Earth Science Chapter 3 Section 2 Combining Matter Earth Science Chapter 3 Section 2

A substance that is composed of atoms of two or more different elements that are chemically combined Examples: Water- two Hydrogen and 1 one Oxygen atoms. Table Salt- 1 Na (Sodium) and 1 CL (Chlorine) atoms Compounds have different properties from the atoms that make them Compounds

Chemical Formulas Compounds represented by chemical formulas Examples: Include the symbol for each element present Also includes number of each atom in subscript If there is only one atom, no subscript is present Examples: H20= 2 Hydrogen, 1 Oxygen atoms NaCL= 1 Sodium and 1 Chlorine atoms Chemical Formulas

Elements stabilize when outermost energy levels are full- chemical bonds can achieve this Force that holds together the elements in a compound Stability achieved by sharing electrons Covalent Bonds: The attraction of two atoms for a shared pair of electrons that hold the atoms together Covalent Bonds

Covalent Bonds

Molecule Composed of two or more atoms held together by a covalent bonds No electrical charge- protons and electrons match A compound comprised of molecules is called a molecular compound Molecules

Polar molecules Electrons of water are not shared equally. Hydrogen electrons spend more time around oxygen Polar molecules have a slightly positive and slightly negative end. Polar molecules

Ionic Bonds Ionic Bonds The attractive forces between two ions of opposite charges One or more electron are removed from an atom and attached to another atom Results: The positive ion attracted to the negative ion Molecules formed by ionic bonds are called ionic compounds Ionic Bonds

Table Salt Outermost electron from Sodium atom is taken by Chlorine. Ions Na+ and Cl- are formed. The charges of the ions of Na+ and Cl- attract each other. Ionic Bonds

Metallic Bonding In metals Electrons are shared by all atoms Not just adjacent atoms a group of positive metal ions surrounded by freely moving negative electrons Allows metals to conduct electricity Metallic Bonding

Metallic Bonding Configuration of metallic bonding Metals can be deformed When hammered, atoms are moved aside Only the shape is changed Metallic Bonding

Chemical Reactions Compounds can break down into simpler substances The change of one or more substances into other substances Reactions described in chemical equations Chemical Reactions

Chemical Reactions When a chemical equation is written There must be the same number of specific atoms on each side of the equation Same amount of matter before and after the reaction Called a balanced equation Chemical Reactions

Mixtures and Solutions Combination of two or more compounds that retain their identities Example: Salt and pepper Nuts and bolts Heterogeneous mixture Particles can’t be distinguished from each other and retain their original properties Examples: Sugar water Molten rock Metal alloys Homogeneous mixture Mixtures and Solutions

Mixtures and Solutions Can be solid, liquid or gas solutions mixture Mixtures and Solutions

Acids and Bases Acids Bases Solution containing a substance that produces hydrogen ions (H+) Loses an electron Ph value reading below 7 Lower ph, the more acidic Substance that produces hydroxide ions (OH-) in water Base can neutralize an acid Ph value reading above 7 Higher the ph, the more basic Acids and Bases