1. Candle
In our first experiment of today's lab, we have a candle, a cylindrical container, and a tube. First, we make some predictions about what would happen when we put the candle to the end of the container. We predict that the fire will burn out.
From the experiment, we can see that our prediction is correct. The fire burnt out because during burning, it requires wax gas and oxygen gas. The container cannot hold too much oxygen and the candle burns oxygen too fast. The carbon dioxide will prevent the fresh oxygen coming in.
Then we put the tube just above the flame. We predict whether the fire will be the same, or being dimmer, or burns out. We predict that the flame will be the same.
Our prediction is correct. When we put the tube on it, the carbon dioxide the candle products will be released by the tube, and the fresh oxygen will goes to the container to provide oxygen for it to burn. We keep lifting the tube to see how much can we lift to keep the fire from burning out. The fact is that the flame won't go off until we fully lift the tube out of the container.
We watch the video of a free full of a bottle which has a fire is burning inside. We predict that the flame will not burn out, but it will be dimmer.
Our Prediction is C, that the fire will be less bright (will be dimmer.)
In a sealed container in free fall, there are no convection currents and so the flame is not long like it usually is. In free fall, there are diffusion currents which approach the flame from all sides, giving it the round and smaller flame. Therefore, the flame was dimmer due to the diffusion.
2. Activphysics
In these questions, we use the equations we derive previously and the knowledge we learned before to answer the question.
3. Four Progress of Graph
. We make some predictions of the graph for isobaric, isothermal, isochoric and adiabatic.
An isobaric process is constant pressure, so P vs. V graph is a straight line.
Isochoric process is constant volume, so P vs. V graph is a vertical line.
For Isothermal and adiabatic process, they both have a hyperbola shape, but the slopes of them are different.
Adiabatic process is faster than an isothermal process.
4. Apparatus
In this experiment, it is an isothermal process. Professor Mason spins the handle so that it increases the pressure and decreases the volume in the tube. From the picture, the digital thermometer tells us the temperature is kept at 22.0ºC all the time. Because temperature is constant, it is an isothermal process. So the heat added to the system is equal to the work done on the system. Using data gathered from the gas law apparatus, we solved for the work done on the gas. Using W=Q=P1V1ln(V2/V1), we get -2.57 J. It makes sense as well because it is very easy to spin it. Also, since work is being done on the system and not by the system, it is negative.
5. Heat Engine
A rubber band was used in order to develop a mass lifting engine. We show 4 steps a mass lifting engine cycle need for it to work. First we put the can on a rubber, then we heat up the rubber, then we unload it, and finally the rubber band would be cooled. After the rubber band is cooled, the steps would repeat.
A good model of a heat engine can be seen in the video below. As the gas molecules are being heated, the ball moves. When temperature increases, the piston starts to move back and forth due to a change in pressure and volume. The piston starts to slow down when it loses pressure, but when adjusted, the system begins again.
Conclusion:
In today’s class, we learn the 4 process: isothermal, isobaric, isochromic and adiabatic. We also learn the P-V graph of the four process. We learn how the heat engine works and the four steps needed in the cycle.
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