Atoms are the building blocks of most matter.

Solids can be described in terms of crystal structure, density, and elasticity.

In the liquid phase, molecules can flow freely from position to position by sliding over one another. A liquid takes the shape of its container.

Gas molecules are far apart and can move freely between collisions.

Unit II: Properties of Matter (Chapters 17-20) I. Elements (17.1) A. atoms– the building blocks of matter B. Element– material made up of only one kindof atom 1. Earth formed from only about a dozen elements 2. Many elements are relatively rare.

3. Living things composed primarily of 5 elements (oxygen (O), carbon (C), hydrogen (H), nitrogen (N), and calcium (Ca)

4. lightest element is Hydrogen (H) a. Most abundant element in the universe (90% of all atoms in known universe)

b. Helium makes up most of the remaining 10% (second lightest element. Relatively rare on Earth however)

5. Heavier elements by hydrogen fusion reactions within stars. 6. Nearly all elements on Earth are remnants of stars that exploded before the solar system came into being

II. Molecules (17.5) A. molecule– when two or more atoms combine to form larger particle. B. Matter that is gas or liquid at room temperature is usually made of molecules

1. Matter made of molecules may contain all the same kind of molecule, or be a mixture of different kinds of molecules

2. Metals and crystalline minerals made of atoms that are not joined in molecules

III. Compounds (17.6) A. compound– substance made of atoms of different elements in a fixed proportion 1. chemical formula– tells proportions of each kind of atom in compound 2. A compound may or may not be made of molecules Alpha Lipoic Acid C 8 H 14 O 2 S 2 Chemical formula

B. Compounds have different properties from the elements of which they are made

IV. The Atomic Nucleus (17.7) A. nucleus– center of atom containing protons and neutrons 1. Almost all mass of atom exists here 2. Nucleus occupies only trillionth of the volume of an atom

B. Contains protons (+ charge) and neutrons (neutrally charged) 1. Atoms with same number of protons belong to same element 2. Number of neutrons may vary for given element (called isotopes of that element)

C. Atomic number– number of protons found in nucleus. Used to classify atoms

V. Electrons in the Atom (17.8) A. electrons- (-) charged particle that orbits the nucleus of atom

1. Electron number usually equals number of protons (say that it is electrically neutral atom) 2. electron mass 1/1800 of proton or neutron

B. Periodic table– a chart that lists atoms by their atomic number and their electron arrangement

V. The Phases of Matter (17.9) A. Matter exists in 4 phases (solid, liquid, gas, plasma) 1. plasma– predominant phase of matter in universe a.consists of positive ions and free electrons b. exists only at very high temperatures

B. In all phases of matter, atoms are in constant motion 1. solids– atoms and molecules vibrate about fixed positions.

2. liquids– increased vibration cause molecules to “shake apart” into nonfixed positions (taking shape of container)

3. gasses– when additional energy added to cause molecules to break away from one another

C. All substances can be transformed from one phase to another

1.The number of different elements known to humankind are a.approximately 115. b.more than a thousand. c.in the millions. d.in the billions. Assessment Questions

1.The number of different elements known to humankind are a.approximately 115. b.more than a thousand. c.in the millions. d.in the billions. Answer: A Assessment Questions

2.Compared with the wavelength of visible light, atoms are a.about the same size. b.smaller. c.larger. d.fuzzier. Assessment Questions

2.Compared with the wavelength of visible light, atoms are a.about the same size. b.smaller. c.larger. d.fuzzier. Answer: B Assessment Questions

3.Which of these statements is correct? a.Atoms that make up your body were formed in ancient stars. b.Atoms that make up your body were previously a part of your neighbors’ bodies. c.Atoms that make up your body are in motion at all times. d.all of these Assessment Questions

3.Which of these statements is correct? a.Atoms that make up your body were formed in ancient stars. b.Atoms that make up your body were previously a part of your neighbors’ bodies. c.Atoms that make up your body are in motion at all times. d.all of these Answer: D Assessment Questions

4.Brownian motion has to do with the a.size of atoms. b.vibrations of atoms. c.random motions of atoms and molecules. d.rhythmic movements of Brownians. Assessment Questions

4.Brownian motion has to do with the a.size of atoms. b.vibrations of atoms. c.random motions of atoms and molecules. d.rhythmic movements of Brownians. Answer: C Assessment Questions

5.Molecules are composed of a.atoms. b.electrons and protons. c.atomic nuclei. d.particles larger than atoms. Assessment Questions

5.Molecules are composed of a.atoms. b.electrons and protons. c.atomic nuclei. d.particles larger than atoms. Answer: A Assessment Questions

6.A compound is composed of different kinds of atoms a.mixed together. b.moving at the same speed. c.in definite proportions. d.in the gaseous form. Assessment Questions

6.A compound is composed of different kinds of atoms a.mixed together. b.moving at the same speed. c.in definite proportions. d.in the gaseous form. Answer: C Assessment Questions

7.Most of the mass of an atom is in its a.isotopes. b.nucleus. c.electrons. d.electric charge. Assessment Questions

7.Most of the mass of an atom is in its a.isotopes. b.nucleus. c.electrons. d.electric charge. Answer: B Assessment Questions

8.The shell model of the atom views electrons as occupying a.shells. b.three-dimensional orbitals. c.circular or elliptical orbits. d.standing waves. Assessment Questions

8.The shell model of the atom views electrons as occupying a.shells. b.three-dimensional orbitals. c.circular or elliptical orbits. d.standing waves. Answer: A Assessment Questions

9.A plasma a.is an electrically charged mixture of ions and electrons. b.is a mixture of neutrons and protons with no charge. c.exists at very low temperatures. d.is another name for the solid phase of matter. Assessment Questions

9.A plasma a.is an electrically charged mixture of ions and electrons. b.is a mixture of neutrons and protons with no charge. c.exists at very low temperatures. d.is another name for the solid phase of matter. Answer: A Assessment Questions