CHEMISTRY Composition of Matter n Matter Everything in

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CHEMISTRY

CHEMISTRY

Composition of Matter n Matter - Everything in universe is composed of matter n

Composition of Matter n Matter - Everything in universe is composed of matter n Matter is anything that occupies space or has mass n Mass – quantity of matter an object has n Weight – pull of gravity on an object

Elements n n Pure substances that cannot be broken down chemically into simpler kinds

Elements n n Pure substances that cannot be broken down chemically into simpler kinds of matter More than 100 elements (92 naturally occurring)

n n 90% of the mass of a living thing is composed of 4

n n 90% of the mass of a living thing is composed of 4 elements (oxygen, carbon, hydrogen and nitrogen) Each element is represented by a chemical symbol n Consists of 1 -2 letters n First letter is always capitalized

Atoms n The smallest particle of an element Nucleus Neutrons 0 Protons + Electrons

Atoms n The smallest particle of an element Nucleus Neutrons 0 Protons + Electrons -

The Nucleus n n n 2 main regions: Nucleus & electron shell Nucleus consists

The Nucleus n n n 2 main regions: Nucleus & electron shell Nucleus consists of positive charged protons and neutral neutrons Nucleus contains most of the mass of the atom

The Protons n All atoms of the same element have the same number of

The Protons n All atoms of the same element have the same number of protons Atomic number Atomic symbol Element name Atomic mass

The Neutrons n n The number varies slightly among atoms of the same element

The Neutrons n n The number varies slightly among atoms of the same element Atoms of the same element with different number of neutrons are called Isotopes

Atomic Mass n n The number of protons PLUS neutrons in an atom determines

Atomic Mass n n The number of protons PLUS neutrons in an atom determines its atomic mass number. The number of electrons is equal to the number of protons in an atom.

The Electrons n n Negatively charged high energy particles with little or no mass

The Electrons n n Negatively charged high energy particles with little or no mass Travel at very high speeds at various distances (energy levels) outside of the nucleus

Periodic Table n n n Elements are arranged by their atomic number on the

Periodic Table n n n Elements are arranged by their atomic number on the Periodic Table The horizontal rows are called Periods & tell the number of energy levels Vertical groups are called Families & tell the outermost number of electrons

n n n A compound is a pure substance made up of atoms of

n n n A compound is a pure substance made up of atoms of two or more elements Chemical formula is used to represent a compound. Examples: n H 20, CH 4, CO 2

n n Molecules are the smallest part of a compound. Some molecules are large

n n Molecules are the smallest part of a compound. Some molecules are large and complex

Chemical Formulas n n Subscript after a symbol tell the number of atoms of

Chemical Formulas n n Subscript after a symbol tell the number of atoms of each element H 20 has 2 atoms of hydrogen & 1 atom of oxygen Coefficients before a formula tell the number of molecules 3 O 2 represents 3 molecules of oxygen or (3 x 2) or 6 atoms of oxygen

n The properties of a compound are different from properties of its elements.

n The properties of a compound are different from properties of its elements.

n n The outermost electrons in elements determine if they will combine/bond with others.

n n The outermost electrons in elements determine if they will combine/bond with others. Elements react/bond with other elements to fill their outer energy level – becoming more stable.

n n n Most atoms are not stable in their natural state Tend to

n n n Most atoms are not stable in their natural state Tend to react (combine) with other atoms in order to become more stable (undergo chemical reactions) In chemical reactions bonds are broken; atoms rearranged and new chemical bonds are formed that store energy.

Covalent Bonds n Formed when two atoms share one or more pairs of electrons

Covalent Bonds n Formed when two atoms share one or more pairs of electrons

Ionic Bonds n n n Some atoms become stable by losing or gaining electrons.

Ionic Bonds n n n Some atoms become stable by losing or gaining electrons. These atoms are called Ions. Atoms that lose electrons are called positive ions. Atoms that gain electrons are called negative ions.

n Because positive and negative electrical charges attract each other ionic bonds form =

n Because positive and negative electrical charges attract each other ionic bonds form = attraction between a positive ion and negative ion.

States of Matter n n Atoms are in constant motion The rate at which

States of Matter n n Atoms are in constant motion The rate at which atoms or molecules in a substance move determines its state.

Solutions

Solutions

Solutions n A solution is a mixture in which 2 or more substances are

Solutions n A solution is a mixture in which 2 or more substances are uniformly distributed in another substance

n n n Solute is the substance dissolved in the solution n Particles may

n n n Solute is the substance dissolved in the solution n Particles may be ions, atoms, or molecules Solvent is the substance in which the solute is dissolved Water is the universal solvent

n n n Solutions can be composed of varying proportions of a given solute

n n n Solutions can be composed of varying proportions of a given solute in a given solvent --- vary in concentration (measurement of the amount of solute) A saturated solution is one in which no more solute can be dissolved. Aqueous solution (water as solvent) are universally important to living things

n Dissociation of water n Breaking apart of the water molecule into two ions

n Dissociation of water n Breaking apart of the water molecule into two ions of opposite charge n H 2 O H+ + OH- is the hydroxide ion H+ is the hydrogen ion

Acids and Bases n n n One of the most important aspects of a

Acids and Bases n n n One of the most important aspects of a living system is the degree of acidity or basicity Acids produce H+ ions Bases produce OH- ions

p. H Scale n n p. H scale measures the concentration of H+ ions

p. H Scale n n p. H scale measures the concentration of H+ ions and goes from 1 to 14 1 -7 are acids 7 is neutral 8 -14 are bases § Each p. H is 10 X stronger than next § e. g. ph 1 is 10 times stronger than ph 2

Buffers n n Control of p. H is very important Most enzymes function only

Buffers n n Control of p. H is very important Most enzymes function only within a very narrow p. H Control is accomplished with buffers made by the body Buffers keep a neutral p. H (p. H 7)

n n Buffers neutralize small amounts of either an acid or base added to

n n Buffers neutralize small amounts of either an acid or base added to a solution Complex buffering systems maintain the p. H values of your body’s many fluids at normal and safe levels