When you warm up leftovers, have you ever wondered why the microwave heats the food and not the plate? (Well, some plates, anyway.) It has to do with the way microwaves work.
Microwaves generate high energy electromagnetic waves that when aimed at water molecules, makes these molecules get super-excited and start bouncing around a lot.
We see this happen when we heat water in a pot on the stove. When you add energy to the pot (by turning on the stove), the water molecules start vibrating and moving around faster and faster the more heat you add. Eventually, when the pot of water boils, the top layer of molecules are so excited they vibrate free and float up as steam.
When you add more energy to the water molecule, either by using your stove top or your nearest microwave, you cause those water molecules to vibrate faster. We detect these faster vibrations by measuring an increase in the temperature of the water molecules (or in the food containing water). Which is why it’s dangerous to heat anything not containing water in your microwave, as there’s nowhere for that energy to go, since the electromagnetic radiation is tuned to excite water molecules.
To explain this to younger kids (who might confuse radio waves with sounds waves) you might try this:
There’s light everywhere, some of which you can see (like rainbows) and others that you can’t see (like the infrared beam coming from your TV remote, or the UV rays from the sun that give you a sunburn). The microwave shoots invisible light beams at your food that are tuned to heat up the water molecule.
The microwave radiation emitted by the microwave oven can also excite other polarized molecules in addition to the water molecule, which is why some plates also get hot. The soap in this experiment below will show you how a bar of Ivory soap contains air, and that air contains water vapor which will get heated by the microwave radiation and expand. Are you ready?
Here’s what you need:
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We loved this! Owen says, “It puffed up like a giant piece of popcorn and felt like a giant piece of popcorn!” Thanks for a great experiment 🙂
You’ll want to read over ALL the comments for this experiment to understand why… I give detailed explanations as to what happened with each case. 🙂
Why do you not want us to use a new microwave.
Ivory is the best, as it has a lot of air (which also has water vapor – the reason why this works!) whipped inside. Most soap which floats in water will give you good results.
is there any other kind of soap we can use? Or is ivory the best kind?
It feels like tissue paper.
Tissue soap sounds odd..
luv it, it is soo cool!!
I did this experiment today with my daughter. It was sooo cool. When the soap came out of the microwave, it looked and felt like whipped cream. Really cool! Loved it.
Mary Lord
Tiny warning: We had so much fun that we decided to do it two more times. Bad idea….our microwave overheated and stopped working. Thank heavens that it started working again after 15 minutes. Whew!
My kids were Thrilled to see the soap bubble up. They thought it looked like a cloud or cool whip. What an great experiment.
Hi aurora,
My name is Kade and I am 9. I was wondering if you can use the soap brand exact.
Thanks.
Soap is the best one that doesn’t release toxic fumes in the house… 🙂
Dear Aurora
We started with a used bar of ivory soap but since there was water on the outside of the bar although it did bubble it more melted than bubbled. My youngest Cameron said that it looked like an egg when it’s cooking. We then changed to a new bar and it worked just as yours did. The kids were very excited and they love their new soap mountain they get to wash with.
Thanks for such a fun experiment
Stacey – from Dryden Ontario, Canada
That was AWESOME!!!!!!!!!!The soap looked funny.
Does anything alse do stuff like that?
Reese
Making it was fun but the smell stank peewee
This was soooo fun. The bar started breaking in half and then it started moving across the plate 😀 It looked like a train chugging around the track 😛
I love soap because it smells so nice. The soap bubbles and it has a hole in the middle.- Iera-Michelle 6
It was really cool how the soap bubbled and floated out of the soap bar – Stephan 9
We enjoyed this experiment and the conversation around it. Now just to clean the oven! Thanks for the fun, Aurora
Christine, mom of the 2 above
We used lever 2000 and it turned into a seal-shaped puff. Ha ha ha ha ha ha!
The amount of ‘fluff-out’ depends on how much water vapor is inside the bar of soap. 🙂
We used a very old bar of Ivory soap. It only fluffied a little before starting to burn. Does the age of the bar change the results????
We then tried a Dial bar. The Dial was very fluffy. Much excitment at our house!
Dear Aurora – Thank you for showing that! I thought it was cool! I can’t wait for my big brothers and sisters to try more experiments. I want to learn more about science. from Amelie (age 5)
My 13 year old daughter said, “This is so cool! I love science! Well, at least THIS science!”
As they watched the soap in the microwave, the 4 children were watching and talking about what was going on. They were feeding off of each others comments and answering the questions! Amazing to watch my kids learning like that.
Thank you!
We did this experiment today in our homeschool science. It was cool to see the diiference between Lever2000 and Ivory soap. The kids love playing with the soap shreds from the Ivory bar. We noticed that Ivory had a lot more air in it than Lever 2000 and the Lever soap retained heat longer.
Try making a paste with baking soda and water and use this to lightly wipe out the inside of the oven. The smell should completely disappear.
we did this last year (it was in a book Connor had). He added googly eyes & other stuff to make it into a “soap monster” – he cried when i finally had to get rid of it. Don’t pop popcorn in your microwave immediately after doing the soap – it absorbs the smell – nasty. We tried microwaving a cup of vinegar to get rid of the smell, it seemed to work a little.
Well, be sure you keep your grandma happy, or she might not let you borrow the microwave for your science lessons! 🙂 How big it gets depends on the power of your microwave, the amount of water vapor in the soap, and how long you leave it in. What happens if you dunk your soap in water overnight and THEN put it in?
the soap in our microwave was getting so huge after just minute and 40 seconds. thats when we stopped. we actually had fun playing with the microwaved ivory soap. grandma wasnt crazy about the idea, she was watching the news, perhaps we will try it again tomorrow night! we wonder how big it will get when we do it tomorrow. what do you think folks?
Oh, no! What if you make a paste out of baking soda and water (so it’s like toothpaste-consistency) and scrub the inside with it? Does that help? That’s how we get stubborn smells out of our lab.
And you want to use a soap that has a lot of air mixed in – so much that it will float in water. The trick is that the Ivory company sells you soap + air, while other companies sell you just the soap. You want one with mots of air mixed in.
Oh boy! We should have stopped after the Ivory soap… Irish Spring soap ruined our microwave! We couldn’t get the smell out of it. 🙁
It was awsome!! The Ivory soap completely filled up the plate and almost overflowed it. We also tried a bar of Dove soap to see if it will expand, but it didn’t (it probably didn’t have enough air in it). My brother discovered that he can use the leftover Ivory soap as clay, but it was messy when he made a snowball.
Benjamin (7th grade)
It sounds like it worked – you don’t want to leave it in too long or it will burn, as you discovered. For soap that doesn’t turn fluffy at all but only burns, there was not enough water in the soap… which is to say there wasn’t enough air (which contains water vapor) inside your soap. The soap you want should at least float… does yours? Ivory tends to work the best for this experiment.
Our soap became fluffy first, and then burned. It was an awful smell.
Then we tried a handmade soap and this one melted like butter. What does this say about the composition of the soap?
Henny and Jared
Awesome experiment! Filled a dinner plate~
We used Lever 2000 and it covered the plate and nearly filled the microwave! Very cool. Thank you so much.
Try it! (You’ll want one that floats in water – that tells you that it has enough air trapped inside the soap).
can i use any soap?
it sound like fun were doing it after supper 😉
natasha scribnock
This experiment is part of Unit 3: Matter, Lesson 2: Solids. If you look in the upper right, there’s a menu of more experiments for this area as well as reading and an introductory video. Do you see it?
We just did the experiment. It was great fun but where is the lesson that goes with it? I don’t see it.
That was awesome! I loved watching it inflate in the microwave! There is no bit that is not fluffy.
Mirella
🙂
that soape thing is awesome we used dove
cool
It was awesome! It was so big we had ti poot it in a huge bowl!
your experiments are so cool!
abbey mercer
Hard and fluffy at the same time – it’s still a solid.
Is the soap supossed to be hard after taking it out of the microwave?
It’s so cool Dalton More broth of lexi Moore
dear Aurora, I’m Lexi Moore.I just tried the stuff with soap . It was very cool !I loved it sooooooooooooooo much. You are very goodat your job and u are very pretty.Ireally wish I could meet u.Hey, I also did your plasma grape . It was sooooooooooooooo awesome! Your are so cooooooooooooolllllllllllllll. Love, Lexi Moore dathger of Tara Moore
It was so COOL!!!
Thank you! We’re going to try it tomorrow.
Yes, this experiment is actually part of unit 3 lesson 2 …you can see this in the menu on the upper right corner of the page.
Is there a unit of study that you would suggest I could use this experiment as an introduction to the unit? You know, I can say, “We are going to start studying (the unit you suggest) and before we get started let’s do this ‘Microwaving Soap” Experiment!
Thank you,
Looks like whipped cream, feels (and smells) like soap. Feathery-soft and hot at first.
Is the soap soft after you microwave it? I mean, like whip cream, sort of?
That is an excellent idea!
“I learned something – how to make handsoap powder from cooking Ivory Soap”. This was a fun experiment. Thank you also for sending the DVD as it is much easier for us to see on DVD than the site. Science is fun. Next experiment, we will weigh Ivory soap before microwave and after. We think the soap will lose mass, but we may not have accurate enough scale to measure that.
You can any bar you want, but try to get one that floats when placed in water. This way it has a high air content, and since air contains water vapor, it will work for this experiment.
Why can’t we use any other kind of bar?
Great! You’ve found the links in the upper right corner that go with the lesson. Since these are just simple activities you can start with, it’s not at all obvious they are part of a much larger lesson and unit! 🙂
Found the extra materials. Hurray. This is going to be so much fun.
Sweet regards,
Rebecca
OK…I am new here and this is really cool. Are there other materials that go with this to “expand” the learning? Or is the point that the soap has water molecules contained in the air molecules that are whipped into it and that the microwave uses directed “light” waves to excite the water molecules? I am just wondering if there is more or if science for the day can be as simple as that? Of course we can make predictions, try different power settings, soaps, chart results, etc…, but I was just wondering if there is anything else already prepared on the site that goes with this. I can tell this is going to be fun once I figure it all out.
Rebecca
We are going to the dollar store today so we are going to get different brands of soap and chart any differences in the brands and why we think one did differently than another (like maybe one bar was denser then another). Plus I think my microwave will go into shock from being used for once lol!
Now how cool is that?
Aurora, Wow, what fun! This is our first day and our first experiment.
We are having a ball. My boys are so excited and fell out laughing at the sight of the crazy soap!
It took a while for it to start expanding, but when it did it was so cool! When we flipped it over at the end it looked a bit like a pancake. We didn’t use Ivory Soap, we used Sunlight Soap (Australian brand). When it was finished the whole house smelt like soap!
Laura Fiebig
We loved this. When it deflated my daughter said it reminded her of the pyramid in Despicable Me.:) The fluffy pile also reminded us of kleenex that had gone through the laundry.
You’ll want to read over ALL the comments – I’ve talked about what, why, and how this experiment works – it might be near the bottom of the page… 🙂
We have a farily new microwave. Is this experiment not safe enough to use it? What could happen to it?
You want a bar of soap that floats on top of the water. 🙂
does this experiment have to be Ivory soap or will any brand work?
It’s just that I’m not there with you in the kitchen and can’t tell you what’s going to happen or not with your particular microwave. So use an old one you don’t care about and read over the comments in this section before giving it a try to see how other folks have done the experiment and what kinds of results they have received (along with my notes about what happened and what to expect). 🙂
Hi. We picked up a few bars of Ivory and a few getting ready for the fun. Before we start though, please clarify something: your instructions included the comment “don’t use a new or expensive microwave!” Why not? What can happen that would be harmful? Our microwave isn’t new, but it’s not so old that I don’t care if it gets damaged. So, please tell me the risk or downside of doing this experiment. Thanks
that is so cool
That was so Funny
Hmmm… that can happen if you’re not logged in. Go back to the main page and log in under the video on the right. Did that help?
Aurora, we can’t pull up the ivory soap video, can you help us?
SOOOOOOOO AWESOME, this was a cool project because it was like the soap turned inside-out. ours didn’t get as big as yours because we think that our microwave is to old or it did not conduct enough heat.
thanks again, Liam Floyd 12
That was awesome! I was on the edge of my seat! Jasmin & Isabel
We did this awsome experiment 3 times. The aroma of Ivory filled the house and the microwave. A great tip to get rid of the odor is just put a tablespoon of lemon juice in a cup of water let it heat in the microwave for a few minutes and the odor should be gone.
We had a blast doing this experiment and have then enjoyed ‘fooling’ friends with our whip cream mound on the kitchen counter or in the bathroom. The only reason to stop doing this over and over again, is running out of soaps. Not sure how many mounds of soap I am willing to store in the bathroom ….
You’re right – placement in the microwave (both horizontally and vertically) will make a difference, as well as the power setting. This isn’t as crucial as with the Plasma Grape experiment, though, as the bar of soap is much larger than the grape-skin bridge. Have fun!
This was a fun experiment! We compared a fresh bar of Ivory soap and a similar-sized bar made from shavings from Ivory soap (the shavings were left over from a carving session we had). We looked at symmetry of expansion and discussed possible effects – one seeming to be placement of the bar on the plate and the plate within the microwave, We need a few more bars to get any conclusive findings though.
We used the Castle soap you get from CrackerBarrel. Worked like a charm and added lots of questions. Great to see the kids so excited about learning! Makes an interesting shape for the soap dish.
It was so COOL!!! After the experiment, the soap looked and felt like tissue.I still used it as soap!
well, this was our first time… and guess what it was great! i have five fearless boys and the 7 year old put his fingers right on top of the hot soap… so DONT touch soap is really hot inside… VERY FUN!
Yesterday finally got started on Super Charged Science, and we picked this as our first experiment. Wow! this science is going to be fun! Our Ivory soap bar was fresh and moist, and it just about filled the microwave.
Our bar of Ivory grew so much we had to stop it mid-cycle, remove all the fluff and put the remainder back in for another go at it. We enjoyed it so much that when Dad got home we dragged him to the microwave to watch another whole bar (stopped mid-cycle and restarted again!). Thanks for an enjoyable experiment!
We used a old bar of ivory soap so it didn’t work very well. It had some water so it expanded a little bit but not a lot.
Martin Betts
This worked great. The bar of soap became a huge mound of puffiness. This soap will be fun to use in the bath.
Hey, there – welcome back! Don’t worry – the Chemistry unit will be up forever… so you have time. 🙂
Sorry I have not been active here for a while :P, but I am back! Btw, we did not do unit 8 because the chemicals accidentally got taken to storage. :(. but, I’m back! 😀
That sounds so fun… you can always post pictures here:
http://sciencelearningspace.shutterfly.com/
We used some perfumed hotel soap and it was very impressive. Foamed up beautifully! The odor afterwards sent us scurrying to open windows and turn on the fan. All the kids grabbed their gift candles from Christmas and stuck there noses in the jars for a bit. Wish I had also gotten a picture of that!
i worked great!
Sometimes if an ‘old bar’ stays sealed enough, the water vapor inside the bar will remain IN the bar, otherwise it will evaporate out over time and when you place it int he microwave, the microwave has no water molecules to excite so it winds up cooking and burning the bar.
We tried two bars of Ivory and neither puffed up like on the video. We also tried some other hotel bars. One with perfume and it burned a little. And it left a very unpleasant smell in our house for a while.
I thought maybe our Ivory was too old, but Mary Beth posted using an old bar, so not quite sure what happened. It just cracked.
But the kids had fun doing this experiment anyway.
This was such a great start to our Science at home. I was actualy at work and wanted my kids to get chores done. I told them I had a great surprise in store for them when chores were done. I sent my oldest daughter the link and directions and they called me when they were done with the experiement. They LOVED it!! My son even took a bath after with the “cool” soap.
So, not only were chores done and Science covered, I had a clean boy when I got home 🙂
What fun! We found an old bar of Ivory soap (nobody knows where it came from!) and used it. It was cool to watch and my boys loved it! The boys said our microwave oven must be more powerful than the one on the video demonstration because the soap actually started to burn in just over a minute! I think it might also be because we don’t have a rotating plate in it. (It’s pretty old.)
I love watching the the soap form weird shapes in the microwave.
Holly Thomson
This is SO cool!
Holly Thomson
Hmmm… sounds like Dove has air mixed into it as well… you’re actually getting less soap for your money when you buy these brands, but they are the ones that work in this experiment the best!
Just as awesome the “Plasma Grape”! We used Dove soap and not Ivory but it still worked wonderfully? Is there a reason that two different soaps worked the same?
sevy keble
🙂