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Scientific_Method_Protocol-1 - Scientific Method and...

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Scientific Method and Measurements/1 KLE 12/14/09 Scientific Method and Measurements Pre-Lab Before you begin, read through the experimental steps and determine the purpose of this experiment. Fill in the blanks to the question: “How does __________________________________________________________ affect ___________________________________________________?” Now, answer the question with your hypothesis: “If _________________________________ then ___________________________________________________________.” Background and Theory In this laboratory exercise, you will be applying the scientific method to study the accuracy of various measuring devices commonly found in a laboratory. These devices include beakers, graduated cylinders, and conical tubes. In the first part of the lab, you will attempt to measure 40ml of water ACCURATELY using these devices. You will use the value for the density of tap water at room temperature (~20 o C) to evaluate your results and draw your conclusions. The density of water at 20 o C is 0.998g/ml. You can use this value to convert your experimental data from grams (which you will measure) into milliliters. In other words, you THINK you measured 40ml of water, but how accurate were you? You can then determine the percent (%) error for each measurement by using the following equation: % error = [measured value - expected value] ÷ expected value x 100 A positive (+) % error means you OVERMEASURED and have more than 40ml in the beaker. A negative (-) % error means you UNDERMEASURED and have less than 40ml in the beaker. You can also report your % error in absolute values. The second part of the lab will introduce you to the micropipettor, review pipettes, and allow you to practice your pipetting skills for accuracy. After finishing this lab, you should be able to list and describe the steps of the scientific method identify the steps of the scientific method in an experiment apply the scientific method to study a question ask a question and design an experiment (including appropriate controls) to test a hypothesis explain what controls are and give examples follow a protocol
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Scientific Method and Measurements/2 KLE 12/14/09 identify laboratory equipment used in this lab make careful measurements using standard laboratory equipment use/read a balance use/read pipettes of 1ml, 2ml, 5ml, 10ml use/read micropipettors of p20, p200, p1000 select appropriate measuring devices for desired volumes calculate percent error evaluate your experimental results to draw a conclusion Materials Your Group (of 2) Will Need pipettes (one each: 1ml, 2ml, 5ml, 10ml) two propipettes (pump) micropipettors (one each: p20, p200, p1000) and tips boxes one 50ml beaker one 50ml conical tube (plastic, capped, centrifuge test-tubes) one 50ml graduated cylinder one large, white plastic beaker (to use as a “sink”) one balance (may have to share one per lab table instead of one per pair) weigh boats (stored in same cabinet as balances) Procedures – Part I: Accuracy of Measuring 40ml of Water 1. Obtain a 50ml beaker, a 50ml graduated cylinder, and a 50ml conical tube.
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Scientific_Method_Protocol-1 - Scientific Method and...

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