GLASSWARE

LAB 3 -  Why so Many Beakers?

Purpose:To familiarize yourself with the use of various lab equipment and techniques
To know which pieces of glassware are the most accurate.

Theory: Accuracy is how close your value comes to a true value. Accuracy is truth. If  you step on the scales at home and you weight 15 pounds then your home scales are not reading true, they are not accurate. Every time you step on these scales they always read 15 pounds, without fail. Although they are not accurate they are precise. Precision is a measure of repeatability.

A lab has a lot of glassware. We are concerned with its accuracy. How correct is each piece? Some glassware are only used for carrying or mixing and it does not have to be very accurate, whereas others are used in calculating molar amounts and have to be right on the true value.

 Materials:    (1) 100ml beaker
                     (1) 10ml pipette 
                     (1) burette ring stand 
                     (1) Erlenmeyer flask
                     (1) balance 
                     (2) 50ml beakers 

Procedure:

1. Obtain a 100 ml beaker, a 100ml volumetric flask, a 10 ml pipette, and two 50 ml beakers (labeled 1 and 2), graduated cylinder. Weigh each piece of equipment and record the mass.

2. Place 10 ml of water in the beaker, and weigh it again.

3. Place 10 ml in the pipette and drain it into a pre-weighed 50 ml beaker. Record the weight.

4. Fill the volumetric flask to the 100 ml mark and record the weight.

5. Set up, and prepare, a clean burette and fill it close to the 0.00ml mark with water. Drain 10 ml of water into a pre-weighted, clean and dry 50 ml beaker and record the weight.

6. Weigh a 100ml graduated cylinder and weight again with 10 ml water.

7. At 200C water weights very close to 1.0g for each 1.0 ml, so your weights on a calibrated 0.010g top loading balance is the final arbitrator of the amounts of water each container holds.
 

DATA TABLE 
                                                                                                 Mass(g)

1) mass of volumetric flask (with 100 ml water)	1)
2) mass of 100 ml volumetric flask dry	2)
3) mass of 100 ml beaker (with 10 ml of water)	3)
4) mass of the dry 100 ml beaker	4)
5)  mass dry 50 ml beaker (1) used with pipette	5)
6) mass 50 ml beaker (1) ( + 10 ml from pipette)	6)
7) mass dry 50 ml beaker (2) (used with burette)	7)
8) mass 50 ml beaker (2) (+10 ml from burette).	8)
9) mass 100 ml dry graduated cylinder	9)
10) mass 100 ml with 10 ml water	10)

Questions:

1. Which piece of glassware is least accurate?
2. Which pieces are most accurate?
3. When would a beaker be the best choice of equipment and when would you use a volumetric 
    flask?

Conclusion:

1. Why does a lab have so much glassware, don't they all do the same job, hold liquids?
 

By Michale Duke and Jeff Hollings