1) Is the picture to the right a chemical reaction or a physical reaction? Why? 2) Is the following equation balanced? CH 4 + 2O 2 CO H 2 O 3) Put the particles in order of slowest to fastest; gas, solid, liquid. Welcome to class. Do Now Flammable C:1 H:4 O:4 Yes! Solid, liquid, gas

2 Homework and Announcement Due: Conservation of Matter worksheet Word Find and Section Review Achieve 3000 – Your choice, choose 2 due 20th 2

L.O: To determine whether a reaction is endothermic or exothermic. ENERGY AND MATTER

Chemical Reactions process of breaking of chemical bonds reforming of new bonds creates new substances. When you make pizza, which changes are physical and which are chemical changes?

Evidence of chemical change Four indicators : 1.Formation of new gas 2.Formation of new solid 3.Release of energy (heat or light) 4.Color change

Pair Share Tell your neighbor two indicators of chemical change.

Reactants:  Will be changed into new substance.  What you start with. Products:  New Substance formed in chemical reaction.  What you end up with. LETS REVIEW: REACTANTS  PRODUCTS

Reactants and products In the reaction, methane (a natural gas) is burned or combusted. Some energy is added to get the reaction started.

Conservation of Matter CH 4 + 2O 2 CO 2 + 2H 2 O (1 C, 4H, 4 O) In a chemical reaction atoms are not created or destroyed, they are only rearranged.

Formula mass The sum of the atomic mass values of the atoms in a chemical formula

Avogadro’s Number 6.02 x atoms or molecules. The Avogadro number was named in honor of Amedeo Avogadro who discovered that a mole of any gas under the same conditions has the same number of molecules. Johann Josef Loschmidt, a German physicist, named and discovered the Avogadro number. He realized that a mole of any substance—be it a gas, liquid, or solid—contains 6.02 x atoms or molecules.

Molar Mass The mass (in grams) of one mole of a compound 1 mole H 2 O = g H 2 O Example

What is the molar mass of one mole of CaCO 3 ?  We Know chemical formula CaCO 3 # amu in formula = molar mass in grams Solving Problems

 Solution Solving Problems Formula mass CaC0 3 = g 1 mole CaC0 3 = g CaCO 3

In this reaction, chalcocite (a mineral) reacts with oxygen in the presence of heat. The products are a type of copper oxide and sulfur dioxide. Balance this equation: __Cu 2 S + __O 2 → ___Cu 2 O + ___SO 2 Balancing Equations Solving Problems

Think about it… Coefficients can be added in front of any chemical formula in a chemical equation. When a coefficient is added in front of a chemical formula, all atoms in that formula are multiplied by that number. Use common denominators to help choose coefficients to try.

Solution- Trial and error Solve

What makes these reactions happen? Heat Electricity Synthesizers

Thermal Energy:  Movement of “Heat”;  always flows warmer matter to cooler matter.  Released or absorbed  Higher temperature = faster particles = more thermal energy

Which of the following has more thermal energy? A melted chocolate bar. A solid chocolate bar. Why? Higher temperature = higher thermal energy

Endothermic change:  Endo - In Thermos - heat  Heat is absorbed (heat is taken in)  Heat is a reactant.  Example:  Ice + Heat  Water (Physical change)  Ca + Cu + Heat  CaCu (Chemical change)

Which of these is endothermic? Liquid water changes to Solid ice Solid ice changes to Liquid water Why? Heat is absorbed so the particles move faster.

Exothermic change:  Exo - Out Thermos - Heat  Heat is released (heat exits)  Heat is a product.  Example:  2Mg + O 2  Heat + Light + 2MgO (Chemical change)  Water  Heat + Ice (Physical change)

Which of these is a exothermic change? Instant cold packs Instant hand warmer pack Why? Because the hand warmer is releasing heat.

Pair Share  1. Photosynthesis.  (CO2 + H2O + Energy  O2 + Glucose)  Endothermic. Energy is a reactant.  2. Fireworks exploding?  Exothermic. Energy is a product.  Powder + O2  Heat + Light + Gas  3. Baking a cake?  Endothermic. Energy is a reactant.  Batter + Heat  Cake Endothermic or Exothermic, Why?

Summary: 3-4 sentences about your notes. 1. What is molar mass? 2. What is the difference between endothermic and exothermic reactions? 3. Give an example of an endothermic reaction. 4. Give an example of an exothermic reaction.

Remember your Homework  Science Homework:  Achieve 3000 – Your choice choose 2