Activity 5: Density

One of the most common attributes of chemical materials that we observe and feel on a daily basis is the density of materials.  One of the things we notice in the structures of atoms, is that the atom is mostly space, with a small heavy nucleus and very light electrons orbiting the nucleus. So, how heavy something feels is related to how many protons and neutrons are in the nucleus of atoms that make up molecules.  For example, aluminum is much lighter than iron.  The "heaviness" of a material is quantified through a characteristic called density.
For this activity, and future ones, we will introduce the usage of simulations and gaming to aid in our understanding of chemical principles. The simulation package we will utilize can be found at this site:
http://phet.colorado.edu/
There are many of this types of things being developed on the web, I have found this one to be excellent for many reasons.
1. It is free!  This is an activity supported by the National Science Foundation and many others to aid students and educators.
2. I find the interface to be easy and good for entry level science students and even advanced students.  I have found that my 2nd grade son can use these simulations.
3. The science principles covered are very good, and the simulations are quite "real."
4. There is a developing support community for these simulations.  For example there is a section for teachers in which there are pre-developed activities and a way to share your own activities.
For future educators and parents, I encourage you to encourage your future school districts to utilize these types of simulations in science education.  Students tend to become engaged, and it can alleviate some of the costs and struggles of doing actual experiments in the classroom.

To complete Activity 5, complete the tasks below:
1. Run the Build an Atom simulation http://phet.colorado.edu/en/simulation/build-an-atom and build a neutral lithium atom and a neutral boron atom.  Take a picture, or a screen shot, of these two atoms and place them on your blog.  List the number of protons, neutrons and electrons for each. Also look up and post the density for each of the elements on your blog.

Lithium
Protons:3
Neutrons:3
Electrons:3
Density: 0.534 g·cm⁻³

Boron
Protons: 5
Neutrons: 6
Electrons: 5
Density: 2.08 g·cm⁻³

2. Define density and the equation for density and post on your blog.

•  
  the degree of compactness of a substance
•  density=mass/volume

3. Run the Density simulation http://phet.colorado.edu/en/simulation/density and complete one(your choice) of the prepared Teaching Ideas and post your results on your blog. The activity you choose should be one of the student intended activities.

 

Density

Introduction:  Density is a physical property of matter that is calculated by dividing the mass of an object by its volume.  Volume can be computed for a regular object by multiplying length x width x height.  Another way to compute volume is by submerging an object into a liquid.  You must record the starting volume of the liquid and the final volume after the object has been submerged.  Then subtract the starting volume from the final volume. 

Procedure:

• Open the internet browser and enter the address:  http://phet.colorado.edu
• Click on “Play with Sims” and select “Chemistry” from the menu on the left.
• Open the “Density” Simulation and select “Run Now”

Objectives:

• Describe how the concept of density relates to an object's mass and volume.
• Explain how objects of similar mass can have differing volume, and how objects of similar volume can have differing mass.
• Measure the volume of an object by observing the amount of fluid it displaces.
• Identify an unknown material by calculating its density and comparing to a table of known densities.

Investigate:

1.      On the Blocks menu (top right) select Same Mass. 

2.     One at a time, take a block, lower it into the liquid, and record its volume.  If it floats, you will need to hold it under the water to record its volume.  Then compute each block’s density.

SAME MASS

Blue:               
 mass:5 kg =1.0 kg/L
volume:5 L

Yellow                      
mass: 5kg=0.5 kg/L                                  

 Volume: 10 L

Green                     
mass : 5=2 kg/L 
 Volume: 2.50

Red                          
mass: 5=4.0 kg/L                                  

 Volume: 1.25 L

3.     Repeat for Same Volume.

Blue:                
mass: 6 kg = 1.2 kg/L                           
 volume 5 L         

Yellow                     
 mass: 6 kg= 1.6 kg/L              

 volume: 5 L

Green                     
mass: 4 kg= 0.8 kg/L                                    

volume: 5 L

Red                          
mass: 2kg= 0.4 kg/L 
volume: 5 L

4.     Repeat for Same Density

Blue:               
 mass: 3kg=0.8kg/L                         
 volume: 3.75 L          

Yellow                      
mass: 4 kg=0.8kg/L                                                   

volume: 5 L

Green                      
 mass: 2 kg=0.8kg/L                              

   volume: 2.5L

Red                          
 mass: 1kg=0.8kg/L

  Volume: 1.25L

5.     Repeat for Mystery.  This time  you will also have to take the mass of each object.  After computing the density,  select Show Table and identify each object.

          IDENTIFICATION

A:  Blue                    
mass:0.64kg=0.64 kg/L                        APPLE                                 
volume:1L          

B : Yellow 
 mass: 65.14kg=19.27kg/L                 GOLD            
 volume: 3.38 L

C  :Green                              
mass: 4.08kg=0.70kg/L                      GASOLINE              

volume: 5.83 L

D : Red                                
 mass: 3.10kg=0.92kg/L                           ICE                      

Volume: 3.38 L

E:Purple                                 
mass: 3.53kg =3.53kg/L                       DIAMOND
Volume: 1 L    

4. Complete the Mystery Blocks activity on the Density simulation.  Post on your blog the data you collected (mass, volume, and density) and the identification of the material and the known density.
5. Identify and post on your blog the Science Standards that could be met through these activities completed in Activity 5

A.4.2 When faced with a science-related problem, decide what evidence, models, or explanations previously studied can be used to better understand what is happening now

 

 C.4.4 Use simple science equipment safely and effectively, including rulers, balances, graduated cylinders, hand lenses, thermometers, and computers, to collect data relevant to questions and investigations