Saturday, February 22, 2014

Particle Diffusion (Water and Food Coloring)

So, I may have overestimated SK's attention this week.  We had a good time, but her questions and observations went to a different place.  But, hey!  This is science, not cooking.

First, the science.

All matter is made of molecules.  These molecules are constantly in motion. The motion is random...that is, the movement of each individual particle is unpredictable.  As we zoom out, the pattern holds.  The phenomenon was first observed in 1827 by Robert Brown.  He observed pollen grains in water.  Today, in his honor, we refer to it as Brownian motion.

As we continue to zoom out, the sum of the speed and direction of these particles (physics and math people call these vectors) equal zero.  This makes sense.  The chair you are sitting on, stays a chair.  Its solid.  Even though its particles are in motion, together they stay relatively still.

That's great, but what does this have to do with food coloring?  I thought we were going to make frosting!  Actually, so did the Science Kid.

Stick with me.  Even though the sum total of the particles motion is zero, if there are different types of particles in a mixture, they will ultimately mix.  This process is diffusion.  Particles move form an area of high concentration to low.  You've experienced this when someone wearing to much cologne walks in a room.  Those closest to the offender begin to cough and snicker.  Over time, the cologne diffuses until everyone in the room can smell it.

We took it a step further.  When temperature increases, so does the speed of these particles.  At some point, the speed becomes so great, the molecules of a solid break apart and become a liquid, and then ultimately a gas (some day we'll get to phase changes, don't worry!).

Lesson over...on to the fashion report.  We got safety glasses for today.  Knowing the SK, I knew what I had to do: PINK!  No magic wand or lab coat, but Doc McStuffins was represented on the T-Shirt.

We started with tap water in a glass.  We put two drops of McCormack's Food Coloring (I tested my fancy organic food coloring gel ahead of time and it took FOREVER to dissolve) into the glass.  Instead of stirring, we watched the drops spread throughout the glass.  We talked about how pieces of water, called molecules, were moving all about. SK was not that into it.  She REALLY wanted to stir, so we stirred.  I pointed out the the pieces of water were moving even faster, and that the pieces of food coloring could mix faster.

Next, we did the same with near boiling water.  I explained that the molecules of the hot water were moving SUPER fast.  We watched the food coloring diffuse quickly.  This actually caught her attention, but first more stirring.

Now, we tried water that had been chilling in the fridge.  "If the food coloring spread quickly in the hot water, what will happen in the cold water?"  "It will go sloooooowwww!"  And, so it did.

I then asked her if we were done, but of course we weren't.  There was one more color, so I asked what type of water we should use.  SK thought about it, and said warm.  Makes sense, we did hot, tap and cold water, so warm was next.  Turns out she just wanted to stir more.

Today's lesson may have been more for me, then for SK; go where the questions take you.

So, your homework:

  1. Was your SK into it?
  2. Did you try anything other than different temperatures of water?
  3. You could even try measuring the temperature of the water or measuring the seconds it takes for the the food coloring to diffuse.
There you go...Time to Science!

Saturday, February 15, 2014

Acetic Acid and Sodium Bicarbonate (AKA Vinegar and Baking Soda)

For our inaugural Saturday, we went with the old stand-by: Vinegar and Baking Soda.  Really?  The Bobby Brady volcano?  Yup!  That's the one.

First, the science.

Solid Baking Soda (Sodium bicarbonate:  NaHCO3) and aqueous (or dissovled in water) Vinegar (Aceitc acid: CH3COOH) react to become liquid Water (H2O), gaseous Carbon dioxide (CO2) and Sodium acetate (C2H3NaO2).  If you want to get all chemistry about it:
NaHCO3(s) + CH3COOH (aq) à H2O(l) + CO­2(g) + C2H­3NaO2(aq)

The reactants, or ingredients, are commonly found in any kitchen.  Vinegar is usually about 5% (by volume) Acetic acid.  The other 95% is water.  Sodium bicarbonate is a solid, which is not mixed with anything, traditionally (except in Baking Powder...don't use Baking Powder!).

The reaction is slightly exothermic, meaning that it releases a small amount of heat.  The product, Carbon dioxide, is released as gas, and is seen as bubbles rising to the surface.  The product, Sodium acetate, is soluble, meaning it dissolves in water.

There are a few pieces of evidence that a reaction can produce:
  1. Color Change
  2. Temperature Change
  3. Bubbles
  4. Appearance or disappearance of a solid (called a precipitate).  This can sometimes be seen as cloudiness in the solution.
In this reaction, our primary evidence is the gas release, causing bubbles.  The temperature change is slight and the Sodium acetate can't be seen because its dissolved.

Are you sweating yet?  Don't worry.  That's the end of the Chemistry lesson.

When I told the Science Kid that it was time to do an experiment, she ran upstairs to put on her Minnie Mouse dress and to grab a magic wand.  Seems logically enough.

I asked her what she thought would happen when I mixed the two together.  She held up her hands and said "I don't know!"  And why should she?  So we mixed 1/8 cup of vinegar and 1 teaspoon of baking soda (we'll get to the metric system later....don't worry!).  Bubbles.  "Whoa!"

Next, we kept with the same amount of vinegar, but measured out two teaspoons.  BEFORE, she dumped it in, I made the SK predict what she thought would happen.  "More Bubbles!" and again in another glass with three teaspoons.

We used the same type of glass each time, so we could see how far up the bubbles reached.  We marked the highest spot with a dry erase marker.  This way, we could compare after the reaction was finished.

SK made an observation that there was still 'white stuff' at the bottom of the glasses.  How do we get rid of it?  More vinegar!  Now we abandoned measuring, and just had some fun.

Eventually, there stopped being so many bubbles.  Why?  SK once again threw up here hands "I don't know!".  We looked at the bottom of the glass and noticed that the baking soda was almost gone.  In science talk, the reactant was depleted.

We then turned our attention to one of the other glasses.  Even though we left it alone, there were still bubbles emerging slowly from the baking soda at the bottom of the glass.  When the vinegar was in low concentration, the reaction still took place, but very slowly.

First Science Saturday in the bag.  Bath time!  While we are splashing with bubbles, I get the question "What happens if we mix the baking soda with water?".  Apparently SK is a better scientist than her dad, because SHE remembered that we needed a control group!  SK made a prediction, we tried it out.  Nothing.  Because, as we discussed you need both reactants to make the reaction happen.  SK waved her magic wand, and thus concluded our first Science Saturday!

Now its your turn!
  1. What did you try?
  2. Did your SK surprise you?
  3. What was your SK's outfit of choice?

Saturday, February 8, 2014

Welcome to Science Saturday!

The Science Kid
Hi there!  Welcome to Science Saturday.  Every week (or as often as Science Kid allows) I'll bring you a scientific investigation that can be done at home with common (or easily obtained) materials.  Nothing will be ground breaking.  You've probably done all of these yourself at some point.  We aren't going to write your doctoral dissertation or win a Nobel Prize with these investigations, but we will work your Science Kids through some basic scientific processing.

What kinds of things will we be investigating?

Biology, Chemistry, Physics, Geology, name it!  We are surrounded by all of these sciences every day.  Kids are naturally curious about the world around us, so we'll try to work through some things that the SKs are thinking about anyway.

Are we just going to do cool stuff?  Is that science?

Hardly!  Science has nothing to do with the reaction, the dissection or the equipment.  Science has everything to do with the questioning.  We'll talk through some basic questioning techniques.  We'll try to get the SKs to ask their own questions.  We'll make predictions and even get through some basic math analysis.

Why should we listen to you?  Are you Mr. Wizard or something?

I wish!  He was my favorite...along with the great Carl Sagan.  Like I said, the science isn't going to be revolutionary.  The two things that I have going for me are that I have taught all levels and types of High School science for over a decade and I have an SK that asks a TON of questions.

Why do you keep saying 'we'?

Science is collaborative.  Science is cooperative.  The days of the old guy locking himself in a laboratory making an earth-shattering discovery are over.  Today, the best science happens when teams work together, share ideas and question each other.  Most discoveries are not only done with multiple people, but they often span multiple disciplines, multiple universities, multiple countries, and even multiple languages!

Science Saturday will work best as a partnership.  Tell us how it went.  What kinds of questions did your SK ask?  Did you change the investigation?  What worked?  What didn't?  The more interactive we make the investigations, the better an experience we can make for our SKs.

If you are interested in following along with Science Saturday, be sure to subscribe to the blog, like it on Facebook and let other parents know!