Biology 102 A Properties of Water And Acids/Bases

Warm Up Your best friend thinks that fire is a living thing because it moves, needs oxygen and responds to wind. State your belief and give three reasons to support it.

. Living Things Use & Need Energy a.) energy comes from food, used to maintain body b.) AUTOTROPH: produce own food c.) HETEROTROPH: must consume food d.) DECOMPOSER: breaks down dead material for food

. Living things respond to their surroundings a.) they react to a stimulus b.) an action causes a reaction c. ) reaction is called a response d.) this involves one individual

Describe the properties of water that make it important to living things. Water is polar: it has an uneven distribution of electrons between the hydrogen and oxygen atoms One side of water is positive and the other is negative

Water properties:  Water is cohesive  Cohesion: attraction between same molecules, causes molecules to draw inward at surface  Ex: allows some insects & spiders can “walk” on the surface  Water is adhesive  Adhesion: attraction between different molecules, causes water to bend at the surface  Ex: capillary action-pulls column of water up to the top of a plant

Water properties :  Water is called “Universal solvent”: dissolves many other substances due to polarity  Differences in charges pulls/pushes substances apart  Water exhibits evaporative cooling: removes heat when it evaporates from a surface  Ex: sweating cools skin  Water expands during freezing: expands into crystal formation releasing heat  Ex: rocks broken up by ice creating soil; ice layer protects fruit from freezing

Acids, Bases and the pH scale  The pH scale measures the concentration of H+ ions (how acidic something is)  Ranges from 0-14  At 7: H+ ions and OH- ions are equal so it is neutral  0-7: acidic, has more H+ ions  7-14: basic, has more OH- ions

 ACIDS: release H+ when mixed with water  Sour, corrosive  Ex: HCl, H 2 SO 4  Always have H at front of formula  BASES: release OH- when mixed with water  Bitter, slippery, usually in cleaners  NaOH, CaOH  Always have OH at end of formula

What is a buffer?  Buffers are weak acids or bases that react with strong acids and bases to prevent sharp changes in pH  Helps to neutralize  Help to control pH in blood, digestive tract, etc. to maintain homeostasis

Reinforcement 1.Your saliva measures 7 on the pH scale, it is a(n) ___ solution? a. acidic b. basic c. neutral 2.The ___ property of water helps in the formation of soil. a. capillary action b. expansion during freezing c. evaporative cooling 3.Laundry detergent typically has a pH of 3 which indicates a(n) ___ solution? a. acidic b. basic c. neutral 4.The use of ___ helps to maintain a certain pH in our bodies maintaining homeostasis. a. buffers b. bases c. acids 5.The ___ property of water removes heat helping to cool your skin through sweating. a. capillary action b. evaporation c. cohesion