Accelerated Chemistry Blog #2

Diffusion of food coloring in water.

In chapter 2 thus far, we have discussed many interesting topics and concepts.  The first of these included the motion of particles in matter and  how the speed and movement of these is affected by temperature.  To discover more about these ideas, we performed several activities in class.  The first of these was when Mr. Grosshuesch sprayed an apple-scented substance into the air.  We, the students, were instructed to raise our hands when the scent reached where we were sitting.  We noticed that over time, the students farthest from where the substance was sprayed began to raise their hands.  This showed us that over time, the spray which was in the form of gas, completely filled the room due to collisions.  This is called diffusion.

The second activity pertaining to particle motion was when we dropped food coloring into two different containers of water.  One contained hot water, and one contained cold water.  We observed that the food coloring moved more quickly in the container that had the hot water.  This helped us discover that the rate of diffusion, or how quickly a substance fills a container, increases when the temperature increases.

The third activity pertaining to the motion of particles was when we watched internet simulations of particle movement and answered questions about theses simulations.  This showed us the effect collisions between particles have on each other.  One particle in the collision will slow down and the other will speed up.  Although the total energy has stayed the same, it has been transferred from one particle to another.

The final activities we did that pertained to the motion of particles were the rising of the colored liquid up the pipette as the beaker with water was heated below and the blowing of the garbage bags.  This showed that as the colored liquid heated up, there was more particle movement.  This caused it to rise up the pipette.  In the garbage bag demonstration, we blew on straws into the garbage bag, inflating it.  This happened because the air particles continually collided with the sides of the bag and bounced back.

The second big concept we discussed were solids, liquids, and gases and how they are similar and different.  We learned about this through Mr. Grosshuesch doing simple demonstrations and by watching "Eureka" videos.  Through all of this we discovered solids have a definite shape and volume whereas liquids have a definite volume but they take the shape of their container.  Gases have an indefinite volume and also take the shape of their container.  In addition, gasesn are compressible, liquids are slightly compressible, and solids are not compressible.

The third concept we covered was that of temperature and thermal energy.  Thermal energy is the speed of particles whereas temperature is what is used to measure this speed.  Although there are many temperature scales, many scientists use the Kelvin scale.  You can convert Celsius, another common temperature scale, to Kelvin by adding 273.  At 0 K, there is no particle motion and it is called "absolute zero."

The fourth concept we explored was air, atmospheric, and gas pressure.  Air/atmospheric pressure is pressure exerted by air particles in all directions.  Gas pressure is caused by the collisions of gas particles with the walls of a container.  Gas pressure is measured using mm Hg, atm, or kPa (760 mm Hg = 1 atm = 101.3 kPa).  The final notes we took on this topic were about manometers.  A manometer is an instrument used to measure gas pressure.

To illustrate this fourth concept, we performed a few experiments and demonstrations.  The first of these was heating a soda can with water inside.  After heating we placed the can upside down in a beaker of cold water.  The can exploded and crushed.  This occurred because while heating, the air pressure could escape out of the top of the can.  However, when we turned it upside down, the air pressure was too strong and crushed the can.  The second demonstration we did was creating a barometer.  We did this by filling a 3 foot tube with mercury and placing it upside down in an evaporating dish filled with more mercury.  Instead of the mercury all draining into the dish, it was held up in the tube by air pressure.  We measured how high the mercury stood in the tube and found out what the air pressure in the room was.