How can I explain with illustrations the cohesive forces of water molecules?

Question

Jeremiah Adams · Accepted Answer

When I teach about the intermolecular forces in water I get the students to bet on how many water droplets they can place on top of a penny without any falling off. They usually bet about 10, and then find out when they do the experiment that with care about 40 drops can be added.

We can then go on to talk about how hydrogen bonds form between the lone pairs on the oxygen atoms in water molecules and the #delta+# hydrogen atoms in other water molecules, and how since each water molecule has two lone pairs and two such hydrogens, a network of hydrogen bonds can be built up, leading to surface tension. We'd also draw the hydrogen bonds:

Finally we'd look at other anomalous properties of water such as relatively high melting and boiling point (for a Group 6 hydride), and the fact that ice floats as it has a lower density than liquid water.

Jeremiah Adams · Answer

undefined Cohesive forces between water molecules are due to hydrogen bonding. Each water molecule consists of two hydrogen atoms and one oxygen atom. The oxygen atom has a slightly negative charge, and the hydrogen atoms have slightly positive charges. This polarity allows water molecules to attract each other.

Imagine water molecules as tiny magnets. The positive ends of one molecule are attracted to the negative ends of neighboring molecules, forming hydrogen bonds. These bonds hold the water molecules together, giving water its cohesive properties.

Illustration: Picture water molecules as small, bent structures with oxygen in the center and hydrogen atoms sticking out like arms. Draw dashed lines between the oxygen atom of one molecule and the hydrogen atoms of neighboring molecules to represent hydrogen bonds. This illustrates how water molecules are attracted to each other due to their polarity, forming a cohesive network.