Week 2 Day 2

Today we did some labs that the pressure is constant while the temperature and volume changes.

The piston is free to move. thus the pressure inside is equal to surrounding pressure. Then, as we put the flask into hot water, the volume will increase.

We can use w=p*\delta V for constant pressure. We did this thermal expansion problem from the picture above.

We also consider the kinetic energy of molecules inside the container. The final formula was shown in the picture above.

Base on the formula before, we can calculate the relationship between percent change in T and V.

Lastly, we did a problem that uses the formula we got today as above.

week 2 day 1

This day, we were still on thermal dynamics. We focused on the same gas but different conditions in terms of pressure, volume, and temperature.

The first little lab was that heating up a can with half filled with water, then put the can into cold water facing down. The can squized. when the can was heat up, the water molecules take more space. but when its put into  cold water, temperature dramaticly decreases. PV have to decrease too based on p1v1/t1=p2v2/t2.

Then we heated up the can with only air inside. then we put it into cold water facing down. the can didnt change shape, but it sucked up some water into the can. When the can was put into cold water after being heated, the sudden decrease in temperature caused the volume of gas decrease, so it sucked up some water to fill the space.

Then we looked into the relationship between pressure and volume. The graph above shows everything.

Then we looked into the relationship between the pressure and temperature.

We worked on this problem.

Solution to this problem was above.

We did a lab about pressure.

we evacuate the air inside the tank. we noticed the balloon gets bigger.

because the amount of air inside the balloon was constant. when the outside pressure decreases, air inside the balloon trys to go out to balance the pressure.

Physics 4B Week 1 Day 2

We were covering thermal expansion on this day

There were a metal ball attached with a handle and a ring that has smaller radius than the ball too.

Obviously the ball cannot pass through the ring at room temperature. We made some guesses on what will happen after both ring and the ball were heat up.

It's kind of like common sense that when you heat something up, it will expand. We made similar guess. And we were right.

We took it into more depth than just some observation and common sense. We did the formula about thermal expansion as above.

We also did and experiment on the linear expansion of this long and thin piece of medal "staff"

We heat it up, and expect the length will increase a little.

We also made the calculations based on equation.

However the result didn't really match the actual value.

Then we notice the uncertainty of this experiment.

we assumed the original length to be 1m when it's probably not exactly 1 m, it has an uncertainty of 0.1 m. the initial temperature was anounced by the professor which has no back up but only random guesses. Due to these bad habits of experimenting, our result was off. And it should been off.

Then we did an experiment of heating water.

We calculate the energy put in by multiply the power of the heater by the time.

Then based on q=mc\delta T, we can figure out the change in temperature from loggerpro.

We knew heat capacity of water is 4.18J/mol*C, then we calculated the mass of the water.

Then prof. mason randomly spill a lot of water on other students' table, and assume those water was boiled away. 

We looked into the idea of latent heat which is the energy required to change phase on one gram of water.

Through the calculation, we figured out how much water was boiled away based on the amount of heat put in.

Then we did this pressure in a tube lab.

It was really fun to see Isai blow the water out of the tube.

We didn't take this part in our data. It was just fun to watch, thus I uploaded it.

Calculations were above. We figured out the pressure Isai blow. Good thing is that we don't need to know the crosssection area of the tube. The A cancels out in the calculation.

It was the second day of physics 4b. things got better. We got into habits of taking photoes of the white boards as our notes.

Physics 4B Thermol Dynamics week 1 day 1

So the first day of physics 4B turns pretty good. I noticed the totally different teaching style from prof. Mason that he gives lecture which experiments go along with. This is really nice since we could exactly know how those formulas were figured out; while at the same time, we were actually discovering theories ourselves.

I'm new to his "white board" thing on the first day of school. We were asked to take pictures of our progression. For the lack of knowing how things work, I wrote down random things that I'm having hard time recalling while posting this blog.

Anyways, we started with some estimation about the room temperature. Of course every group gives different values base on how everyone feels about the temperature. Some gives two decimals, some gives no decimals. Then we find the average value from all the groups. We found the difference between the average temperature and each value, which gives us the precision of our answers.

Then we start the real thermoldynamics stuff.

We were given the mass of alluminum and different temperature.

We were able to calculate the heat q which follows q=mc*\delta T

You probably want to turn yourself around to view this picture. Sorry for that, the first time using this blog, will need some time to figure out things :)
This question was about the heat transfer from a hot object to a cold object. The total heat was constant. Therefore the total heat transfered from each object will add up to zero; since hot object loses heat while the cold object gains heat.
When mass and specific heat capacity were given, it was easy to calculate the change in temperature. then we would find out the initial temperature or the final temperature.

Then as a whole group of class size, we did an experiment of mixing two cups of water. One was hot, the other one was at room temperature.

After we got this result, we realized that the exothermic process is relatively more dramatic than he endothermic process. Because the upper graph which represents the temperature of hot water drops down very fast while the bottom graph which represents the temperature of cold water rise in a slow rate.

Then we did some calculations around heat transfer within the system that contains aluminum and copper.

then we figured out that since the temperature between aluminum and copper were the same, then we can calculate the temeperature in the middle from both side and get the same result.

We did another experiment to find out the relationship between heat and temperature.

And we did it. The graph's slope is the rate of change of heat with respect to temperature.

q=mc*delta T, since m and c are constant, dq/dT=mc  after knowing the slope of the graph, we can calculate what c is.

So this day was not that bad. We did some experiment to figure out the formulas ourselves.