Unit A Thermochemical Changes

The Plan Section 11.1-Energy demands & sources. gy-slam-poem

Energy Energy is the capacity to do work. The direction of energy flow can be expressed as either: exothermic (out) or endothermic (in).

Energy will flow from "hot" to "cold" until "thermal" equilibrium is attained, that is, the substance and environment are at the same temperature!

Photosynthesis Major natural contributor to stored chemical energy on Earth. Takes energy from the Sun (radiant – electromagnetic energy) & converts it into chemical energy.

Photosynthesis Carbon dioxide and water react in plants in the presence of sunlight to produce glucose & oxygen. It is an endothermic reaction. The equation below represents the simplified process of photosynthesis. 6 CO 2(g) + 6 H 2 O (l) + energy → C 6 H 12 O 6(aq) + 6 O 2(g)

Cellular Respiration The chemical energy stored in the process of photosynthesis is accessed during the process of cellular respiration. In this process, glucose and oxygen react to produce carbon dioxide, liquid water, & energy. It is an exothermic reaction. The equation below represents the process of cellular respiration C 6 H 12 O 6(s) + 6O 2(g) → 6CO 2(g) + 6H 2 O (l) + energy

Hydrocarbon Combustion Hydrocarbon combustion is an exothermic reaction just like cellular respiration. E.g., Propane: C 3 H 8(g) + 5O 2(g) →3CO 2(g) + 4H 2 O (g) + energy Notice that in hydrocarbon combustion, water vapor is formed, whereas in cellular respiration, liquid water is formed. Other than that, the equations are almost identical.

Fossil Fuels Biogenic hypothesis: Fossil fuels (e.g., coal & natural gas) had their origins in deposits of plants & animal matter, which got their energy from the sun. Supports the claim that fossil-fuel energy has its origins in the solar energy from our sun. fossil-fuel

Fossil Fuels Fossil fuels are a major store of chemical energy that we use in everyday lives. In Alberta, ~20% of jobs are in the energy sector. There are four major demands for energy from fossil fuels: 1.Heating (15%) 2.Transportation (30%) 3.Industry (40%) 4.Commercial & institutional (15%)

Some Alternative Energy Sources solar heating geothermal energy biomass gas hydroelectricity nuclear power toward-better-solar-energy-systems.html

Alternative Lifestyle Improved insulation and design Walking, biking, mass transit Alcohol/gasohol & hydrogen fuels Improved efficiency & waste heat recovery Water & heat conservation

Chemical Change The reactant(s) have different chemical composition than the product(s). E.g., H 2 O (l)  O 2(g) + H 2(g) Some possible energy conversions:

Energy from Chemical Changes "EXOTHERMIC" HeatLight ElectricityMechanical Energy FurnaceFirefly BatteryCar Engine

Energy Stored in Chemicals "ENDOTHERMIC" HeatLight ElectricityMechanical Energy CookingPhotosynthesis Electrolysis NH 3(g) Production

Chemical Change In chemical reactions, the products have different chemical compositions than do the reactants. Also, the total potential energy of all the products is different than the total potential energy of the reactants. This is why energy is always either absorbed or released in any chemical reaction. Exothermic reactions release energy & endothermic reactions absorb energy

Society's major source of energy is from chemical reactions. Examples include: 1.burning coal (carbon) and oil (hydrocarbons) to generate steam to turn electrical generators. 2.burning gasoline/diesel (hydrocarbons) to propel vehicles. 3.burning natural gas or heating oil (hydrocarbons) to heat buildings and water. 4.electrochemical reactions in batteries. 5.producing, refining and shaping metals and plastics (industry). 6.food consumption (humans, animals). 7.fertilizer production.

When is it predicted that fossil fuels in Alberta will be depleted? 2020!

In the News Efforts aimed at making it easier to invest in green energy improvements that in the past have been impractical or unaffordable.

New Research Integrating solar technologies into coal-fired power plants could ease the transition from fossil fuels to renewable energy sources.

Read p Section 11.1 Questions #1-8 (omit 2 & 6), 11a & 12.

Enzymes

Read pgs. 535 – 541 pg. 542 Section 12.3 Questions #’s 1 – 6