Molecular Structure of Matter

n Compounds: two or more atoms or ions bind to one another.

• Water (H20) Sugar (C6H12O6)

n Mixtures are variable combinations of atoms, ions, or molecules.

• Honey (several sugars + water)

Air (gas mixture: nitrogen, oxygen, etc)

n Ions are electrically charged particles.

n Atom loses electrons = positively charged

n Atom gains electrons = negatively charged

NaCl à Na+ + Cl- (in water)

Acids, Bases, and pH

n Acid - a compound that releases hydrogen ions in water solution.

n Base - a compound that accepts hydrogen ions in water solution.

n pH indicatorshows acidity or hydrogen ion concentration.

• The scale is inverse and logarithmic

n pH = 7: neutral

n 0 < pH < 7: acidic (more H+ than OH-)

n 7 < pH < 14: basic (less H+ than OH-)

n Organic matter consists of molecules containing carbon atoms that are bonded to form chains or rings.

• All living things contain molecules of organic compounds.

n Chemical bonds in organic molecules contain a large amount of chemical energy that can be released when the bonds are broken.

n Essential Elements of Life:

• carbon, hydrogen, oxygen, and nitrogen

• make up 96% of living matter

Chemical Reactions

When chemical bonds are formed or broken, a chemical reaction occurs:

o Exothermic reaction: heat is released

o Endothermic reaction: heat is absorbed

Дата добавления: 2015-09-01