The pre meeting should focus on:

• Making sure the students understand the nature of Brownian motion and Einstein's theory describing it.
• Understanding that the goal of the experiment is to investigate how the diffusion constant for Brownian motion varies with particle size.
• Understanding the overview of the process. I.e. sample preparation, using the microscope to find and focus on the particles, recording a video of the particle motion, importing the video into the TrackPy script, analyzing the motion of the particles in 2 dimensions, and calibrating the image scale.
• Setting goals for the first two days of work in the lab.

You do not need to go over details of how the camera software works, or how TrackPy works, those things will be handled in the lab.

• Create a sample solution for one type of particle (silica/polystyrene).
• Record a short, about 50 frame, video from this sample.
• Analyze video in TrackPy. Try different particle selection criteria to get a feel for how they impact the measured diffusion constant for the same sample. Different particle mass limits, etc. Most likely students will find that the measured diffusion constants to not depend much on the values chosen so long as their eye tells them the software is selecting things which are clearly particles. This should give students confidence that they do not have to worry about getting just the right values for these parameters.
• Calibrate the image scale.
• Repeat for a similar size particle of the other type (polystyrene/silica).

The main goal is to get comfortable with preparing samples, using the microscope, using TrackPy, etc. If they get results for both types of particle they can compare the results to predictions and maybe say something about whether the different materials matter.

• Finish up day work if necessary.
• Investigate how the particle density impacts the measured diffusion constant. The purpose would be to establish a valid range of particle densities for the solutions containing different particle sizes.

• Both students should have independently analyzed all of the data they took in the lab up to and including obtaining values for the diffusion constants in real world units.
• They should have looked carefully at their data to identify any anomalies. Examples would be too many displacements equal to zero which may indicate stationary particles were selected, or an odd discontinuous jump in the ensemble movement which could indicate the sample was disturbed during recording.

• Clearing up any issues with first two days of work.
• Investigating how diffusion constant varies with particle size.