Science for Kindergarteners (and the rest of us): Magnets

by RobinsFlight

Last month I posted about a set of science experiments on color that I did in my son's kindergarten class.  This month I returned with another set of experiments to try, this time working with magnetism.

The classroom already has a few activities that involve magnets.  My favorite is this floating magnetic ring set.  It has disk magnets that can fit on a stand which also has a disc magnet in its base and a point sticking up from the base that will fit through the holes of the magnets- like a magnetic ring toss.  Because the poles of the magnets are on the flat sides, they either attract or repel based on which sides you put together.  By stacking the magnets so they are repelling each other they float.  And giving a gentle push to the top one, you can make the magnets jump quite far into the air.

Because they had already talked about magnets in class some, I decided to try some experiments that took their understanding a bit further.  We magnetized needles to create our own compasses and made electromagnets!

First we reviewed a bit.  Magnets always have two poles, a north and a south, or put another way, a positive and a negative.  They are magnetic because the free electrons within the atoms they are made of are all spinning in the same direction.  This creates a magnetic field that attracts other substances that have free electrons that are easily adjusted based on that field, such as metals like iron.

Magnetizing a needle

Here comes the fun part:  You can make a magnet out of something that is attracted to a magnet, like a metal needle or a nail.  We used embroidery needles.  Hold the needle firmly at one end (for some of the kids it was easier to hold the needle against the table).  Then take a magnet and stroke it down the needle, using only down strokes (pick it up and the end and start back at the top).  Do not turn the magnet while you are doing this, but keep the poles aligned the same way with each stroke.  Depending on the metal you are using and the strength of the magnet, this could take 50 strokes or 150.  How does this work?  The magnet being rubbed on one direction down the metal needle gradually pulls the electrons in the needle to have the same spin.  The more times you rub the magnet along the needle and the stronger the magnet, the greater the amount of the metal atoms in the needle have the same spin, and the greater the strength of the magnetic field around the needle.

Test your new magnet with another piece of metal to see how strong it is.  If you want to use it for a compass, it only needs a slight pull towards the metal.

Our magnetic needle compass

The earth also has a weak magnetic field and magnetic north and south poles.  The magnetic bar in a compass is attracted to the opposite poles of the earth, allowing it to find due north.  To make a compass out of your new magnet needle, fill a bowl with water.  Float a lightweight object like a bottle cap or a cork (in the pictures I used a milk jug lid) on top of the water.  Carefully place your magnetic needle on top so it can spin.  One end of the needle should point north and the other south.  In the picture, you can see that I labelled a paper with the compass points for our demonstration. 

So making a compass is pretty cool.  And we learned about electrons moving in the same direction.  Well, what else has electrons moving the the same direction?  You guessed it...electricity!  The current running through a wire wrapped around a nail will actually align the spins in those metal atoms in the same way that the magnet did with our needle, but this only happens while the current is flowing.  Once the current stops, the magnetic field in our nail is gone again.

To make an electromagnet, you will need a D cell battery, a piece or two of coated copper wire about 9-12" long with the ends stripped, an iron nail about 3" long, and electrical tape.  First, coil the wire around the nail a few times.  Depending on the gauge of your wire, this could be a big difficult.  The wire we used was a bit on the thick side, I think.  It doesn't matter whether the wire is coiled clockwise or counterclockwise, but the coils can't overlap each other.  The more coils you make, the stronger your magnet will be.  In our experiments we used a wire with 5 coils and a wire with 10 coils and tested each one.


Next, use electrical tape to attach the stripped ends of the wires to the battery.  I found that the wires still tended to slip out from under the tape unless I held them.  Be careful, the ends of the battery can get hot, so you won't want to hold them for too long!  A pair of wooden tongs would have been a useful tool for this experiment.





In our experiment, the wire coiled 5 times magnetized the nail enough to lift up the end of this small piece of metal, but not enough to pick it up off of the table.   (See picture to the left.)














But when we used the wire coiled 10 times, the magnetized nail was strong enough to lift the piece of metal off the table and hold it suspended in the air.  How cool is that!?  (See picture to the right.)  It also got hot a lot faster.  We also tried connecting two batteries in sequence to the 5 coil wire.  It seemed somewhat stronger than with only one battery, but not as strong as the wire with more coils.

The kids had a lot of fun with this one, and I did too.  I'm not sure what the next science day will hold, but I'm sure it'll be interesting.  And now, where did they put that floating magnetic ring set?  I want to make some magnets fly!

Science for Kindergarteners (and the rest of us): Colors

by RobinsFlight

Last week I did a series of science experiments with my son's kindergarten class.  After all, I used to be a real scientist who did cancer research until I decided that raising my family was a more important job than even that.  My son's teacher was more than happy to let me find some interesting things to do, based on that month's topic of discussion: colors.

In class they had already discussed how the primary colors of red, blue and yellow can be mixed to create orange, green and violet.  They have some nifty experiments of their own.  They had mixed colors of playdoh to create new ones.  They split a stalk of celery into two at the base and put each side onto different colored water to see what happened as the colors rose up the stalk.  And they mixed their own paints- the most fun being shaving cream paint.

I arrived hoping to expand their concepts a bit.  And we did have fun.  The experiments were did were spinning colored plates, playing with prisms to create rainbows, and marker chromatography.

The plate spinning was first.  I use small paper plates, though you could use circles of cardstock of paper glued to cardboard.  I colored half of each of 3 plates with the primary colors: red/blue, red/yellow and blue/yellow.  I also made a colorwheel on a fourth plate, with sixth of each of the primary and secondary colors.
  


I borrowed my daughter's snap circuits spinner for this one, though it could be done by threading string through two holes punched in the center of the plates and spinning that way also.  I did try making a top out of the plates with either a toothpick or a pen, but it was hard to get them spinning fast enough to see the colors blend.  I taped the propeller to the bottom of each plate, started the spinner, and we saw the primary colors blend to create their secondary color.  Interestingly, the camera really didn't catch this nearly as seamlessly as our eyes did.




I also let the kids color their own plates with designs and colors they of their choosing.  It was fun to see their designs turn to circles of color when the plates were spun. 











With the colorwheel plate, the results are interesting.  The colors blend to create a brownish shade, as you would expect if you were mixing paints.  Yet if you looked at the edges where the plate was curving away from you, or if you slowed the motion somewhat, the colors paled, approximating white!  The lesson?  Combining all the colors makes white!

This led to our second experiment: playing with prisms.  Most people have seen or even toyed around with a standard triangular prism.  If not, imagine the iconic Pink Floyd symbol of the white light breaking into the rainbow as it shines through the prism.  But more fun was trying out the multi-faceted prisms my husband happens to have.  Rainbows galore!  So we talked about how a rainbow in the sky is created by the sun shining through the rain, which breaks the white light into its colors.

Along with same line, do you know why the sky looks blue?  If we look at the prism, we see that the blue and violet wavelengths (which are shorter) are bent more than the red and orange wavelengths (which are longer).  The molecules of our atmosphere, the nitrogen and oxygen, scatter the light in the same way but to a much greater degree.  Therefore, the blue parts of the sunlight are scattered significantly more- think of them bouncing around more and in many directions- than the red parts, which are virtually unchanged in terms of the direction they travel.  So as we look at the sky, we see the blue light that has been scattered in every direction by the molecules in the atmosphere.  As we look towards the horizon, the blue color gets paler because more of the blue light has been scattered elsewhere and we see more of just the complete white light.  The violet wavelengths are also scattered.  However, not only is there less violet in the light we see, since much of it is absorbed by the upper atmosphere (as are some of the ultraviolet rays that cause sunburn), but our eyes also don't detect the violet as well, and we interpret the combination of blue/violet and the complete white light as the light blue of the sky.  At sunset, the light looks more yellow to red because you are seeing more of the unscattered light as it flows through the edge of the atmosphere.  Clear air tends to have a yellow shade at sunset, while more particulates in the air cause a more reddish hue.

Markers, clockwise from top: green, pink, black, brown, orange

In the class, once we talked about rainbows, we transitioned to pigments- the colors that make up paint and, for our experiment, the ink in markers: marker chromatography.  While it sounds impressive, it's basically separating pigments in the marker using water on filter paper- in this case, coffee filters.  FYI, this experiment seems to work best with inexpensive markers.  We flattened coffee filters on paper plates, and drew lines of different colors on the filters.  Then with eye droppers, we put a drop or two of water near the lines and watched as the colors spread and separated as the water bled through the filters.  Not only is it interesting to see what colors separate out of different markers, but this makes for a fun art project also!  It does work best using only thin lines, not blocks of color, and only a few drops of water, as too much water just makes the marker bleed out of the filter and onto the plate below.

Did the kids learn a lot about colors?  I don't know.  Sometimes they absorb more than you think they do.  But they definitely had fun playing with colors.  And the teacher wants me to come back again when they move to a different topic: sound!

One child's marker filter before water

Marker filter after water separation of marker pigments