13 Lab 3: Thermal Motion

Acknowledgment

This project is made possible with funding by the Government of Ontario and through eCampusOntario’s support of the Virtual Learning Strategy. To learn more about the Virtual Learning Strategy visit: https://vls.ecampusontario.ca.

PHY100 Stay-at-home Experiment 3

Thermal Motion and Entropy

What you will do

Shoot a time-lapse video of the diffusion of food coloring in water, and share it on Quercus Discussion Board.

What you will need

• A smartphone or a camera that is capable of shooting time-lapse videos
• A white or transparent container with a bottom larger than 10 cm in diameter (for example, a wide bowl or a meal box)
• Food coloring (from the experiment kit)

Procedures

1. Fill the container with cold water.
2. Open the camera app of your cell phone and switch to “time-lapse” mode. If the time-lapse mode has a speed setting, choose the 30X speed (i.e., 30 seconds of recording → 1 second of video). If your phone does not have a speed setting, you do not need to change the speed setting.
3. Use some other object to hold the phone so that it can shoot a video of the bottom of the container from above. Do NOT hold the phone by hand.
4. Drop a few drops of food coloring into the cold water. Immediately start recording the time-lapse video.
5. Record for about 5 minutes. Then stop the recording.
6. Discard the colored water and wash the container clean. Then fill the container with hot water.
7. Drop a few drops of food coloring into the hot water. Immediately start recording another time-lapse video.
8. Record for about 5 minutes. Then stop the recording.
9. Crop your videos to show only the container area (using your phone). Go to ezgif.com (or any other website for creating gifs), and convert both of your videos to gif animations. Use the following settings: Size = 320xAUTO; Frame rate = 10; Check “optimize for static background”. Download the gif files to your device after conversion.

Reporting and discussions

1. Post the gif of the cold water to Quercus discussion board under thread “Experiment 3: Diffusion in Cold Water”. Post the gif of the hot water to Quercus discussion board under thread “Experiment 3: Diffusion in Hot Water”.
2. (2/5 marks) Attach screenshots of both of your posts in your report.
3. (1/5 mark) In all of the posts that you see on the discussion board (by you and your classmates), the flood coloring probably always “spreads out” rather than “staying in the drop”. Explain why the food coloring would spontaneously “spread out” rather than “staying in the drop”.
4. (1/5 mark) Explain why the diffusion (i.e., spreading) of food coloring is faster in hot water from a microscopic (molecular level) point of view.
5. (1/5 mark) Is it always true that any two fluids tend to mix with each other rather than separating from each other? If so, briefly explain why. If not, give an example of two fluids that do not mix.

NOTE: the word limit for all questions is 100.