Electron Distribution using a Pencil
September 23, 2008
Electron Distribution using A Pencil Prelab Questions:1) Why isn’t it possible to determine the exact path of an electron in an atom? (leave space for answer)2) What does quantum theory of the atom tell you about the location of the electron in an atom?3) What do the pencil marks represent in this lab? Procedures:1) Take out a piece of paper. On the paper, in the center, make a mark. Measure 1.5 cm , 3cm, 4.5cm, 6cm, and 7.5cm from the mark and mark a mark at each point. Do this for all four directions on the paper, up down, left and right.2) Connect the four marks at 1.5cm to make a circle. 3) Do this with the marks at 3cm, 4.5 cm, 6cm and 7.5cm so that you have 5 concentric rings.4) Put the paper on the floor and drop a pencil form table height on to the paper 100 times. ( try to aim for the center dot which represents the nucleus of the atom.)5) Pick up the paper and count the dots in each circle and record in data table. Data Table:
| Ring | Distance from Nucleus | Number of pencil marks in ring |
| 1 | 3cm | |
| 2 | 6cm | |
| 3 | 9cm | |
| 4 | 12cm | |
| 5 | 15cm | |
| Outside the rings | Beyond 15cm |
Calculations:1) Using the data in your table make a bar graph of the number of pencil marks in each ring. Number of marks Y axis and ring on the X axis. Analysis: 1) Using your graph, in which region would you most likely to find electrons? In which region would you be least likely to find electrons?2) Were you able to determine the exact path by which the pencil traveled to make the mark? How does this relate to quantum theory?3) What would your graph look like if you dropped the pencil 200 times? Conclusion:a) What did you learn?b) Why do the pencil drops represent electrons and how does this relate to quantum theory?c) Problems?d) Improvements?
The Cheese Lab
September 16, 2008
The Cheese Lab
Materials:
1 ½ liters of whole milk
(optional) 100ml of Cultured Buttermilk
Rennet
Calcium Chloride
Salt
White Vinegar
Pot/Pan: Stainless Steel, glass ceramic
Colander
Knife
Big Spoon
Wood Spatula (may be a wooden spoon)
Thermometer
Glass containers
Balance
10ml pipette
Gauze
Procedures: (Decide at which step you should add your special ingredient)
Part A: Curd
1) Wash your hands and put on gloves. Make sure all of the materials you are going to use are clean.
2) Calculate the correct amount of rennet you need and indicate how you would aliquot that amount. (rennet on the package states that 5ml will cure 13 liters of milk)
3) Weigh out 1.00g of Calcium Chloride and dissolve in 2ml of cold deionized water.
4) Warm your 1.5L of milk to 32° C to 36°. DO NOT OVERHEAT! Add calcium chloride solution, stir gently and add your rennet. Stir gently and let sit for one to two hours. (mine took 55 min.)
5) After one hour, test for a clean break, insert your knife into the milk and if it is ready, it should be clean. If not, let stand 20 more minutes and try again. This is called curd.
6) Cut the curd into cubes about 2cm wide.
7) Warm to 38° C and stir the curd to help release the whey. STIR GENTLY NOT TO DESTROY THE CURD!
When you reach temperature stop heating and stir gently for five minutes. Then let the curds set for a few more minutes.
9) Retire the whey and save in sterile containers.
10) Add 1g of table salt to the curds. (you may vary this amount from 0.5g to 1.5g)
11) Pass the curds through a colander, which serves as a mold. Cover the colander with gauze and pass the curds to the colander with a spoon. Be sure to catch the whey from the colander.
12) When all the curd is in the colander gently press the spoon against the curds to press out any remaining whey.
13) Let it drain out for another 30 min or so turn over with the gauze and refrigerate for 24 hours to facilitate draining.
14) Next day your cheese is ready to eat.
Part B: Whey
1) Take your remaining refrigerated whey proteins and add 30-50 ml of white vinegar.
2) Warm it and stir to near boiling, 92-95° C, foam will build up.
3) Stop warming and cool to room temperature.
4) Carefully remove the whey curds, use the same method as with the other curd.
5) Drain and you have Ricotta cheese.
6) Ricotta needs to be consumed quickly, but you won’t get much.
Conclusion:
Your opinion of your cheese and its “secrete ingredient”
Your opinion of the Ricotta cheese
What did you learn?
Why did things happen? (Enzymatic action, denaturing, coagulation, etc.)
Problems you encountered
Improvements to the lab
Finding the Density of Solids
September 16, 2008
finding-the-density-of-solids.doc
Finding the Density of Solids Hypothesis: All solids have the same density. (yes or no) Procedures:1) Today we will measure the density of eight different solid blocks and one unknown irregular object. Obtain one of the blocks and measure its mass on the balance to the nearest 0.01 g. Record in data table.2) Measure the length, width and height of the block and record in data table.3) Repeat steps one and two with the other seven remaining blocks.4) When finished, obtain an unknown sample from your teacher. Weigh on the balance and record mass in data table to the nearest 0.01 g.5) Fill the graduated cylinder with 10.00ml of water. Carefully place the unknown in the graduated cylinder and record the new volume in your data table. Subtract 10.00 ml from the volume and record volume of unknown in data table.6) Return all supplies to front and clean your lab station. Data Table:
|
Item |
Mass (g) | Length (cm) | Width (cm) | Height (cm) | Volume | Density |
| White plastic | ||||||
| Gray plastic | ||||||
| Light wood | ||||||
| Darker wood | ||||||
| Brass | ||||||
| Copper | ||||||
| Aluminum | ||||||
| Steel | ||||||
| Unknown | XXXXXXXXXXXX | XXXXXXXXXXXXXXXX | Volume in Cylinder | Volume – 10ml |
Calculations: 1) Find the volume of each block by multiplying the length X width X height and record in data table.2) Calculate the density of each item by dividing the mass by the volume. Record in data table.3) Rank all the blocks from most dense to least dense.4) Using this ranking identify the most likely composition of the unknown material. Conclusion:
September 3, 2008
