Accel. Chem. Blog 2

            Recently in chemistry, we have been learning about particles and particle movement and how that relates to the states of matter.  We completed several activities to illustrate this concept and I believe that they did a good job of teaching us about particle motion.  The way that we showed movement was through “wooshies” which were like little tails on the particles to show speed and direction of particle movement.

			For some reason, I cannot delete the table. Sorry!

            One key term was diffusion.  Diffusion is the effect of particles moving in all directions due to collisions to completely fill a container.  This container could be as small as a beaker or as big as a room.  Particles are in constant, random motion.  They change direction when they collide with each other or the container.  To illustrate diffusion, we did a spray activity.  A spray bottle filled with a scent was sprayed at the front of the room and as we began to smell it, we had to raise our hand.  This way, we could actually see how the particles moved through the room because it took longer for the people at the back of the room to smell the spray because the particles needed time to get around.

            Another illustration of diffusion is to have two beakers: one with hot water, one with cold water.  Put food coloring in both of them and observe how they spread out.

The red water is hot, the blue is cold.  The hot water spreads the dye out faster, because the particles are moving faster, colliding with the dye particles and moving them all around in the beaker.  The cold water particles are moving slower so they take longer to spread out because they collide with the dye particles less often.  We did a computer simulation to show this.  It showed how the particles moved and collided.  It also showed another important concept.  Energy is a quantity that has the capacity to cause change and is conserved.  Conserved is the key word.  Energy is transferred between particles when particles collide, but the total energy does not change.  The speed of the particles tells us temperature or thermal energy.  We learned about this through the Eureka videos.

            So basically, there are three states of matter.  Solids have a definite volume a definite shape, are not compressible, and their particles are in a vibrating, regular lattice.  Liquids have a definite volume, take the shape of their container, are slightly compressible, and their particles are free to move past and along each other.  Gasses have no definite volume, take the shape of their container, are compressible, and their particles move randomly in all directions. 

            When particles are heated up, they expand in any way they can.  This was shown through an activity where we had a tube of colored liquid that was placed in a beaker of heating water.  A rubber stopper held a long, clear tube.  As the liquid heated, the particles wanted to expand, so they traveled up the tube.  Another activity that showed this concept was where we had a large, sealed garbage bag with straws at every corner to blow into.  Four people blew into the bag while one person sat on the bag.  The hot air particles from our breath bounced all around and hit the inside of the bag to the point where the bag expanded enough to hold the person off of the ground.

            Most recently, we have learned about gas pressure.  The air that is all around us was once thought to be weightless, but we know that there is indeed weight to the air, and we call this air pressure.  Air pressure changes with altitude and with the weather.  The higher up you go, for example, Mount Everest, the less air pressure there is, because there is just that much less than if you were at sea level.  Air pressure is measured in mmHg, atm, and kPa.  We did an activity to illustrate air pressure with Kool-Aid pouches.  Almost everyone thinks that when you use a straw, you simply suck the straw, and that is how the juice gets to your mouth.  But the scientific answer is that you suck the air out of the straw on top, and then the air pressure around the juice pushes down and forces the juice up the straw. 

This leads me to wondering if it would be harder to suck through a straw if you were at a higher elevation, like Mount Everest.  If I were to climb it, I would be sure to test this.  We also learned with this that a barometer works better with Mercury than with water, because if you used water in a barometer, it would need to be an extremely long tube because of the amount of air pressure.

            Most people would wonder what any of this has to do with “real life”.  But I have been thinking about this all a lot, recently.  In indoor emergency sprinkler systems, knowledge of particle movement is used because of the heat that a fire generates.  Understanding particle movement is important because everything is made up of particles.  We are in constant contact with particles.  And knowledge of particles may lead to great inventions and ideas.  It might be a little hard to grasp at times because they are so small, but with enough effort, you can understand particles well.