1a. Describe situations in which opposite quantities combine to make 0. For example, a hydrogen atom has 0 charge because its two constituents are oppositely charged.

They say opposites attract, but when it comes to the math world, what really happens is opposites utterly obliterate each other in a haze of smoke and a shower of sparks. Although if we're being honest, that might not be too far off from your students' dating lives. (Heyo!)

For this part of the standard, students should know that positive and negative versions of the same quantity will cancel each other out. We'll get to this numerically in the next substandard, but for now, just go ahead and emphasize different examples of how this works in the real world. Or to truly satisfy this standard—have students give you those examples.

Atoms and ions are a cool way to visualize this, since positive and negative charges cancel each other out just like numbers do. A sodium atom has 11 protons (which have a positive charge) and 11 electrons (which are all negatively charged), so it's overall charge is 0. But if a very tiny burglar came along and stole one of those electrons, we'd have a positive charge overall instead (technically, a sodium ion) since 11 – 10 = 1.

And you can totally show this visually, with different-colored items representing each kind of charge. It's always helpful for students to think about this concept with quantities of actual objects before moving on to the number line, so feel free to get as creative as you like.

The good news about this standard is that it's pretty intuitive no matter what examples we use. Hot water cancels out cold water when we turn both shower knobs on full-blast, burning 500 Calories on a jog cancels out that milkshake we had earlier, etc.

Okay, okay, you caught us—we had two milkshakes.