• 6-8: 4D/M6c. Carbon and hydrogen are common elements of living matter.
• 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: 4D/M11. Substances react chemically in characteristic ways with other substances to form new substances with different characteristic properties.
• 9-12: 4D/H2. The number of protons in the nucleus determines what an atom's electron configuration can be and so defines the element. An atom's electron configuration, particularly the outermost electrons, determines how the atom can interact with other atoms. Atoms form bonds to other atoms by transferring or sharing electrons.
• 9-12: 4D/H7a. Atoms often join with one another in various combinations in distinct molecules or in repeating three-dimensional crystal patterns.

• 9-12: 4G/H2a. Electric forces acting within and between atoms are vastly stronger than the gravitational forces acting between the atoms. At larger scales, gravitational forces accumulate to produce a large and noticeable effect, whereas electric forces tend to cancel each other out.

• 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: 11D/M3. Natural phenomena often involve sizes, durations, and speeds that are extremely small or extremely large. These phenomena may be difficult to appreciate because they involve magnitudes far outside human experience.

What causes molecules to attract each other? In this activity, students manipulate models to see how the strength of attraction is affected by distance from one molecule to another, by heating the substance, and by mixing polar and non-polar substances. Part II of the activity is devoted to hydrogen bonds. Middle school teachers may wish to confine the activity to Parts 1, 2, 3, 6, and 7.

• Physics First Matter and Interactions Unit
• Conceptual Physics Matter and Interactions Unit
• Algebra-Based Physics Matter and Interactions Unit
• AP/Calculus-Based Physics Matter and Interactions Unit

What causes molecules to attract each other? In this activity, students manipulate models to see how the strength of attraction is affected by distance from one molecule to another, by heating the substance, and by mixing polar and non-polar substances. Part II of the activity is devoted to hydrogen bonds. Middle school teachers may wish to confine the activity to Parts 1, 2, 3, 6, and 7.

• Physical Sciences K-8 Matter and Interactions Unit