Unit 1: Chemistry of Life

Properties of Water

Goals Examine the properties of water and why it is so important for life: Surface tension Adhesion Cohesion Polarity pH

Water Molecule “Mickey Mouse” molecule

Water Molecule Oxygen has a slight negative charge Hydrogen has a slight positive charge This makes water a polar molecule Uneven distribution of electrons

Water molecule Hydrogen bond – forms between two water molecules Gives water many of its special properties Polarity causes attraction between water molecules-magnets

Cohesion vs. Adhesion Cohesion-attraction between molecules of same substance Water sticks to water Adhesion-attraction between molecules of different substance Water molecules “stick” to a surface Capillary action-in plants and surface tension

Solute vs. Solvent Solute-substance getting dissolved (salt, sugar) Solvent-substance in which the solute dissolves (water) VS. Water is the greatest SOLVENT in the world!!!!!!!!

Density Definition: The degree of compactness of something Formula: density= mass/volume Temperature is a measure of how much energy molecules have Water at room temp has MORE energy than cold water The density of room temp water is LESS because there is more energy which causes the molecules to be further apart When water cools down, there is LESS energy so the molecules move closer together When water reaches freezing, electrostatic forces push molecules further way from each other and form ice

So Why does Ice float? Water is LESS dense in ice form! Why is this important for life on Earth?