Water Single most abundant compound in organisms. Exists on Earth in all 3 phases. Unlike most compounds, it expands when frozen and it becomes less dense. Due to its distribution of electrons it is slightly charged on each end (polar).

Polarity of Water The water molecule is neutral, but the larger (O) atom pulls the electrons more than the (H) atom does. This pull by the (O) atom bends the shape of the molecule and gives it a slight charge.

Bonding Hydrogen Bonds- Because of polarity water molecules can attract each other. Cohesion- Attraction between molecules of the same substance. Adhesion- An attraction between molecules of different substances

Mixture 2 or more substances physically mixed together make a mixture. 2 types of Mixtures. 1.Solution- All components are evenly distributed. Solute- The substance that is dissolved. Solvent- The substance doing the dissolving Water is called the universal solvent.

Solutions Continued Acids- compounds that release hydrogen (H) ions into solutions. Bases- Compounds that produce (OH-) or Hydroxide ions in solutions are called basic or bases. Buffers- Weak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in pH.

pH Scale A measurement system used to indicate the relative concentration Hydrogen and Hydroxide ions in a solution. (pH) Stands for potential of Hydrogen. The scale runs from 0 (most acidic) to 14 (most basic) 7 is neutral. Acid ( #H+ > #OH-) Base (#OH- > #H+) Most body fluids have a pH between 6.5-7.5, controlling this is important to maintaining homeostasis.

pH Scale

Mixture 2.Suspensions- Mixture of water and a material that doesn’t dissolve. Some biological fluids are solutions and suspensions Blood has dissolved and un-dissolved substances.