Night Hike and Stargazing Discussion

Setting the Scene

• A night hike for stargazing with a friend.
• Importance of bringing plenty of water for hydration.
• Arrival at a favorite lookout point to observe the stars.

Discussion about Stars and Water Molecules

Stars in the Galaxy

• Friend mentions the vast number of stars, noting more than 100 billion in the galaxy.

Chemistry Perspective on Water Molecules

• Introduction of the concept that water molecules in a bottle far exceed the number of stars.
• Explanation of water density: 1 gram/mL.

Calculation of Water Molecules

1. Weight of Water in Bottle:
   • 500 mL of water = 500 grams.
2. Mass of Water Molecule:
   • 1 water molecule = 18 atomic mass units (O=16, H=1 each).
3. Moles of Water:
   • 500 grams / 18 grams/mole = 27.78 moles.
4. Avogadro's Number:
   • 1 mole = 6.022 × 10^23 particles.
   • Total water molecules = 27.78 moles × 6.022 × 10^23 = ~1.67 × 10^25 molecules.
   • Conclusion: More water molecules in a bottle than stars in the visible universe.

Hypothetical Reversal: Stars as Water Molecules

1. Stars as Water Molecules:
   • 100 billion stars = 10^11.
2. Converting to Moles:
   • 10^11 molecules / 6.022 × 10^23 = 1.66 × 10^-12 moles.
3. Mass of Water Hypothetically:
   • 1.66 × 10^-12 moles × 18 grams/mole = 2.99 × 10^-11 grams.
   • Result: Insufficient to fill a bottle, thimble, or even visible to the naked eye.

Conclusion

• Molecules vastly outnumber stars, highlighting the enormity of Avogadro's number and the small scale of molecules compared to cosmic scales.