• 6-8: 4D/M1a. All matter is made up of atoms, which are far too small to see directly through a microscope.
• 6-8: 4D/M3ab. Atoms and molecules are perpetually in motion. Increased temperature means greater average energy of motion, so most substances expand when heated.
• 6-8: 4D/M3cd. In solids, the atoms or molecules are closely locked in position and can only vibrate. In liquids, they have higher energy, are more loosely connected, and can slide past one another; some molecules may get enough energy to escape into a gas. In gases, the atoms or molecules have still more energy and are free of one another except during occasional collisions.
• 6-8: 4D/M8. Most substances can exist as a solid, liquid, or gas depending on temperature.
• 6-8: 4D/M10. A substance has characteristic properties such as density, a boiling point, and solubility, all of which are independent of the amount of the substance and can be used to identify it.

• 6-8: 11B/M1. Models are often used to think about processes that happen too slowly, too quickly, or on too small a scale to observe directly. They are also used for processes that are too vast, too complex, or too dangerous to study.
• 6-8: 11B/M6. A model can sometimes be used to get ideas about how the thing being modeled actually works, but there is no guarantee that these ideas are correct if they are based on the model alone.

This multimedia activity from the American Chemical Society takes a close look at what's happening on a molecular level to make the liquid in an alcohol thermometer go up or down. Animations provide visualizations of molecules moving in a solid, liquid, and gas. The module also includes a hands-on experiment and a lab where kids construct their own molecular models.

• Physical Sciences K-8 The Relationship Between Heat and Temperature Unit
• Physics First The Relationship Between Heat and Temperature Unit