"Irrigation of the land with seawater desalinated by fusion powers is ancient. It's called rain." - Michael McClary
Monday, October 29
I'll return lab books with your reports on measuring the Density of Homogeneous Materials. If you didn't get a top "3" grade on at least one of your data reports - other than the first water report – then your homework is to rewrite (at least) one data report perfectly. Remember units and the "circle numbers" that show how you crunched the numbers. Do this even if you have bad data – but try to say something about what's wrong with your measurements.
We have work time this week to measure these four quantities of your chosen material:
- Pore space (%)
- Bulk density (g/cm3)
- Particle density (g/cm3)
- Water retention (%)
Lab reports are tentatively due next Monday, November 5. It's ok to use the xerox worksheet for your data IF you fasten it in your lab book as part of your report. I expect you to explain each of these four measurements in your own words, and give the results you measured for your material. The more interesting question is why your results are different from our class experiment with marbles. You should think about this in your conclusion – how is your material different from perfect glass marbles? What does your data tell us about soil?
I want to see your rough-draft written question and hypothesis in your lab book BEFORE you get to work today or tomorrow. Work in groups, but please do your own writing and thinking. You can do this in class today.
Tuesday, October 30
Density lab report rewrites are due at the start of class. Show me!
We'll have work time on porosity experiments, but show me rough-draft written question and hypothesis in your lab book BEFORE you get to work!
Your measurements show go fast, but expect difficulties. What do you do if your material floats and you can't figure volume by water displacement? Keep an eye on the clock, and don't start something you can't finish!
Wednesday, October 31
Work time measuring porosity, density, and water retention of different materials.
No tricks – the treat is that nothing is due until Monday. Get your work done in class, and have fun tonight!
Thursday, October 25
Final work time for measuring porosity, density, and water retention of different materials.
Final lab reports are due on Monday, November 5. We'll make another Excel spreadsheet to collect all our data. Be sure to get your data on the computer!
On Your Own:
Think about figuring pore space as a math/geometry stumper. It's easiest to think in a 2-D space with circles stacked above each other or nestled in between like the slice of a stack of cannonballs. Find the unit volume and subtract the solid volume. It's almost the same in a 3-D space, but the formula for volume is more complicated. This stumper gets nasty with random packing. Try a Google search on "
optimal packing for circles and spheres"!
Treebeard's Stumper for the week:
Halloween is fun. Chaparral wildfires driven by Santa Ana winds are scary! We've been lucky, so far. The local Sedgwick Fire was contained because the winds didn't happen, though this smoky fire weather is scary enough. Why didn't we get the dangerous Santa Ana (or Santana?) winds? We do have local Sundowner winds, so what's the difference? Heat rises, but all of these devil winds get hotter and drier as they blow down the canyons. How does this work? The real stumper is how should we live in a natural landscape that is adapted to burn?