Comet Tempel 1 as seen last week by the Stardust-NeXT spacecraft. This is the second visit to this comet. The first involved the “Deep Impact” mission.

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 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. K.E. P.E. R.E.

(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 the average kinetic energy. Heat (thermal energy) is the total kinetic energy. lower T higher T less heat more heat same T

Sound waves are a form of kinetic energy on a microscopic level (organized vibration of molecules)

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

Mass-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

Radiative energy: energy carried by electromagnetic radiation (light).

Light Light as a wave Light as a particle (photon) A vibration in an electromagnetic field through which energy is transported. Light as a wave Light as a particle (photon)

Properties of Waves WAVELENGTH (: Distance between adjacent crests FREQUENCY (f): number of crests that pass through a point each second. It is measured in units of hertz (Hz), which are the number of cycles per second. AMPLITUDE: A measure of the strength of the wave. SPEED (s): how fast the wave pattern moves. For any wave: s = f 

The speed of light is a constant: s = c !!! Light as a Wave The speed of light is a constant: s = c !!! Therefore, for light: f  = c The higher f is, the smaller  is, and vice versa. In the visible part of the spectrum, our eyes recognize f (or ) as color!

Light as a Particle Light can also be treated as photons – packets of energy. The energy carried by each photon depends on its frequency (color) Energy: E = hf = hc/  [“h” is called Planck’s Constant] Shorter wavelength light carries more energy per photon.

The Electromagnetic Spectrum lower energy higher energy

Light as Information Bearer Spectrum: light separated into its different wavelengths. Spectroscopy: The quantitative analysis of spectra The spectrum of an object can reveal the object’s: Composition Temperature Velocity

“Matter” and Light

Four Ways in Which Light can Interact with Matter emission – matter releases energy as light absorption – matter takes energy from light transmission – matter allows light to pass through it reflection – matter reflects light

Emission, absorption, transmission, reflection The type of interaction between light and matter is determined by characteristics of the “matter” and by the wavelength of light.

A Brief Review of “Matter”

Atom nucleus electron p+ e- n (proton,neutrons) electron p+ e- n Number of protons determines the element Number of neutrons determines the isotope 10,000,000 atoms can fit across a period in your textbook. The nucleus is nearly 100,000 times smaller than the entire atom (if atom filled the classroom auditorium, the nucleus would be barely visible at its center). Although it is the smallest part of the atom, most of the atom’s mass is contained in the nucleus.

Electrons do not “orbit” the nucleus; they are “smeared out” in a cloud which give the atom its size. Incorrect view better view

The number of protons determines the type of element

Hydrogen e- p+ atomic number (protons) = 1 atomic mass number (protons + neutrons)= 1

Helium e- p+ p+ n n e- atomic number (protons) = 2 atomic mass number (protons + neutrons)= 4

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)

Relative abundances of elements in the universe

Every element has different “isotopes” same number of protons (same element) different number of neutrons

Hydrogen isotope of hydrogen p+ e- atomic number (protons) = 1 atomic mass number (protons + neutrons)= 1

Hydrogen isotope of hydrogen p+ n e- atomic number (protons) = 1 (Deuterium) isotope of hydrogen p+ n e- atomic number (protons) = 1 atomic mass number (protons + neutrons)= 2

Hydrogen isotope of hydrogen p+ n n e- atomic number (protons) = 1 (Tritium) isotope of hydrogen p+ n n e- atomic number (protons) = 1 atomic mass number (protons + neutrons)= 3

Every element has multiple isotopes Every element has multiple isotopes (same number of protons, different numbers of neutrons) some of which may not be stable (“radioactive”) Carbon-14 half-life = 5,730 yrs

Unstable (“radioactive”) isotopes “decay”, producing a new type of atom, i.e., an atom of a different element, or a different isotope of the original element. One half of the atoms of an unstable isotope decay in one “half-life” of that isotope.

Three isotopes of Carbon, two stable, one unstable. 5730 yrs 14C  14N + electron + antineutrino + energy Initial Mass (14C) > Final Mass (14N + electron + antineutrino)  difference in mass is converted into energy: E = mc2

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 H2O (water) p+ p+ 8p+ Sharing of electrons (chemistry) is involved in the construction of molecules 8n