Experiment 1 Physical Properties

1. Experiment 1Physical Properties

2. Goal To identify an unknown substance based on its physical properties.

3. Background Physical Property – Characteristic of a substance which can be measured without changing the chemical identity of the substance. Examples: color solubility density melting point boiling point

4. Background Whole books have been published which contain nothing but physical properties Chemical Rubber Company Handbook of Chemisty and Physics

5. Background In this experiment we will consider three physical properties: Solubility Density Boiling point These measured properties will then be compared to a table of known compounds to identify your unknown substance

6. Technique – Care Of The Electronic Balance Never place chemicals directly on a balance pan. Do not place hot objects on a balance pan. Inform your laboratory instructor if the balance is not level or at the zero mark when empty. Always make sure that the balance is at zero before you begin weighting and after you finish weighing. Immediately clean up any chemical spills on or near the balance.

7. Technique - Using the Electronic Balance Check that the balance reads 0.000g, if not press the “tare” button. Place the empty container or weighing paper on the balance, wait for the balance to settle, and record the mass. Remove the container from the balance and place the substance or object to be weighed in the container. Replace the container on the balance, wait for the balance to settle, and record the mass. The mass of the sample can be obtained by subtracting the mass of the container from the mass of the container AND the mass of the sample.

8. Technique - Using a Graduated Cylinder A graduated cylinder is a device used to accurately contain a known volume of a substance.

9. Technique - Using a Graduated Cylinder A graduated cylinder is a device used to accurately contain a known volume of a substance. The cylinders are usually marked in units that are 1% of the cylinder’s total volume.

10. Technique - Using a Graduated Cylinder A graduated cylinder is a device used to accurately contain a known volume of a substance. The cylinders are usually marked in units that are 1% of the cylinder’s total volume. To read the cylinder correctly, the volume must be read at the bottom of the meniscus.

11. Technique - Using a Graduated Cylinder A graduated cylinder is a device used to accurately contain a known volume of a substance. The cylinders are usually marked in units that are 1% of the cylinder’s total volume. To read the cylinder correctly, the volume must be read at the bottom of the meniscus. To ensure an accurate reading, place the graduated cylinder on the counter and get at “eye-level” to read the cylinder. Be sure to record as many numbers (digits) as reasonable for the graduated cylinder you are using.

12. Technique - Solubility

13. Density

14. Density

15. Technique - Solubility

16. Technique - Solubility

17. Technique - Solubility

18. Technique - Boiling Point Place 30 drops unknown liquid in a 10mm x 75mm (small) test tube. Place a capillary tube into the test tube open end down. Using a rubber band, attach a thermometer to the test tube.

19. Technique - Boiling Point Place 30 drops unknown liquid in a 10mm x 75mm (small) test tube. Place a capillary tube into the test tube open end down. Using a rubber band, attach a thermometer to the test tube. Place the entire apparatus into a water bath.

20. Technique - Boiling Point Warm the water bath (and your apparatus) until a fast, steady, stream of bubbles appears at the capillary. Remove the water bath from the heat. Watch the apparatus carefully. When the bubbles quit emerging from the capillary, read the thermometer. This is the boiling point of the liquid.

21. Example Data Part A - Solubility Soluble Insoluble 1. Solubility in water ___S____ ________ 2. Solubility in 95% ethanol ___S____ ________ Solubility in acetone ___S____ ________ Solubility in cyclohexane ___S____ ________ Part B - Density of Liquid Trial #1 Trial #2 1. Mass of 10 mL graduated cylinder _25.312g__ _25.313g__ 2. Mass of 10 mL grad. cylinder + unknown _27.5635g_ _27.855g__ 3. Mass of unknown __2.2515g_ __2.542g__ Volume of unknown __2.85mL_ __3.10mL_ Density of unknown _0.79g/mL_ _0.82g/mL_ 6. Average density of unknown _0.81g/mL___ Part C - Boiling Point of Liquid ___68oC__ _72oC___ Average Boiling Point of Liquid 70oC

22. Example Data Solubility: Water, Acetone, Ethanol, Cyclohexane Matching Compounds: Substance Density(g/mL) Boiling Point(oC) Acetone 0.79 56 2-Butanone 0.81 80 t-Butyl alcohol 0.79 82 Ethanol 0.79 79 Ethyl Acetate 0.90 77 Methanol 0.79 65 1-Propanol 0.80 97 2-Propanol 0.79 82

23. Example Data Density: 0.81g/mL Matching Compounds: Substance Density(g/mL) Boiling Point(oC) Acetone 0.79 56 2-Butanone 0.81 80 t-Butyl alcohol 0.79 82 Ethanol 0.79 79 Ethyl Acetate 0.90 77 Methanol 0.79 65 1-Propanol 0.80 97 2-Propanol 0.79 82

24. Example Data Boiling Point: 70oC Matching Compounds: Substance Density(g/mL) Boiling Point(oC) Acetone 0.79 56 2-Butanone 0.81 80 t-Butyl alcohol 0.79 82 Ethanol 0.79 79 Ethyl Acetate 0.90 77 Methanol 0.79 65 1-Propanol 0.80 97 2-Propanol 0.79 82

25. Example Data Based on the data, the unknown is: Methanol Notice that the data did not fit exactly

26. Textbook Corrections Page 4, table 1.1 Add the following substance:Methyl tert-butyl ether (MTBE) density: 0.74 boiling pt.: 55oC solubility:  water: I acetone: S ethanol: S cyclohexane: S

27. Textbook Corrections Page 5, Part A, 5. Repeat part B, #1 - should be “A” Page 5, Part B,2. Repeat part A, #1 - should be “B” Page 82. In part B,  - should be “A”

28. Safety Unknowns and solvents (acetone, ethanol and cyclohexane) are flammable. Glassware and stands may be hot.

29. Waste Disposal Solvents and unknowns go into the waste container in fume hood.