This week our young chemists learned about states of matter and how some liquids are heavier than others even if they look the same! We began by talking about the three states of matter. In particular we talked about how the tiny stuff that makes up matter are called molecules and how the way they are organized is what makes something a solid, a liquid, or a gas. First we looked at what the molecules look like in each state:
To help them understand this concept we played a game in which students had to pretend they were all molecules and had to become a solid, a liquid, and then a gas. They did a great job collaborating and discussing their ideas. Their models were fantastic! For a solid they all hugged and huddled up together in a tight "ball". For a liquid they held hands, but only pinkies. To demonstrate a gas they all separated and some jumped, others walked around each other, some even bumped heads to demonstrate how gas molecules are in constant motion!
Once everyone had a firm grasp for what each state of matter looks like we then talked about liquids in particular. Can one liquid be heavier than another? How could we test the idea? I explained that we would test out the idea by comparing two liquids that look very much alike: rubbing alcohol and water. To do so, the young students used a constructed scale using cups, a ruler, and a pencil (had to throw in some engineering!) and 2 paper bag strips dipped in alcohol and water respectively. The idea is that the ruler would tip over to the heavier side. We discussed why the ruler tipping to one side could signify that one liquid was heavier than the other. Students predicted that one liquid would begin to dry up faster than the other. We talked about what "drying up" means and our chemists said that it meant "the molecules would separate" and become "a gas." These young chemists are quite inquisitive and observant! The students shared their predictions about which liquid - water or alcohol, would "dry up" first. Here they are setting up the experiment.
While we waited for the liquids to "dry up", we conducted a demonstration to see if it would give us yet another clue as to what liquid was heavier. To do so, I set up a beaker with green (food coloring) water to boil, then filled a cup with alcohol and put a couple of red food coloring drops. I asked the students to predict what would happen if I poured the red alcohol into the green boiling water. Some students thought that an explosion would take place so we all put on goggles to be safe. Before pouring in the red alcohol into the green water we talked about colors and what color is made when you mix red and green, students thought that a dark color would appear. We went ahead a mixed it, to their surprise nothing blew up and the red alcohol went to the top of the beaker where it would disappear.
I asked our chemists to share with a friend why they thought the red alcohol was not mixing with the green water. Some students thought that perhaps alcohol was "lighter" than water, others were wondering where the alcohol went since it was leaving the top as well? We then talked about liquids and gases once again and how perhaps alcohol is not as heavy as water because it becomes a gas faster. We went back to check on our constructed scale experiment to check if indeed our predictions were correct or not. Below are some pictures of what students saw:
Students made the observation that the paper strip that had the alcohol was completely dry while the strip that had the water was still a little wet. Students also noted that the side that had the strip with alcohol was dipped while the side that had the strip with water was higher. Based on their observations our young chemists concluded that although water and alcohol look the same, alcohol is actually a "heavier" liquid.
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