Warm Up: Partner sitting closest to the door silently write down what happens during a synthesis reaction. Partner sitting closest to the window silently write down what happens during a decomposition reaction. Now: explain them to each other, compare/contrast the reactions door partner go first

Balancing Equations

Q: How could you chemically describe this reaction? Look at this rusty bike wheel. It has been left outside in damp weather too many times, so the iron in the metal parts has rusted. Iron rusts when it combines with oxygen in the air. Iron rusting is an example of a chemical reaction. In a chemical reaction, substances change into entirely different substances. For example, the iron in the bike and the oxygen in the air have changed into rust.

Q: How could you chemically describe this reaction without using words Q: How could you chemically describe this reaction without using words? Scientists use an equation. Look at this rusty bike wheel. It has been left outside in damp weather too many times, so the iron in the metal parts has rusted. Iron rusts when it combines with oxygen in the air. Iron rusting is an example of a chemical reaction. In a chemical reaction, substances change into entirely different substances. For example, the iron in the bike and the oxygen in the air have changed into rust.

A: Chemical equations are used to represent: chemical reactions

What is the general equation for the reaction in which iron rusts? Fe + O2 → Fe2O3 Look at this rusty bike wheel. It has been left outside in damp weather too many times, so the iron in the metal parts has rusted. Iron rusts when it combines with oxygen in the air. Iron rusting is an example of a chemical reaction. In a chemical reaction, substances change into entirely different substances. For example, the iron in the bike and the oxygen in the air have changed into rust. Iron + Oxygen → Iron Oxide (RUST) What type of bond forms in the product? Ionic (metal+nonmetal)

What type of chemical reaction is this? How do you know that? Fe + O2 → Fe2O3 Look at this rusty bike wheel. It has been left outside in damp weather too many times, so the iron in the metal parts has rusted. Iron rusts when it combines with oxygen in the air. Iron rusting is an example of a chemical reaction. In a chemical reaction, substances change into entirely different substances. For example, the iron in the bike and the oxygen in the air have changed into rust. Synthesis: Two separate elements chemically join to form one new compound

What are the reactants and products? Fe + O2 → Fe2O3 Reactants Products The atoms/compounds you have BEFORE the reaction occurs. The atoms/compounds you have AFTER the reaction occurs.

2Al(s) + 3I2(s)  Al2I6(s) VIDEO: Aluminum and Iodine Reaction Watch the video and tell me how you know that this is a chemical change, and what type of bond forms in the product: 2Al(s) + 3I2(s)  Al2I6(s) VIDEO: Aluminum and Iodine Reaction

When is an equation balanced? When there is the same the number of each type of atom on both sides BEFORE: 4 White (H) 1 Black (C) 4 Red (O) AFTER: 4 White (H) 1 Black (C) 4 Red (O)

Chemical Equations coefficients 4 Al (s) + 3 O2 (g)  2 Al2O3 (s) Coefficients are: numbers in front of the letters, represents how many molecules you have

Chemical Equations 4 Al (s) + 3 O2 (g)  2 Al2O3 (s) subscripts Subscripts are: numbers behind the letters, represent how many atoms are in that molecule

Chemical Equations 4 Al (s) + 3 O2 (g)  2 Al2O3 (s) The letters (s) solid, (g) gas, and (l)liquid are the physical states, (aq) means aqueous The arrow means : yield/create/produce/form

Learning Check 2Li (s) + 2H2O (l)  2LiOH (aq) + H2 (g) What does “2“ mean in front of LiOH? Number of molecules What does “2“ to the right of “H2” mean? Number of atoms of H What does “(aq)“ to the right of LiOH mean? Aqueous solution What does ““ mean? Yield, form, produce

Q: What is the chemical equation for this reaction? A: The chemical equation is: C + O 2 → CO 2

Q: How have the atoms of the reactants been rearranged in the products of the reaction? C + O 2 → CO 2 A: Carbon atom chemically bonds with two oxygen atoms.

What bonds are broken and what new bonds have formed? C + O 2 → CO 2 C + O=O → O=C=O Bonds Break New Bonds Form A: Bonds between the Oxygen atoms have broken New bonds have formed between Carbon and the 2 Oxygens

Q: What type of bond has formed between the Carbon and 2 Oxygens? C + O 2 → CO 2 C + O=O → O=C=O Bonds Break New Bonds Form Q: What type of bond has formed between the Carbon and 2 Oxygens? A: COVALENT Bond (Nonmetal to nonmetal)

What type of chemical reaction is this and how do you know? C + O 2 → CO 2 A: Synthesis: Two separate elements chemically join to form one new compound

Is this a balanced equation? The charcoal used in a grill is basically carbon. The carbon reacts with oxygen to yield carbon dioxide. The chemical equation for this reaction, C + O2  CO2, R P Count the number of atoms of each element found in the reaction. 1 C 1 C 2 O 2 O Is this a balanced equation? YES

Yes, this is a chemical change, but what type of reaction is it Yes, this is a chemical change, but what type of reaction is it? How do you know that? C + O2  CO2, Combustion: O2 present, give off heat, light, CO2,

Learning Check Q: What needs to happen for a chemical reaction (change) to take place? A: Bonds between atoms of the reactants break and NEW bonds form to create the products

Q: Is this chemical reaction correct? Explain why. Learning Check Q: Is this chemical reaction correct? Explain why. +  A: No. The numbers of each type of square on both sides are not equal

Learning Check +  Why is this reaction correct? The numbers of each type of atom on both sides are equal. (so the atoms rearranged) +  NEW PRODUCTS

For example: O2 is Oxygen but O3 is Ozone Remember: To Balance an equation, you are only allowed to add Coefficients (the numbers in front of chemical formulas in the equation) You CANNOT add or change the subscripts because this would change the identity of the molecules For example: O2 is Oxygen but O3 is Ozone The order of the Coefficients in the Chemical Equation is important because this is how you write the COEFFICIENT RATIO.

Balancing using shapes ____H2 + ____O2  ____H2O 2 1 2 Is this reaction balanced? NO BALANCED ! Now fix the H on the left.

Balancing Equations using T-chart ___ H2(g) + ___ O2(g)  ___ H2O(l) 1. Count the number of atoms of each element found in the reaction. R P H - 2 H - 2 O - 2 O - 1 This equation is NOT balanced!

Balancing Equations using T-chart 2 1 ___ H2(g) + ___ O2(g) ---> ___ H2O(l) 2 R P H - 2 H - 2 O - 2 O - 1 2. Add coefficients to balance the atoms 4 4 2 3. Don’t forget to recount. Now it is balanced! Now fix the H on the left. Don’t forget there is a 1 in front of O2.

_____Fe + ____O2  ____Fe2O3 Now You Try! Now fix the Fe atoms 2 x 2 = 4 _____Fe + ____O2  ____Fe2O3 4 3 2 6 Find the common denominator: 6/3 = 2 6/2 = 3 Coefficient ratio: 4:3:2

2:3 – find a common multiple Now You Try Again! RULE: Balance O and H Last! Al + O2  Al2O3 2 3 2 R P 4 2 2 Al 2 x 2 = 4 1 Al 2 x 3 = 6 2 O 3 O 3 x 2 = 6 2:3 – find a common multiple Coefficient ratio: 4:3:2

Meaningful Talk Door partner: explain how to balance an equation without looking at your notes Window partner: look at your notes while they explain, let them know if they explained it correctly, correct them if they are wrong Questions?