Questions
How would you  measure:
1)  the volume of a small test tube,
2)  the mass of a regularly shaped solid, and
3)  the number of drops of water in one milliliter of water ?

Background Information
Volume measurements
The volume of liquids can be measured using various pieces of equipment. The type of equipment used depends on the desired accuracy.  Volumetric pipets are used to measure the exact volumes with high accuracy. Burets are used to deliver the volumes of solutions in increments and with  high accuracy.
Graduated cylinders with various capacities (10 ml, 50 ml, 100 ml, , etc. can be used to measure the volumes of liquids when such high accuracy  is not required.  Most of the time, during this semester, you will  need to know only  approximate volumes of liquids. You will use graduated cylinder to measure the volumes. Only one time will you use the buret.
It is important  to remember that the liquid in a glass container has a concave (downward curved) surface, called meniscus. To determine the  actual volume in the glass cylinder, read the level of the liquid at the  bottom of the meniscus. Make sure that your eyes are at the same level as the bottom of the  meniscus, and you see only a single  concave line, not the surface.
The surface of the liquid in theplastic cylinder is flat. When reading the volume, make sure that your eyes are at the level of the liquid surface.
Sometimes, the volume may be measured with calibrated plastic transfer pipets. Such pipets are provided with most of the reagent bottles used in our labs.

Mass measurements
The mass is measured  in our labs using either top-loading or analytical balances.  Your lab section will be using only top-loading balances.
Please refer to the slide show: Weighing Using a Top-loading Balance ) to review the weghing technique before coming to lab.
It is crucial to always use a container in which the weighed object is placed, before it is weighed. Never place anything directly on the balance pan  or you may damage it. The container's mass may be  determined before the weighed object is placed in it, then subtracted from the recorded  combined mass of the container and the object. Or, the container may be tared (zeroed) and the mass of the weighed object read directly from the balance display.

Using a medicine dropper or a  transfer pippette
Medicine dropper, glass Pasteur pippette or a plastic transfer  pipette  may be used to deliver drops of  liquid chemicals and solutions.
Please refer to the slide show: Transferring Liquids to review  various liquid transfer techniques, including the transfer with a medicine dropper,  before coming to lab.
To measure the number of drops of a liquid in a given volume of that liquid, the  smallest possible graduated cylinder may be used. It is important to remember that this determination is not extremely repeatable. To minimize the error involved in such determination, the measurement  must be performed  at least three times, then the values averaged. Sometimes, to minimize error,  it is beneficial to use a  larger volume to count drops, then divide the number of drops by  that volume to find the nmber of drops in 1 milliliter.

YOUR TASK
Your  class will  be divided into groups of four and each group will have to:
1) develop the procedures for the  three tasks described in the paragraph Questions,
2) write down the draft  procedures in an organized, step-wise manner ,
3) develop data sheets for the measurements performed and record all measurements
4) perform any necesary calculations that will lead to numerical answers to the questions posed,
5) rewrite the procedures including all modifications made as you were performing the measurements (this part may be done at home, as a post lab assignment, but remember to record all modification that were mad e in the lab in your notes)
6) the following week, provide your  instructor with a complete report (procedure, data sheet and the numerical results- all organized and  written legibly).

Of course, you may ask your instructor questions when in doubt. She or he will ba happy to provide some help, but do not count on the instructor "doing it for you".

PRELAB
As you prelab assignment, please review all slide shows listed in the text above.
To return to this document from the slide show, you will have to use the Back button in the upper left-hand corner of the screen. You may need to click on it several times, depending on how many pages of the slide show exist.