In this week's session our young chemists learned about how fascinating density can be! We first reviewed what molecules are (2nd session) and how molecules of different things look different and behave differently. We then talked about three particular types of molecules: water, alcohol, and oil. The little chemists recalled how alcohol was 'lighter' than water from a previous session and we talked about how things 'mix' and what that means. I introduced the word "DENSITY" and we talked about how the size of the molecules is important when mixing things - Which molecules are the smallest? Can certain types of molecules 'get by' or 'push through' other types of molecules? Density was defined as how 'big' something is and how much space it takes up in the world - like how water can take up some or most space in a container. We then made predictions about what would happen if we mixed all of the three types of molecules: water, alcohol, and oil.
To be able to identify the three different types of molecules we used food coloring: yellow for water, red for alcohol, and green for oil. Then it was time to begin testing our ideas and see if our predictions were correct!
Right from the get-go the chemists made some discoveries and observations about the liquids - What type of smells were coming from the containers? What what going on with the green food coloring in the oil? Why did it look like bubbles?
Once all three liquids were mixed, the little chemists continued to make observations - they noticed how the green 'bubbles' in the oil were moving downward towards the yellow water and was mixing with it! They noticed that the red alcohol was "going through" the oil, which molecules were 'bigger and took more space? What were these molecules showing us about density?
To conclude our session I added a new component to our experiment - we mixed two solids into the mixed liquids to see how these solids would react with the liquids and their densities. We added some baking soda powder along with a tablet of alka seltzer! Our young chemists predicted once again what would happen and the majority predicted an explosion so we all had put our goggles on for safety. Below is a pic of what the chemists observed.
Yes, all of the chemists held their tops down as they saw the red and green colors mix and rise to the top. Thankfully there were no explosions but the chemists did observe how bottle expanded at the bottom/base and how the plastic tightened. Yes, something fishy happened with density - the entire bottle showed that all these molecules mixed together created something 'bigger' which was took more than the space allotted by the original bottle. Hopefully none of the chemists bottles exploded on the way home. (I apologize if they did!) - DENSITY!
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