Mystery of the Miraculous Molecular Material

Purpose: to observe the properties of ionic and molecular compounds and use these observations to determine which mystery material(s) is(are) molecular

Background:

The ions in ionic substances are held togther by electric charges. All of the ions have charges so they all stick together to make crystals. While in some ionic substances the ions will separate when the substance dissolves in water, in air they stick together tightly in solid crystals. It takes a lot of heat to get the ions to flow over each other to create a liquid and even more heat to make them separate into a gas.

The atoms in molecular substances are held together in molecules by extremely strong covalent bonds. However, the molecules have very little attraction for other molecules of the substance. This means that it will take very little heat to make the molecules flow over each other to form a liquid or separate from each other to form a gas. Some molecules will separate from some solid molecular substances at room temperature. Human beings come equipped with a special proboscis that allows us to detect the presence of many chemicals in the air. We will use this tool to detect whether any molecules escape from the solid.

Materials:

Bunsen burner Mystery Material A

test tube Mystery Material B

extra long test tube Mystery Material C

test tube tongs Mystery Material D

safety glasses Mystery Material E

human proboscis Mystery Material F

Safety instructions:

Do not touch any of the mystery materials!!!

Material B is toxic. Do not snort material B.

Material C is flammable. Do not bring any flames near Material C.

Mystery Material F is toxic and corrosive. Do not smell Mystery Material F! Do not allow vapours from Mystery Material F to escape into the laboratory. Do not inhale vapours from Material F. Mystery Material F is also notable for its staining ability. If it touches your skin or your uniform, it will not wash off!

Don't mess with Mystery Material F!

Note: Hot test tubes look exactly like cold test tubes, only the hot ones can melt your fingers.

Procedure:

1. Observe materials A-E using the observation table as a guideline.

2. Obtain several crystals of Material E in a test tube from your lab station.

Hold the test tube with test tube tongs and heat it over a Bunsen burner. Record any changes in state and how much time was required. Allow the test tube to cool.

3. Obtain a couple of crystals of Material F in an extra long test tube from the instructor.

Hold the test tube with test tube tongs and heat it over a Bunsen burner for no longer than 20 seconds. Stop heating if the vapours reach halfway up the test tube. Do not allow the vapours to escape into the laboratory. Record any changes in state and how much time was required. Allow the test tube to cool in an upright position so that no vapours escape.

Don't mess with Mystery Material F!

4. Place the test tube with material E in it into the tub of water.

Place the test tube with material F in it into the box it came from.

Observations and Conclusions:

Do not heat material F for longer than 20 seconds!

Conclusions:

Using your observations, decided whether each material was ionic or molecular.

Your instructor will provide the formula for each material. Look at the types of elements in each material. Were you correct about which ones were molecular?