Answers to homework #2 must be submitted no later than Friday, February 3, 5:00 pm.

Competing models for the Universe: Geocentric Heliocentric How do we decide?

Observe: Patterns are seen in the locations and motions of stars, sun, moon, and planets in the sky – observed facts Question: What causes these patterns Hypothesis: Develop a model – must be testable Test: Test the model

A hallmark of science is that theories are testable

(Some of) Galileo’s Observations Galileo saw craters and shadows cast by the mountains on the Moon (Moon had a landscape; it was a “place”, not a perfect heavenly body) Sunspots (sun not “perfect”) Rotation of sun Moons of Jupiter (Heavenly bodies existed which did not orbit the earth) Phases of Venus, all phases seen.

Changes in the appearance of Venus

Phases of Venus 2002

Galileo observed all phases! Galileo’s observation of the phases of Venus was the final evidence that buried the geocentric model. Geocentric Heliocentric No gibbous or full phases! All phases are seen! Galileo observed all phases!

The revolution was nearly complete… The structure of the universe had been totally changed. The motions of the planets were understood, at least from a geometrical perspective. Earth was no longer a “special” place in the universe. The crowning achievement was yet to come - discovering the laws of nature and that naturally led to the newly determined structure.

A Universe of Matter and Energy What is matter? What is energy?

Matter – material such as rocks, water, air; “stuff” composed of atoms Energy – makes or has the potential to make matter move! The history of the universe, including biological organisms, is based upon the interplay between matter and energy.

Three Basic Types of Energy kinetic energy of motion potential stored energy; e.g., chemical, gravitational, electrical, etc. radiative energy transported by light (electromagetic radiation)

Conservation of Energy. P.E. K.E. R.E. Energy cannot be created or destroyed, but it can change forms and be transferred from one object to another.

Conservation of Energy Fundamental law of nature Energy can be neither created nor destroyed It can change form or be exchanged between objects. The total energy content of the Universe was determined in the Big Bang and remains the same today.

Some Units of Energy ergs, joules (107 joules) – metric units of energy calorie - energy needed to raise 1 gram of water by 1o C (=4,184 joules) Calorie - 1000 calories, unit of food energy Kilowatt-hour – 3,600,000 joules BTU – “British Thermal Unit” - English unit of energy. Energy required to raise one pound of water (measured at sea-level) by 1o F (= 1055 joules)

(m is mass, v is velocity) energy of motion K.E. = 1/2 mv2 (m is mass, v is velocity) Kinetic Energy (K.E.):

temperature On the microscopic level: is a measure of the average kinetic energy of particles within a substance

Temperature Scales

Temperature vs. Heat Temperature is a measure of the average kinetic energy. Heat (thermal energy) is a measure of the total kinetic energy. lower T higher T less heat more heat same T

Sound waves also involve kinetic energy on a microscopic level (organized vibration of molecules)

Applying what we’ve learned - pizza vs. soup caution in the kitchen

The very first ever Blonde GUY joke..... And well worth the wait!

An Irishman, a Mexican and a Blonde Guy were doing construction work on scaffolding on the 20th floor of a building. They were eating lunch and the Irishman said, "Corned beef and cabbage! If I get corned beef and cabbage one more time for lunch, I'm going to jump off this building." The Mexican opened his lunch box and exclaimed, "Burritos again! If I get Burritos one more time I'm going to jump off, too." The blond opened his lunch and said, " Bologna again! If I get a bologna sandwich one more time, I'm jumping too."

The next day, the Irishman opened his lunch box, saw corned beef and cabbage, and jumped to his death. The Mexican opened his lunch, saw a Burrito, and jumped, too. The blonde guy opened his lunch, saw the bologna and jumped to his death as well.

"Don't look at me. He makes his own lunch" At the funerals, the Irishman's wife was weeping. She said, "If I'd known how really tired he was of corned beef and cabbage, I never would have given it to him again!" The Mexican's wife also wept and said, "I could have given him tacos or enchiladas ! I didn't realize he hated Burritos so much." Everyone turned and stared at the blonde's wife. The blonde's wife said … "Don't look at me. He makes his own lunch"

Potential Energy: Energy that is “stored” within an object and that has the potential of being released in a different form

Gravitational Potential Energy gravitational potential energy is the energy which an object stores due to its ability to fall It depends on: the object’s mass (m) the strength of gravity (g) the distance which it can fall (d) g m d P.E. = mgd

gravitational potential energy P.E. = mgd

Masss-Energy Potential Energy mass-energy: energy is stored in matter itself this mass-energy is what would be released if an amount of mass, m, were converted into energy E = mc2 [ c = 3 x 108 m/s is the speed of light]

Chemical Potential Energy Chemical potential energy: energy stored chemical bounds

There are many additional examples of potential energy. e. g There are many additional examples of potential energy. e.g., stretched springs, …

Energy, while conserved, can be transformed from one type of energy to another Potential Kinetic

Potential Kinetic

Kinetic Potential

Orbits & Energy Uphill Maximum Potential Energy Maximum Kinetic Energy Downhill

From the perspective of energy, which planet is more difficult to reach from the Earth? Mars Venus

From the perspective of energy, which planet is more difficult to reach from the Earth? Mars It is “uphill”

ConceptTest The gravitational potential energy of an interstellar cloud of gas that is slowly shrinking in size … (yellow) stays the same (red) slowing changes into other forms of energy (green) slowly increases (blue) interstellar clouds do not have gravitational potential energy

ConceptTest The gravitational potential energy of an interstellar cloud of gas that is slowly shrinking in size … (yellow) stays the same (red) slowing changes into other forms of energy (green) slowly increases (blue) interstellar clouds do not have gravitational potential energy

Got here (green) slowly increases (blue) interstellar clouds do not have gravitational potential energy

ConceptTest In the not too distant future scientists will develop an engine that produces more energy than it uses. This statement is … (yellow) likely to be true (red) false (green) difficult to determine if this will happen or not. (blue) this has already happened, but the government is suppressing this discovery.

ConceptTest In the not too distant future scientists will develop an engine that produces more energy than it uses. This statement is … (yellow) likely to be true (red) false (green) difficult to determine if this will happen or not. (blue) this has already happened, but the government is suppressing this discovery.

Radiative energy: energy carried by electromagnetic radiation. We will discuss electromagnetic radiation following a brief discussion of matter.

Concepts to know… What is the basic structure of an atom? Distinguish between atomic number and atomic mass number. What are the phases of matter? How do phases of matter change with increasing temperature?

Atom nucleus electron p+ e- n proton neutron

Although it is the smallest part of the atom, most of the atom’s mass is contained in the nucleus.

Protons have a positive electrical charge Electrons have a negative electrical charge In a typical neutral atom, there are equal numbers of protons and electrons The electrons do not “orbit” the nucleus; they are “smeared out” in a cloud which give the atom its size.

Incorrect view better view

The particles in the nucleus determine the element & isotope.

Type of element is determined by #protons atomic number = #protons Other value of importance: atomic mass number atomic mass no. = #protons + #neutrons

Different Elements (different # protons) Hydrogen e- Helium p+ p+ p+ n n e- atomic number = 1 atomic number = 2 atomic mass number = 1 atomic mass number = 4

Different Isotopes (same # protons, different # neutrons) 1H 2H 3H p+ p+ p+ n n n atomic number = 1 atomic mass number = 1 atomic number = 1 atomic mass number = 2 atomic number = 1 atomic mass number = 3

Atomic Number. Element. 1. Hydrogen (H). 2. Helium (He). 3 Atomic Number Element 1 Hydrogen (H) 2 Helium (He) 3 Lithium (Li) 4 Beryllium (Be) 5 Boron (B) 6 Carbon (C) 7 Nitrogen (N) 8 Oxygen (O) Each of these have multiple isotopes, some of which are not stable

Some isotopes of an element may be stable, while other isotopes may be unstable (“Radioactive”) Unstable isotopes “decay”, producing a new type of atom, i.e., an atom of a different element.

Three isotopes of Carbon, two stable, one unstable. Three isotopes of Hydrogen, two stable, one unstable. 1H 2H 3H 12.32yr 99.9816% 0.0184%

One half of the atoms of an unstable isotope decay in one “half-life” of that isotope.

P

What if an electron is missing? ion e- p+ p+ n n atomic number = 2 He+1 atomic mass number = 4

What if two or more atoms combine to form a particle? molecule p+ p+ 8p+ Sharing of electrons (chemistry) is involved in the construction of molecules 8n H2O (water)

ConceptTest If you added a proton to an atom to create a new stable, isolated atom, you would have created (blue) an isotope of the original element (orange) a fission reaction (red) a different element with a positive charge (green) a neutron and a positron

ConceptTest If you added a proton to an atom to create a new stable, isolated atom, you would have created (blue) an isotope of the original element (orange) a fission reaction (red) a different element with a positive charge (green) a neutron and a positron

Concept Test If you removed an electron from an atom, you would have created (blue) an isotope of the original element (orange) a fission reaction (red) a different element with a positive charge (green) an ionized atom

Concept Test If you removed an electron from an atom, you would have created (blue) an isotope of the original element (orange) a fission reaction (red) a different element with a positive charge (green) an ionized atom

Concept Test Some nitrogen atoms have 7 neutrons and some have 8 neutrons. This makes these two forms of nitrogen (yellow) ions of each other (blue) isotopes of each other (red) different elements (green) phases of each other

Concept Test Some nitrogen atoms have 7 neutrons and some have 8 neutrons. This makes these two forms of nitrogen (yellow) ions of each other (blue) isotopes of each other (red) different elements (green) phases of each other

Concept Test If you combined two atoms such that they shared electrons to create a new stable object, you would have created (blue) an isotope of the original element (orange) a molecule (red) a different element (green) an ionized atom

Concept Test If you combined two atoms such that they shared electrons to create a new stable object, you would have created (blue) an isotope of the original element (orange) a molecule (red) a different element (green) an ionized atom

Phases of Matter solid liquid gas plasma the phases solid liquid gas plasma depend on how tightly the atoms and/or molecules are bound to each other As temperature increases, these bonds are loosened:

In thinking about phases of matter, recall that temperature measures the average kinetic energy of particles. Faster particles can escape electrical bonds easier.