Chemistry Review Matter- anything that has mass and takes up space Matter Anti- matter

Chemistry Review Properties of Matter 1)Physical- property that describes the look or feel of a substance without changing the identity of the substance. Ex- boiling point, melting point, density, color, hardness Density = mass of substance volume of substance

Chemistry Review Properties of Matter 2) Chemical- property that determines how a substance will react and change when exposed to other substances.

Chemistry Review Matter is made of elements –Element is a substance that has a distinct set of physical and chemical properties –Atom is the smallest unit of an element Proton (+charge, nucleus, ~1 amu) Neutron (neutral charge, nucleus, ~ 1 amu) Electron (- charge, orbits nucleus, ~ 0 amu)

Chemistry Review Atomic Number- unique to the atoms of each element –Atomic number = # of protons in the nucleus Atomic mass- average of all isotopes for a given element –Mass # = # of protons + # of neutrons

Chemistry Review Atoms of the same element MUST contain the same number of protons, but can differ in the number of neutrons and/or electrons Isotopes- atoms of an element that vary in the number of neutrons Ions- atoms that have a charge because they have gained or lost electrons

Isotopes of Hydrogen

Chemistry Review Recall the phases of matter- solid, liquid, gas, and plasma –Gas: indefinite shape and indefinite volume –Liquid: indefinite shape and definite volume –Solid: definite shape and definite volume Phase changes occur by a gain or loss of heat energy

Phases of Matter

Combinations of Atoms Compound- formed when two or more atoms chemically combine –Chemical properties are different for the compound as compared to the individual elements which make it up –2 H 2 (g) + O 2 (g) → 2 H 2 O(l) Molecule- smallest complete unit of a compound

Combinations of Atoms As atoms react to form new compounds, their chemical and physical properties are changed NaCl, CaCO 3, H 2 0 and other examples

Combinations of Atoms Most of chemistry is based on the movement of electrons between atoms –Ionic bonds –Covalent bonds –Metallic bonds

Chemical Bonds Ionic Bonds –Formed by the transfer of electrons from one atom to another –Usually formed between metals and nonmetals –Solid crystals in nature that dissolve in water to form electrically charged ions

Chemical Bonds

Covalent Bonds –Formed by the sharing of electrons Uneven sharing results in polar molecules such as water Even sharing results in nonpolar molecules –Can be solid, liquid, or gas in nature Nonpolar bonds are weaker than polar bonds which in turn are weaker than ionic bonds

Chemical Bonds Metallic Bonds –Electrons are free to move from one atom to the next of the metal –This leads to the luster of the metal and the ease in conducting electricity (which is merely the flow of electrons through a substance)

Chemical Formulas Indicates what elements are combined in a given compound and the relative number of each element in that compound –Methane gas - CH 4 Contains one atom of carbon to every four atoms of hydrogen Subscripts are used to indicate the number of atoms of a particular element in a compound

Chemical Reactions Every reaction has reactants and products Chemical properties of reactants determine how a reaction will occur Products will have different chemical and/or physical properties than the reactants

Chemical Reactions Reaction Indicators –Evolution of gas –Formation of a precipitate (solid) –Color change –Temperature change: warmer or cooler

Mixtures A mixture is a material that contains two or more substances that are NOT chemically combined –Heterogeneous mixture- the different components can be seen as individual substances –Homogenous mixture- have the same composition throughout the mixture. You can’t tell one substance in the mixture from another

Mixtures Homogenous Mixtures –Solution- all components are in the same phase and the solute is so fine that it won’t settle out of the solvent Can be solid (alloy), liquid, or gas (air) –Colloid- Very fine particles that appear to be completely dissolved but can reflect light (Tyndall Effect) –Suspension- Components are in different phases (milk, blood, smog)