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CHEMISTRY NOTES. VOIGT, 7 TH GRADE PALMETTO SCHOLARS ACADEMY. ATOMS. Atoms have mass and take up space They are the smallest part of an element that has the properties of that element They’re too small to be seen with a microscope. Elements.
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CHEMISTRY NOTES VOIGT, 7TH GRADE PALMETTO SCHOLARS ACADEMY
ATOMS • Atoms have mass and take up space • They are the smallest part of an element that has the properties of that element • They’re too small to be seen with a microscope
Elements • These are pure substances that can’t be changed into simpler substances • Elements are composed of one type of atom
Compounds • Pure substances composed of two or more elements that are chemically combined • Compounds can only be broken down into their basic elements through chemical changes • If two elements share an electron, then they form a bond called a covalent bond to form a compound • When a covalent bond is formed, the result is a MOLECULE
Mixtures • Mixtures are composed of two or more elements that are physically combined but still retain their own individual properties • They can be separated by filtration, sifting, or evaporation • May be heterogeneous or homogeneous • Heterogeneous means that it is NOT unform throughout the mixture • Homogeneous means that it is uniform throughout the mixture; particles are so small that they can’t be easily seen; homogeneous mixture is also called a solution
Metals vs. Nonmetals • These are two different groups with specific properties • Properties of Metals: • Luster – shiny or reflect light brightly • Conductors – Heat & electricity move through them easily • Malleable – Ability to be hammered into different shapes • Ductile – Ability to be drawn into a wire • High density – Heavy for their size
Metals vs. Nonmetals • Properties of non-metals • Dull – Not shiny • Nonconductors – Heat and electricity do not move through them easily • Brittle – break or shatter easily
Periodic Table • Horizontal row on the table is called a period • Elements are arranged in increasing order of atomic number • Families are vertical columns of elements and have similar properties • Metals are on the left side of the table, nonmetals are on the right
Symbols • You must memorize the following symbols and names for these elements: • Na – Sodium • Cl – Chlorine • H – Hydrogen • O – Oxygen • C – Carbon • N -- Nitrogen
Compounds and Chemical Formulas • Compounds are made of more than one element and have formulas showing the different elements and numbers of atoms in those elements • Subscript is small number written to the lower right of the element symbol and represents how many of each kind of atom are in the compound • If no subscript is written, only one atom of that element exist
Let’s 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!
Answers • Na -1; O – 1; H-1 • Na – 1; Cl – 1 • N – 1; H – 3 • C – 1; O - 2 • H – 2; O – 2 • H – 2; O – 1 • Ca – 1; Cl - 2 • C – 1; H – 4 • Cu – 1; S – 1; O – 4 • H – 1; Cl – 1 • Fe – 1; O – 2 • C – 6; H – 12; O – 6 • H – 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 Matter • Matter cannot be created or destroyed • The number of atoms in reactants must equal the number in products • Equation is “BALANCED” when that occurs