SIGNS OF CHEMICAL CHANGES Chemical Property -The ability of a substance to undergo a change that alters its identity. -A characteristic that cannot be observed without altering the substance Chemical Change Change in which the composition of a substance changes Changes are not easily reversed Signs of Chemical Changes 1.Change in Color 2.Change in Temperature 3. Change in Odor 4.Bubbles- Gas produced 5. Precipitate (solid) is formed + Atom The smallest particle of any pure element. Only 1 atom Example: 1 atom of H Element A substance made up of the SAME type of atom Example: O 2 Compound -a substance made up of atoms of two or more DIFFERENT elements combined in a specific ratio Ex. NaCl or H 2 O Molecule -Group of 2 or more atoms held together by chemical bonds. Atoms may or may not be of the same element EX. NaCl or O 2 Chemical Formula -a way of describing the number of atoms that make up one molecule of a compound Ex. C 6 H H 2 0 Subscript -the number of atoms of that particular element SUB-Below EX. H 2 0 or CH 4 Coefficient -determines the number of molecules (groups) of the formula -This number will be DISTRIBUTED just like in math. It applies to each element and is multiplied by each subscript to find the total number of atoms of each element and a total number of atoms in the molecule. EX. 2H 2 O 4Al 2 (SO 4 ) 3 CH 4 C H H H H 2H 2 0 H O H HH O Atom Element Compound Molecule C, O, H, N C,C 2, O, O 2, H, H 2, N,N 2 CH 4, H 2 O, CO 2 CH 4, H 2 O, H 2, O 2, CO 2 2H 2 O, 3O 2, 2CO 2 Identify the Elements, give the number of atoms of each element, and the total number of atoms in the formula 1)2FeCl 3 2)KMnO 4 3)3HgO 4)C 6 H 5 COOH 5)2HCl 6.4Fe 2 O 3 7.NaClO 8.ZnCl 2 9.KClO F Al 2 (SO 2 ) 3 Chemical Reaction -a change in which one or more chemical substances are rearranged to form different substances. Chemical Equation -a way to show a chemical reaction using chemical formulas. -made up of reactants and products ReactantsProducts Yield the amount of product obtained as a result of a chemical reaction Components of chemical reaction Reactants -are indicated on the left side -substances that react in a chemical reaction -inputs -Ingredients Products -are indicated on the right side -new substances created/ PRODUCED in a chemical reaction -Outputs -Cake Example CH 4 + 2O 2 CO 2 + 2H 2 O ProductsReactants Coefficient (# of molecules) # of atoms of that element Law of Conservation of Mass -what goes into a chemical reaction will come out of a chemical reaction. -atoms found on the reactants side will also be found on the products side. They will be broken apart and rearranged to create new substances. -creates a Balanced equation CH 4 + 2O 2 CO 2 + 2H 2 O 6CO 2 + 6H 2 O C 6 H 12 O 6 + O 2 Modeling Balanced/Unbalanced Equations 4P + 5O 2 P 4 O 10 Mg + O 2 MgO 2Al 2 O 3 4Al + 3O 2 2HgO 2Hg + O 2 BaCl 2 + H 2 SO 4 BaSO 4 + HCl Identify Balanced Equations 1)2Fe + 3Cl 2 2FeCl 3 2)KMnO 4 + HCl KCl + MnCl 2 + H 2 O + Cl 2 3)HgO Hg + O 2 4)C 6 H 5 COOH + O 2 CO 2 + H 2 O 5)H 2 + Cl 2 2 HCl 6)2Fe + 3O 2 Fe 2 O 3 7)2NaOH + Cl 2 NaCl + NaClO + H 2 O 8)Zn + 2HCl ZnCl 2 + H 2 9)KClO 3 KCl + O 2 10)S F 2 8SF 6 Balancing Equations 1)Determine number of atoms for each element. 2) Pick an element that is not equal on both sides of the equation. 3)Add a coefficient in front of the formula with that element and adjust your counts. 4) Continue adding coefficients to get the same number of atoms of each element on each side. Balancing Equations N 2 + H 2 NH 3 Balancing Equations NaCl + F 2 NaF + Cl 2 Balancing Equations Practice 1.P + O 2 P 2 O 5 2.KClO 3 KCl + O 2 3.H 2 + O 2 H H O 2 H 2 O 2 5. K + MgBr KBr + Mg