Tuesday, April 7, 2009 - Block 4A

Students wrote down content objectives in their notebooks.

1. Successfully perform a fractional distillation
2. Using a microscope, describe and sketch a diagnostic crystal shape
3. Determine the density of liquids
4. Use the flammability test to determine if liquids are flammable.

Told students to sketch a large, diagnostic picture of the new crystals. Since they do not have to write down the temperature every 30 seconds, one partner can monitor the distillation while the other checks out the crystals. If they have good crystals, they do not have to redo the crystal part of this lab.

Went over procedure to find the density of liquids. Drew pictures and wrote description for each step.
1. Find mass of 5 ml graduated cylinder using electronic balance
2. Using a pipette put 5 ml of liquid into the 5 ml graduated cylinder. (If you don't have 5 ml of liquid, use what you do have)
3. Measure the liquid volume at eye level at the bottom of the meniscus
This will give you the volume of the liquid you use in the density calculation.
4. Find mass of the graduated cylinder + liquid
5. Subtract the mass of the graduated cylinder+liquid - mass of empty graduated cylinder to find the mass of the liquid.
6. Calculate the density using density = mass of liquid/volume liquid. Units of density should be g/cm^3

This time I remembered to sketch the data table on the board so students could see how to organize their data.

Demonstrated how to do the flammability test. Note that this is different from the "flame test" which we will cover later.
Alcohol lamp is on the left, coffee can with 2-3 inches of water is on the right. Move hand from left to right and then drop strip into can of water. Make sure you remove the flammability strips from the water and throw them into the garbage before dumping the water into the sink.

Went over the graphs from Day 1 Fractional Distillation. Boiling points of liquid 1 ranged from 80-85 deg C. Told students to swap out test tubes at 85 deg C.
Boiling point of second liquid ranged from 98-101 deg C. Told students to swap out at 97 deg C.

Students did the Fractional Distillation Day 2. The liquid density and flammability will have to wait until next time.