How To Learn More from Making a Tin-Can Phone

Everybody's made a tin-can phone or string phone as a child. They're fun, they work (Can you hear me? Yes!!!), and they're quick and easy to make. But what can we as parents and teachers do to increase the fun and learning? Read on for the basics of how to make a tin-can phone, and then read some ideas for experimenting for more fun and learning!

photo by Florian Seroussi (CC BY-NC-SA 2.0)

Making a string phone is easy. Here's what you need.

• Two paper cups.
• A length of non-stretchy string.
• Something to poke holes in the cups (a sharp pencil will do).
• Two paper clips (big ones work best).

And here's what you do.

1.  Poke small holes in the bottom of your cups.
2. Poke string through the bottom of each hole.
3. Tie a knot around each paper clip so that the that the paper clips are inside the cups. This anchors the string and prevents it from pulling through the hole in the cup when you pull the string taut.
4. Decorate as desired.
5. Enjoy your phone by holding the string tight between two people. One talks, and the other listens. 

 Then experiment!

 

My students experimenting with string phones

Kids will probably have lots of ideas for experimenting with their string phones, but here are some to get you started.

• Make a phone for each person and connect them so everyone has an earpiece and a mouthpiece as in the photo above (They could hear each other well).
• Try different materials: cans or plastic cups instead of paper cups, different kinds of string or twine.
• Experiment with the string length. How long of a string can you use before the sound is too weak to hear? The video after this list shows people who really push the limits.
• Do the people on the phone need to be in a a straight line? Try talking with the string going around a wall corner. How about around the leg of a chair.
• Will the phone work if the string passes under a rug? What if it's wet? What if someone pinches the string?

Can You Hear Me?: The Longest Tin Can Phone Ever.

 

What do kids learn from string phones?

Kids often understand intuitively why things work if they get hands-on and experiment a lot, but it never hurts to ask the "why" question and see how much they really understand and what needs to be taught. Depending on the interests and abilities of your children, they can learn about sound waves and what media sound travels through, how signal can be dampened and amplified (maybe focused is a better word). They can also learn some engineering when they try to keep the line tense without it ripping through the cup. Kids can learn about real telephones which operate on the same basic concept, except the sound signal is electronic instead of accoustic. (Here's a page about how telephones work.)

Enjoy your string phones, and if you have questions or ideas for further experiments, please leave a comment!

Home-Made Hot Air Balloon

The first human flight took place in a hot air balloon in France over 100 years before Orville Wright took to the air. It's not easy to make a working airplane, but balloon technology is simple--just heat the air inside a balloon so that the air inside and the contraption itself are lighter than the air that is displaced.

We made our balloon with a thin trash bag, straws, aluminum foil, tape, and six birthday candles, following the excellent instructions from sciencetoymaker.com.

Here is our balloon's second attempt at flight, after trimming some weight from the straws, trash bag, and foil.

 

 A fun way to add some literacy and history to this activity for younger kids is with Hot Air, the story of the first balloon flight with passengers aboard (animal passengers). For older kids, The Twenty-One Balloons a fun mix of fiction, history, and balloonology is recommended.

Enjoy making your balloon, and keep a fire extinguisher or bucket of water handy just in case!

 

Anti-Pattern Recognition

Math is largely about recognizing and creating patterns. But sometimes the best way to practice something is doing the opposite. Hmmm. Is avoiding a pattern another way of creating a pattern?

Take from a deck of cards all the Aces, Kings, Queens and Jacks.

Arrange them in a 4 × 4 square so that every row, column and diagonal contains one card of each value (A,J,Q,K) and one card of each suit (Heart, Spade, Diamond, Club). source

It's really tough not to have cards of the same value or suit in any row, column, or diagonal, but look at the sense of accomplishment on the faces of these ten-year-olds who stuck with it and solved the puzzle.

Four Fours and Making Math Fun

Today I gave my kids the "four fours" challenge. Here it is:

Find a mathematical expression for all the numbers from zero to twenty using common symbols (+, -, x, ÷, √, and !), parentheses, and exactly four 4s. The simpler the expression, the better.

To get you started:
4x4÷4-4=0
4x4÷4÷4=1

I had to teach my daughter what √4 and 4! mean. She was very motivated to learn them because they were a great tool to solve the challenge.

It turns out that "four fours" is a common challenge, but I found it in Jo Boaler's excellent What's Math Got to Do with It?: How Parents and Teachers Can Help Children Learn to Love Their Least Favorite Subject (amazon affiliate link). The book is full of research-backed suggestions for parents and teachers to help their kids thrive in math. Dr. Boaler will be teaching a course called "How to Learn Math" on Stanford University's free online platform. It's from July 15 to September 27, 2013. You can find out more about it here. I'll be taking the course. Please let me know if you will be.

Student-Created Math Questions

Student assessment can take many forms. One thing I like to do is ask the students to create their own questions, answer them themselves, and share the questions with others.

The raw material I gave the students is from the well-known "Eric the Sheep" problem (Here's another blog about it).

Eric the sheep is lining up to be shorn. He is last in the line. Each time the shearer takes one sheep from the front of the line, Eric sneaks past two sheep to get closer to the front. There are 50 sheep in front of Eric to start with. It takes the shearer ten minutes to take a sheep from the line and shear it. The shearer never takes a break! Each sheep produces 5 kg of wool.

Use the information in the story of Eric the sheep to make up an interesting story problem that you can answer. You don't need to use all of the information.

And here are my students' questions with the their ages (I teach a multi-age class). I had to help a few students polish their questions to get rid of excessive wordiness or vagueness.

1. How many times does Eric pass two sheep? (10 year-old)

2. How many minutes does it take to pass 24 sheep? (10 year-old)

3. After 60 minutes, what place was Eric in? (10 year-old)

4. How many kilograms of wool did all of the sheep provide? (8 year-old)

5. What number is Eric to be sheared? (11 year-old)

6. How many grams of wool were sheared altogether? (11 year-old)

7. How much wool is sheared before Eric is sheared? (12 year-old)

8. How many sheep did Eric pass? (12 year-old)

9. How long does the shearer shear before shearing Eric? (12 year-old)

10. If Shawn, who started at number 34, skips one sheep every time the shearer takes a sheep, who arrives to the front of the line first, Shawn or Eric? (12 year-old)

11. One-third of the sheep are pink, two-sixths of the sheep are vomit green, and the rest are purple. (a) How many purple sheep are there, and (b) how many kilograms of purple wool were there? (13 year-old)

These questions cover all the types of questions I would have asked and then some (number 10!). Some of the students missed their own questions on the first try, but were very motivated to find the correct answer.

This kind of activity is excellent assessment for learning. We can see what the students are and aren't comfortable with, and we can be sure that if their answer is incorrect, it certainly can't be because they misunderstood the question. After all, they wrote it!

Over 100 Words in Signature

Today my students found over 100 words hiding in the word "signature." Most of the kids are English language learners. It was a fun way for them to think about spelling and learn some new vocabulary.

It all started with me pointing out that the word "sign" is the root of "signature," which is a spelling word for some kids this week. A student pointed out that the word also contains "gnat." Someone else found "nature," and we were off to the races.

Right after taking this photo, a student found "granite." Can you find any other words? Add them in the comments.

Over 100 words in "signature"