* Mass Comparison: The statement "the mass of water is 4.5 times greater than helium" tells us about the relative masses of entire substances (water vs. helium), not individual molecules or atoms.
* Molecules vs. Atoms:
* Atom: The smallest unit of an element that retains the chemical properties of that element. Examples: Helium (He), Oxygen (O), Hydrogen (H).
* Molecule: Two or more atoms held together by chemical bonds. Examples: Water (H₂O), Oxygen gas (O₂).
Here's how the comparison works:
1. Helium (He): Helium is an element, and its atoms are single, independent entities.
2. Water (H₂O): Water is a molecule composed of two hydrogen atoms and one oxygen atom bonded together.
The Key Point: The mass of a water molecule is greater than the mass of a helium atom because:
* A water molecule contains three atoms (2 hydrogen + 1 oxygen).
* Oxygen atoms are significantly heavier than helium atoms.
In Summary:
The statement about the mass of water being greater than helium tells us about the overall mass of the substances. However, the comparison of a water molecule to a helium atom is about the number and types of atoms within each. A water molecule is heavier than a helium atom because it contains more atoms, including a heavier oxygen atom.
