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Today in the class of chemistry, we discussed colligative properties, which are properties that focus on the amount of particles in a solution and not their actual identities. There are 4 colligative properties, but we only need to know 3 of them: vapor pressure lowering, boiling point elevation, and freezing point depression. Osmotic pressure is the fourth. Vapor pressure change can be expressed by multiplying the vapor pressure of the solvent by the mole fraction of the solute. A change in boiling point can be calculated by subtracting the BP of the solvent from the BP of the solution. For freezing, do the opposite and subtract the FP of the solution from the FP of the solvent. We also had a demo where a bottle of unopened club soda was placed into a beaker of ice and salt in order to change its freezing point. After a few minutes, Mr. Lieberman took out the soda and opened it, causing it to instantly freeze and have the carbonation come bubbling out. That's about it for Tuesday March 22 in chem. Do the worksheets and webassigns for Friday and study for the test! The next scribe will be Zoe S

The pressure is on

Today in class, we learned about pressure and saw a few demos. We saw Mr. Lieberman lay down on a bed of nails, and then a few of us got to try as well. The reason people didn't get stabbed to death by the nails is that pressure equals force divided by area (P=F/A). He explained that no matter how big or small an object is, the force remains the same. The dependent part is the area. The bigger the object on the nail bed, the less pressure is on them due to the increase in area.
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We also learned the different units for measuring pressure, and the conversions between them. They are: pounds per square inch (psi), atmosphere (atm), Torr, or millimeters of mercury (mmHg), and pascal (Pa). The conversions are: 14.7 psi=1 atm=760 mmHg=100 kPa. We also went over how barometers and manometers work, with the atmosphere pushing down to show the pressure.

We went over Dalton's law too, which states that the sum of partial pressures of gases equals the total pressure of the gases when combined. So, if gas 1 is 1 atm and gas 2 is 2 atm, when they are combined the pressure is 3 atm. Boyle's law deals with pressure and volume, stating that the product of the pressure and volume for a gas equals a constant, k (PV=k). So no matter what differences in pressure or volume occur, P1V1=P2V2.

We also got to see Brandon and Zoe get stuffed in a trash bag and have the air sucked out to demonstrate the actual air pressure here on earth, as well as see an inflated balloon expand when the air is sucked out. Happy late arrival tomorrow, and the next scribe is Peter W.
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ChemThink gases

Yesterday in chemistry, we went over our new unit, which will end on Friday the 17th with the unit test. After that, we went on the computers to do a ChemThink on the properties of gases. We learned that gas atoms can be affected by temperature as well as size, which changes their speed. We also learned that the pressure of a gas equals its force divided by area. Pressure is caused by gas atoms' impact on the sides of their container. Pressure goes up as the temperature rises due to the fact that there are more collisions, and that they're more forceful. Also, as the number of atoms rises, the pressure rises because there are more collisions. As the volume of the container increases, the pressure goes down because there are less collisions. So overall, we looked at four properties of gases: temperature, pressure, number of atoms, and volume.

Chemicals React!!

Today in chemistry, we basically started where we'd left off yesterday in the Chemical Reactions lab.
First, we combined hydrochloric acid with 6 different substances to observe changes that would take place. The acid by itself was just a clear liquid. When litmus paper was inserted into it, the paper turned pink confirming that it was acidic. The acid was then mixed liquids like sodium hydroxide, which raised the temperature to 24.1°C; sodium bicarbonate, which caused bubbles and lowered the temperature; and silver nitrate, which caused the mixture to turn whiter. It was then mixed with solids like mossy zinc, aluminum and magnesium ribbons. The zinc blackened and fizzed, the aluminum bubbled, and the magnesium fizzed and rose to 37°C.
For the second part of the lab, we mixed cupric chloride with 6 substances. Initially, it was light blue with a temperature of 22.7°C. We mixed it with solids like aluminum shot, aluminum foil and zinc which all blackened and caused fizzing and bubbling. Then the cupric chloride was mixed with liquids. Ammonium hydroxide, sodium carbonate, and silver nitrate all caused different colored precipitates and temperature changes.
Finally, a flask had some cupric chloride put into it. A test tube was then filled with silver nitrate and placed into the flask and the two were mixed. The mixture turned blue and formed small precipitates.
And that's the way the cookie crumbles. The scribe for Friday will be Matt P.