after an evacuation to a fridge and freezer working normally. However, if you find the penny at the bottom of an almost-full glass of solid ice, you can toss your bags of food in the trash without even opening them. The penny at the bottom of the glass of ice means that power was out long enough for the ice to melt all the way through. Long enough so that the stuff in the bags is surely re-frozen and re-chilled spoiled food.

That’s the #anyqs game, everybody. Take what you find interesting and turn it into something challenging, something provocative for someone else. We’re great at assigning questions, at writing them down in textbooks or on the whiteboard and using the power of the state to force students to answer them. (“Do you want a bad grade?!”) We have much less practice at provoking questions, at putting students in situations that make them wonder, “Whoa. What just happened back there?”

This has been an attempt at that.

BTW: The big behind-the-scenes dilemma, for whatever it’s worth, was whether or not to include a final shot showing me dump a bunch of food from the freezer into the trash.

Featured Comment:

There is a better way, however. Take a used water-bottle, put a little water in it, and freeze it *upside down*. Then store it in the freezer *right side up*. If you ever find the ice at the bottom of the bottle, there has been a thaw. This eliminates the uncertainty introduced by the “ice skate effect”.

I'm Dan and this is my blog. I'm a former high school math teacher and current head of teaching at Desmos. More here.

1. #### Telannia Norfar

September 1, 2011 - 5:28 pm -

Some people do bell ringers. I think this would be a great video to watch to just get the brains going.

2. #### Paul Wolf

September 1, 2011 - 5:38 pm -

My question, if I’m wearing my student hat would be “what word did you bleep,” which of course leads to the question, “why did you swear,” which could lead a few students to ask “how long does it take a cup of ice to melt?”

My teacher question is then, “What does act 2 look like?”

3. #### James Cleveland

September 1, 2011 - 5:54 pm -

I think the shot of you throwing out the food would have been good, otherwise I think the first question would be “what’s going on, what’s wrong?”

4. #### Craig

September 1, 2011 - 11:04 pm -

What would the melting time difference be if we used a quarter instead? Or a Looney (Canadian dollar coin)? Or a Gold Doubloon?

5. #### CalcDave

September 2, 2011 - 3:46 am -

I didn’t understand the point from the original video. I guess I wondered what “magic of science” let the coin fall to the bottom. Like, somehow ice-water is still fluid enough if you give it enough time to let the more dense coin sink? Or maybe you have some trick freezer?

Maybe at the beginning of the clip you could say a line like, “Are you packed yet? We have to be at the airport in 30 minutes!” Then at the end show a blinking clock before opening the freezer. That would have let me know the point a bit better.

6. #### sheaphysics

September 2, 2011 - 4:12 am -

Is three days really long enough for it to fully defrost and refreeze?
Remember, the freezer is pretty well insulated and if it is not opened things are going to stay frozen for a few days (as I experienced throwing out all my still frosty food on day 2.5/4 with no power this week).

7. #### Rhett

September 2, 2011 - 5:36 am -

A couple of comments. First, great video. Very artistic.

Second, I have evacuated for a hurricane before. My best analogy is Han trying to get the Millenium Falcon ready to leave Hoth (“Why do you take this apart now? I’m trying to get us out of here and you pull both of these.”)

Third, yes – stuff in a freezer can melt in a day. It depends on how good your freezer is. Some of them are old and not so insulated. Also, it depends on what else is in there. If you have a frozen turkey, this will help keep things cold (or better yet, fill the freezer with milk jugs of frozen water).

8. #### DMT

September 2, 2011 - 8:56 am -

I’m not quite sure, but I think it seems some people might be misundestanding the science. I think the point is that the penny will sink to the bottom not matter what. The weight of the penny will melt the ice locally, which will refreeze quickly.

I don’t know how long it would take, but coming back at different times would find the penny part way down frozen in ice.

I think colder freezers will slow this process a bit, but I don’t know the direct relationship offhand to temperature.

My act two would be showing those in between shots with the penny part way down, but still in ice.

9. #### Bre Wheat

September 4, 2011 - 1:38 pm -

Love it! I had my kids (ages 14 and11) watch it. The both had to think about it, but figured it out. I agree that it would make a great bell ringer.

10. #### Eugene

September 4, 2011 - 7:46 pm -

Unfortunately your example is context sensitive. In my neighbourhood, when there is a power outage, the circuit breaker will trip and has to be turned on manually.

11. #### Frank

September 5, 2011 - 10:29 am -

I agree with those who point out the coin will melt its way down through solid ice because of its own weight. We did an experiment along those lines in middle school science class with a wire and an ice cube and I’ve done it with a penny laid on an ice cube in the ice cube tray.

There is a better way, however. Take a used water-bottle, put a little water in it, and freeze it *upside down*. Then store it in the freezer *right side up*. If you ever find the ice at the bottom of the bottle, there has been a thaw. This eliminates the uncertainty introduced by the “ice skate effect”.

(Plus you can store it that way indefinitely so as to catch unexpected outages. It doubles as a lovely demonstration of sublimation as the ice vapors recrystallize in a downy beard down the side of the bottle over months.)

A second alternative is to massage your bags of frozen vegetables. If they are frozen solid, they have refrozen.

12. #### Nate

September 8, 2011 - 6:34 pm -

“The penny at the bottom of the glass of ice means that power was out long enough for the ice to melt all the way through.”

On the contrary, it seems to me that the penny may slide off the top of a partially melted ice chunk. The ice is not going to simply melt from the bottom up or top down, but I rather think there would be a stage with a big ball of ice floating in the cup, with a gap between the cup and the ice. This could roll or shift as it melts, resulting in a penny at the bottom long before the glass of ice has melted all the way through.

If this is true, then the penny could hit the bottom of the glass long before any food spoiled, and it would be a shame to chuck a freezer full of edible food. Are we assuming that the food is instantly spoiled when it is unfrozen? For some people, the logical difference between “conditions that thaw water” and “conditions that spoil a freezer full of food” is a non-trivial difference.

13. #### Chera

September 15, 2011 - 3:36 pm -

I love this and the thought provoking questions that a video like this ignites is phenomenal. I had to watch this video twice because I wanted to know why, how and what that had to do with the hurricane. I continued to read, so I did not think and draw my own conclusion, but I love that these videos do exactly that.

14. #### Susan

September 18, 2011 - 8:28 am -

This is something that I never actually thought to do myself. And being that I never had to worry about a hurricane hitting my area of the country head on before Irene, why would I? This video provided me with some food for thought. How else would you know if your food was spoiled before you ate it? Maybe I will pose this question to my science class…