Chemistry Unit 1 Name:________________________
(Procedures A—D are courtesy of Mr. Sogo) Lab Partners:__________________
Overview: You will obtain a sample of white powder. This powder is actually a mixture of two chemical substances. You will investigate the properties of this mixture and compare them to the properties of the individual components.
Procedure A: General
1. Weigh out about 2.5 grams of powder Mixture into a weighing boat. Record the mass exactly. (i.e. if you get 2.7 grams, write down 2.7 grams, not 2.5 grams) Mass:______________
2. Observe the powder and try to distinguish the two types of chemicals. Record your observations.
3. Obtain a scoop of powder A in a small test tube. Powder A has the chemical formula CaCO3.
4. Obtain a scoop of powder B in a small test tube. Powder B is a "mystery" compound.
Procedure B: Fire!
5. Get out your Bunsen burner and light it. Adjust the flame according to your instructor’s guidelines. Note: for the next few steps, try to heat gently--don't "burn to a crisp "
6. Heat the small test tube with powder A in the Bunsen burner flame. Record observations of any change that occurs here.
7. Heat the small test tube with powder B in the Bunsen burner flame. Record observations of any change that occurs here.
8. Hypothesize what you will see if you heat a sample of the mixture in the Bunsen burner flame. (Write this hypothesis before you go on to the next step.)
9. Go ahead and try heating a sample of the mixture taken from your weighing boat in the Bunsen burner flame. Record observations and give a statement that relates to your hypothesis.
10. Throw out the cooled blackened tubes. Empty the other tube into the trash and then rinse out the tube and set it to dry upside down on a test tube rack.
Procedure C: Acid
11. Pour some 1 M HCl into three clean medium-sized test tubes. Try to fill the tubes about half-way full.
12. Add a scoop of powder A to the first tube. Record observations.
13. Add a scoop of powder B to the second tube. Record observations.
14. Hypothesize what you will see if you add a scoop of the mixture to the third tube:
15. Perform the experiment and record observations. Make a statement that relates to your hypothesis.
Procedure D (BONUS): Separating the mixture
16. Using whatever methods you see fit, separate the mixture into pure components. By now you should have some idea as to the identity of the "mystery substance" powder B. If the only way you can separate the mixture is by "destroying" one of the substances, that's OK. If you get ONE of the components pure, demonstrate this to the teacher and clearly describe your method below, you will receive the bonus. You will need to do at least one test to PROVE that what you end up with is pure. Note: the best method for separating these two substances will require you to think beyond "fire" and "acid". In other words, you will need to think a bit creatively.
For bonus credit, describe your method(s) in detail in the space below and discuss your results. Also describe how you test for the purity of your final product.
1. Calcium carbonate is made up of three types of atoms
a) What types of atoms are in calcium carbonate?
b) Why is calcium carbonate NOT considered to be a mixture?
c) Calcium oxalate has the formula CaC2O4. In what way is this like calcium carbonate, and in what way is it different? Do you think calcium oxalate would behave the same as calcium carbonate?
2. In the space below, list some "properties" of substance A and substance B. Note: a property is anything which could be used to describe the substance.
Substance A Substance B
3. Consider the following statement: An element or a compound has one set of properties, but a mixture retains the properties of each of its constituents.
Do the experiments you did in this lab support this statement? Explain.
Going a Step Further – Does Anything Happen to Powder A?
(Actually I have substituted NaHCO3 for CaCO3 as Powder A. They are similar but not the same!)
PROCEDURE:
1. Weigh a clean, dry and empty crucible and lid. Record the mass. Mass (1)___________
2. Put about 3 grams of Powder A into the crucible and weigh the new combination accurately. Mass (2) ____________
3. Observe the powder and record your observations.
4. Put the crucible on a clay triangle suspended above a bunsen burner on a ring stand.
5. Light the bunsen burner and adjust height of the ring and the flame so that the tip of the smaller light blue flame is contacting the bottom of the crucible.
6. Heat the covered crucible for 5 minutes.
7. Let this cool.
8. Weigh the cool crucible and powder. Record the mass and any changes in the appearance of the powder. Mass (3) ____________
9. Heat the covered crucible and powder again for 3 minutes.
10. Again let this cool and weigh it. Record the mass. Mass (4) ____________
11. Has the mass (4) changed from mass (3)? If these two differ by more than 0.1 gram, then heat the crucible a third time for 2 minutes.
12. Let the crucible cool and weight it. Mass (5) ____________
CALCULATIONS:
1. Determine the mass of Powder A before it was heated.
2. Determine the mass of Powder A that was “lost” during the heating.
QUESTIONS: (Feel free to answer questions on another sheet if necessary.)
1. Did you notice any difference in appearance in the powder before and after heating? If so, what difference?
2. Given the chemical formula of Powder A is NaHCO3, what do you think caused the loss of mass from the powder?
3. Has the law of conservation of matter been broken in this experiment? Explain.
