Thursday, November 23, 2017

Properties of Solutions

Next we discussed colligative properties. If you add solute to a solution, like salt to water, it changes the properties of the solution, particularly the boiling point or freezing point. We put salt on the roads to lower the freezing point of water so ice does not form on the roads. 

Electrolytes can conduct electricity because the solute breaks up into ions and the ions can carry the electric current. Pure water does not conduct electricity - but water with solutes in it can. We did an in-class demo similar to this one to test some solutions. Salt water does conduct electricity, but sugar water does not because of the carbon. Gatorade conducts electricity but barely because of the high sugar amount in the drink.

Finally we talked about Molarity. Molarity is moles/Liters and is a quantitative way to measure concentration. Molarity describes with numbers if a solution is dilute or concentrated. It is a pretty easy formula so students zoomed through it. Molarity changes with the amount of solute OR the amount of solvent (liquid).

The formula is M1V1=M2V2. These questions will mention molarity twice and volume twice and will not mention moles. Three numbers are given and the fourth needs to be solved for by isolating it through division.

When diluting substances the molarity (concentration) decreases or becomes more dilute because more water is added to the original solution. The number of moles of solute stays the same, but the molarity changes because the volume increases.

Wednesday, November 22, 2017

Solutions and Solubility


Today in class we discussed solutions. Solutions are homo- geneous mixtures comprised of solutes dispersed in a solvent. Water is the universal solvent, but not the only solvent. For example, a marshmallow is a solid (sugar) solute dispersed in a gaseous solvent (air).

Solubility is how well something dissolves. Some things are very soluble, and some are insoluble (do not dissolve).
Solutions are said to be saturated if they are holding all the solute that they can. When the solute starts to build up on the bottom, you know a solution is definitely saturated (like the dark blue solution on the right). Solutions are unsaturated if they can dissolve more solute (like the two light blue solutions on the left).


Solutions can be super-saturated if they are heated because they can hold more solute than normal. Even if you cool these solutions back down, they will still hold this  additional solute in solution. Sweet Tea and all candies are made by first making super-saturated solutions and then cooling them.

For an excellent website about all of these topics and others regarding solutions that have and will be covered in this unit - check out this useful website.

Tuesday, November 21, 2017

More info on Acids Bases, and Nuclear

For acids and bases, use the universal indicator test, from this link. Be sure to make your predictions first.

And here is a TED-Ed on the strengths and weaknesses of acids and bases.

Click here for the Online radiation quiz from Hanford and OMSI. Be sure to write down the numbers that apply to you.

If you are finished…
C2. Take a Radiation Quiz à “How Stuff Works Radiation Quiz” http://science.howstuffworks.com/nuclear-radiation-quiz.htm


C3. Try running a Nuclear Power Plant à “Kennesaw Nuclear Demo” 
C4. Try detonating a Nuclear Bomb à “Nuclear Bomb Simulation” https://nuclearsecrecy.com/nukemap/

There are lots of Ted Talks on Nuclear topics... check them out. 

People often ask about Chernobyl and here is a TEDtalk about the people who refused to relocate. There is also a lot of information here at National Geographic.

Density

 
We have made sure that everyone had a good handle on density in regards to definition, math and formulas, and what it actually means.

Density measures matter in a given volume or the amount of stuff in a space. It can also refer to the amount of space between molecules. We looked at some diagrams and discussed scientifically why a person cannot walk through walls, why moving through air is easy, and why moving through water is slightly more difficult.

Density is how close together the particles are in a substance. If they are close together the substance is more dense. If the particles are far apart, the substance is less dense. I do not float in Lake Anna, but I do float in the ocean - therefore I am more dense than Lake Anna and less dense than the ocean.



Things that are more dense-sink, things that are less dense-rise to the top, things with similar densities-mix. If you were to pour liquids in a random order layers form because of the differences in density. Here is a photo of a demo.

Monday, November 20, 2017

Phases and Phase Changes

We discussed solids, liquids, and gases. We talked about the amount of energy the particles had and how the particles move. We discussed whether they had definite or indefinite volumes and shapes. We talked about why exactly we can't walk through walls, but why we can walk through gases and liquids.



Next we discussed the phase changes that happen between solids, liquids, and gases. These changes can be represented on one of two graphs. We talked about the graphs, labeled them, and and answered questions about them. 

Tuesday, November 7, 2017

Volatile and NonVolatile Substances


Volatile substances are more likely to vaporize.
•Examples – Acetone, Alcohols, Smelly Liquids
•They have high vapor pressures, weak intermolecular forces, and low boiling points
•Tend to be flammable and more reactive

Nonvolatile substances are more stable and less likely to vaporize.
•Examples – Water, Salts, Liquid Mercury
•They have low vapor pressures, strong intermolecular forces, and high boiling points 

Monday, November 6, 2017

Vapor Pressure

For notes today we discussed vapor pressure and boiling point. The boiling point of a liquid is when the vapor pressure equals the external pressure. When the pressures are equal it is easier for liquids to boil and vaporize into gases and steam away. We discussed definitions and answered questions about vapor pressure graphs. STP is 101.3kpa, 1 atm, or 760 torr.

Vapor pressure is measured with a manometer. A "normal" manometer is when the levels in the U are even. A "HOT" manometer has increased vaporization and increased particle movement so the liquid levels in the U are pushed away.


Friday, November 3, 2017

Combined Gas Law


The combined gas law combines the work of Charles, Boyle, and Gay-Lussac.

PV = PV
nT     nT

Basically, memorize one formula and then use only the variables you need, so sometimes you need PV = PV, and sometimes V/T = V/T.

This will help you with placement and deciding whether you should multiply or divide.

Thursday, November 2, 2017

Ideal Gas Law


Ideal gases do not actually exist, but we pretend they do and use the Ideal Gas Formula of PV=nRT.

One of these variables will not be given to you and you have to solve for it. This does not seem difficult after stoich, so students dove in and did well.

Wednesday, November 1, 2017

Beginning Gases and Partial Pressure

Today we started learning about the behavior of gases and the factors that affect them. Gases are lightweight fast moving particles that generally have a lot of empty space between them. Because of this, they are easily compressible (pictured left). If not contained, gases can spread (or diffuse) to fill any size and shape container.

Gases are affected by pressure, volume, number of moles, and temperature. Changing any one of these variables, changes all the others.

Today we also learned the formula for the Law of Partial Pressure. Basically partial pressures add up to form total pressure. If the total pressure  is given then you subtract the partial pressures.