Density Lab B

[Nba2302]

Understanding PV=nRT

[UTF-8 U+6211 U+662F]

Understanding PV=nRT

The pressure of a gas is inversely proportional to the volume when the temperature is held constant. This is called Boyle's Law. This make sense because when you press a gas with more force, it shrinks, and the volume decreases.

When the pressure is held constant, the volume is directly proportional to the temperature. This is called Charles's Law. When a gas gets hotter, the particles in it start moving faster, so the gas gets bigger.

When the volume is held constant, the pressure is directly proportional to the temperature. This is called Gay-Lussac's Law. When the particles in the gas get faster, they start exerting more force, so it makes sense that an increase in pressure results in an increase in temperature.

Combining all three of these laws together gives PV = some constant * T.

There's one more thing that we have to take into consideration, which is the number of particles of the gas. More particles, more force, more volume, and less average energy. Since gases have so many particles, we count the number of particles in moles, similar to how we count eggs in dozens. A mole is 602214076000000000000000 particles (Avogadro's number). So, we multiply by the number of particles.

PV = n * some other constant * T.

R is the ideal gas constant. It turns out that all gases have the same volume under the same pressure-temperature conditions! This is Avogadro's law. That means that R is the same thing for all ideal gases. In the end, we have PV = nRT.

In SI base units, pressure is measured in pascals, volume is measured in cubic meters, amount of particles is measured in moles, temperature is measured in kelvins/degrees Celsius, and the units of the ideal gas constant work out to be (pascals * cubic meters)/(moles * kelvins).

[Nba2302]

What are the best websites for this event(besides Density Wiki page)? Any links?

[Galahad]

What are the best websites for this event(besides Density Wiki page)? Any links?

NASA has some pretty good practice problems, and ChemIX has every periodic table number you'll ever need.

Other than that, everything else is from obscure websites.

Khan Academy and Physics Classroom explains stuff pretty well, and shows you how to do certain calcs.

[Nba2302]

Can anyone help me? Im stuck on Part 2, hands on task. Number 3(the helium balloon) and number 4 ( depth of which object will sink). Are there any links, that will tell me how, or explain?

[someone1580]

Can anyone help me? Im stuck on Part 2, hands on task. Number 3(the helium balloon) and number 4 ( depth of which object will sink). Are there any links, that will tell me how, or explain?

For number 4 I believe we can use specific gravity to figure out whether the object will sink or float. Then using the Archimedes principle and buoyant force we can calculate how deep the object will sink. Search it up

For number 3 hopefully this link can get you an idea:https://www.grc.nasa.gov/www/k-12/WindT ... swer5.html

[Nba2302]

2 days left until my meet. I only have 7 pages of notes. What should I do? It feels like I covered everything

[MattChina]

2 days left until my meet. I only have 7 pages of notes. What should I do? It feels like I covered everything

I feel like 7 notes is sufficient for this event, I mean theres not much to cover.

[Nba2302]

I feel like I am overdoing the hands on task, part 3 and 4(the helium balloon and the depth it will sink). It took half a page(and bunch of formulas) just to find out how much the balloon can lift, same with part 4. Am i doing it wrong?

[UTF-8 U+6211 U+662F]

I feel like I am overdoing the hands on task, part 3 and 4(the helium balloon and the depth it will sink). It took half a page(and bunch of formulas) just to find out how much the balloon can lift, same with part 4. Am i doing it wrong?

Use Archimedes' principle: "Archimedes' principle states that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces"

In both problems, the buoyant force must cancel out the downward force of weight.

#3 would probably require the density of helium.
For #4, I would assume the object has a constant density. That means we could use the weight of the object and the density of water to find the volume of the object submerged. Then, finding the height should be simple if the object is an easy shape like a cube.