Physical Science 
Density - 

We started by brainstorming all we know about density.  Density is basically how much stuff is in things.  It is the relationship between an object's mass and volume.  So, the volume of two objects is the same.  We can find out the mass by weighing the objects.  The object with the greater weight will have the greater density.
(Density = mass divided by volume)

To test this, we chose several liquids:  liquid soap, rubbing alcohol 91%, baby oil, and water.  Found these at the dollar store!  

We measured 20mL of each liquid and recorded the amounts in our notebooks.  We made observations of each liquid, describing its properties.

Next, we measured the mass of each.

We looked in our text book and were reminded that objects with less density float, and objects with higher density sink, as seen in a picture with a cork floating and a rock sinking.  Which brought discussion of the sink and float experiments they do in the lower grade.  They related this to solids, but had difficulty with the liquids.

We then made predictions about the density and how this would be observable. 
We then mixed the rubbing alcohol and baby oil.

The students recorded observations and watched as the liquids bubbled, the separated forming two layers.  

Then, I asked the students to tell me which liquid was the top, and which was on the bottom.  Even with their data, they had a hard time deciding which was which.  We decided that if we colored one liquid it would be easier to see.  I demonstrated adding food coloring to baby oil and rubbing alcohol separately and found that the baby oil did not mix with the food coloring, while rubbing alcohol did.  (this will be covered next week with mixtures and solutions).  Therefore, if we mix food coloring with the liquids, the one that turned red would be the rubbing alcohol.  

First, the students dropped 4 drops of food coloring into the vial.  It displayed quite a show as it dropped down through the liquids.  What does that say about its density?  We will come back to that.  Then the student gave it a shake.  When it finally settled, there was a red layer and a clear layer.

The students wrote their conclusions based on their recording. Since the liquids had the same volume, the liquids that weigh more have a higher density and will sink below that with a lower weight and density.

This will lead to a discussion about recent oil spills and clean up.  How have engineers developed a method of clean up based on the density of the liquids?