CH. 2 Chemistry of lifeSection 1 Nature of matter
Atoms
•Atom- is the smallest unit ofmatter that cannot be brokendown by chemical means.
•Atoms consist of 3 kinds ofparticles: electrons, protons andneutrons.
CH. 2 Chemistry of lifeSection 1 Nature of matter
Electron, protons, and Neutrons
•Electrons have a negative charge (-), andare located outside the nucleus in theelectron cloud.
•Protons have a positive charge (+), andare located in the nucleus or core of anatom.
•Neutrons have no charge, located in thenucleus or core of an atom.
CH. 2 Chemistry of lifeSection 1 Nature of matter
Electrons, Protons, and Neutrons
•Because electrons have a negative charethe electron cloud of an atom is alwaysnegative
•Because protons are positive andneutrons are neutral the nucleus of anatom is always positive.
•Because electrons and protons areoppositely charged they attract oneanother.
CH. 2 Chemistry of lifeSection 1 Nature of matter
Elements
•Element- a pure substance made of onlyone kind of atom.
•There are more than 100 knownelements, and each is represented by aone, two, or three letter symbol. Ex.Hydrogen (H) Carbon (C).
•Elements differ in the number ofprotons their atoms contain.
CH. 2 Chemistry of lifeSection 1 Nature of matter
Chemical Bonding
•Atoms can join with other atoms to formstable substances.
•A force that joins atoms is called achemical bond.
• compound-a substance made of thejoined atoms of two or more differentelements.
CH. 2 Chemistry of lifeSection 1 Nature of matter
Covalent Bonds
•Molecule-smallest unit of a substance thatkeeps all of the properties of that substance;it can consist of one atom or two or moreatoms bonded together.
•Covalent bonds form when two or moreatoms share electrons to form a molecule.
•A molecule such as the water moleculeshown below, is a group of atoms heldtogether by covalent bonds.
CH. 2 Chemistry of lifeSection 1 Nature of matter
Covalent Bonds
•The arrangement of their electronsdetermines how atoms bond together.
•An atom becomes stable when its outerelectron level is full. If the outer electronlevel is not full, an atom will reactreadily with atoms that can provideelectrons to fill its outer level.
CH. 2 Chemistry of lifeSection 1 Nature of matter
Ionic Bonds
•Sometimes atoms or molecules gain or loseelectrons.
•Ion-An atom or molecule that has gained orlost one or more electrons.
•Ions have an electrical charge because theycontain an unequal number of electrons andprotons. Ions of opposite charge mayinteract to form an ionic bond.
Ch. 2 Chemistry of life
Section 2 Water andsolutions
CH. 2 Chemistry of lifeSection 2 Water and solutions
Water in living things
•70 % of your body is madeup of water.
•2/3 of molecules in yourbody are water molecules.
CH. 2 Chemistry of lifeSection 2 Water and solutions
Storage of Energy
•Many organisms release excess heat throughwater evaporation.
•In organisms, this ability to controltemperature enables cells to maintain aconstant internal temperature when theexternal temperature changes.
•In this way, water helps cells maintainhomeostasis.
CH. 2 Chemistry of lifeSection 2 Water and solutions
Cohesion and Adhesion
•Cohesion-is an attraction between substances ofthe same kind.
•Because of cohesion, water and other liquids formthin films and drops.
•Molecules at the surface of water are linkedtogether by hydrogen bonds like a crowd of peoplelinked by holding hands. This attraction betweenwater molecules causes a condition known assurface tension.
CH. 2 Chemistry of lifeSection 2 Water and solutions
Cohesion and Adhesion
•Adhesion-is an attraction between differentsubstances.
Aqueous Solutions
•Solution-a mixture in which one or more substancesare evenly distributed in another substance.
•Substances can dissolve in water, they can moreeasily move within and between cells.
CH. 2 Chemistry of lifeSection 2 Water and solutions
Polarity
•The polarity of water enables many substances todissolve in water.
•When ionic compounds dissolve in water ionsbecome surrounded by polar water molecules.
•The resulting solution is a mixture of watermolecules and ions.
•Nonpolar molecules do not dissolve well in water.
CH. 2 Chemistry of lifeSection 2 Water and solutions
Acids and Bases
•Acids-compounds that from hydrogen ions whendissolved in water.
•When an acid is added to water, the concentrationof hydrogen ions in the solution is increased abovethat of pure water.
•Bases-compounds that reduce the concentration ofhydrogen ions in a solution.
•The pH scale measures the concentration ofhydrogen ions in a solution.
Chapter 2 Chemistryof life
Section 3 Chemistry ofcells
CH. 2 Chemistry of lifeSection 3 Chemistry of cells
Carbon Compounds
•Four principal classes of organic compoundsare found in living things: Carbohydrates,lipids, proteins, and nucleic acids.
•Without these compounds cells could notfunction.
CH. 2 Chemistry of lifeSection 3 Chemistry of cells
Carbohydrates