1. The problem asks: How many hydrogen atoms are in 4 molecules of water (H₂O)? 2. Each water molecule (H₂O) contains 2 hydrogen atoms. 3. To find the total number of hydrogen atoms in 4 water molecules, multiply the number of molecules by the number of hydrogen atoms per molecule: $$\text{Total hydrogen atoms} = 4 \times 2$$ 4. Calculate the multiplication: $$4 \times 2 = 8$$ 5. Therefore, there are 8 hydrogen atoms in 4 molecules of water. Final answer: **8** hydrogen atoms.