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Matter Lab 6-8 / Week 06 / Wednesday
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Week 06 · Atoms Team Up: Molecules

Wednesday

Bench Lab: Build the molecules
// The recipe for a substance
⏱ about 20 min

Wednesday: Bench Lab: Build the Molecules

The Bench is covered in paper circles: big blue ones for oxygen, small white ones for hydrogen, black ones for carbon.

"Build order!" Rocket says. "Water, carbon dioxide, oxygen gas, hydrogen peroxide."

Raven lays out the formulas on cards. "Build each one, then check it against its card. What do you notice about CO2?"

Rocket places a black circle between two blue ones. "Carbon in the middle, oxygen on both sides. Three atoms."

Nova hovers over a sheet of grid paper. "Salt is different," she says. "Try a pattern instead of a molecule."

Raven starts a checkerboard: yellow, green, yellow, green. "It just keeps going," she says.

"Molecules stop. Crystals do not," Rocket says. Nova brightens. "Write that down. It is the whole lesson."

Your mission

Today you build models of five substances from paper circles or dry beans. Then you build a salt crystal pattern.

For each model, count the atoms of each kind and the total. Check every count against the formula.

  • Paper and a marker, or three kinds of dry beans in different sizes or colors
  • Scissors for the grown-up to cut about thirty paper circles
  • Tape or glue, and a sheet of grid paper or a drawn grid
  • The formula cards: H2O, CO2, O2, H2O2, O3
  • Your Bench Log
Safety first
The beans and paper circles are models. Nothing goes in your mouth, and nothing is eaten.
A grown-up handles the scissors or any cutting.
Keep small pieces away from younger children and pets. Put every piece away when you finish.
  1. Choose a color or a bean for each element: hydrogen, oxygen and carbon. Write a key in your Bench Log.
  2. Build H2O: two hydrogen touching one oxygen. Count the atoms and write the total.
  3. Build CO2: one carbon with an oxygen on each side. Count and record.
  4. Build O2: two oxygen atoms touching. Then build O3 with three. Count and record each.
  5. Build H2O2: two hydrogen and two oxygen. Set it next to your H2O model and compare.
  6. On the grid paper, make a salt pattern: one color for sodium, another for chlorine, alternating in every row.
  7. Fill at least four rows of four. Notice that the pattern could keep going in every direction.
  8. Tape or glue your favorite model into your Bench Log, or photograph it with a grown-up's help.
PREDICT BEFORE YOU BUILD
  • Read the question.
  • Tap your answer.
How many paper circles will one CO2 model use?
How many oxygen circles will you need for one H2O and one H2O2 together?
Which model should not stop at a fixed number of atoms?
ModelFormulaAtoms of each kindTotal atomsChecked against card?
WaterH2O
Carbon dioxideCO2
Oxygen gasO2
OzoneO3
Hydrogen peroxideH2O2
Salt crystalNaCl patternkeeps going

Reading the result

Your models are drawings in three dimensions. Scientists use drawings, ball and stick models and computer pictures the same way.

A model shows the kinds and numbers of atoms. It does not show the real size. Real atoms are far smaller than a billionth of a meter.

Your salt pattern shows the big idea of an extended structure: repeating units with no single molecule to pick out.

What the lab showsTrue or false?
A CO2 model uses one carbon and two oxygen atoms.?
The salt pattern could keep repeating in every direction.?
A bean model shows the real size of an atom.?
H2O and H2O2 use the same number of oxygen atoms.?
WHY THIS EXERCISEA good model shows the counts and the pattern, and you know what it leaves out.
How many atoms did your five molecule models use in total? Type a number.
WHY THIS EXERCISEAdding up atoms across models is practice for next week, when atoms regroup in a reaction.
Draw your five models in a row with their formulas beneath them. Then draw a corner of your salt pattern.

Careful building. Tomorrow you will read the periodic table, the list of every kind of atom, from the national database that keeps it.

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