Properties of Matter Lab

Introduction

Matter is anything that has mass and occupies space, that is, everything you see and a large number of things that you don’t see. In order to distinguish between different types of matter, we consider their properties or characteristics.

Properties can be divided into physical and chemical properties. Physical properties are those that may be investigated without changing the composition of the substance. Chemical properties describe how the substance may change its composition – either spontaneously, or in combination with other substances. For example, heating alcohol to the boiling point will produce a gas. This is a physical change because the substance did not change, just its state of matter. Whereas burning alcohol with oxygen to give carbon dioxide and water is a chemical change. New substances are created after a chemical change.

Liquids are the most convenient physical state to study physical and chemical properties. In today’s laboratory, you will examine an unknown liquid for both its physical and chemical properties. The objectives of the experiment are:

  1. To learn the difference between physical and chemical properties.
  2. To learn how to make observations in the lab.
  3. To make conclusions based on observations in the lab.
  4. To familiarize you with the lab environment.

PART 1: OBSERVING PHYSICAL PROPERTIES

In this part of the experiment, you will examine a variety of physical properties of your unknown. By comparing your observations to a list of properties of “known” substances, you will be able to identify your particular sample.

  1. Appearance and odor
  1. Obtain about 10 mL of an unknown in a small beaker. A letter will identify the unknown. Write the letter of your unknown on your data sheet.
  2. Describe the appearance on the Data Sheet – Line 1 (Appearance.) Use this 10 mL for the rest of the experiment. Appearance may include color, clearness/cloudiness, and viscosity (how thick the liquid is.) A final caution: colors can vary. Even if a slight amount of impurity is present, a “clear” sample can look yellow. The take-home message is that the “appearance and odor” of a sample is helpful, but they are not enough to make a conclusion about the identity of your unknown.
  3. Raise the beaker containing the unknown so that it is level with and about three inches away from your nose. Wave your hand over the top of the beaker to waft the odor toward you. Describe any odor on Line 2 (Odor) on the Data Sheet. Odors are often described by relating them to common smells found in the home.
  1. Density
  1. Take a clean, dry beaker and place a clean, dry test tube inside. Weigh both together. This is the tare weight. Write the mass on line 4 (Mass of beaker + test tube, g). (Yes, you did skip line 3.)
  2. Pipet about 2 mL of your unknown into the test tube. Record the exact volume on line 6 (volume of unknown, mL).
  3. Reweigh the beaker + test tube + unknown. This is the gross weight. Record your results on line 3 (Mass of beaker + test tube + unknown, g).
  4. Calculate the mass of the liquid you added and record it on line 5 (Mass of unknown, g). This is the net weight.

  1. Calculate the density in g/mL by dividing the mass on line 5 by the volume on line 6. Record the density on line 7 (Density of unknown, g/mL). Density is an excellent physical property for identification. The main caution for you is the possibility of obtaining an incorrect value if the liquid is volatile (evaporates quickly). If you do not weigh your sample quickly, some of the liquid may evaporate. This would give you a very low value for the density.
  1. Boiling point
  1. Assemble the heating arrangement shown in the diagram using a ring stand, ring, wire gauze, and Bunsen burner.
  1. Half-fill a beaker with water. Place the beaker on the gauze.
  2. Pipet some unknown into a test tube to a depth of about 1 inch. Put the test tube inside the beaker. Make sure that the level of the unknown is below the level of the water.
  3. Add a boiling chip to the unknown inside the test tube.
  4. Start the Bunsen burner and adjust it until there is a blue flame.
  5. Begin heating the water bath.
  6. Watch your unknown liquid while it’s heating.
  7. When the unknown begins to boil, measure its temperature by inserting a thermometer into the unknown liquid. Sometimes, the water may boil before the unknown boils. This is because the sample's boiling point is above 100 oC and you can not determine its boiling point from this procedure. Merely note that the boiling point as "above 100 oC." Be sure a boiling chip sits in the unknown, to ensure a bubble source so that you will know whether the sample is boiling. The temperature of a slowly boiling (simmering) or a vigorously boiling liquid are at the same temperature, but that it is easy to mistake simple effervescing of dissolved gases as “simmering.” Vigorous boiling will let you know for sure. Also be aware that if the sample is vigorously boiling, the vapors immediately above the liquid are also at the boiling temperature – you may want to play with this phenomenon, observing that the thermometer reading is the same both in the liquid and immediately above (a few millimeters).
  8. Record this temperature on line 8 (Boiling point of unknown, oC).
  1. Solubility
  1. Pipet about 2 mL of your unknown into two test tubes.
  2. To the first test tube, carefully add about 2 mL of water. Mix the liquids as the teacher demonstrated for you. Do the liquids mix or separate and form two layers?

If they mix, then the unknown is soluble or miscible with water, otherwise it is insoluble. Record your observation on line 9 (Soluble in water?)

  1. To the second test tube, add 2 mL of cyclohexane. Record the solubility or insolubility of the unknown in cyclohexane on line 10 (Soluble in cyclohexane?)

Discussion: Actually, all substances are at least partially soluble in all other substances. For example, even though methyl benzoate is listed as not soluble in water, about 100 mg will dissolve in a liter of water. However, here we are discussing extreme solubility where both substances will dissolve in any proportion with the other.

  1. Identification

Compare the data in Table 1 to your observations. Try to identify your unknown just by its physical properties. Record your compound on line 11 (Identification.)

PART 2: TESTING CHEMICAL PROPERTIES

Chemical properties may be more difficult to describe in detail than physical properties, but they are more accurate for identifying substances. Indeed, before the days of accurate measurement of weight, volume, and temperature, it was chemical properties – reaction with other compounds, evolution of gas, changes of color, evolution of heat, production of stinky smells, etc. – that characterized and identified a substance. In this section, you will observe a sampling of chemical properties.

  1. Combustion in Air
  1. Pipet 1 mL of your first unknown into an evaporating dish.
  2. Light a splint away from the dish.
  3. Carefully attempt to ignite the unknown in the evaporating dish.
  4. Record your observation on line 12 (Flammable?)
  1. Reaction with sodium (to be performed in the hood by the teacher.)
  1. Put about one inch depth of each unknown into separate beakers.
  2. Take these to the hood and have your teacher bring a piece of sodium.
  3. Using the tweezers, take the piece of sodium and lay it on a paper towel.
  4. Dry the sodium and quickly add it to the sample of your first unknown.
  5. Record your observations on line 13 (Reaction with sodium?)

CAUTION: Sodium reacts violently with water.

Do NOT touch with hands or ingest !!!!!

Data Sheet

Properties of Matter

Name: ______

Letter of Unknown ______Date: ______Period: ______

PHYSICAL PROPERTIES
1. Appearance
(color, clearness/cloudiness, viscosity)
2. Odor
3. Mass of beaker + test tube + unknown, g
4. Mass of beaker + test tube, g
5. Mass of unknown, g
(Step 3 - Step 4)
6. Volume of unknown, mL
7. Density of unknown, g/mL
(Step 5 / step 6)
8. Boiling point of unknown, oC
9. Soluble in water? (Yes or No)
10. Soluble in cyclohexane? (Yes or No)
11. Identification
CHEMICAL PROPERTIES
12. Flammable?
13. Reaction with sodium? (Describe the reaction.)
14. Do the chemical properties agree with your identification in 11? If not, what is your final identification?
Table 1: Properties of Various Liquids
Substance / Appearance/Odor / Density
(g/mL) / Melting Point, oC / Boiling Point, oC / Solubility / Chemical Properties
Water / Cyclo-hexane / Flamma-bility / Reaction with Na
Acetone / Clear, mobile, solvent odor / 0.79 / -94 / 56 / Yes / Yes / Yes / No
Benzaldehyde / Clear, oily, almond color / 1.05 / -26 / 179 / No / Yes / Yes / No
Carbon tetrachloride / Clear, heavy, solvent odor / 1.60 / -23 / 77 / No / Yes / No / No
Chloroform / Clear, heavy, sweet odor / 1.50 / -63 / 62 / No / Yes / No / No
Cyclohexane / Clear, mobile, sweetish odor / 0.78 / 6 / 81 / No / Yes / Yes / No
Dichloro-methane / Clear, mobile, sweetish odor / 1.33 / -95 / 40 / No / Yes / No / No
Ethyl acetate / Clear, mobile, solvent odor / 0.91 / -84 / 77 / No / Yes / Yes / No
Ethyl alcohol / Clear, mobile, spirit odor / 0.79 / -114 / 78 / Yes / Yes / Yes / Slow
Ethylene glycol / Clear, syrupy, no odor / 1.11 / -16 / 198 / Yes / No / Difficult / Slow
Glycerin / Clear, syrupy, no odor / 1.26 / 18 / 290 / Yes / No / Difficult / Slow
Hexane / Clear, mobile, sweetish odor / 0.66 / -95 / 69 / No / Yes / Yes / No
Methyl benzoate / Clear, oily, pleasant odor / 1.09 / -12 / 200 / No / Yes / Yes / No
Nitrobenzene / Off-white, almond odor / 1.20 / 6 / 211 / No / Yes / Yes / No
Toluene / Clear, refractive, benzene-like odor / 0.87 / -95 / 111 / No / Yes / Yes / No
Water / Clear, no odor / 1.00 / 0 / 100 / Yes / No / No / Yes