The Rainbow Density Lab With new and improve d significant figures for doing calculations!!!!!!!!

Background Information:

            Density is a physical property that can be used to identify a substance.  The density of an object is the same regardless of how much of the substance is present.  For example, the density of gold is 19.3 g /cm³.  Whether you have a pure gold earring, brick or crown, their densities will always be 19.3 g /cm³.  The density of water is 1.00 g/ml.  Whether you have a drop, glass, or a bucket the density will always be 1.00 g/ml.

The equation for density is                         

Procedure:

1.        Clean dry and mass a 10 ml graduated cylinder.  If there is a small amount of water in the bottom of the cylinder shake the water out as demonstrated by your teacher.

2.       Fill the graduated cylinder with between 6.0 and 9.0 ml of Solution A

3.       Record the exact volume with the correct number of significant figures on your data table.

4.       Find the mass of the graduated cylinder + Solution A and record this value on the data table.

5.       Calculate the mass of Solution A.  Record the value in your data table.

6.       Calculate the density of Solution A.  Keep track of significant digits.

7.       Discard Solution A in the sink. 

8.       Wash out the graduated cylinder and repeat steps 1-6 for solutions B, C, and D.

9.       When completed show your table to your teacher before moving on to the next step.

Data: Make sure to include units with all of the values

	Color	Mass of empty cylinder	Mass of cylinder with solution	Mass of solution	Volume of Solution	Density of Solution
Solution A
Solution B
Solution C
Solution D

 

Part II

1.       Obtain a small test tube from your instructor.  Add a small amount of your most dense solution to create a bottom layer.  The exact amount is not important, but the layer needs to be visible.

2.      Add the remaining solutions in order of decreasing density.  TAKE GREAT CARE when adding additional samples by tilting the test tube at an angle and inserting the pipette near the surface of the liquid.

3.      Congratulations!!!! You have made a density rainbow.  Show the rainbow to your teacher to have your lab initialed                                                          

Teacher’s Initials _____________

                                                OR

Sorry, you did not make a density rainbow.  You can try again tomorrow before school if you do not want to lose points on this part of the lab.  (before then think about what you could have done wrong.)

Questions:

1.       What is the purpose of a significant digit?

 

2.      How do you handle significant figures when adding and subtracting?

 

3.      How do you handle significant figures when multiplying and dividing?

 

4.      What are some possible sources for error in this experiement?