BellringerWhat two elements make up one water molecule,

and how many atoms of each are there?

The Properties of Water

Notes

The Structure of Water

•Atoms join together to form molecules. A water molecule is made up of two hydrogen atoms attached to one oxygen atom.

•H2O

•H2 = Two hydrogen atoms

•O = One oxygen atom

The Structure of Water

•Water is made up of polar water molecules. A polar molecule has electrically charged areas. The oxygen end of a water molecule has a negative charge. The hydrogen ends each have a positive charge.

•Polar molecules are like magnets. In magnets, opposite poles attract each other. In polar molecules, atoms with opposite charges attract each other.

•As a result, water molecules tend to “stick” together.

Key Properties of Water

•Capillary action is the combined attraction among water molecules and between water molecules and other molecules. One result of capillary action is that water rises in a tube.

•Clothing the “wicks” away moisture from your body uses capillary action to pull the sweat away from your skin.

Key Properties of Water

•Surface tension is the tightness across the surface of water. Some insects can even walk across water because surface tension keeps them from sinking.

•Droplets are a phenomenon of surface tension.

Key Properties of Water

•Many substances dissolve in water. A solution is a mixture that forms when one substance dissolves in another. The substance that does the dissolving is called a solvent. Because so many substances dissolve into water, water is called the “universal solvent.”

•Solvent = substance does the dissolving

•Solute = substance that is dissolved

Solvent

Solute

= Solution

Key Properties of Water

•Specific heat is the amount of heat needed to increase the temperature of a substance by 1°C. Different substances have different specific heats. Water needs a lot of heat to increase its temperature - therefore water has a very high specific heat.

Key Properties of Water

•In summer, the sun’s heat warms the land more quickly than the water (ocean). As a result, the air is warmer inland than on the coast.

•The opposite effect occurs in winter - land loses heat more quickly then water, so the air above the land is cooler.

•Remember these; we’ll need them again for the weather unit.

Changing State•Water is the only substance on Earth that is

commonly found in three different states of matter - as a gas (water vapor), a liquid (water droplets), and as a solid (water ice).

•Liquid water can become a gas when it is boiled. I can also become a gas by evaporation. Evaporation is when molecules at the surface of a liquid spontaneously change into a gas.

•For evaporation to occur, heat is taken away from the environment. This is a cooling process. (i.e. - sweating)

Liquid Water

Water Vapor

Changing State• The way a gas changes into a liquid is called

condensation. When you fog up a window by breathing on it, you see the effects of condensation.

• For condensation of water to occur, it must have a solid surface to condense onto, such as leaves, windows, or dirt particles in the air. This is known as nucleation.

• For condensation to occur, heat is released into the environment. This is a warming process.

Changing State

•When water freezes, water changes from a liquid to a solid. When ice melts, water changes from a solid to a liquid.

•Melting takes heat away from the environment.

•Freezing releases heat into the environment.

Changing States

•Water freezes AND melts at 0°C.

•Water boils AND condenses at 100°C.

•The only difference is where the heat is going.