Balance and Graduated Cylinder

You may have received a balance and graduated cylinder when you began this course, or you could be using school materials. What do you do with a balance and graduated cylinder?

Unpack the balance carefully. Save the box for repacking it later. Place the balance on a flat surface. Always carry the balance by the base!

You may have one of two types of balances, a double pan balance (two pans on either side) or a triple beam balance (one pan and three mass bars).

Double Pan Balance

If you have the double pan balance follow this course of directions:

1. Place the pans onto the balance. They are color coded. The red pan goes on the left of the balance, the yellow on the right. You do not need to permanently attach the pans. Save those nuts for when you return the balance to us. Put them back into the packing box.

double pan balance

2. Before placing anything on the pans, the balance pointer should line up with the middle mark on the scale. If it does not, you can adjust the balance left and right with the adjusting wheel to the right of the pointer. Once it is adjusted, you will probably only have to change it if you move the balance.

3. When you weigh substances, place them in the left (red) pan. We try to save the finish on the pans by using a piece of paper under loose substances like salt or sugar. This paper can be weighed and subtracted from the total weight of the substance.

4. To find the weight of an object, place weights in the right pan until the pointer lines up with the center mark again. Add up the weights to get the total weight of the object. To use extra weights to get the pointer closer to the center, use the ideas below:

One (1) square inch of regular graph paper (cut carefully) has a mass of 0.05 grams.
Two (2) square inches of regular graph paper have a mass of 0.1 grams.

i inch graph, 2 square inch graph

One 1/4-inch circle cut from a soda straw has a mass of 0.005 grams 1/4 inch disk

One(1) standard staple has a mass of 0.033 grams (staples are more precise than the graph paper).

Use these smaller masses to find the mass of a small paper clip. Set this paper clip with your masses when you find its mass. Record its mass for future reference.

Use your smaller masses to find the mass of a large paper clip. Set this paper clip with your masses when you find its mass. Record its mass for future reference.

Use your smaller masses to find the mass of a penny. Set this paper clip with your masses when you find its mass. Record its mass for future reference.

You should now be able to determine masses fairly accurately. Play with your balance for a while to get used to taking the mass of objects. You may want to use your larger masses to find objects that are equivalent to larger amounts for massing heavy objects.

If you have questions, e-mail your instructor!

Triple Beam Balance

If you have the triple beam balance (has only one pan and three bars) follow this course of directions:

triple beam balance

To measure mass:

1. Make sure that when there is nothing on the pan, the pointer on the right points to the zero. If it does not, there is a little knob under the pan. Making small adjustments by turning this knob will allow you to "zero out" the balance.

2. Depending on the size of the object, you can estimate the bar and mass to begin with: For example a large object with a big mass I would start on the bar that measures 100s of grams and then work my way to the tenth of a gram bar. For a very small object I might begin with the bar that measures grams and tenths of grams...

3. For the five pennies in the Don't Break the Law Lab, I would start with the 10-gram bar, the back one.

4. Move the mass on the bar to the right so that it sits in the notch just above the number. If the pointer hits the bottom, move it back either one notch or all the way to the left, depending on how far you went—so that it is not sitting on the bottom as in the picture.

5. Go to the bar that measures grams and tenths of a gram, the front bar. Begin moving the small weight slowly to the right until the pointer points to the zero.

6. Then you must ADD the amounts on the bars. Example: the back bar reads 20 grams, the front bar reads 2.7 (two grams plus seven of the little tiny lines between the whole numbers). Add these 20 + 2.7 = 22.7g.

7. Always add the numbers on the bars together. If you are only reading the front bar, each whole number represents one gram and the lines in between are tenths. . . 1.1, 1.2, 1.3 and so on until the 2, then 2.1, 2.2 and so on....

Graduated Cylinder

graduated cylinder Note: 1ml = 1cm3 of volume