Mystery Powder Lab

Mystery Powder Lab - With a twist!

I had this tucked away in my files and decided to pull it out.  We are looking at the properties of matter.  This is a great 5E activity using the holidays as motivation.

Chemical Changes

So much fun!  This activity is done after reading about states of matter, physical and chemical changes.
Before doing any experiments, we review our safety standards and decided that this was a 6.  It is glue and will make a horrible mess with fabric, as well as your hair.  So, roll up your sleeves and tie back your hair!


GAK - from Steve Spangler's Science

1tbs Borax laundry booster (found at Target)
50mL warm water
mix until Borax is dissolved

In large zip lock bag mix
1 bottle 8oz glue
200mL water
food coloring

Add Borax mixture to glue mixture

Knead with hands until it forms a lump.  Keep mixing until there isn't water left.  It will feel like smooshing grapes.

The students then explore the properties of GAK.  We listed the solid and liquid properties and discussed what the students thought it was.

We looked up information about polymers and non-Newtonian substances.
We also discussed the effects of pressure.

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?