1) Is the picture to the right a chemical reaction or a physical reaction? Why?

2) Is the following equation balanced?CH4 + 2O2 CO2 + 2 H2O

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 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 changeFour indicators :

1. Formation of new gas

2. Formation of new solid

3. Release of energy (heat or light)

4. Color change

Pair ShareTell 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

CH4 + 2O2 CO2 + 2H2O

(1 C, 4H , 4 O) (1 C, 4 H, 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 1023 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 1023 atoms or molecules.

Molar MassThe mass (in grams) of one mole of a compound

1 mole H2O = 18.02 g H2O

Example

What is the molar mass of one mole of CaCO3?

1. We Know

• chemical formula CaCO3

• # amu in formula = molar mass in grams

Solving Problems

4. Solution

Solving Problems

Formula mass CaC03 = 100.09 g

1 mole CaC03 = 100.19 g CaCO3

• 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:

__Cu2S + __O2 → ___Cu2O + ___SO2

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 + O2 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