Teachers Being Students: How Many Molecules Are in a Drop of Water?

Middle school students are often afraid of being perceived as stupid when trying to solve problems in class. When they see adults, in this case their teachers, go through the same struggles, they are more willing in the future to test and share their ideas. I want to thank the very courageous non-science teachers at my school for volunteering to be a part of this video. This activity covers NGSS practices: (2) Developing and using models. (5) Using mathematics and computational thinking. It also covers the NGSS crosscutting concepts: (3) Scale, proportion, and quantity.

Sources used: The Naked Scientists and The Mega Penny Project

Teachers Being Students: "What is Mass?"

Four brave non science teachers at my school were asked the question, "What is mass?"  The teachers struggled to answer the question. Students learn science concepts best by confronting what they know about a concept, usually a misconception, and then trying to fit new and often conflicting information with that knowledge. Students often view this as confusing, but studies have shown that they learn a science concept better (see Veritasium's talk on effective education movies). The purpose of this video is to show my students that teachers/adults go through the exact same process.

Does Mass Affect the Sinking/Floating of Objects?

Students have a major misconception that mass determines whether an object floats or sinks. This is an activity that forces students to deal with that misconception and hopefully break it. The following materials are needed:

1. large pumice stone
2. Density Sphere Experiment Kit
3. large fish tank of water 

Have the students read the statement, "Objects that are high in mass, sink in water." Have the students show in some way if they agree with the statement, disagree with the statement, or are somewhat in between. Have them explain why they think that way and give examples. Then present the students with the list of all of the items to be placed into the tank, arranged according to their masses. Do not show the objects to the students. Have them write a hypothesis for each item (on whether they will sink or float) based only the property of mass. Then drop each item one by one, in order of their masses, into the water. Have students record the results. The students will realize that mass has nothing to do with whether an object sinks or floats. Then show the students the objects' densities. Hopefully they see the pattern of those objects with densities less than one float, and those with densities greater than one sink. It is not important to explain what density is at that point, but just that it is a property of matter that is vital in determining if an object floats or sinks.

Mixtures

A major standard our students have to learn is the difference between elements and compounds. Compounds are substances that are made of two or more elements bonded together. The elements that comprise a compound have different properties when they are bonded together than when they are separated. Students have great difficulty with this. I introduce the unit by doing a simple activity on mixtures. Educational Innovations sells a simple Mixture Separation Challenge kit. Students are first forced to separate the mixture into 3 groups. Students usually use the simplest property of color to do it. There are other properties such as relative density or optical properties (opaqueness, transparency, etc.). The main idea is that the substances can be separated by their properties, because those properties do not change when forming a mixture, unlike when a compound is formed.

Conservation of Matter: Heavy Whipping Cream

I found a new way to teach the conservation of mass/matter this past year. Previously I taught it by having steel wool (iron) react with oxygen. Since our periods are shorter this year, I couldn't really do that reaction anymore. Now students mix heavy whipping cream and vinegar in an open system. The vinegar reacts with the casein proteins in the heavy whipping cream to form a solid cheese-like substance (basically it is cheese). It's not a very  glamourous reaction, but is also a way to teach students about precipitation. Students have a difficult time understanding the concept of two liquids reacting to make a solid. This is a simple way for students to visualize that type of chemical change.