Lab 1 - Boiling water lab experiment PDF

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The point of this lab exercise is for students to experientially practice core scientific techniques required for many general laboratory/practical course experiments. Our initial lab exercise will take advantage of household items so that we can (re)create explicitly quantitative results in spite o...

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Name: Richa Gomes Date: 25/09/2020

Practical 1: Making quantitative observations The point of this lab exercise is for students to experientially practice core scientific techniques required for many general laboratory/practical course experiments. Our initial lab exercise will take advantage of household items so that we can (re)create explicitly quantitative results in spite of the continuing pandemic measures that limit face-to-face interactions. I fully acknowledge that the ‘virtual lab’ approach is somewhat unsettling, given that we would typically perform our experiments in an analytical lab environment, but I think that the use of household items will force us all to think about hydrology in a more creative and intimate way, without loss of key quantitative skills, which are crucial for career development in science, arts, and business alike! Indeed, tough decisions are a common aspect in many professions, including science, and this week’s exercise will feature: • • • •

setting up a simple experiment making precise measurements, observations, plots, interpretations keeping quantitative data organized exploring precision (i.e., reproducibility), uncertainty, and data structure

Boiling Water Lab Experiment These are the materials you need for this lab: water, a pot, a thermometer (I have a cheap digital thermometer [Gefu Scala 21820; £20]), a stove or other source of heat, and a watch or other timer. If you don’t have access to some of these materials, don’t worry! You can use the video I uploaded to Vision/Blackboard to complete this assignment :) I do recommend that you attempt to run your own at-home experiment, though, because you will learn more effectively. I think that performing household experiments is more fun than watching someone else do the experiment, too ;) Part 1: Procedure 1. 2. 3.

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Measure a specific volume of water (you can choose the volume) into your pot. Record this volume! Measure the starting temperature of the water. Record this initial temperature. Put the pot on the stove and turn on the stove (you can choose how high to turn it up, but keep the level constant). Describe each step of what you did in a way that another person could follow you or that you could go back and reproduce your own steps. Measure the temperature of the water at regular intervals of 2-5 minutes. It is up to you to decide how often you need to make measurements ;) Record these measurement times and temperatures. When the water boils, note the time, and remove the pot from the heat. Record this time and record the temperature. Continue to make regular measurements (every 5-10 minutes, as it will be slower than the heating phase) of the temperature of the water until it cools back down to the initial temperature from step 2. Record these measurements. Measure the volume of water at the end of your experiment. Record this volume.

Name: Richa Gomes Date: 25/09/2020

Part 1: Data and Questions Initial volume of water: 1400ml Final volume of water: 1380ml Starting water temperature: 15.4°C Final water temperature: 84.7°C The table below is a guide. You may make as many measurements as you wish. Be sure to record units of time and temperature so another person would know exactly what you measured. Elapsed Time

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Temperature

0 minutes

15.4 °C

2 minutes

35.3 °C

4 minutes

45.1 °C

6 minutes

55.2 °C

8 minutes

66.5 °C

10 minutes

76.7 °C

12 minutes

86.7 °C

14 minutes

96.2 °C

16 minutes

97.7 °C

18 minutes

95.5 °C

20 minutes

93.7 °C

22 minutes

91.6 °C

24 minutes

89.9 °C

26 minutes

88.2 °C

28 minutes

86.4 °C

30 minutes

84.7 °C

Name: Richa Gomes Date: 25/09/2020 Stove procedure: describe each step below

1) Measure a specific volume of water using, for instance, a measuring jug. In this case, measure out 1400ml, then put the water into a pot on the stove. Make sure to record the starting volume of water. 2) Measure the starting temperature of the water using a thermometer. Again, make sure to record this starting temperature. 3) Turn the stove on at medium heat (medium heat allows the water to get hot fairly quickly, while keeping the experiment safe, as working with a flame may be dangerous sometimes). Whatever the heat level, always make sure to keep it constant, so that it does not interfere with the experiment findings. Remember to set the thermometer inside, so you can easily record the temperatures. 4) Set a timer, and record the temperature of the water, the thermometer shows, at regular intervals of 2 minutes. Write down the time and then the temperature next to it. It is best suggested to use a table to keep things neat and easy to read at the end of the experiment. 5) As soon as the water starts boiling, record the time and temperature, then turn the stove off. 6) Continue to note down the time and temperature at an interval of 2 minutes, as the water starts cooling down. Notice the rate at which it cools down is slower than when it was heating up. 7) At the end of 30 minutes, stop your timer and record the final temperature of the water. 8) Measure the volume of water at the end of your experiment, using the measuring jug from step 1. Record this volume.

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Name: Richa Gomes Date: 25/09/2020

Answer the following questions about Part 1: 1. How did you measure the volume of water into your pot? How precise do you think your measurement was? Ø The water was measured using a measuring jug. Its scale went up to the volume of 700ml, so it was filled up twice to get the volume of 1400ml. In this case, a measuring jug was adequate, but if you wanted to take more precise measurements, using a balance, a graduated cylinder or other more accurate measuring devices would be more suitable. 2. Was it easy or difficult for you to decide when to “know” that the water was boiling? How did you decide? (i.e. based on observing the water or based on observing your thermometer, or another way?) Ø It was fairly easy, as you could see bubbles forming and gradually getting bigger then rising up, as well as the jar fogging up and steam coming out from the top. 3. When you observed the water boil, did your thermometer read 100 °C (or 212 °F)? If not, discuss possible reasons why not. Ø The thermometer did not read 100 °C. This could have been because of the atmospheric pressure, as due to low atmospheric pressure, water boils at less than 100 degrees Celsius. A liquid at high pressure has a higher boiling point. The vapor pressure must have been high, as liquids with high vapor pressures have lower boiling points. 4. How much time elapsed between the beginning of the experiment until the water boiled? Ø The water started boiling at the 13-minute mark, so 13 minutes. 5. How much time elapsed between the boiling time and the end of the experiment (i.e., water was at room temperature again)? Ø 15 minutes elapsed. The temperature at the end of the experiment was 84.7 °C. 6. How often did you record a temperature measurement? Did you decide how often to take data before you began your experiment? Did you change your measurement interval during the experiment? If you did (or did not), why? Ø A temperature, along with the time shown on the stopwatch used, was recorded every 2 minutes. It was decided to how often to take data before the experiment started in order for it to run more smoothly, and it was not changed during the experiment to keep the variables constant. The time of 2 minutes was enough to show how the temperatures increased and decreased up until 30 minutes.

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Name: Richa Gomes Date: 25/09/2020

7) Plot your data for this experiment. Your plot must have a title, a labeled x-axis, and a labeled y-axis. You must choose how to represent your data on this plot. I suggest that the best way to represent your data is with a scatter plot in which each measurement of temperature at a particular time is recorded with a symbol.

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Name: Richa Gomes Date: 25/09/2020

8) If you were going to do this experiment again, discuss whether you would change anything about your procedure and why. Ø Heating the water at a higher temperature would lead to higher temperatures recorded. Ø Using a balance instead of a measuring jug would help to gain a more accurate measurement of volume.

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Name: Richa Gomes Date: 25/09/2020

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