Angela's Tools · Chapter 2 · Molecules and Extended Structures Worksheet 1 of 10

Pencil Core and Saw Blade: Two Solids Made of the Same Atoms

Learning target: I can record observations about materials built from the same kind of atom, draw on what I already know, and write a first explanation of how so few kinds of atoms can make so many different substances.

Phenomenon explorationAbout 25 minIndividual MS-PS1-1 · supports discussionwriting
NameDatePeriod

Directions

Read the two descriptions and study the figure and the tables. Do not look anything up yet. Part A asks for what you notice and wonder; use only facts that are given. Part B asks what you think right now, and there is no penalty for being wrong. Part C asks for your first explanation. Write in complete sentences. You will return to this page at the end of the chapter to see how your thinking changed.

You will need: This worksheet, Pencil, Optional: a pencil with exposed core, a piece of glass and a hand lens for the teacher demonstration

Two things on Mr. Okafor's desk

Mr. Okafor holds up a pencil with the wood shaved away so that the gray core shows. He drags it across paper: it leaves a dark line, and a little gray dust comes off on his fingers. Then he holds up a tile saw blade. Its edge is dotted with tiny, hard, glittering chips. He scrapes the edge across a piece of glass, and it leaves a scratch. He drags the same edge across the paper, and it leaves no mark at all. Then he says the thing that makes the class go quiet: 'The pencil core is graphite. The chips on the blade are diamond. Both are made of nothing but carbon atoms.'

Two solids, one kind of atom Two solids, one kind of atom Pencil core (graphite) Made only of carbon atoms Leaves a dark mark on paper A fingernail can scratch it Feels slippery between the fingers Dull gray, opaque Saw-blade chips (diamond) Made only of carbon atoms Leaves no mark on paper Scratches glass and steel Nothing ordinary can scratch it Clear and glassy when pure Observations from the demonstration. Both materials are pure carbon.
Same atoms in both columns. Everything that differs must come from something other than the kind of atom.
Scratch hardness of some materials (real values, Mohs scale, rounded)
MaterialMohs hardnessWhat it means
Graphite1 to 2Softer than a fingernail (2.5)
Copper coin3Scratches graphite, not glass
Window glass5.5Scratched by a steel knife
Quartz (sand grains)7Scratches glass easily
Diamond10The hardest natural material
On the Mohs scale a material can scratch anything with a lower number.
A few everyday substances and the kinds of atoms in them (real)
SubstanceKinds of atomsAtoms in one particle
Waterhydrogen, oxygen2 hydrogen, 1 oxygen
Hydrogen peroxide (a disinfectant)hydrogen, oxygen2 hydrogen, 2 oxygen
Methane (natural gas)carbon, hydrogen1 carbon, 4 hydrogen
Ethanol (the alcohol in hand sanitizer)carbon, hydrogen, oxygen2 carbon, 6 hydrogen, 1 oxygen
Table sugar (sucrose)carbon, hydrogen, oxygen12 carbon, 22 hydrogen, 11 oxygen
Vitamin Ccarbon, hydrogen, oxygen6 carbon, 8 hydrogen, 6 oxygen
Fewer than one hundred kinds of atoms occur naturally on Earth, yet chemists have cataloged more than one hundred million different substances.

Part A: Notice and wonder

1.List three things you notice in the description, the figure or the tables. Use only facts that were observed or given, not explanations. Number them 1, 2, 3.
2.Write two questions you wonder about. At least one must be a question that could be answered with evidence, not just an opinion.
3.Look at the second table. Which three substances are built from exactly the same three kinds of atoms? Since the kinds of atoms are the same, what is different about them?

Part B: What do you think right now?

4.Which statement is closest to what you believe right now about why graphite and diamond are so different? Circle one. (No penalty for a wrong choice.)
5.Pick one option in q4 that you did not circle. What observation or fact from this page argues against it?

Part C: Your first explanation

6.Write your first explanation of this puzzle: If there are fewer than one hundred kinds of atoms, how can there be more than one hundred million substances, and how can one kind of atom make two solids as different as graphite and diamond? You may use a comparison (letters and words, bricks and buildings, beads and necklaces) if it helps. It is fine if your explanation is incomplete.
7.Predict: if a diamond chip were ground into a fine powder, would the powder write on paper the way graphite does? Explain your reasoning in one or two sentences.
8.Under a magnifier, grains of table salt tend to look like tiny cubes, and water droplets that freeze slowly in the air tend to grow six-sided snow crystals. Write one question these facts raise about the invisible particles inside the solids.

Sentence starters for Part C

If you are not sure how to begin q6, try one of these: 'I think the number of substances is so large because atoms can ...' or 'Graphite and diamond might be different because their carbon atoms are ...' Then add one sentence that uses a fact from the figure or a table as support. A guess with a reason is exactly what a first explanation should be.

Test the letters idea

The English alphabet has 26 letters. Using only the four letters A, E, S and T, how many different three-letter arrangements can you write if a letter may repeat (for example, ATE, TEA, EAT, SET, TTT)? Calculate the number instead of listing them all, then list five arrangements that are real English words and five that are not. Write two sentences on what this suggests about atoms: does the number of kinds of atoms limit the number of possible substances, and does every arrangement have to exist?

Angela's Tools · Chapter 2 · Molecules and Extended StructuresWorksheet 1 of 10