2.2 Quick Review What is the atomic number and mass number for the element shown below? Is this a neutral atom or an ion? How do you know? Atomic number = 6 Mass number = 12 Neutral…same # of p+ and e-

Review Questions What type of macromolecule is being put together in the picture below? protein

2-3 What Happens When Matter Undergoes Change? Concept 2-3 Whenever matter undergoes a physical or chemical change, no atoms are created or destroyed (the law of conservation of matter).

Matter Undergoes Physical, Chemical, and Nuclear Changes Physical change No change in chemical ___________________ Ex: Ice cap ____________ back into liquid water Chemical change, chemical reaction Change in chemical composition ________________ and ___________________ Ex: coal (C) + oxygen gas (O2)  carbon dioxide (CO2) Nuclear change Natural radioactive decay through ________________ isotopes Nuclear fission – when nuclei ___________ Nuclear fusion – when nuclei ______________ composition melts products reactants unstable split combine

Beta particle (electron) Radioactive decay Alpha particle (helium-4 nucleus) Radioactive isotope Gamma rays Figure 2.9: There are three types of nuclear changes: natural radioactive decay (top), nuclear fission (middle), and nuclear fusion (bottom). Beta particle (electron) Radioactive decay occurs when nuclei of unstable isotopes spontaneously emit fast-moving chunks of matter (alpha particles or beta particles), high-energy radiation (gamma rays), or both at a fixed rate. A particular radioactive isotope may emit any one or a combination of the three items shown in the diagram. Fig. 2-9a, p. 43

Nuclear fission Uranium-235 Energy Fission fragment n n Neutron n n Figure 2.9: There are three types of nuclear changes: natural radioactive decay (top), nuclear fission (middle), and nuclear fusion (bottom). Radioactive isotope Radioactive decay occurs when nuclei of unstable isotopes spontaneously emit fast-moving chunks of matter (alpha particles or beta particles), high-energy radiation (gamma rays), or both at a fixed rate. A particular radioactive isotope may emit any one or a combination of the three items shown in the diagram. Fig. 2-9b, p. 43

Nuclear fusion occurs when two isotopes of light elements, such Reaction conditions Fuel Products Proton Neutron Helium-4 nucleus Hydrogen-2 (deuterium nucleus) 100 million °C Energy Figure 2.9: There are three types of nuclear changes: natural radioactive decay (top), nuclear fission (middle), and nuclear fusion (bottom). Hydrogen-3 (tritium nucleus) Neutron Nuclear fusion occurs when two isotopes of light elements, such as hydrogen, are forced together at extremely high temperatures until they fuse to form a heavier nucleus and release a tremendous amount of energy. Fig. 2-9c, p. 43

We Cannot Create or Destroy Matter Law of conservation of matter Whenever matter undergoes a physical or chemical change, no atoms are created or destroyed The atoms are simply __________________ According to this law, can we really ever just throw something away? rearranged No…it may sit in a landfill or be recycled

2-4 What is Energy and What Happens When It Undergoes Change? Concept 2-4A When energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed (first law of thermodynamics). Concept 2-4B Whenever energy is changed from one form to another in a physical or chemical change, we end up with lower-quality or less usable energy than we started with (second law of thermodynamics).

Energy Comes in Many Forms (1) work Energy is the capacity to do ____________ or transfer __________ Work is done any time an object is ________ a certain distance Work = force x distance Example: picking up your textbook Heat transfer example: heat flowing from your stove to your finger heat moved

Energy Comes in Many Forms Two Main Types of Energy 1. Kinetic energy - ______________ energy Flowing water Wind Heat – the total kinetic energy of all moving _________________ Electromagnetic radiation – energy travels in the form of a ____________ motion particles waves

The Electromagnetic Spectrum There are many different forms of electromagnetic radiation…each have a different ______________ and ____________________ wavelength energy content Figure 2.11: The electromagnetic spectrum consists of a range of electromagnetic waves, which differ in wavelength (the distance between successive peaks or troughs) and energy content. Fig. 2-11, p. 45

Potential Energy 2. Potential Energy - ____________ and potentially available for use Examples: Water stored behind a dam Chemical energy stored in the carbon atoms of coal stored Figure 2.12: The water stored in this reservoir behind a dam in the U.S. state of Tennessee has potential energy, which becomes kinetic energy when the water flows through channels built into the dam where it spins a turbine and produces electricity—another form of kinetic energy. Fig. 2-12, p. 45

We change potential energy to kinetic energy Examples Holding your book and ______________ it gasoline  kinetic energy that ________ a car  heat transferred to environment Water behind a dam  flowing water  spinning turbine  ___________________ dropping propels electricity

Nuclear Energy to Electromagnetic Radiation Nuclear energy from _________ that occurs in the sun converts to electromagnetic _______________ fusion radiation Figure 2.13: Energy from the sun supports life and human economies. This energy is produced far away from the earth by nuclear fusion (Figure 2-9, bottom). In this process, nuclei of light elements such as hydrogen are forced together at extremely high temperatures until they fuse to form a heavier nucleus. This results in the release of a massive amount of energy that is radiated out through space. Fig. 2-13, p. 46

Energy Comes in Many Forms Sun provides _______ of earth’s energy Warms earth to comfortable temperature Provides plants with the energy for photosynthesis  provides all other organisms with ___________ All of this energy is provided at ____ cost to us…keeping with our solar energy principle of ___________________ 99% food no sustainability

Energy Comes in Many Forms The sun’s direct input of solar energy also produces several indirect forms of _____________ solar energy Wind Hydropower – falling or flowing __________ Biomass – all of the energy stored in in the chemical bonds within ____________ renewable water plants

Commercial energy sold in the market place make the remaining ______ of the energy we use Main source – burning ______, ________, and natural _______ These fuels are called __________________ because they were formed over millions of years from the decaying remains of ancient plants and animals (aka fossils) 1% oil coal gas fossil fuels

Fossil fuels Figure 2.14: Fossil fuels: Oil, coal, and natural gas (left, center, and right, respectively) supply most of the commercial energy that we use to supplement energy from the sun. Burning fossil fuels provides us with many benefits such as heat, electricity, air conditioning, manufacturing, and mobility. But when we burn these fuels, we automatically add carbon dioxide and various other pollutants to the atmosphere. Fig. 2-14a, p. 46

Some Types of Energy Are More Useful Than Others High-quality energy _______________...so it has a high capacity to do work High-temperature heat Strong winds Fossil fuels Low-quality energy ______________....so low capacity to do work Low energy heat created by moving molecules in the atmosphere or ocean Concentrated Dispersed

Ocean Heat Is Low-Quality Energy Figure 2.15: A huge amount of the sun’s energy is stored as heat in the world’s oceans. But the temperature of this widely dispersed energy is so low that we cannot use it to heat matter to a high temperature. Thus, the ocean’s stored heat is low-quality energy. Question: Why is direct solar energy a higher-quality form of energy than the ocean’s heat is? Fig. 2-15, p. 47

Energy Changes Are Governed by Two Scientific Laws Thermodynamics – the study of energy ________________ Energy transfers are governed by two Main Laws transformations First Law of Thermodynamics (Law of conservation of energy) Energy is neither ______________ nor ______________ in physical and chemical changes…it can only be __________________ created destroyed transferred

When your car’s tank runs out of gasoline, what are you actually losing? Second Law of Thermodynamics Energy always goes from a ___________ useful to a less ______________ form when it changes from one form to another Example: Resulting low quality energy often takes the form of __________ that flows into the environment…random motion of air or water molecules further _______________ this heat High quality energy more useful heat dispersed

This is why we need to use technologies that conserve energy…. We can recycle ______________ and reuse it, but not high-quality energy This is why we need to use technologies that conserve energy…. Some bad examples… Incandescent light bulbs and internal combustion engines matter

Energy-Wasting Technologies Both technologies waste high-quality energy through poor ___________ and large heat transfers design 87% of h.q.e. converted to heat Figure 2.16: Two widely used technologies waste enormous amounts of energy. In an incandescent lightbulb (right), about 95% of the electrical energy flowing into it becomes heat; just 5% becomes light. By comparison, in a compact fluorescent bulb (left) with the same brightness, about 20% of the energy input becomes light. In the internal combustion engine (right photo) found in most motor vehicles, about 87% of the chemical energy provided in its gasoline fuel flows into the environment as low-quality heat. (Data from U.S. Department of Energy and Amory Lovins; see his Guest Essay at CengageNOW.) 80% of h.q.e. converted to heat (fluorescent) 95% of h.q.e. converted to heat (incandescent) Fig. 2-16a, p. 48

Review Questions What is the difference between physical, chemical, and nuclear changes? What do we call the study of energy transformations? No composition change Unstable isotope causes change in nucleus composition change…new product thermodynamics

Which picture below represents low quality energy Which picture below represents low quality energy? And high quality energy? high low Fossil fuel Ocean heat