Experiment 2- Andrew Do

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Lone Star College System, North Harris *

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Chemistry

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Jan 9, 2024

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Experiment 2: Measurements Required reading: -Law of Conservation of mass - Measurements and Significant Figures: accuracy and precision - SI Units - Derived units (density) Learning Goals: • To follow a procedure. • To make mass, volume and temperature measurements correctly, choosing appropriate scales and glassware. • To record data in an organized manner in your notebook (data pages). • To correctly use measuring units and significant figures. • To keep a lab notebook and write an informal report. Background information and theory: Matter is everything around you. Matter can be defined as anything that occupies space and has mass. Mass is the quantity of matter in a material. Mass can be measured in a balance. When we record mass in a digital balance or scale all the digits must be recorded as they are all significant. Volume is a measurement of the space occupied by a sample. To measure volume, we can use different instruments. In general, the more divisions we find in an instrument the closer we will be able to read the volume. Beakers and Erlenmeyer flasks are not very reliable instruments to measure volume, however, graduate cylinders, and burets can be used to determine volume with great precision. When reading these instruments, one must look at the bottom part of the meniscus (the curve formed on the surface of a liquid when it is inside a container). The instruments we will use to measure volume in this experiment must be read to 1/10 of the smallest division, that means, if the smallest division is 10 mL, then the volume contained in that glassware can be read to 1 mL. Watch this video to understand how to read a beaker. https://youtu.be/aqAYYx8GUzQ . To better understand how to do proper reading of a graduated cylinder watch the following video: https://www.youtube.com/watch?v=sObrGonT71k . The same explanation applies to reading a thermometer. Density is basically how much “stuff” is packed into a particular volume. It’s a comparison between an object’s mass and its volume. Remember the all-important equation: density = mass ÷ volume The units of density are usually given in g/mL. Density is an important physical property of a material and it can be used to identify a substance. Version 2022-2023

Temperature is a measurement of how hot an object is. Temperature is determine using a thermometer. Thermometers may have different scales. One can change from one scale to another scale using appropriate formulas (see section 1.6 in your textbook). Precision is a measurement of how close your results are to each other. Accuracy is how close your average result is from a theoretical value. In order to talk about accuracy, you need to have a theoretical or “real” value to compare to. In this experiment you will be doing measurements of mass, volume and temperature. In part one you will be reading measurements of mass and volume to determine the density of different objects and find the identity of one of them. In part 2 you will evaluate the relative reliability of two instruments used to measure liquids and in part 3 you will practice how to correctly read a thermometer. In the last part a short at home activity will be done by students to compare relative densities of objects. While performing this lab make sure you write all your data in your lab notebook (data pages). In order to complete the measurements you will need some instruments and glassware. These are pictures of the most commonly used glassware and equipment: Materials : Videos, textbook, lab manual, calculator, internet access, pencil, computer. 3 glass jars or transparent plastic cups Top loading balance F u n n e l B e a k e r Erlenmeyer flask Weighting boat (with a solid sample) Graduated cylinder Version 2022-2023

Large transparent jar Water Oil Corn syrup Raisins Paperclips Cork Penny Food coloring 2 objects that fit in the jars that won’t absorb liquid, like a plastic toy, ball, piece of metal Safety concerns to note with this lab: All glassware must be handled with care to avoid cuts and accidents. Clean all the materials after using them. Procedure: Part 1: Measurement of density 1) Watch the following video using the link: https://lonestar.yuja.com/V/Video? v=5550023&node=24376778&a=623718860&autoplay=1 2) In this video the mass of different objects is measured in a scale. Record the mass of the first object in the corresponding table (see next page: Data) 3) After determining the mass of the object, the object is placed in a graduated cylinder that contains water. Record the volume of water contained in the cylinder before the object is placed inside it. 4) Record the volume of water in the cylinder after placing the object. 5) The change in volume is equivalent to the volume of the object submerged in the water. Subtracting these two volumes will give you the volume of the object. Determine the volume of the object and record it in your table. 6) Determine the density of the object by dividing the mass by the volume of the object. Don’t forget to add units to your measurements. 7) Repeat steps 2-6 for the remaining 5 objects in the video. 8) Using your experimental values of density determine which crown is made of gold. You will need to find the density of gold. Part 2: Measurement of volume 1) Watch the following video using the link: h t t p s : / / l o n e s t a r . y u j a . c o m / V / V i d e o ? v=5550024&node=24376793&a=107057996&autoplay=1 2) In this video 100 mL of distilled (DI) water is placed in a 250 mL beaker. Note that the error in the beaker is ± 1 mL. 3) Carefully the liquid is transferred into a 100 mL graduated cylinder. 4) Record the volume from the graduated cylinder in your data table. Make sure you include all the digits you can read plus one extra one that you are estimating. Remember to observe the bottom part of the meniscus for correct reading. 5) Repeat steps 2-4 three more times. Record all your data in your data table. Version 2022-2023

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Part 3: Measurement of temperature 1) ) Watch the following video using the link: h t t p s : / / l o n e s t a r . y u j a . c o m / V / V i d e o ? v=5550026&node=24376813&a=288715372&autoplay=1 2) Observe the thermometer on the right, this thermometer shows the temperature inside the beaker. Record the initial temperature for the beaker in your data table. Remember to use the correct number of significant digits. 3) Observe the thermometer on the left, this thermometer shows the temperature inside the calorimeter (the device on the left, you will learn more about it later). Record the initial temperature for the calorimeter in your data table. 4) Observe in the video how the temperature increases upon adding heat to the containers. Record the final temperature for the beaker and for the calorimeter. 5) Repeat steps 2-4 one more time and record the new values from the video. 6) Convert the initial and final temperature obtained during the second trial for the beaker to Kelvin and then to Fahrenheit. Part 4: AT HOME: Relative densities: You will be doing two simple experiments at home to further study density. Follow the instructions for each experiment and write your observations in the data tables provided. Experiment 1: Sink or Swim? Question & hypothesis: 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? Instructions: 1) Pour about 2/3 cup of water into container #1, 2/3 cup of corn syrup into container #2, and 2/3 cup of vegetable oil into container #3. 2) Gently set a raisin in each container. 3) Observe and record your observations. 4) Remove the raisins out of the containers and try a different object (paperclip, penny, cork and two other objects that fit in the jar/cup) 5) Record what happens in each container 6) Take a picture of your experiment and include it in your report. In the picture add a paper with your name and the day you completed the experiment. 7) Based on your results write a conclusion. Make sure you answer the following when formulating your conclusion: Were your predictions right? Did the raisins and other objects sink and float when you expected them to? Did they float in one liquid and sink in another? Why do you think they acted the way they did? Answer this in your data paper. The denser a liquid is, the easier it is for an object to float on it. 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? Answer in your data paper. Version 2022-2023

Experiment 2: Relative densities of liquids. Question & hypothesis: 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. Instructions: 1) Place a few drops of food coloring into the container of water. (This is not necessary if you are using dark corn syrup.) 2) Carefully pour each of the liquids into a large jar. 3) Do not mix, let them settle. 4) Observe and record what happened and answer the questions: 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? 5) Write a conclusion. Was your prediction right? If so, the liquid you thought was densest should be at the bottom of the jar. The next dense will float on top of that, and the least dense will float at the very top. 6) Take a picture of the jar with the 3 liquids and attach it to your report. In the picture add a paper with your name and the day you completed the experiment. NOTE : Reports without a picture of the experiment with your name and date on a paper in the picture will not get credit for the at home activity portion. This applies to ALL reports that include at home activities. Waste Disposal and Clean-Up: 1) Water samples can be disposed in the sink. 2) Clean glassware thoroughly by rinsing with soap and water. Dry with paper towel when possible. 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. 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. 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. Object Mass Volume Density 1 19.5 g 14.0cm^3 1.4mL 2 11.0 g 9.0cm^3 1.2mL 3 3.0g 5.0cm^3 0.6mL Crown A 325.0g 65.0cm^3 5mL Crown B 1255.0g 65cm^3 19.3mL Crown C 306.0g 65cm^3 4.7mL Instrument used V o l u m e measured, Trial 1 V o l u m e measured, Trial 2 V o l u m e measured, Trial 3 V o l u m e measured, Trial 4 Volume of water in Beaker ( ± 1 mL) 100.0mL 100.0mL 98.0mL 99.0ml Volume of water in 100 mL Graduated cylinder ( ± 0.1 mL) 100.0mL 100.5mL 98.0mL 99.0mL Instrument used I n i t i a l temperature, Trial 1( ± 0.1 °C) F i n a l temperature, Trial 1( ± 0.1 °C) I n i t i a l temperature, Trial 2( ± 0.1 °C) F i n a l temperature, Trial 2( ± 0.1 °C) Version 2022-2023

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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) I think more items will float in corn syrup and oil because the density and consistency is higher. For water, the only thing that float is the cork 2) Complete the following table with the observations from each object in the different liquids. Thermometer in beaker 26.5 c 71.0 c 26.5 c 83.0 c Thermometer in calorimeter 15.5 c 23.0 c 15.5 c 23.5 c Object used water Corn syrup Oil Raisin Sink Sink Sink Paper clip Swim Sink Swim penny Sink Sink Sink cork Swim Swim Swim Version 2022-2023

3) Add pictures of your experiment on this page. Make sure you add a paper next to your jars with your name and the date you completed the experiment. Object 1: Float Sink Sink Object 2: Paper Clip remover Sink Sink Sink Version 2022-2023 Caption

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4) Conclusion : Write your conclusion, make sure you answer all the questions indicated in the procedure. Denser object tend to sink 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? If it less dense than water that it float 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) I think water is going to be the top follow by syrup and then oil. 7) a) Did the three liquids mix together or separate into layers? b) Which liquid is at the bottom of the jar? Syrup c) Which is at the top? Oil 8) Conclusion : Write your conclusion, make sure you answer all the questions indicated in the procedure. Syrup is the dense liquid of the 3 9) Add pictures of your jar with the 3 liquids here. Don’t forget to add a paper with your name and date next to the jar. Version 2022-2023

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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: how close your average result is from a theoretical value b) Precision: measurement of how close your results are to each other c) Random Error: A chance difference between the observed and true value d) Systematic Error: Measurements of the same thing will vary in predictable ways 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 is accurate because of how close they are to the true volume container of 24.20 mL. Students a at worst is off by .3 mL and at best .1 mL. While Students B is precise because they are off .6+ mL. Student A Student B 24.3 mL 24.89 mL 24.4 mL 24.87 mL 24.5 mL 24.88 mL Version 2022-2023

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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 Version 2022-2023 Caption

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? d=M/V Crown B is made of gold because 1255 divide by 65 is 19.3. 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? You start with the initial volume with out the crown and subtract it by the number after the crown is placed which is 65 cm^3 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? Graduated cylinder because of how narrow it is. 7) Observe your data for the volume of water in the graduated cylinder: Are your results accurate? Are they precise? Explain. Accurate because you can’t see the decimal after that. Version 2022-2023

8) For the measurement of temperature complete the following table for the temperature of the beaker, second trial: Show your work for the change in temperature units. (26 °C × 9/5) + 32 = 78.8 °F (46 °C × 9/5) + 32 = 114.8 °F 26 °C + 273.15 = 299.15 K 46 °C + 273.15 = 319.15 K 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. 1. 4.56 mL 2. 11.86 mL 3. 81.5 mL 4. 12.5 mL 5. 330.5 mL T e m p e r a t u r e measured, Celsius Te m p e r a t u r e i n Fahrenheit Temperature in Kelvin Initial temperature, t h e r m o m e t e r i n beaker trial 2 26 c 78.8 f 299.15 K Final temperature, t h e r m o m e t e r i n beaker trial 2 46 c 114.8 f 319.15 K Version 2022-2023

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