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CHEM 1011 Laboratory Techniques: Using the Laboratory Gas Burner; Making Laboratory Measurements.

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Presentation on theme: "CHEM 1011 Laboratory Techniques: Using the Laboratory Gas Burner; Making Laboratory Measurements."— Presentation transcript:

1 CHEM 1011 Laboratory Techniques: Using the Laboratory Gas Burner; Making Laboratory Measurements

2 Safety Put on Goggles And Apron

3 Objectives Learn to use Bunsen burner Learn to use laboratory equipment Learn to take Measurements Record Measurements using the proper number of significant figures

4 Bunsen Burner Allows Controlled Mixture of Gas and Air Hottest Flame –Nonluminous –Violet outer cone –Complete combustion occurs CH 4 (g) +2O 2 (g) → CO 2 (g) + 2H 2 O (g)

5 Bunsen Burner Cooler Flame –Less Air –Luminous Yellow Flame –No Inner Cone –Smokey due to incomplete combustion

6 Glassware Glassware in lab is a borosilicate glass –Consists of silica and borax –Does not soften much under 800˚C –Pyrex or Kimax –Low thermal Expansion coefficient Unlike soft Glass (SiO 2 ) – softens from ˚C –High thermal Expansion coefficient

7 Laboratory Measurements Metric system uses base 10 for measurements and conversions Conversions are done by multiplying or dividing by 10

8 Laboratory Measurements Evaluate physical and chemical environment –length, volume, mass, energy, and temperature Good laboratory techniques are invaluable

9 Accuracy Closest to the true value –True value = Device measures – – –34.877

10 Precision Reproducibility of the measurement Little variability –True value = Device measures – – –

11 Precision and Accuracy

12 Significant Figures When measuring: –(1) uncertainty in last digit recorded –(2) the # of significant figures contains all known #’s + one estimated – known = 25.4; estimated = 0.05

13 Examples

14 Division The Answer’s # of sig. fig. are same as number with the fewest digits being divided 12.3 ÷ = = 1.97

15 Multiplication The Answer’s # of sig. fig. are same as number with the fewest digits being multiplied 0.72 × = = 0.82

16 Addition The Answer’s # of sig. fig. are same as number with the fewest digits behind decimal being added = = 15.37

17 Subtraction The Answer’s # of sig. fig. are same as number with the fewest digits behind decimal being subtracted – 3.63 = = 3.21

18 Calculations Length: Record measurement to the nearest 16 th of an inch

19 Conversion Table

20 Calculations (Measurement) Record measurements Conversions can be made by dividing or multiplying by powers of 10 Ex. 34 cm × 10 mm/1 cm = 340 mm Area L × W (340 mm × 23 mm) = 8160 mm 2

21 Calculations (Volume) Record Volume Convert using the conversion chart e.g., 48 mL × 1 L/1000 mL = L Calculate percent error = (theoretical value – actual value)/ theoretical value × 100

22 Calculations (Mass) Record values Convert from g to mg e.g., 15 g × 1000mg/1g = mg

23 Calculations (Temperature) Record the Value in degrees Celsius Convert to Degrees Fahrenheit and Kelvin Degrees Fahrenheit use (9/5 (C) + 32 Degrees Kelvin use (C + 273)


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