Sammy Keyes and the Killer Cruise by Wendelin Van Draanen

him.
    “Hey,” I call after him, because now I feel really bad. “Sorry. I’m just stressed out by this stupid homework assignment.”
    “Is it chemistry?” he asks from halfway across the room. And I’m thinking, Oh, yeah—Kensingtons and chemistry. Like peanut butter and jelly.
    But
then
it flashes through my mind that maybe he
hates
chemistry. Maybe he’s sick to death of his granddad being Dr. Fragrance. Maybe he secretly thinks of him as being Dr. Fragrance-stein! Maybe he wants to torch the secret family formula and is embarrassed to be the nephew of the chemistry jokes guy!
    So I go ahead and say it. “I hate molar conversions.”
    And you know what he says?
    He says, “Why?”
    “Because they’re hard! And I don’t really understand them! And I’m stuck with a three-page work sheet that I have to do on my birthday cruise!”
    He takes a step forward. “It’s your birthday?”
    “Tomorrow is. Which I guess is already today. Never mind. The point is, I hate this.”
    He takes another step forward. “You want help?”
    I hesitate, then shove the paper at him. “You know how to do this?”
    He looks it over and starts nodding. “Sure.”
    “Sure?” I snatch the paper back.
“Sure?”
    He nods. “I love that stuff.”
    I just stare at him. And then, even though I hear a voice inside my head screaming DON’T! out of my mouth comes, “Could you help me with just one?”
    “I don’t have much time, but sure.”
    So he sits down next to me and reads the first problem out loud. “ ‘Calculate the molarity of the solution formed when seventy-five grams of magnesium chloride is dissolved in five hundred milliliters of solution.’ ” He nods and grabs one of my pencils and a piece of paper. “Piece of cake.”
    So yeah. I’m sitting next to a know-it-all Kensington, feeling like a boulder brain. “More like stinky cheese, if you ask me.”
    “Huh?”
    “Never mind.”
    “The molarity is just moles divided by liters. But you’re not given moles here, so you have to calculate them first, then divide by liters.”
    I want to tell him that I hate moles. That moles put me in a deep, dark place, and that I would much rather be calculating birds or sunflowers or one-eyed bats, for that matter. But what comes out of my mouth is “So how do I calculate moles?”
    He grabs the periodic chart. “With this.” He grins. “Grandfather says this is the most elegant single sheet of knowledge ever created.” Then his face kind of falls, and he goes back to the chart. “Anyway, every square in the chart has the element’s atomic number, symbol, name, and atomic mass. For example”—he points to asquare—“phosphorus is element fifteen, has P as its symbol, and an atomic mass of 30.97.” He hands me the chart. “You try. What’s the atomic mass of gold?”
    Now, it’s not like the chart’s in alphabetic order. Plus, it turns out that gold’s symbol isn’t G like phosphorus’ is P. And since there are over a hundred elements on the chart, I’m feeling miffed and tricked when I finally find it. “It’s element seventy-nine, its symbol is Au, and it has an atomic mass of 196.97.”
    “Right!” he says, like I’m a star student. Then he rereads the problem on the work sheet and says, “Do you know the formula for magnesium chloride?”
    Ms. Rothhammer had given us a list of chemical formulas that were used in the problems, so I look at it and say, “MgCl 2 .”
    “Right.” He jots
MgCl
2 on the paper and says, “The first step is to find the atomic mass of magnesium.”
    I look on the chart and find Mg easily. “It’s 24.31.”
    “Right. Now, what’s the atomic mass of chlorine?”
    Cl is also easy to find. “It’s 35.45.”
    “And how many chlorines do you have?”
    “Two.”
    “So what is the sum of the two chlorines?”
    I double 35.45 in my mind. “Is it 70.9?”
    “Exactly. Now add up the magnesium and the chlorines, and what do you get?”
    I scribble down the