Experiment 2- Measurements 2022-2023

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University of Houston *

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1311

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Chemistry

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Feb 20, 2024

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Version 2022-2023 Name: ____________________________________ Measurements Data Collect all your data and observations from the video on these tables. You will submit these pages as part of your report. Show your work when indicated. Part 1: Measurement of density Collect all your data in this table. Include units and all the significant digits in the measurements and calculations. Object Mass Volume Density 1 2 3 Crown A Crown B Crown C Part 2: Measurement of volume Collect all your data in this table. Include units and all the digits that can be read in the glassware used plus one more that you will estimate, they are all significant. Instrument used Volume measured, Trial 1 Volume measured, Trial 2 Volume measured, Trial 3 Volume measured, Trial 4 Volume of water in Beaker (  1 mL) Volume of water in 100 mL Graduated cylinder (  0.1 mL) Part 3: Measurement of temperature Collect all your data and observations in your notebook (data pages). Include units and all the digits that can be read on the thermometer plus one more that you will estimate, they are all significant. Show all your work for the change of temperature scales. Instrument used Initial temperature, Trial 1(  0.1 °C) Final temperature, Trial 1(  0.1 °C) Initial temperature, Trial 2(  0.1 °C) Final temperature, Trial 2(  0.1 °C) Thermometer in beaker Thermometer in calorimeter

Version 2022-2023 Part 4: AT HOME Experiment 1: Sink or Swim? Question: Will a raisin, paperclip, penny, small cork and other small objects sink or float if they are placed in water, corn syrup and vegetable oil? 1) Hypothesis Write down what you think will happen when you place each object into the three different liquids.(Formulate a hypothesis) 2) Complete the following table with the observations from each object in the different liquids. Object used water Corn syrup Oil Raisin Paper clip penny cork Object 1: Object 2:

Version 2022-2023

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Version 2022-2023 4) Conclusion : Write your conclusion, make sure you answer all the questions indicated in the procedure. 5) If one of your objects floated in the corn syrup but sank in the water, what does that tell you about the densities of water and corn syrup? Experiment 2: Relative densities of liquids. Question: Which is the most dense: water, corn syrup, or vegetable oil? Which is the least dense? Based on your results from experiment #1, predict which liquid you think is the most dense and which you think is the least dense. 6) Hypothesis Write down what you think will happen when you combine the three different liquids.(Formulate a hypothesis) 7) a) Did the three liquids mix together or separate into layers? b) Which liquid is at the bottom of the jar? c) Which is at the top? 8) Conclusion : Write your conclusion, make sure you answer all the questions indicated in the procedure.

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Version 2022-2023 Name: ____________________________________ Measurements Postlab questions: Your instructor may ask you to answer these in your lab notebook, or to answer directly on this page and turn it in, or to include these answers in a formal lab report. Follow your instructor’s directions. 1) Define the following: a) Accuracy: b) Precision: c) Random Error: d) Systematic Error: 2) Two students determined the volume of a glass container three separate times (see table below). The true volume of the container is 24.20 mL. What can you say about the students’ results in terms of accuracy and precision? Who was more precise, who was more accurate? Explain in detail. Student A Student B 24.3 mL 24.89 mL 24.4 mL 24.87 mL 24.5 mL 24.88 mL

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Version 2022-2023 3) To evaluate the accuracy of results we can calculate a % error by comparing the experimental result with the expected result. Ideally, the percent error would be 0%. Scientists don’t get to see that too often. Determine the average for each set of data from the last question and compare to the true value using the % error determination. The formula for % error is: % error = |expected value – experimental value| expected value × 100 4) For the measurement of density: The density of gold is 19.3 g/mL. Using the data from part 1, which of the 3 crown is made of gold? Explain how did you find your answer? 5) For the measurement of volume : How do your measurements in the beaker and the graduated cylinder differ? are they the same? What is the difference?

Version 2022-2023 6) Which instrument do you think will give you a better measurement of volume: a beaker or a graduated cylinder? Why do you think so? 7) Observe your data for the volume of water in the graduated cylinder: Are your results accurate? Are they precise? Explain. 8) For the measurement of temperature complete the following table for the temperature of the beaker, second trial: Temperature measured, Celsius Temperature in Fahrenheit Temperature in Kelvin Initial temperature, thermometer in beaker trial 2 Final temperature, thermometer in beaker trial 2 Show your work for the change in temperature units.

Version 2022-2023 9) Reading glassware: Record the volume contained in the following graduated cylinders. Remember you should write all the digits you can read plus one digit that you are estimating.

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