IB Biology 1 Unit 1- Properties of Water

Why does ice float?

-Density of ice is lower than that of a liquid -Liquid water shrinks and becomes more dense when cooled -When cooled to 4C, volume stops decreasing and molecules are beginning to approach solid state

Solvent properties

-Good at dissolving ions and polar molecules, but poor at dissolving nonpolar molecules.

Thermal properties

-Hydrogen bonds absorb heat without using a lot of energy since hydrogen bonding is one of the strongest intermolecular attractions (meaning stronger than van der waals but weaker than ionic or covalent bonds) -Takes a lot of energy to break bonds -Water is a coolant -High specific heat and vaporization levels -Water can regulate heat without much change in temperature

High Specific Heat

Def: Amount of energy required to raise the temperature of a substance by 1C The high specific heat capacity of water has a great deal to do with regulating extremes in the environment. For instance, fish in ponds don't need to worry because the heat capacity of the water in the pond means the temperature of the water will stay relatively the same from day to night. This same concept can be expanded to a world-wide scale. Cities near the oceans will tend to have less change and less extreme temperatures than inland cities. EX: A Midwest state, such as Nebraska, will have colder winters and hotter summers than Oregon, which has a higher latitude but has the Pacific Ocean nearby.

High Heat of Vaporization

Def: Amount of energy required to transform one gram of liquid water into water vapor. The high heat of vaporization of water makes it an effective coolant (a liquid or gas that is used to remove heat from something) for the human body via evaporation of perspiration

Capillary Action

Def: Rising of liquids in narrow tubes Adhesion and cohesion of water allows for capillary action. A combination of cohesive forces of the liquid and the adhesive forces between the liquid and tube material. These forces pull the liquid into the tube.

Adhesion

Def: The attraction between water molecules and other molecules When water "climbs" up the tube placed in a glass of water. This is because the water molecules are attracted to the charged glass walls of the capillary more than they are to each other and therefore adhere to it. This type of adhesion is called capillary action.

Surface Tension

Def: The capacity of a substance to withstand being ruptured when placed under tension or stress

Cohesion

Def: Water molecules are attracted to each other Hydrogen bonds (intermolecular forces) between water molecules causes them to cohere- hold together. The cohesion of water is responsible for surface tension and allows water to travel in columns