WATER Its magical powers and why it is so important in biology.

WATER MOLECULE -1 oxygen atom and 2 hydrogen atoms share pairs of electrons (covalent bonds) -Since oxygen is larger and has 8 protons (+) to pull on the 10 electrons it has the tendency to pull (hog) the electrons from the smaller hydrogen atoms with only 1 proton

WATER MOLECULE The result of this pull causes the region around the oxygen atom to have a slightly negative charge and the regions around the hydrogen atoms to have a slightly positive charge. The result of this pull causes the region around the oxygen atom to have a slightly negative charge and the regions around the hydrogen atoms to have a slightly positive charge.

POLARITY Defined as an uneven pattern of charge Defined as an uneven pattern of charge This uneven pattern of charge gives water many special characteristics.

CHARACTERISTICS OF WATER 1. DISSOLVES IONIC COMPOUNDS the charges of the water molecule pull apart the weak ionic bonds 2. DISSOLVES other POLAR SUBSTANCES- such as sugars and proteins

CHARACTERISTICS OF WATER 3. WATER BONDS TIGHTLY TO ITSELF- the hydrogen of one water molecule is attracted to the oxygen of another molecule called a HYDROGEN BOND-

CHARACTERISTICS OF WATER COHESION- attractive forces between like particles Examples- why water appears in drops, why some animals can float on water “SURFACE TENSION”

CHARACTERISTICS OF WATER ADHESION- the attraction of non similar substances to one another. CAPILLARY ACTION- pulls water up into small tubes-

CHARACTERISTICS OF WATER HIGH HEAT CAPACITY- “temperature moderation”- water must gain or lose a relatively large amount of energy for its temperature to change Examples- body temperature, “ocean effect”

CHARACTERISTICS OF WATER WATER EXPANDS WHEN IT FREEZES- ice is less dense than water and therefore it floats on top of the water WATER EXPANDS WHEN IT FREEZES- ice is less dense than water and therefore it floats on top of the water

BROWNIAN MOTION BROWNIAN MOTION- all objects have energy of motion called kinetic energy. A moving particle of matter moves in a straight line until it collides with another particle. After the collision each particle rebounds into another direction

DIFFUSION Random movement of particles from an area of high concentration to an area of low concentration Random movement of particles from an area of high concentration to an area of low concentration -Diffusion is slow because it relies on random motion

DIFFUSION 3 ways to increase diffusion 1. increase temperature (particles will move faster) 2. increase pressure ( particles will collide more often ) 3. increase the concentration ( more particles will be involved in the collisions ) 3. increase the concentration ( more particles will be involved in the collisions )

DIFFUSION Diffusion will continue until the random movement of particles INTO the area equals the random movement of particles OUT of the area. Diffusion will continue until the random movement of particles INTO the area equals the random movement of particles OUT of the area. DYNAMIC EQUILIBRIUM- DYNAMIC EQUILIBRIUM-

Why is diffusion important to living things Cells use diffusion to get particles into the cell. Cells use diffusion to get particles into the cell. Examples- water, oxygen, CO 2 Examples- water, oxygen, CO 2

MIXTURES AND SOLUTIONS

MIXTURE a combination of substances in which the individual components retain their own properties. a combination of substances in which the individual components retain their own properties. EXAMPLES; EXAMPLES;

SOLUTION Mixture in which one or more substances are distributed evenly in another substance Mixture in which one or more substances are distributed evenly in another substanceExamples: SOLUTE- the substance that YOU put into the solution (gets dissolved) SOLVENT- the substance that does the dissolving

How do we measure solutions? CONCENTRATION- amount of solute dissolved in a fixed amount of solution. (usually 100mL) CONCENTRATION- amount of solute dissolved in a fixed amount of solution. (usually 100mL) SATUARATED SOLUTION- when no more solute can be dissolved in the solution SATUARATED SOLUTION- when no more solute can be dissolved in the solution

Differences between a mixture and solution Solution has a uniform color Solution has a uniform color Mixture is much easier to separate out the substances Mixture is much easier to separate out the substances

ACIDS AND BASES Created by the DISSOCIATION of a water molecule. DISSOCIATION- is the breaking apart of a water molecule H 2 O  H + + OH - OH - is known as the HYDROXIDE ION and a high number of these makes the solution a base (alkaline)

ACIDS AND BASES The H+ ion can bond with other water molecules to form a HYDRONIUM ION H 3 O + The H+ ion can bond with other water molecules to form a HYDRONIUM ION H 3 O + A high amount of HYDRONIUM IONS makes the solution an acid. A high amount of HYDRONIUM IONS makes the solution an acid.

pH SCALE

pH SCALE We measure the acidity or alkalinity (basicity) by finding the ratio of hydroxide ions to hydronium ions. We measure the acidity or alkalinity (basicity) by finding the ratio of hydroxide ions to hydronium ions. We measure it on a pH scale of 0 to 14 with 7 being neutral. We measure it on a pH scale of 0 to 14 with 7 being neutral. Pure water has a pH of 7. Pure water has a pH of 7.

ACID ACID- has a greater number of hydronium ions ACID- has a greater number of hydronium ions -have sour taste (examples) -highly corrosive to metal - 0 to 6.9 on the pH scale

BASE BASE- has a greater number of OH- ions -has a bitter taste (examples) - highly corrosive to organic matter -7.1 to 14 on the pH scale -feels slippery

pH SCALE How to use the pH scale. Moving one number away from neutral increases the strength 10X Example: In order to NEUTRALIZE an acid it is best to use a base of the same strength. Example: