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SURVEY OF CHEMISTRY LABORATORY I CHEM 1151L DETERMINATION OF THE DENSITY OF WATER.

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Presentation on theme: "SURVEY OF CHEMISTRY LABORATORY I CHEM 1151L DETERMINATION OF THE DENSITY OF WATER."— Presentation transcript:

1 SURVEY OF CHEMISTRY LABORATORY I CHEM 1151L DETERMINATION OF THE DENSITY OF WATER

2 CAUTION!!! BE SURE TO WEAR SAFETY GLASSES AT ALL TIMES IN THE LABORATORY NO EXCEPTIONS TO THIS RULE!

3 This experiment is designed for students to - familiarize themselves with common measuring devices in the laboratory - demonstrate an understanding of mathematical and computer skills (graphing, linear equations, slopes and intercepts) Measuring Devices to be Used - Thermometer - Mass balance - Graduated cylinder - Buret DETERMINATION OF THE DENSITY OF WATER

4 DENSITY - The amount of mass in a unit volume of a substance Density = Units Solids: grams per cubic centimeter (g/cm 3 ) Liquids: grams per milliliter (g/mL) Gases: grams per liter (g/L) - Density of 1.00 g/mL implies 1.00 grams per 1 mL - Density usually changes with change in temperature

5 MASS MEASUREMENT - Mass is the amount of matter in an object - SI unit is the gram (g) - The mass balance is used to measure the mass of samples in the laboratory - The mass rather than the weight of a sample is measured

6 Volume is the amount of space that the matter takes up Unit: milliliter (mL) Measuring Devices - Buret - Graduated Cylinder VOLUME MEASUREMENT

7 MASS AN OBJECT - Mass any object on you (watch, ring, coin, necklace, etc.) - Record all digits shown on the mass balance (DO NOT ROUND-OFF)

8 ROOM TEMPERATURE - Measure the room temperature using a thermometer - Hold thermometer upright (do not touch the bulb) - Take the reading to the nearest 0.1 o C This reads 23.0 o C

9 Obtain - a 125 mL Erlenmeyer flask - a 50 mL graduated cylinder - Record all volumes to one decimal place GRADUATED CYLINDER

10 - Fill the graduated cylinder with distilled H Fill to the 50.0 mL mark - Read and record the initial volume (one decimal place) of water in the graduated cylinder - Read at eye level and at the bottom of the meniscus (the concave “crescent” shaped surface of the liquid) GRADUATED CYLINDER

11 - Tare (zero) the mass balance - Do this by pressing ‘TARE’ GRADUATED CYLINDER

12 - Mass the empty flask (should be dry) GRADUATED CYLINDER

13 - Pour mL of H 2 0 from the cylinder into the flask GRADUATED CYLINDER

14 - Read and record the volume of H 2 0 remaining in the graduated cylinder - This is the final volume for trial 1 GRADUATED CYLINDER

15 - Measure and record the mass of flask and H 2 0 GRADUATED CYLINDER

16 - Do not empty flask - Final volume of trial 1 is the initial volume of trial 2 - Pour another mL of H 2 0 from the cylinder into the flask - Record the final volume for trial 2 GRADUATED CYLINDER

17 - Measure and record the mass of flask and H 2 0 GRADUATED CYLINDER

18 - Repeat steps for the remaining trials without emptying the flask - Refill the graduated cylinder if necessary (read and record new initial volume in such cases) GRADUATED CYLINDER

19 GRADUATED CYLINDER SAMPLE TABLE OF VALUES Initial Reading (mL) Final Reading (mL) Volume of H 2 O delivered (mL) Total volume of H 2 O (mL) Mass of the flask and H 2 O (g) Trial Trial Trial

20 Obtain - a 125 mL Erlenmeyer flask - a 50 mL buret - Record all volumes to two decimal places BURET

21 - Wash and rinse buret with faucet water and with distilled water - Allow water to drain through the tip to rinse the tip - Buret tip is closed when in horizontal position and opened when in vertical position BURET

22 - Obtain a stand and a buret clamp - Put buret in place as shown BURET

23 - Use a small beaker to fill the buret with distilled H Do not use a funnel - Fill past the 0.00 mL mark - Open the tip in order to fill the tip and eliminate bubbles BURET

24 - Read and record the initial volume (two decimal places) - Place a white card behind buret for easy reading BURET

25 - Read at eye level and at the bottom of the meniscus (the concave “crescent” shaped surface of the liquid) - Note that buret reading is the opposite of that of the graduated cylinder - For instance, the initial buret reading would be 0.00 mL but not mL BURET

26 - Each small graduation is 0.10 mL - 10 graduations per 1.00 mL BURET

27 - Mass the empty flask (should be dry) BURET

28 - Allow mL of H 2 0 to drain into the flask BURET

29 - Read and record the final buret reading - This is the final volume for trial 1 BURET

30 - Measure and record the mass of flask and H 2 0 BURET

31 - Do not empty flask - Final volume of trial 1 is the initial volume of trial 2 - Drain another mL of H 2 0 from the buret into the flask - Record the final volume for trial 2 BURET

32 - Measure and record the mass of flask and H 2 0 BURET

33 - Repeat steps for the remaining trials without emptying the flask - Refill the buret if necessary (read and record new initial volume in such cases) - Note that you cannot go beyond the mL mark STOP and refill the buret BURET

34 GRADUATED CYLINDER SAMPLE TABLE OF VALUES Final Reading (mL) Initial Reading (mL) Volume of H 2 O delivered (mL) Total volume of H 2 O (mL) Mass of the flask and H 2 O (g) Trial Trial Trial

35 DATA ANALYSIS - Construct two graphs using Microsoft Excel’s Chart Wizard - Graph 1 – Graduated cylinter - Graph 2 – Buret - Draw a trendline (the best straight line) for each - Horintal axis is the Volume axis - Vertical axis is the Mass - Label all axes (with correct units) and give titles - Include equations of the trendlines - Answer all questions that follow


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