CHEMISTRY NOTES

CHEMISTRY NOTESVOIGT, 7TH GRADEPALMETTO SCHOLARS ACADEMYATOMSAtoms have mass and take up spaceThey are the smallest part of an element that has the properties of that elementTheyre too small to be seen with a microscopeElementsThese are pure substances that cant be changed into simpler substancesElements are composed of one type of atom

CompoundsPure substances composed of two or more elements that are chemically combinedCompounds can only be broken down into their basic elements through chemical changesIf two elements share an electron, then they form a bond called a covalent bond to form a compoundWhen a covalent bond is formed, the result is a MOLECULE MixturesMixtures are composed of two or more elements that are physically combined but still retain their own individual propertiesThey can be separated by filtration, sifting, or evaporationMay be heterogeneous or homogeneousHeterogeneous means that it is NOT unform throughout the mixtureHomogeneous means that it is uniform throughout the mixture; particles are so small that they cant be easily seen; homogeneous mixture is also called a solutionGraphic Organizer

Metals vs. NonmetalsThese are two different groups with specific propertiesProperties of Metals:Luster shiny or reflect light brightlyConductors Heat & electricity move through them easilyMalleable Ability to be hammered into different shapesDuctile Ability to be drawn into a wireHigh density Heavy for their sizeMetals vs. NonmetalsProperties of non-metalsDull Not shinyNonconductors Heat and electricity do not move through them easilyBrittle break or shatter easily

Periodic TableHorizontal row on the table is called a periodElements are arranged in increasing order of atomic numberFamilies are vertical columns of elements and have similar propertiesMetals are on the left side of the table, nonmetals are on the right

SymbolsYou must memorize the following symbols and names for these elements:Na SodiumCl ChlorineH HydrogenO OxygenC CarbonN -- NitrogenCompounds and Chemical FormulasCompounds are made of more than one element and have formulas showing the different elements and numbers of atoms in those elementsSubscript is small number written to the lower right of the element symbol and represents how many of each kind of atom are in the compoundIf no subscript is written, only one atom of that element exist

Lets Practice!Write down how many atoms are in each compound! Write down each compound and break it down into how many atoms of each element are present in each compound.Answers are on next slide!

AnswersNa -1; O 1; H-1Na 1; Cl 1N 1; H 3C 1; O - 2H 2; O 2H 2; O 1Ca 1; Cl - 2C 1; H 4Cu 1; S 1; O 4H 1; Cl 1Fe 1; O 2C 6; H 12; O 6H 2; S 1; O - 4

Chemical Equations-- Used to represent a chemical reaction that has occurred-- Contains the elements or formulas involved in the reaction--An arrow is used to distnguish between the substances that are broken down or combined from the substances formed in a reaction

This equation reads: 2 H2 + O2 YIELDS 2 water molecules.Law of Conservation of MatterMatter cannot be created or destroyedThe number of atoms in reactants must equal the number in productsEquation is BALANCED when that occurs