Post on 17-Jan-2016
Chemistry:Chemistry:Composition of Matter
Matter • Anything that occupies space and mass
• Mass: amount of matter in an object
• Mass ≠ Weight
• Chemical changes are essential to all life
• Non-living substance living substances
Elements• Pure substances that cannot be broken
down chemically into simpler kinds of matter
• 100+ identified• Less than 30 important to living things• IMPORTANT ELEMENTS: CHON
– Carbon– Hydrogen– Oxygen– Nitrogen
• Symbol: consist of one or two letters
• Atomic number: number of protons
• Atomic mass: sum of protons and neutrons in nucleus
Atoms• Simplest particle of an element that retains
all of the properties of the element• So small, structures cannot be observed• Scientists created models• Models:
– NOT meant to show how atom looks
– Help understand structure of atom
– Predict how atom will act
Atomic Structure
• Nucleus
• Electrons
Nucleus• Central core
• Two kinds of particles:– Proton: POSITIVE electrical charge– Neutron: NO electrical charge
Electrons
• HIGH ENERGY particles with very little mass
• move around nucleus at very high speeds in one of several different energy levels
Energy Levels• Outer levels have MORE energy than inner
levels
• First energy level can only hold TWO electrons
• Second energy level can hold up to EIGHT electrons
Atomic Number
• Number of protons
• Proton number same in ALL atoms of same element
• Protons=Electrons
• Positive=Negative=Neutral
Compounds• Pure substance made up of atoms of two
or more elements
• Naturally elements do NOT exist by themselves
Chemical Formulas
• Show kind and proportion of atoms of each element in compound
• Ex: H2O
• Physical and chemical properties of COMPOUNDS differ from individual ELEMENTS
• Atom is most stable when outermost energy level is filled
• Most atoms NOT stable in natural state so they make compounds
Chemical Reactions • Typically unstable elements
combine in ways that cause their atoms to become stable
• Types:– Covalent– Ionic
• Process:1. chemical bond broken
2. Atoms rearranged
3. New chemical bonds (attachments) formed
Covalent Bonds• Forms when two atoms share one or more
pairs of electrons
• Molecule: simplest part of a substance that retains all the properties of that substance
Ionic Bonds
• Ion: an atom or molecule with an electrical charge ( + or - )
• When two oppositely charge atoms combine and one electrons is transferred
Energy
Energy and Matter• Energy: the ability to do work or cause change
• Amount of energy in universe remains the same
• Energy changes in form
• Flow of energy from sun to living things is the chemistry of living things
Energy in Living Things• Important forms of energy:
– chemical energy– thermal energy– electrical energy– mechanical energy
• Free Energy: the energy is a system that is available for work
• Breakfast thermal, mechanical energy
States of Matter• All atoms of any
substance are in constant motion
• Rate of atoms or molecules motion determine state of substance
• Types of state:– Solid– Liquid– Gas
Solid• Particles
– tightly linked together
– in definite shape– vibrate in place
• Maintains fixed volume and shape
Liquid• Particles
– Not as tightly linked as a solid
– Move more freely than a solid FLOW
• Flow to conform to shape of container
• Maintain fixed volume
Gas
• Particles– move most freely
and RAPIDLY– little to no
attraction to each other
• Fill volume of container they occupy
Changing State of Matter
• THERMAL ENERGY must be added to substance
Energy and Chemical Reactions• Living things undergo
thousands of chemical reactions
• VERY complex (interrelated and multistep)
• Reactants: what you start with, the LEFT side of equation
• Products: what you end with the RIGHT side of equation
Energy Transfer
• Main energy supply of body : SUGAR
• Chemical Reactions: Sugars CO2 + H2O
• Types:– Exergonic Reaction:
release free energy– Endergonic Reaction:
absorbs free energy
Activation Energy• Amount of energy
needed to start reaction
• Catalyst: reduce the amount of activation energy needed
• Enzyme: important class of catalysts in living things
• Single organisms may have thousands of different kind
Reduction-Oxidation Reactions• Redox reactions: Electrons
transferred between atoms• Oxidations reaction:
reactant lose 1+ electrons; results in positive charge
• Reduction reaction: reactant gains 1+ electron; results in negative charge
• Electron given up by one substance and accepted by another
Solutions
Why?
• Most mass of living things is WATER
• Chemical reactions of life occur mostly in water solutions
• Electricity of nerves transmits through watery pathways of dissolved ions
• Chemical messengers move through watery medium of body
Solution
• A mixture in which one or more substances are uniformly distributed in another substance
• Can be:– liquid– solid– gas
Parts of a Solution
• Solute: substance dissolved in solution
• Solvent: substance in which the solute is dissolved
• Saturated solution: no more solute can be dissolved
Aqueous Solution
• Water is solvent
• VERY important to living things
• Marine microorganisms, plant nutrients, cells
Dissociation of Water
• Force of attraction between atoms so strong, oxygen atoms steals hydrogen atom from another water molecule
• Water molecule 2 ions with opposite charges
hydronium hydroixde ion ion
Acid
• Hydronium ions > Hydroxide ions
• Sour tasting
Base
• Hydroxide ions > Hydronium ions
• Bitter tasting
• Feel slippery
pH scale• Scale to compare
relative concentration of hydronium ions and hydrogen ions in a solution
Buffers
• Enzymes can only function at certain pH levels
• Buffers: chemical substances that neutralize small amounts of acid or base