Experiment 2- Andrew Do

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Lone Star College System, North Harris *

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1411

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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

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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