The Chemical Reactions of LifeAnd Energy

Physical vs Chemical

• Physical changes involve changes of appearance, orientation or state. They include; bending, cutting, breaking, melting or boiling. The substance itself is not changed ( ice is still water, still H2O just arranged differently).

• Chemical changes involve the formation of a new substance(s) called the product(s), from original substance(s) called the reactant(s). Examples of chemical changes are digesting, rotting, corroding and burning.

Sings of a Chemical Reaction

• precipitate forms from mixing fluids• unexpected color change• Smoke or gas bubbles form• The change is difficult to reverse• Energy (heat or light) is absorbed or released

without providing a heat or cooling source.

Sort the following

• Melting ice• Cooking and egg• Painting a fence• Bending metal• Burning wood• Rusting iron• Welding metal

Writing Chemical ReactionsDear Chemical Reaction, I hope this letter finds you well and in good spirits…….

• First we need to understand the Law of Conservation of Matter. This states matter is neither created nor destroyed during chemical reactions. (nor does it mysteriously appear or disappear).

• A balanced, complete chemical reaction must have equal numbers of each type of atom on both the reactant side and the product side.

Respiration and Photsynthesis

Respiration, Aerobic • C6H1206 + 6O2 -> 6CO2 +

6H2O• Energy released • as chemical bonds in the

sugar are broken more energy is released than is absorbed as chemical bonds form in CO2 and H 2O

• Exothermic, or exergonic

Photo synthesis • 6CO2 + 6 H2O -> C6H12O6

+6O2

• Energy is absorbed (sunlight)

• Energy stored in the chemical bonds of sugar

• Endothermic, or endergonic

Activation EnergyThe Spark

• the energy that must be overcome in order for a chemical reaction to occur.

• Or the minimum energy required to start a chemical reaction “Ea

• Enzymes work by lowering (or raising) the needed activation energy.

Affect of Enzyme Catalyst

Assignment

• Peruse pages 78-86 of text• Answer concept check ques. 1,2,4 page 80• Answer concept check ques 1,2,4,5 page 86