narrated notes_ water and pH

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Notes taken on 2/19. Topic - water and pH.

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T 2/19/13: Water and pH:

T 2/19/13: Water and pH Today’s objectives: Understand how the properties of water make it important for all life Explain what the pH scale means, and how to tell what is an acid and what is a base Warm-up: Why is chemistry important in biology?

How do biology and chemistry go together?:

How do biology and chemistry go together? Biology focuses on studying living things, but living things depend on atoms, molecules, and compounds.

Quick Chemistry Review:

Quick Chemistry Review What is an atom The smallest unit of matter (atoms are shown on the periodic table) What is an electron? Negatively charged particle that moves in the space around the nucleus of the atom What is a chemical bond? When two or more atoms are joined together by sharing their electrons What is a molecule? A group of atoms held together by chemical bonds

Atoms (elements) essential for life:

Atoms (elements) essential for life Symbol Element % human body weight O Oxygen 65.0% C Carbon 18.5% H Hydrogen 9.5% N Nitrogen 3.3% Ca Calcium 1.5% P Phosphorus 1.0% K Potassium 0.4% S Sulfur 0.3% Na Sodium 0.2% Cl Chlorine 0.2% Mg Magnesium 0.1%

Water:

Water Why is water important? Life first evolved in water. All living things require water more than any other substance. Water is involved in chemical reactions in your body. Cells are made of 70-95% water. Solvent – water can dissolve many different substances Moderates temperature

The Water Molecule:

The Water Molecule Several traits make water a very unique molecule: Polarity Cohesion/Adhesion pH

Water Polarity:

Water Polarity Polarity – when there is an uneven distribution of electrons in a molecule In water, the oxygen pulls the electrons toward itself. Hydrogen bond – the weak bond that forms between water molecules (Makes them stick to each other!) More negative oxygen atom More positive hydrogen atom

Water molecule bonds:

Water molecule bonds Cohesion – attraction between two of the same molecules Surface tension – attraction between water molecules creates a surface that very light things can walk on Adhesion – attraction between two different molecules

Why do cohesion and adhesion matter?:

Why do cohesion and adhesion matter? Transpiration! Plants would not be able to absorb water without cohesion and adhesion!

Water and moderation of temperature:

Water and moderation of temperature Water does not change temperature quickly – allows aquatic creatures to live in a stable environment Evaporation takes heat away Ice floats  allows life to live underneath it without freezing to death

Water is the solvent of life:

Water is the solvent of life Solvent – a liquid that can dissolve other things Most things do dissolve in water, but not everything does! Hydrophilic = water loving Molecules that dissolve in water Includes biological molecules (sugars, amino acids) and gasses (oxygen and carbon dioxide) Hydrophobic = water fearing Molecules that do not dissolve in water Includes fats, oils

Water and pH:

Water and pH Water can dissociate, or break apart H 2 0 H + + OH - Water Hydrogen + Hydroxide ion ion pH = potential for hydrogen

The pH scale:

The pH scale Strong Acid Strong Base 7 = neutral More OH - More H + 7 = same amounts of OH - and H +

What is the difference between an acid and a base?:

What is the difference between an acid and a base? An acid is a solution that has more H+ Examples: sulfuric acid, nitric acid, carbonic acid On pH scale: 0 - 6 A base is a solution that has more OH- Example: bleach, ammonia On pH scale: 8-14 Both can be harmful!

Wrap up 2/19 :

Wrap up 2/19 Name two properties of water that are essential to life. What is the difference between hydrophillic and hydrophobic?

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