BELL WORK: When wood burns, a small amount of ashes is made. Why is the mass of the wood before the fire not equal to the mass of the ashes after the reaction? The mass of the wood has been destroyed. The mass of the wood and the oxygen that allowed it to burn will equal the mass of the ashes and the gas. The mass of the wood and the ashes equals the mass of the oxygen and the smoke given off during the time that the wood burned. The wood has holes in it so it is actually lighter in mass than it appears. The mass of just the wood will equal the mass of just ashes after the burning.

Who’s Ready for TCAP?!!!! SPI 0807.9.1—True or False Electrons are smaller than protons and neutrons. SPI 0807.9.3—Identify the compound. Co He HBr Na Cl SPI 0807.9.9—Elements that are shiny, malleable, and ductile can be found to the __________ of the zigzag line on the periodic table. left SPI 0807.9.11—In the following chemical equation, identify the reactants. CH4 + O2 → CO2 + H2O

Let’s review… 1. The law of conservation of mass says that matter is never _________ or destroyed. 2. According to the law of conservation of mass, if there are 20 atoms on the reactant side, there must be ______ atoms on the product side. 3. The chemical formula for dinitrogen trioxide is written like __________. created 20 N2O3

Sodium sulfate and barium chloride react with each other to form sodium chloride and barium sulfate as shown. Which statement MOST accurately describes the mass of the reactants compared to the mass of the products? The mass of the reactants is the same as the mass of the products. The products have a greater mass because matter was created during the reaction. The reactants have a greater mass because some of the mass was converted to heat. The reactants have a greater mass because some matter was destroyed by the reaction.

Don’t be the last to stand! Stand up whenever the total number of atoms equals 10. 2 Na2O2H 9

2 Na2OH2 10

3 NaCl 6

3 Na2Cl 9

5 Na2 10

4 H2Cl 12

2 H2Cl3 10

2 H4O 10

3 MgOH 9

2 Mg2OH2 10

Does the equation above represent the law of conservation of mass? 1. Reactants 2. Products 4P + 5O3 → P4O10 3. 4. Coefficient Subscript Does the equation above represent the law of conservation of mass?

Balancing Chemical Equations STEP 1: Box around compounds STEP 2: Identify elements STEP 3: Count atoms STEP 4: Add Coefficients STEP 5: Update numbers

Balancing Chemical Equations 3 AlBr3 + K → KBr + Al 3 Al = 1 Br = 3 K = 1 Al = Br = K = Al = 1 Br = 1 K = 1 Al = Br = K = 3 3 3 STEP 1: Box around compounds STEP 2: Identify elements STEP 3: Count atoms STEP 4: Add Coefficients STEP 5: Update numbers

P4 + O2 → P2O3 P4 + 3O2 → 2P2O3

N2 + H2 → NH3 N2 + 3H2 → 2NH3

Chapter 13 Test: Thursday, Feb. 23rd I can use prefixes in a compound to write out a chemical formula. I can count atoms in a chemical formula using subscripts, coefficients, and parentheses. I can explain the law of conservation of mass. I can count and compare atoms in a chemical equation to determine if it represents the law of conservation of mass.

What we still need to know… I will be able to identify chemical reactions (or chemical equations) as a synthesis reaction, decomposition reaction, single- displacement reaction, or double- displacement reaction. I will be able to explain how the rate of a reaction can speed up or slow down. I will be able to identify chemical reactions as endothermic or exothermic reactions.

Endothermic vs. Exothermic Reactions Pg. 76 Let’s remember that there are physical and chemical changes… A physical change doesn’t create something new. The composition (what it’s made of) doesn’t change. A chemical change does create something new. The bonds get rearranged. We have signs to show this: change in color or smell, gives off light or heat, forms a solid…

Is it a physical or chemical change? Let’s Compete! Is it a physical or chemical change? Physical

Is it a physical or chemical change? Let’s Compete! Is it a physical or chemical change? Physical

Is it a physical or chemical change? Let’s Compete! Is it a physical or chemical change? Chemical

Is it a physical or chemical change? Let’s Compete! Is it a physical or chemical change? Physical

Is it a physical or chemical change? Let’s Compete! Is it a physical or chemical change? Chemical

Is it a physical or chemical change? Let’s Compete! Is it a physical or chemical change? Chemical

Is it a physical or chemical change? Let’s Compete! Is it a physical or chemical change? Physical

EXOTHERMIC REACTIONS An exothermic reaction is a reaction that releases energy (or heat). Example: Making ice cubes (physical) Rusting bike (chemical) A candle flame (chemical)

ENDOTHERMIC REACTIONS An endothermic reaction is a reaction that absorbs (or uses) energy. Example: Photosynthesis (chemical) Evaporating liquid water (physical) Melting a crayon (physical) Baking bread (chemical)

Fold the paper hamburger style Around the room… There are 12 questions around the room. Walk around with your notes and a partner and answer all 12 questions. You are only allowed to discuss answers with your partner. Turn in your work when you have finished and pick up a blank sheet of white paper. Sit down in your assigned seat and QUIETLY create a foldable like the one taped to the teacher’s lab table. Synthesis Decomposition Single-Displacement Fold the paper hamburger style Double-Displacement