A brief review of Chemistry

A few general terms…  Anything that takes up space is termed matter.  An element is a substance that cannot be broken down into simpler substances.

Elements Elements are represented by a large letter (or letters) (such as C, N, Na or O) on a large chart called the periodic table.

Symbols you should memorize (Quiz tomorrow)  Carbon =  Sulfur=  Potassium=  Nitrogen=  Hydrogen=  Phosphorus=  Sodium=  Iron=  Oxygen=  Clorine=  Copper=

 The smallest particle of an element which retains the characteristics of that element is an atom.

On the diagram of an atom bellow, label the:  Protons with an A  Electrons with a B  Neutrons with a C  How many protons are there? _____  How man electrons are there? ____  How many neutrons are there? ____  Using the periodic table, can you figure out what element this is?  Hint: Atomic number = the number of protons in the nucleus

 When two or more elements come together to form a new product, the process is called a chemical reaction.  The resulting product, which is a new combination of elements is called a compound.

 Every compound has a unique formula which shows how many atoms of each are in the compound. (eg. CO 2 )  The smallest unit of a compound that still retains the properties of the compound is called a molecule.

Mixtures and Solutions

 Any two substances that are not chemically combined but are together is called a mixture.

 A solution is a class of mixtures in which the molecules are evenly distributed.  The substance being dissolved is the solute.  The medium in which the substance is being dissolved is called the solvent.

 Molecules that can be dissolved are termed soluble.  Molecules that cannot be dissolved are termed insoluble.

Acids and Bases

 The pH scale measures the acidity or basicity of a substance.  An indicator is a chemical used to test for pH.  An acid or base usually produces a color change in the indicator.  Electricity is also used to measure pH.

Acids  An acid has a high concentration of dissolved H+ ions.  It has a pH less than 7  Some examples of acids are sulfuric acid (H 2 SO 4 ); hydrochloric acid ( HCl) and acetic acid (CH 3 COOH)

Bases  A base has a high concentration of OH - ions.  It has a pH of more than 7.  Some examples of bases are ammonia (NH 3 ) and acetate ion (C 2 H 3 O 2 - ).

Introduction to chemical Reactions

 What does the word “chemical” mean to you?  Chemical: a single substance with distinctive properties All matter is in the form of chemicals. A chemical always reacts the same way under any given circumstance.

What is the difference between a chemical change and a physical change?

 Chemical Change: a new chemical is formed  Examples: rusting, rotting, burning  Signs of a chemical change – color change, release of gas, new substance formed, energy released

 Physical Change: NO new chemical is formed  Examples: breaking, dissolving, boiling, evaporating, melting, eroding, freezing, grinding, subliming

Indentify which of the following are chemical (C) or physical (P) changes: 1.a solid stretches when gently pulled ___ 2.a powder dissolves in water __ 3.a solid burns when ignited __ 4.a liquid changes color when exposed to air for a long time __ 5.a solid shatters into small pieces when hit with a hammer __ 6.a gas “pops” when a burning match is placed close by __ 7.solid becomes a gas when slightly warmed __ 8.a liquid evaporates in hot weather __ 9.limewater becomes cloudy when a gas passes through it __

 A chemical change is also called a “chemical reaction.” How do we write a chemical reaction?  Where are the “reactants” in an equation?  Where are the “products” in an equation?  What is the term for all the chemical reactions that occur in an organism? Metabolism

Types of Reactions  Synthesis reactions: ANABOLISM A + B  AB atoms, ions, or molecules combine to form a new molecule  Example: combining of amino acids to form proteins

Types of Reactions  Decomposition Reactions: CATABOLISM AB  A + B Molecule breaks apart to form atoms, ions, or molecules  Example: chemical digestion of food particles into basic nutrients