High surface tension

Surface tension presents as an invisible film that encompasses the surface of water. The attractive forces arising from the intermolecular cohesion holds the surface of water together.

Paper clip on water.

This paperclip would sink if it broke through the surface of the water.

Water strider on water.

This water strider is not on top of the water because it is light. They have long and slender legs that keep weight evenly distributed on top of water, and have tiny hair that repel water. The water strider has not broken through the surface of the water and is therefore, on top of the water.

Cohesive property

Astronaut Clayton Anderson demonstrates the cohesive nature of water in microgravity on board of the shuttle Discovery.

The H-bonds between water molecules are responsible for the cohesive properties of water. Water clings to itself through hydrogen bonding.

Adhesion property

Water climbs the capillary tube by adhesion to the surface.

Hydrogen bonds of water can drive adhesion as evidenced by capillary action.

Water travels through our blood vessel the same way.

Evaporative cooling

The H-bonds are responsible for the high boiling point of water (100 degrees C). Evaporation is the removal of water as vapor at a temperature lower than boiling point and is an endothermic reaction. Evaporative cooling describes how the process of liquid evaporation leaves a surface cool. The energy from the heat that is present is transferred to water in sweat where water molecules use this energy to break H-bonds and escape.

High heat capacity

Specific heat of water. Transfer of energy to boil water explained.

Heat capacity is the amount of energy needed to increase the temperature of a substance. It is measured in calories.

A calorie is defined as the amount of energy required to warm one gram of liquid water by 1ºC. Liquid water requires an abundance of energy to boil because of the hydrogen bonds retain molecules instead of evaporating to release that energy.

In the phase change diagram, you can see that water is liquid in the range of 0 to 100 ºC. The heat energy is used to break the H-bonds. When all the H-bonds are broken, heat is transfer to molecules and change of phase occurs. 80 calories are needed to melt ice cubes and 540 calories are needed to boil water.

Density of ice and water

Hydrogen bonds of water guide the structure of ice.
Density curve of water as a function of the temperature.
6-arm snow flakes of various shapes.

When water cools down to 0ºC, the water molecules move slowly and each molecule makes 4 H-bonds with surrounding water molecules to form an ice lattice. There is more space between water molecules that in liquid water, and there are less water molecules per volume unit. Therefore the density of ice is lower than the density of liquid water.

The curve shows that the density of frozen water is less than the density of liquid water. The density of water is the highest at 4ºC and equals 1kg/m3 or 1g/cm3.

Snow flakes made of water droplets crystalized around air particles form slowly while falling on the ground.

Read here how snow flakes are formed.

Iceberg in the Arctic showing its underside.

Icebergs are large chunk of ice that fell off from glaciers into the Arctic ocean. This photograph illustrates how ice is less dense that liquid water since it floats.