Water, Water, Every Where!!! Properties of Water The Versatile Molecule

I. Water A. Single most abundant compound in most living things (~60%) B. Unique properties: 1. Liquid over much of Earth’s temp. 2. Expands when it freezes (becoming less dense)

Expanding Upon Freezing What if this did not occur?

II. Water Molecule A. This molecule H₂O is neutral (10 e⁻& 10 p⁺) How ever there is more to this story... B. Polarity: an uneven distribution of electrons between two atoms 1. Oxygen atom in water has a stronger attraction to the electrons than hydrogen 2. Water is a bent molecule so the oxygen end is slightly negative while the hydrogen end is slightly positive

III. Hydrogen Bond A. Since polar molecules have a slightly charged end they are attracted one another 1. Slightly positive is written: (+) 2. Slightly negative is written: (-) B. The bonding between the polar water molecules, from one oxygen to a hydrogen is a hydrogen bond Hydrogen bonds are weak bonds but collectively together they are strong!

IV. Cohesion & Adhesion A. The ability of water to form multiple hydrogen bonds gives it unique properties 1. Cohesion: attraction between molecules of the same substance i.e. drops of water form beads on a flat surface (high surface tension) 2. Adhesion: attraction between molecules of a different substance i.e. meniscus in a graduated cylinder and why water flows through a plant (capillary action)

Water Properties Cohesion Adhesion

V. Solutions & Suspensions Water is not always pure A. Mixture: material composed of two or more elements or compounds that are physically mixed together i.e. salt water, salt & pepper, atmosphere B. Two types of mixtures that can be made with water Solutions: all components are evenly distributed Suspensions: mixtures with nondissolved material and separate pieces

VI. Heat Capacity A. Water has a high specific heat. In other words it takes a lot of energy to raise water just by 1 degree. B. This allows organisms that not only live in water but others that are mostly made up of water to maintain a constant body temperature.

Hydrogen Bonds & Pennies Water molecules are polar because there is an uneven of electrons between the oxygen and hydrogen atoms. This causes one end of one water molecule to be attracted the another water molecule. This process is cohesion! Lets test how strong these cohesion forces are by placing drops of water on a penny until the cohesive forces break

Hypothesis: If I place a max of ____ drops of water onto a penny, then the cohesive forces of water will break and water will spill onto the towel Each person will conduct 2 trails and find the average. What’s the IV, DV, Control?