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Thermal Properties of Liquids

Extracts from this document...

Introduction

  • Investigating the Thermal Properties of Liquids
  • In this experiment I looked at liquids of different densities and whether or not this affected their heating rate. For my experiment I had a variety of common liquids (water, salt water, oil, milk etc.) and measured the density of each before heating them under a Bunsen flame for 2 minutes and recording the temperature change. The purpose of this experiment was to find out what effect the density of a liquid has on it’s thermal capacity.
  • Thus I hypothesize that the greater the density of a liquid, the greater the heat capacity. This means that it will take more energy to raise the temperature of the liquid/substance by 1°C and so the lower the heating rate of the liquid. In summary, I hypothesize that the relation between a liquid’s density and its heating rate is inversely proportional.
  • Since I will be using five different liquids/substances (water, milk, pepsi, salt solution and sunflower oil) with varying densities, this will be my independent variable. The density of a liquid is defined as its mass per unit volume. The term ‘per’ in mathematic is defined as a division and the density of any liquid is measured in cubic centimetres (cc) and is equal to 1 mL. To have an accurate and precise density of each liquid, I will be using an electronic scale and all liquids/substances will be weighted beforehand commencing any trial run. However, since I will be weighting the mass of each liquid in a 250 ml glass beaker, I will have to subtract 250 grams to mass given by the electronic scale. (Number 4)
  • Since I hypothesized that the relationship of a liquid’s density and its heating rate is inversely proportional, the heating rate of the liquid will be my dependent variable. However, the heating rate of a liquid is equal to the change in temperature divided by the amount time heated. Hence, using the Logger Pro apparatus and application and the Bunsen burner, I will find out the change in temperature over 2 minutes of heating. However, further calculations and data manipulation will be needed to find out its density and heating rate. This will be ensured through the use of the following two equations:
  • All calculations and the recording of raw data (change in temperature and time) will be done through Microsoft Excel and the Logger Pro application. This will ensure that all my calculations are correct and precise. Furthermore, any result or raw data will be rounded up to two decimal places in order to ensure accuracy. This will leave no room for human error regarding any calculations throughout this investigation.
  • In order to ensure the creditability and the accuracy of my results, each substance/liquid chosen for this experiment will be tested three times following the exact same procedure. Three trial runs for each liquid will ensure that I have sufficient data for an accurate and concise analysis.
  • As I am investigating only one variable that can affect the heating rate of a liquid, I need to ensure through certain measures that other variables are kept constant all throughout the experiment to establish a reasonable, accurate and precise analysis. These will be my controlled variables. Below is a list of the measures I will take.
  • Although I will change liquids through my investigation, I will control the volume of the liquids I will use. The volume of liquid must be kept constant as it is one the factors that can affect their heating rate. Thus I will use 100 ml of each liquid and for each trial run. This volume will be measured using a measuring cylinder of 100 ml   glass beaker (of 250 ml) for heating purposes. A 100ml is the minimum and most acceptable amount when investigating the heating properties of a liquid. Using more then a 100 ml for each trial run would be wasting the limited amount of liquids/substances that I have for this investigation. Also since the measuring cylinder has a volume of exactly a 100ml this will prevent any error or inaccuracy in measuring the amount of liquid desired. (Numbers 1 and 2)
  • Another factor that can affect the heating rate of liquid is amount time spend over the Bunsen burner. This is so that each of the liquids is heated for the same time as heating certain liquids longer or shorter times than others would obviously render my results inaccurate and inconclusive. Consequently the liquid for each trial run will spend exactly two minutes over the Bunsen burner. Two minutes will be sufficient time as for the liquid to overcome their initial thermal capacity. To prevent any human error in timing of my experiment, I will be using the application ‘Logger Pro’ on my computer that will measure both time and temperature change simultaneously in real time. Furthermore, if I were to use different equipment (i.e.: timer and digital hand-held thermometer instead of Logger Pro) these will have singular margins of error. By using a piece of equipment that records every aspect of my raw data, this margin of error will be reduced. The more I limit the amount of electrical equipment in my investigation, the less margins of error needed to account for in my results making my analysis more reasonable and accurate (Numbers 6, 11 and 12)
  • Another factor that might affect the heating rate of a liquid is the shape of the container in which it is withheld. Thus for each trial run and liquid, I will be using a standard issue 250ml glass beaker. For practical purposes, I will be using the same beaker throughout the whole investigation. Having one beaker for each of the 5 substances tested would be most unpractical and nuisance to my classmates. However, between each trial run the beaker will be cleaned and cooled off using tap water and liquid soap. This will be done in order to ensure that the liquids do not mix at that the glass beaker remains at room temperature for each trial run. (Number 1, 15 and 16)

Notes: the numbers at the end of each of the controlled and dependent variables refer to their illustration counter part on the next page and the list of apparatus below. (Diagrams drew by pencil and ruler on a separate page)

Apparatus:

  1. 250ml Standard Issue Glass Beaker
  2. 100ml Measuring Cylinder
  3. Bunsen Burner
  4. Electronic Scale
  5. Clamp Stand
  6. Logger Pro Thermometer/ Temperature recording device
  7. 6 x 100 ml of Water
  8. 330 ml Pepsi can
  9. 3 x 100 ml of Milk
  10. 3 x 30 g of salt
  11. Computer compatible with Logger Pro
  12. Logger Pro ‘software’ application
  13. Tri pod
  14. Heating mat
  15. Running water
  16. Liquid Soap

Having conceiving the design of my experiment, I was ready to commence collecting raw data. Before any else I measured the mass of each liquid and found their density through calculation. The respective masses and densities of each liquid would be recorded in the following tables.

Substance/Liquid

Mass  (g)

Density (g/cm^3 or cc)

Water

Pepsi

Milk

Sunflower Oil

Salt Solution

When recording the mass of each substance/liquid from the electronic, the mass of the 250 ml glass beaker had to be subtracted (250 grams). The mass of the liquid would then be divided by the liquid amount (100 cm^3) through the use of the formula builder in Microsoft Excel. Thus the following mass and densities for each substance/liquid were found.

Substance/Liquid

Mass  (g)

Density (g/cm^3 or cc)

Water

97.3

0.97

Pepsi

99.7

1.00

Milk

99.6

1.00

Sunflower Oil

90.2

0.90

Salt Solution

117.8

1.18

Note: Microsoft Excel through its calculations automatically rounded each density to the nearest second decimal place.

From the table above you can see that pepsi, waster and milk all have similar densities indicating that maybe their heating rates will be similar to another if all other variables remained controlled (ceteris paribus). From this I chose water as my control for all the other substances/liquids as it is the most common liquid to be found and has a density of 1.00 generally (0.97 cc in this case).

Since Logger Pro will record the change in temperature for every second over a course 2 minutes (120 seconds), I chose an interval of 15 seconds for my raw data and the points to be plotted on my graphs. Thus the following table was constructed for each substance and liquid.

Time (s)

Liquid/ Substance Trial 1 Temp  (°C) ±0.6

Liquid/ Substance Trial 2 Temp  (°C) ±0.6

Liquid/ Substance Trial 3 Temp  (°C) ±0.6

Liquid/ Substance Average Temp (°C) ±0.6

0

15

30

45

60

75

90

105

120

Three trial runs will be conducted for each substance and the average temperature for 0, 15, 30, 45, 60, 75, 90, 105 and a 120 second will be calculated through Microsoft Excel by adding each trial and then dividing the total by three. Following this I set up my apparatus as shown by my diagram. To ensure that I had sufficient gas, I placed the gas conduct on full throttle and turned the Bunsen burner flame to a heating flame (‘blue’ flame, this would be the only that I could do to control the heat output upon the liquid tested). I first started with a 100 ml of water measured using the 100ml-measuring cylinder. Simultaneously, I started the recording of data on Logger Pro and placed the Bunsen burner under the tripod to start my investigation. The recording apparatus had a marginal error of ±0.3°C per second (this is mainly due to the Bunsen burner inaccurate heat output).

  • I kept the flame under the beaker for 2 minutes so as to get a better idea of the difference in heating rate between the different fluids. After the 2 minutes, I stopped the recording and took the temperature value at 120 seconds as my final temperature. I then repeated this 2 more times before changing the liquid in the beaker and recording that 3 times as well. In between, each trial run and especially when switching each substance/liquid I cleaned both the glass beaker and measuring cylinder with running water and liquid soap to ensure the accuracy of my results. The exact same procedure as for the water trial runs were conducted for pepsi, salt solution, milk and sunflower oil (Raw Data Tables Below).
...read more.

Middle

25.19

22.98

30

21.69

25.37

26.50

24.52

45

25.00

29.00

29.69

27.90

60

29.06

33.19

33.94

32.06

75

33.69

37.81

38.56

36.69

90

38.06

42.25

42.94

41.08

105

42.37

47.00

47.75

45.71

120

46.75

51.44

52.12

50.10

Time (s)

Pepsi Trial 1 Temperature (°C) ±0.6

Pepsi Trial 2 Temperature (°C) ±0.6

Pepsi Trial 3 Temperature (°C) ±0.6

Pepsi Average Temperature (°C) ±0.6

0

23.19

22.94

23.25

23.12

15

23.06

23.19

23.37

23.21

30

23.81

24.94

24.56

24.44

45

26.75

26.56

27.62

26.98

60

31.25

30.25

31.37

30.96

75

35.75

34.69

35.69

35.37

90

40.06

39.19

39.81

39.69

105

44.69

44.06

44.62

44.46

118

49.37

48.56

48.81

48.92

Time (s)

Milk Trial 1 Temperature (°C) ±0.6

Milk Trial 2 Temperature (°C) ±0.6

Milk Trial 3 Temperature (°C) ±0.6

Milk Average Temperature (°C) ±0.6

0

20.69

19.56

20.81

20.35

15

22.19

19.56

21.12

20.96

30

25.94

19.87

22.44

22.75

45

28.06

21.37

24.44

24.62

60

31.56

24.37

27.56

27.83

75

34.94

28.00

31.19

31.37

90

38.37

31.94

35.06

35.12

105

42.44

35.87

39.06

39.12

120

46.06

39.81

43.19

43.02

Time (s)

Sunflower Oil Trial 1 Temp (°C) ±0.6

Sunflower Oil Trial 2 Temp (°C) ±0.6

Sunflower Oil Trial 3 Temp (°C) ±0.6

Sunflower Oil Average Temp (°C) ±0.6

1

27.69

24.94

26.94

26.52

15

26.06

26.12

27.50

26.56

30

25.94

29.56

28.81

28.10

45

26.69

33.37

31.50

30.52

60

30.56

38.44

34.25

34.42

75

36.87

44.50

39.37

40.25

90

40.81

52.31

44.56

45.90

105

45.69

58.69

50.87

51.75

120

51.69

66.75

56.37

58.27

From all the average temperatures for each substance/liquid a more practical table was created. Thus I would be using the Average Temperature for each substance/

...read more.

Conclusion

±0.3°C for each trial run and liquid tested. Moreover,  a Bunsen burner lets some heat escape, leading to further inaccuracies, whereas a calorimeter is isolated and a controlled environment with no possible outside factors influencing my results. Therefore, a calorimeter would my a viable option for further experimentation.In the set up of my experimentation, I used a clamp stand to hold the substance vertically over the heat source (Bunsen burner). This is both a complicated and inaccurate setup, leading to a higher degree of error. The glass beaker I used is also not ideal. Glass is very malleable under intense heat and could crack or break possibly leading to injuries. Thus for further investigation the use of a calorimeter (made from plastic or any other insulated material) would be a more viable option for more accurate results, analysis and conclusion.Finally, to further reduce error in my analysis, I should have completed 5 trials instead of 3 for each of substance. Also, I should have let each trial run for 3 minutes instead of 2, to more accurately measure the change in slope over time and write a more comprehensive and detailed analysis. These controlled variable would be needed to take into account in further investigation.The density of the substances used are too similar, especially those of water and Pepsi. I should have chosen liquids with a larger density range for the experiment to be conclusive. Further research should have been done, on which liquids to employ for the expirement. However, in further experimentation I could look up the densities for each of the substances used in order to ensure that my investigation and analysis is conclusive and accurate.Taking these errors into account, I may have been able to improve on them in a number of ways in order to further support my conclusion, or even disprove it.

...read more.

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