The Chemical Basis of Life Chapter 4 The Chemical Basis of Life

Matter All living things are made up of matter – anything that has mass and takes up space Water, air, and your body are different substances but are all made up of matter

Mass vs Weight Mass – the amount of matter an object has Weight – the amount of mass an object has plus the force of gravity

States of Matter Matter exists in 4 different states Solid – definite shape and volume Liquid – definite volume, not shape Gas – no definite shape or volume Plasma - high temperature ionized gas

Elements Element – substance made up of the same type of atoms that can not be broken down chemically into a simpler kind of matter 25 elements are important to living things 4 make up 96% of the living matter in your body Oxygen, Carbon, Hydrogen, Nitrogen

Trace elements – elements that make up less than Trace elements – elements that make up less than .01 percent of body mass, but critical to health Ex. 1.5 mg of Iodine each day – affects thyroid gland .004% Iron – important for O2 in your blood

Compounds Compound – substance containing 2 or more elements that are chemically combined in a fixed ratio Ex. H2O Physical and chemical properties differ between the elements that make up the compound and the compound itself Ex. Oxygen and Hydrogen = gases Combined = liquid

Atoms Atom – smallest possible particle of an element Greek atomos = invisible Nucleus – consists of protons and neutrons and makes up most of the mass of the atom Proton – positively charged particle Neutron – neutral; particle with no charge Electron – high energy, negatively charged particle with little mass

Atoms Orbital – 3D region around a nucleus that indicates the probable location of an electron Each orbit holds a certain amount of electrons 1st orbit – 2 e 2nd orbit – 8 e 3rd orbit – 8 e (for the first 18 elements, then it can hold 18e)

Atoms In order to be stable, an atom must have its outer orbit filled with electrons Ex. He and Ne both have 8 e in their outer orbits Atoms have the same number of protons (+) as electrons (-), therefore, an atom is neutral

Atoms Bohr Models Periodic Table – chart that summarizes and organizes the elements Chemical symbol – letters Atomic number – number of protons an atom has Mass number – total number of protons + neutrons Ex: F 9 protons 10 neutrons = 19 atomic mass Chem Table

Bohr Models Rutherford had shown that the atom consisted of a positively charged nucleus, with negatively charged electrons in orbit around it. Bohr expanded upon this theory by proposing that electrons travel only in certain successively larger orbits.

Isotopes Isotopes – atoms of the same element that have the same number of protons, but different number of neutrons Radioactive Isotope – one in which the nucleus decays over time, giving off radiation in the form of matter and energy Used in research and in medicine

Ionic Bonds Ionic bond – the attractive force between oppositely charged ions which form when electrons are transferred from one atom to another Ion – electrically charged atom or molecule Ex. Na+Cl-

Covalent Bonding Covalent bond – forms when two atoms share one or more pairs of electrons Ex. Water Oxygen 6 electrons needs two Hydrogen

Molecules Molecule – 2 or more atoms held together by a covalent bond Ex. H20 or O2 Models of Molecules Chemical formula - #’s and types of atoms Structural formula – how the atoms are linked by bonds Space filling model – 3-D model with colored spheres

Chemical Reactions Chemical Reactions – breaking of old and formation of new chemical bonds resulting in a new substance Reactants – starting materials for a rxn Products – ending materials in a rxn

Acids, Bases, and pH H2O H+ + OH- Hydroxide ion = OH- Hydronium ion = H+ Acid – solution with more H+ Ex. HCl Base – solution with more OH- Ex. NaOH

pH Scale pH scale – scale range from 0-14 that describes how acidic or basic a solution is 0-6 acid 7 neutral 8-14 base

Buffers Buffer – substances that cause a solution to resist changes in pH Important because the slightest change in pH can be harmful to organisms Ex. Blood