PAGES

**4**

WORDS

**515**

"Has been a lifesaver so many times!"

- Catherine Rampell, student @ University of Washington

"Exactly the help I needed."

- Jennifer Hawes, student @ San Jose State

"The best place for brainstorming ideas."

- Michael Majchrowicz, student @ University of Kentucky

Purpose: To check the accuracy of common lab equipment, such as the meter stick, the graduated cylinder and the thermometer and to reinforce the SI system. We will also be testing for precision in these experiments.

Hypothesis: If the lab equipment that we are using is accurate than our results will turn up about the same each time we do the lab.

Procedure:

Experiment A: First obtain a meter stick. Then measure the length and width of your lab book in inches, meters, millimeters and centimeters. Record your results. Next use the standard calculations to check if your measurements correspond. Finally find the volume of the lab book in cm2.

Experiment B: First fill the graduated cylinder about half full. Read what the volume of the water is to the nearest 0.1mL (make sure you read the volume at the bottom of the meniscus). Record your results. Next determine the maximum volume your test tube will hold. Record your results.

Experiment C: Acquire 40mL of water in a 150mL Erlenmeyer. Then weigh and record the mass of a 50mL Erlenmeyer to the nearest 0.1mg. Next measure and record the temperature of the 40mL of water. Using the pipet, pipet exactly 10mL of water into the Erlenmeyer and weigh it to the nearest 0.1mg. Next find the net mass of the 10mL of water. To do this, subtract the mass of the Erlenmeyer from the gross mass of the water and the Erlenmeyer. Do these there times to make sure you are precise. Next find the mean volume delivered by the pipet. To do this, add the three net masses and divide by three. Next find the individual deviation from the mean. To do this, subtract the individual volume by the mean volume. Next find the average deviation from the mean. To do this, add the three deviations together and divide by three.

Experiment D: First weigh a dry 50mL flask to the nearest 0.1mg. Next add 10mL of antifreeze to the flask with your pipet. Weigh the flask and the antifreeze and record the mass. Do this three times. Use the measured mass and the volume to determine the density. The formula for this is D = m/v. Using these values measure the mean density and the average deviation from the mean. This is done like it was done in experiment c.

Calculations: See attached pages

Data: See attached pages

Results: After concluding these experiments, I concluded that the lab equipment that we used is accurate. My hypothesis was correct. In these experiments it was really important that the readings that were taken from the equipment was very accurate and precise. It needs to be both of these to be correct. This is because if you were accurate in the findings, but each time the readings were off, the mean would be of too. Also if you were precise, but not accurate, then the answer would be completely off. After doing this experiment, I now better know the SI system and I better now how to use lab equipment.