Final Exam Review: Properties & Phases of Matter

Matter Matter is anything that has mass and takes up space. Atoms are the building blocks of matter.

ELEMENTS and COMPOUNDS An element is the simplest type of a pure substance. It cannot be broken down into any other substances by chemical or physical means. Elements combine to form compounds. A compound is a substance formed from the chemical union of two or more elements.

Solutions A solution is a well-mixed mixture. Solutions are homogeneous and contain a solute and a solvent. Example- Sugar dissolved in water. Sugar is the solute, water is the solvent.

MIXTURES A mixture is made from two or more substances that are together in the same place but not chemically combined. A heterogeneous mixture appears to be different throughout. A homogeneous mixture appears to be the same throughout.

Compounds Mixtures chemically combined NOT chemically combined do NOT keep their original properties keep their original properties combined in a specific ratio NOT combined in a specific ratio cannot be broken down by simple chemical methods can be broken down by simple chemical methods

Phases of Matter Matter can take 4 different phases or states: Solid Liquid Gas Plasma

Phase Shape Volume Solid Liquid Gas Plasma Definite Definite Indefinite Definite Indefinite Indefinite Indefinite Indefinite

S L Melting L S Freezing L G Evaporating GL Condensing

ATOMIC STRUCTURE Atoms are made up of 3 subatomic particles Protons are positively charged subatomic particles found in the nucleus. They each have a mass of 1 amu. The number of protons is the atomic number of the element and so tells the identity of the element Neutrons have no charge and are also found in the Nucleus of the atom. Atoms of an element may contain Various numbers of neutron which are called isotopes of the element. Neutrons have a mass of 1 amu each. Electrons are negatively charged subatomic particles found in an electron cloud around the nucleus. They are soooooo small that they are not considered to add mass to the atom.

Isotopes Remember that all atoms of a particular element have the same number of protons, but that these atoms may have different numbers of neutrons in the nucleus These all represent the nucleus of a carbon atom (atomic # 6) 6 p+ 6 p+ 6 p+ 6 n 8 n 7 n Each atom of carbon can have different numbers of neutrons. These are 3 Isotopes of the carbon atom.

Information from the periodic table block The atomic number tells the number of protons in the nucleus of the atom. The table is arranged in order of increasing atomic number. The average atomic mass when rounded to the nearest whole number tells the total amu in the nucleus of the atom. If you subtract the number of protons from this number, you will determine the number of neutrons in the nucleus. The electron configuration shows how many electrons there are in each energy level. It allows you to see the number of valence electrons in the outer energy level of the atom. You will also find the name, and the symbol for each element in this block.

Atoms and the periodic table The atomic number is the number of proton in an element Electron configuration indicates the number of electrons in each energy level 8 2 6 O oxygen 15.9994 The average atomic mass is not a whole number because it is an average of the masses of all the isotopes of an element.

PERIODIC LAW Metals are to the LEFT of the Zig-Zag Non-Metals are to the RIGHT of the Zig-Zag METALLOIDS are found along the line

There are 7 rows or periods on the table There are 7 rows or periods on the table. Elements in a periods all have the same number of energy levels. If the element is in period 3, it has 3 energy levels

PROPERTIES OF Metals and nonmetals Metals are electron donors Metals have 3 or less valence electrons Metals are good conductors of heat and electricity and are malleable and ductile Metals are found on the left of the step on the periodic table Nonmetals are electron recipients Metals have 5 or more valence electrons nonmetals are poor conductors of heat and electricity and are britlle Nonmetals are found on the right of the step on the periodic table

Families of elements are found in the columns on the periodic table Families of elements are found in the columns on the periodic table. Elements in a column or family or group have similar chemical properties because they have the same number of valence electrons

CHEMICAL REACTIONS Four types of chemical reactions are synthesis reaction Two simple substance combine to form a more complex substance A + B yields AB Decomposition reaction a complex substance breaks down into two or more simple substances AB yields A + B Single replacement reaction an uncombined element replaces an element in a compound A + BC yields AC + B Double replacement reaction two elements replace each other in two compounds AB + CD yields CB + AD

Chemical reaction continued Evidence that a chemical reaction has occurred is the formation of new substances Each chemical equation must be balanced so that all the atoms of each element are the same on both sides of the arrow. This is called the Law of Conservation of mass and means that matter cannot be created or destroyed during a chemical reaction A chemical reaction that absorbs energy and yields products that are colder than the reactants is ENDOthermic A chemical reaction that releases energy and becomes warmer than the reactants is called EXOthermic To increase the rate of a chemical reaction you can Increase the heat energy Increase the surface area of the substance Increase the concentration of the reactants

ACIDS AND BASES pH is measured by using a scale that goes from 0 to 14. pH is an abbreviation for the presence of H ions in a solution 7 represents a neutral pH The further away from neutral, the stronger the acid or the base So a pH of 12.3 would indicate a very strong base and a pH of 2.1 would indicate a very strong acid.

CONCLUSION WE HAVE CERTAINLY LEARNED A GREAT DEAL ABOUT LIVING THINGS AND CHEMISTRY! I hope this year has been as rewarding and exciting for you as it has been for me. You are a talented and caring group of young people and I will miss you very much. Please be sure to visit when you are in the 8th grade next year. Have a wonderful and restful summer. Always be amazed at the world around you.