The Nature of Matter Chapter 2

Atoms Comes from Greek word “atamos,” (means unable to cut) 100 million atoms in a row is 1cm long! Atoms are the smallest unit of an element  Ex: Gold is made of gold atoms

More stuff about Atoms Atoms are made of 3 parts:  Protons  Neutrons  Electrons Protons and Neutrons together are a nucleus  Protons and Neutrons have the same mass Electrons orbit the Nucleus They have a much smaller mass of 1/1837 the mass of a proton

Elements Elements are pure substances consisting entirely of ONE type of atom. (Ex: Gold -- >) More than 100 are known, but 12 are common in living things 6 are UBER-common  CHONPS

CHONPS Carbon – found in almost all major molecules of the body Hydrogen – found in almost all major molecules of the body Oxygen – found in almost all major molecules of the body Nitrogen – found mostly in proteins and nucleic acids (DNA) Phosphorus – found mostly in nucleic acids Sulfur – found mostly in proteins

Molecules and Ions Molecules – two or more atoms joined by a bond  May be the same element or different elements Ions – atoms with a + or – charge due to their number of electrons

Basic Bonds Bonds hold two atoms together There are many types, but we will focus on 3 in this course The 3 Main types:  Ionic Bonds – hold ion atoms together like strong magnets  Covalent Bonds – the strongest bond; atoms fully share electrons  Hydrogen Bonds – the weakest bond, atoms stay close to each other because of faint magnetic attraction

Cool Stuff About Water It covers 75% of the Earth’s surface It is the most abundant compound in living things About 70 – 80 % of a human is water! Unlike many compounds, it’s a liquid at room temp When it freezes, it expands (Ice is less dense than water and thus floats!) As water cools down, the molecules spread apart as they form a crystal

Solutions and Suspensions Solutions happen when:  Ions break off of large chunks  The ions distribute evenly in liquid (DISSOLVE)  The compound that dissolves is the SOLUTE  The compound that causes dissolving is the SOLVENT  H2O is the Universal Solvent Suspensions happen when:  Materials break into small pieces in liquid  The pieces DON’T distribute evenly (They can settle at the bottom)  Some of the most important biological fluids are SUSPENSIONS EX: Blood MIXTURE: Any two or more elements combined, therefore, solutions and suspensions are BOTH types of mixtures

Acids and Bases The pH scale indicates the amount (concentration) of Hydrogen in solution The scale ranges from 0 to 14  The closer to 0, the more acidic (more H+ ions)  The closer to 14, the more basic (less H+ ions)  7 is Neutral

Acids, Bases, and Buffers Where do the H+ ions in a low pH solution come from?  Acids!  Acids are compounds that produce H+ ions in solution Where do the H+ ions go in a high pH solution?  Bases!  Bases are compounds that decrease the H+ ions in solution BUFFERS: Most fluids in the human body work best at pH 6.5 to 7.5  If the pH is too high or low, chemical reactions necessary for keeping the body healthy won’t happen properly  Buffers are weak acids or bases that react with strong acids and bases to change pH dramatically