Lab Report Day 1 -Heat Transfer As an Energy Exchange Activities 1,2,3,4

Convert Fahrenheit to Celsius (Or Celsius to Fahrenheit) 

      We start our class by transferring from Degree Celsius to Degree Fahrenheit or vice versa. We also draw a graph of Degree Celsius vs Degree Fahrenheit. They are proportional, an they have a linear relationship. It shows us that C=5/9*F-160/9, and F=9/5*C+32

Degree Celsius vs. Degree Fahrenheit Graph

Bubble on Fire

A bubble filled with breath (mainly CO2) will go down because the density of CO2 is heavier than the air. We then make a prediction on whether a bubble filled with CH4 gas going up or going down. We guess it would raise since CH4 is heavier than the air. We draw a FBD (free body diagram) to support our prediction.

The professor is going to let the bubble on fire. We predict which direction the flame will go. The small arrows represents the direction. We predict that it goes outward. 

Here's a video clip.

   We notice that the bubble catches fire and goes upward.When it catches fire, it expands. Since the bubble is moving upward initially, the fire also rises upward.

Mixing Water
We did several calculations on mixing different amount of water at different temperature. Heat will transfer from hot water to cold water, and finally they will reach their equilibrium point.

We predict the final temperature of the mixture of 50 g of 65°C water and 50 g of 25°C water. We predict it to be 45°C.

Then, we make a prediction of mixing 100 g of 25°C water and 50 g of 65°C water. We predict the final temp to be 38.3°C

From the graph, we can see the final temperature goes to 40°C, which is 4.4% off of our calculated value. From the graph, we can see that the temperature drops for hot water is twice as much the temperature drops for cold water.
We then put an experiment of an aluminum can filled with 50 g of hot water into a mug that has 100 g of cold water inside. By the end of this experiment, the temperature almost reached its equilibrium which is about 34°C.

One thing we observe is that it takes much longer for this system to reach equilibrium than the system of just mixing hot and cold water. What causes this is about how the molecules moves. In this system, there are fewer space for the molecules to move and transfer the heat. In the mixing water system, the space between the molecules are big, so the molecules can move freely and fast. So it can transfer heat easily.

We discussed server ways to make the temperature cool down faster. 

We did another several calculations on mixing different amount of water at different temperature.  We calculate the heat flows of copper and aluminum bar.

Heat Transfer as Energy Exchange

 We want to input 6000 J heat into water by using an immersion heater. They are rated to 300 W. In order to get 6000J, we did the following calculation. 

 

However, the power of the immersion heater may not be accurate. So before doing the experiment, we measured the real power to be 284.8 W.

  We place the immersion heater into 200 ml of room temperature water. The initial temperature is 22.8°C. After 20 seconds, it increases to 29.4°C. 

Graph: Temperature vs. Heat


 Graph: Heat vs Temperature

Graph for Heat per Unit Mass vs Temperature

In the graph, we get

Q/m = mx + b -------> Q/m = 4.7 T -94.65

Q is the heat energy it has. m is the heat capacity, which is hot much amount of energy is required to raise 1 g of water 1°C up. T is the temperature. b is the initial heat per grams it has.

Ideally, m should be around 4.2 and b should be around 0. We probably did something wrong that led to this result. Overall, this lab is done well.

If the mass of the water is halved to 100 mL, the slope of the line would be shallower. It would take less heat energy in order to change change in temperature of water. 

Conclusions:

       In Monday's session, we learn some basic lecture on Heat, and learn heat, as an energy, can transfer to another object. We also learn different materials have different heat capacity, and water has a very high heat capacity. We connect the heat with some of the materials we learned before such as FBD.