Today, my students learned how to write, interpret, and build models of chemical formulas. Common examples gone over in class were water, carbon dioxide, and ammonia. One objective is to understand how atoms bond together to form the millions of compounds we encounter in everyday life. Since most students have no reference point for what the compounds, e.g. glucose, are in their everyday lives, we gave them examples to help them remember.
Another objective is the importance of the subscripts in the formula, indicating how many atoms of each element form the molecule. They learned that if you forget to add the correct number of atoms, the results could be very dangerous. For example, if you mean to use carbon dioxide (CO2), but forget the 2, the result is carbon monoxide (CO) which can be fatal if inhaled. Similarly, if you want to clean a wound with hydrogen peroxide (H2O2) but forget the last 2, you only would only clean the wound with water (H2O) and could get an infection.
My favorite quip of the day came from my teacher when she described methane (CH4) as the “not very nice gas”. One brave/comedic soul spoke up, “It’s a FART!” and the class erupted into giggles. Ah, science!