When we’re teaching ideas in chemistry, I liken it to hacking your way through a forest. It’s all this detail.... and you can’t expect students to do the hard work of fighting your way through the forest or the jungle, unless they have a global view of where they’re going.
You can liken teaching chemistry to hacking your way through a forest. It’s a lot of detail, and you can’t expect students to do the hard work of fighting their way through the forest or the jungle, unless they have a global view of where they’re going. Keep going back to applications in the real world. How is it that geckos can crawl up a wall, and sit on the ceiling without falling off? How is it they’re able to stay there with gluey legs or something? How do they maximise the attractions between the molecules in their feet and the molecules in the ceiling?
Use physical and tactile experiences to demonstrate intermolecular forces. For example, If you stretch a plastic grocery bag (made of polyethylene), the length increases and the width decreases. This breaks apart the London Dispersion Forces (induced dipole-induced dipole interactions) and straightens out the polyethylene chains. The covalent bonds remain intact until the plastic rips.
You can get the students to physically feel that liquids are not compressible by giving them three closed syringes: one contains water, say 50 mL, that’s been put in the freezer to become ice; another syringe contains 50 mL of liquid water, and the other one is gas. Ask them to push the syringes and see what happens. They find they cannot push the syringes containing liquid or solid, even though they think there would be some space in the liquid one. The misconception is that liquids fall somewhere between solid and gas and so should be “a bit” compressible.
Keep going back to applications in the real world. How is it that geckos can crawl up a wall, and sit on the ceiling without falling off? How is it they’re able to stay there with gluey legs or something? How do they maximise the attractions between the molecules in their feet and the molecules in the ceiling? Show applications that are powerful, and hopefully interesting, of the ideas that are important.
Use the Vis Chem website, which is Roy Tasker’s resource, and there are links to a Scootle site where you can download visualisations for chemical bonding and pure substances in different states. There is gaseous water and liquid water. You can see they’re close together - they’re crowded. You can talk about ice skating. You can press the ice and it becomes liquid. That’s why the ice skates slide. You can see they’re jiggling away. There’s some space between them.
