Cells: The Importance of Cell Walls

 Cell walls prevent plant cells from bursting. 

Blow up a balloon until it pops.  An animal cell (or a plant cell that's missing a cell wall for some reason) is like this balloon.  Water can flow into the cell until the membranes bursts. 

Now place a balloon into a length of pantyhose and proceed to blow it up.  It will be harder and harder to blow up the balloon because the nylon restricts the balloon.  Virtually impossible to blow it up enough to pop it.  In the same way, the cell wall prevents the cell from reaching its bursting point. 

Newton's 3rd Law: Popping Canisters

 This activity can be done as one activity in a series of stations on Newton's 3rd law, or it could be done as a demonstration if performed on an overhead projector* (does anyone still have those in their classrooms?!?!)

You'll need 2 film canisters (another relic), Alka-Seltzer, water and a pan with a line drawn down the center. 

I took the set-up picture with the transparent canisters, but later switched to the black**

Fill both canisters about half full with water.  You'll want to have the same amount in each canister.  

Cap one of the canisters and lay it on its side so the cap is against the line in the pan. 

For the next portion, you'll need to work quickly....
Add about 1/4 - 1/2 of an Alka-Seltzer tablet to the second canister and cap it.  Then lay that canister so its cap is against the line in the pan. (The two caps should abut one another). 

When the Alka-Seltzer creates enough gas to fill the canister, it will pop the top off.  At the same time it will push the second canister.  Equal force will be applied to each canister, but in opposite directions.  After the explosion, the two canisters will end up in mirrored positions.  

*If you want to do it on an overhead projector, draw a line down the center of a transparency using a permanent marker.  And use a minimal amount of water.  

**This is definitely a demonstration to play around with before you plan to do it in front of your students!  I've done it successfully several times in the past without problems, yet when I went to photograph it, I ran into problem after problem.  The first canisters I grabbed to use leaked so that enough pressure never built up to pop the top off.  Then I used too large a piece of Alka-Seltzer and sent the canister flying out of the pan and off the table (fortunately it didn't go through the brand-new dining room window!).  It's a great little activity, just give yourself a chance to practice it in advance! 

Sound: The Clanging Hanger

This is a simple demonstration that helps make the point that sound needs something to travel through and that air is not a very efficient material for that purpose.

You only need a wire coat hanger and a long length of string.

Tie the string onto the hanger, so that the hanger hangs from the middle of the string.

Swing the hanger from the string so that it bumps into something (a table, chair, wall, etc.) and take note of the sound it makes.  It's kind of a short, clang-y sound.  Nothing very dramatic or melodic about it.

Now, wrap one end of the string around one of your index fingers and the other end around the other index finger.

Place your fingers in your ears (gently, there's no need to jam them in).

Swing the hanger so that bumps into something once again and take note of the sound it makes.  Louder and more like a gong or large bell ringing.

In the first trial, the sound made when the hanger hit the object had to travel through the air to reach your ear drum.  A lot of the sound was lost on the way to your ear.  In the second trial, the sound vibrations travel from the hanger through the string and your fingers to your ear.  Much less sound energy is lost in route and it makes an audible difference. 

Pinterest!!

Science Matters is now on Pinterest!

It took a while, but I've gone through all the past posts and posted each activity onto an appropriate Pinterest board.  I've tried to make the board categories specific enough to be useful, but not so useful as to have too many boards with only a couple things on each.  (If you're looking for a more detailed breakdown, you can always check out the list of blog post labels on the left-hand side of the blog (scroll down a bit to get to it)). 

It may be a bit redundant, but I'm actually finding it to be a really nice visual index of activities and am thinking that I may use it myself to search out activities by topic. 

I know a bunch of my activities have already shown up on Pinterest, but by doing this, I can also make sure that the pins link to the correct page and so forth. 

The next steps will involve using Pinterest to seek out new ideas to test out.  I'm also hoping to run some sort of contest in which those of  you who are Pinners can share some of your favorite science pins/boards with me, but I haven't yet worked out how that should work.  Something to look forward to though!

In the meantime, check it out here!  I'd love to hear what you think of it - leave me a comment!

Dandelion Curls

It's spring in the northeast and that means (at least in my yard): Dandelions!

Did you know you can use dandelion stems to teach a simple (and pretty fun) lesson in osmosis as well as introducing the terms hydrophilic and hydrophobic?

Separate the stem from the flower and pull the stem into long strings.

Drop the strings into a tub of water and watch the stems curl up into all kinds of fun shapes! 

 If you drop the stem pieces one at a time, you can actually watch the curling process take place within just a minute or two.  Or you can dump a whole bunch in and have fun sorting through the results!

 What's happening?

The inside of the stem is hydrophilic, which is sometimes referred to as water-loving.  It's the part of the plant that absorbs the water.  And when it's placed into a tub of water, there's a whole lot of water to absorb!  The water moves into the cells through the process of osmosis. 

The outside of the stem is hydrophobic - it repels water.

The cells that make up the inside of the stem absorb so much water that they swell up.  The cells on the outside of the stem stay the same size.  The increasing size of the cells on the one side of the stem forces the stem into curls of various shapes.  

There's definitely something fun about sitting outside on a warm day and watching the curls form!  And if you can't be outside, grab some dandelions on your way to school and bring a bit of the outdoors in for your students.   

PS The idea of one side expanding more than the other side is similar to the way a bimetallic strip in a thermostat works.  The expansion is caused by temperature instead of water movement and it isn't as drastic as this, but it's conceptually similar. 

Facebook

Science Matters is now on Facebook!  You can find me here. 

While I'm not entirely sure how I'm going to use it in this context, I'd love to have you head on over and say hello.  We'll see how it goes from there!

I'm Baaack...

Well.... it's been awhile since I've been in this space.  But, while I've been gone, I've been hatching all sorts of plans for all things Science Matters.

The blog itself is going through some updating and reformatting.

You'll soon be able to find me on Facebook and Pinterest.  Boy, oh, boy do I have ideas for putting Pinterest to work!

Of course you'll continue to find ideas and instructions for hands-on science activities.  The pace will be slower than it once was - even if I could find the time to write 5 posts a week, I'd run out of things to share much more quickly than I'd like.  It was a good way to work through large stacks of ideas at the start, but it's time to adjust.

I'm also hoping to share the 'paperwork' that goes with some of the ideas I share here.  That one's still on the "Need to get to it" list, but I'm hoping it'll move to the "In progress" list soon!

I've got some other ideas I'm tossing around and I'll be seeking input from you as time goes along to see if others are interested in joining me in some projects.

And I've got plans for some give-aways too!

I know it's likely a hard time to relaunch, as the school year is winding down and summer is just around the corner.  But, if I don't do it now, when I'm excited and ready to jump it, it may get pushed to the bottom of the list.  I hope you'll check in periodically during the summer (you wouldn't want to miss out on the previously mentioned give-aways) and you'll be back for good once your planning for the next school year kicks into gear.

I'd like to thank everyone who's stuck around while I've been away and officially welcome those of you who have arrived during my absence.  I hope you like what you see and can put it to good use, in your home, classroom, scout meeting or wherever.  Enjoy and be sure to subscribe to the emails or sign up for RSS feed.  Now that we're back in business, you won't want to miss anything!