Ms. Barlow’s 8th Grade Physical Science Class What’s the matter? Ms. Barlow’s 8th Grade Physical Science Class

Warm-up Please complete the handout IS IT MATTER. In your explanation, please include the following: Your claim(answer that expresses the answer to the question) Your evidence (information that supports the claim) Your reasoning (the justification that links the evidence to the claim) Write in complete sentences.

Answer Items on the list considered to be matter are rocks, baby powder, milk, air, dust, cells, atoms, smoke, salt, Mars, Jupiter, steam, rotten apples, water, bacteria, oxygen, stars, and dissolved sugar. Fire may be considered matter or energy—the vaporized gases in the flame are matter but the light and heat emitted are energy.

GPS S8P1: Students will examine the scientific view of the nature of matter. Elements: a. Distinguish between atoms and molecules. b.  Describe the difference between pure substances (elements and compounds) and mixtures.

Matter is……….. All matter is made up of particles (e.g., atoms or molecules); has mass; takes up space (has volume); and exists in the forms of solid, liquid, gas, or plasma. In order to be considered matter, an object, material, or substance must meet these characteristics.

Volume is the amount of space an object occupies or takes up. To measure liquid volume, use a graduated cylinder. Unit: mL

Volume of a regularly shaped object: v= l x w x h Unit: m3 or cm3

Volume of an irregularly shaped solid object Measure the volume of water that the object displaces. Unit: cm3 (cubic centimeters)

Atoms Matter is made of particles called atoms and molecules. An atom is the smallest part of an element that can be identified as that element. Or Tiny particles that make up elements. Elements are simple substances that cannot be broken down into any other substances by chemical or physical means.

Atom comes from a Greek term meaning indivisible (cannot be divided) Atom comes from a Greek term meaning indivisible (cannot be divided). (By modern definition, atoms are not indivisible because they are composed of smaller particles)

Just How Small are Atoms? Millions could fit end to end across the period at the end of this sentence and the number in a single drop of water (1022 to 1023 atoms) may exceed the number of stars in the observable universe.

Yet, atoms are composed of smaller particles Nucleus Central Core of the atom Contains protons and neutrons Protons have positive electrical charge Neutrons carry no electrical charge and are considered NEUTRAL (get it???)

Atomic Humor Neutron: How much to enter this nucleus? Proton: For you, no charge (Sorry – it will happen again!)

Electrons Travel in all directions around the nucleus Carry a negative electrical charge Not all the same distance away from the nucleus.

ATOMIC NUMBER: the number of protons in the nucleus of an atom. Atomic Mass – Atomic Number = Number of Neutrons Number of Protons = Number of Electrons

Let’s Practice Atom ATOMIC SYMBOL NUMBER MASS Hydrogen Helium Lithium NUMBER OF PROTONS MASS NEUTRONS ELECTRONS Hydrogen Helium Lithium Beryllium

Valence Electrons Farthest away from the nucleus and are involved in bonding Electron Dot Diagram: Way to show the # of valence electrons. Gain or loss of electrons is called ionization lose an electron; atom becomes positive gain an electron; atom becomes negative

The arrangement of the electrons Each atomic orbital and the electrons in it are associated with a specific amount of energy. The farther an electron is from the nucleus the greater its energy.

Atoms Shells or location of the orbiting electrons Energy Levels will hold only set amounts of electrons 1st shell = 2 4th shell = 32 2nd shell = 8 5th shell = 50 3rd shell = 18 6th shell = 72 Formula 2(N2) = number of electrons in shell 2(12) = 2 2(42) = 32 2(22) = 8 2(52) =50 2(32) = 18 2(62) =72

Oppositely charged particles attract Similarly charged particles repel Electrical Charge Oppositely charged particles attract Similarly charged particles repel The positively charged protons in the nucleus and the negatively charged electrons is what holds the atom together.

Building an Atom Electrons by themselves would be poor building blocks because like charges repel, and they would just repel each other. Protons have the same problem. They repel each other and would build nothing. But electrons are attracted to protons.

Ordinary atoms have identical numbers of electrons and protons making them electrically neutral overall.

Isotopes Atoms with the same number of protons but a different number of neutrons. Example: an atom with one proton, one electron and one neutron is hydrogen. However, if the hydrogen atoms has two particles (neutrons) but the same number of protons (in the case of hydrogen one) it is an isotope of hydrogen.

Atoms Atom Models Thomson Model, 1904 - “plum pudding” model - does not distinguish a nucleus or electron orbits (shells)

Atoms Atom Models Rutherford Model, 1911 - nucleus with orbital rings

Atoms Atom Models Bohr Model, 1913 - nucleus with rings around it – easy to use and understand carbon nitrogen hydrogen

Atoms Atom Models Lewis Structure, 1916 - chemical symbol surrounded with dots representing valence electrons (rather than rings) used in chemical formulas to represent behavior of atoms water oxygen

Atoms Atom Models electron cloud Model, 1920’s - based on x-ray technology

Atoms Studying Atoms began with Democritus; 400’s BC -thought that everything was made up of a few simple parts he called atoms John Dalton started the Atomic Theory -based on experimental support -all matter is made of atoms -chemical reactions are rearrangements of atoms ato atoms scientists can still only see the electron cloud even with the best technology it takes about a million atoms lined up in a row to equal the thickness of a human hair theory continues to change based on the reactions and behaviors of substances during tests

Molecules Consists of two or more atoms joined in a definite ratio. Most are composed of atoms of two or more elements. An element is a substance that cannot be broken down into any other substances by chemical or physical means.

Molecules A molecule consists of two or more atoms of the same element, or different elements, that are chemically bound together. Diatomic molecules are made of two atoms of the same element. Hydrogen – H2 Oxygen – O2

Molecules In the animation above, two nitrogen atoms (N + N = N2) make one Nitrogen molecule .

Covalent Bonding When atoms share one or more pairs of electrons. Example: Oxygen shares one of its electrons with each of the two hydrogen atoms. Oxygen’s outer shell is now filled with 8 electrons. Each hydrogen atom share its 1 electron with the oxygen atoms so they now have 2 electrons in their outer level.

http://faculty. clintoncc. suny. edu/faculty/michael http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20101/bio%20101%20lectures/chemistry/chemistr.htm