Classifying Matter

4.01 – States of Matter Anything with mass that takes up space (volume) is matter. Exists in 4 states Solid Liquid Gas Plasma

4.01 – States of Matter Solid: The particles of a solid are in a tight, fixed position. Since the particles in solids are not free to move around they vibrate just a little. Solids have a set volume and a set shape.

4.01 – States of Matter Liquid: The particles of a liquid are close together, but they are not in a neat arrangement like in a solid. They have enough space to slide past each other. Liquids have a set volume but no set shape.

4.01 – States of Matter Gas: The particles of a gas have a lot of space between them. They move fast and in no order. The volume of gas also increases as temperature increases. Gasses have no set volume and no set shape.

4.01 – States of Matter Plasma: Contains particles that are positively and negatively charged. Atoms begin to lose electrons, creating charged particles that move freely. Plasma, like a gas, has no set volume or shape and can be found in stars, Plasma TVs, and neon signs.

4.01 – States of Matter Kinetic Theory of Matter All matter is composed of tiny particles These particles are in constant, random motion The particles collide with each other and with the walls of any container in which they are held The amount of energy that the particles lose from these collisions is negligible.

4.01 – States of Matter Kinetic Molecular Theory Explains why matter changes states Matter changes states due to gain or loss of energy Explains why a particular state behaves as it does Objects expand when heated Explains why the temperature of a substance increases as you heat it Temperature of an object is a measure of the average kinetic theory of a substance

4.01 – States of Matter Heating Curves A graph of temperature vs. time for heating a substance

4.02 – Classifying Matter Pure Substances Elements – Element and atom are not the same Periodic Table of Elements Compounds – Made from combined elements

4.02 – Classifying Matter

4.02 – Classifying Matter Bromine (Br2) and Oxygen (O2) exist naturally as molecules. Each molecule consists of two atoms bonded together. Even though it is made of molecules it is still an element because it contains only one type of atom.

4.02 – Classifying Matter Element or Compound?? H20 Copper (Cu) C6H12O6 NaCl Oxygen (O2) Sodium (Na)

4.02 – Classifying Matter Mixtures- Heterogeneous Mixtures – Homogeneous Mixtures- Solutions-

4.02 – Classifying Matter Classify the following as an element, compound, or mixture. If mixture, make sure to label homogenous or heterogeneous. 1) soda 4) Nitrogen (N) 2) water (H20) 5) NH4 3) gravel 6) a taco

4.03 – Properties of Matter Physical properties Physical properties are characteristics of a substance that can be measured without changing the identity of the substance. Appearance (for example, color or shape) Odor Melting point and boiling point Density Hardness Ductility and Malleability (ability to change shape) Solubility Electrical and thermal conductivity Magnetism

4.03 – Properties of Matter Chemical properties characteristics of a substance that describe the ways it can react to form new materials. Chemical properties cannot be measured or studied without changing the composition of the substance. Flammability and other tendencies to react with oxygen Reaction with acids and bases Reaction with water Decomposition caused by light or heat Tendency to corrode

4.03 – Properties of Matter Physical Changes Physical changes are changes that do not result in the formation of a new substance. The substance is still the same because chemical bonds have not been broken or formed, and so the atoms of the molecules are still connected in the same way.

4.03 – Properties of Matter Chemical Changes referred to as chemical reactions. always produce new substances with properties that are typically very different from those of the reactants. some clues that can indicate a chemical change has occurred. visible flames color change bubbling or fizzing smoke heat or light given off formation of a substance in a different state (for example, a solid from two liquids) Of these observations, seeing flames is the only sign that always indicates a chemical change. All of the others can sometimes be the result of a physical change.

A tree burns to form ashes Event Physical Chemical Cutting your hair Mixing sugar and water Baking soda reacts with baking soda and forms a gas A piece of paper is crumpled up Baking cookies An aspirin is crushed into a powder A tree burns to form ashes Methanol is burned and leaves a residue Water freezes to ice A piece of metal is bent in half

4.03 – Properties of Matter Mass cannot be created or destroyed Law of Conservation of Mass Mass cannot be created or destroyed To put the law another way, the amount of matter before the change equals the amount of matter after the change.

4.03 – Properties of Matter The law of conservation of mass is also true for physical changes. An ice cube has the same mass as the water produced when it melts. In other cases, conservation of mass is less obvious. If we think about it, we can usually explain cases in which the law of conservation of mass seems to have been violated.

4.04 – Atomic Theory Democritus (400 B.C.) Proposed that matter was composed of tiny indivisible particles Not based on experimental data Greek: atomos

4.04 – Atomic Theory Alchemy (next 2000 years) Mixture of science and mysticism. Lab procedures were developed, but alchemists did not perform controlled experiments like true scientists.

4.04 – Atomic Theory John Dalton (1807) British Schoolteacher based his theory on others’ experimental data Billiard Ball Model atom is a uniform, solid sphere

4.04 – Atomic Theory John Dalton Dalton’s Four Postulates 1. Elements are composed of small indivisible particles called atoms. 2. Atoms of the same element are identical. Atoms of different elements are different. 3. Atoms of different elements combine together in simple proportions to create a compound. 4. In a chemical reaction, atoms are rearranged, but not changed.

4.04 – Atomic Theory J. J. Thomson (1903) Cathode Ray Tube Experiments beam of negative particles Discovered Electrons negative particles within the atom Plum-pudding Model

4.04 – Atomic Theory J. J. Thomson (1903) Plum-pudding Model positive sphere (pudding) with negative electrons (plums) dispersed throughout

4.04 – Atomic Theory Ernest Rutherford (1911) Gold Foil Experiment Discovered the nucleus dense, positive charge in the center of the atom Nuclear Model

4.04 – Atomic Theory Ernest Rutherford (1911) Nuclear Model dense, positive nucleus surrounded by negative electrons

4.04 – Atomic Theory Niels Bohr (1913) Bright-Line Spectrum tried to explain presence of specific colors in hydrogen’s spectrum Energy Levels electrons can only exist in specific energy states Planetary Model

4.04 – Atomic Theory Niels Bohr (1913) Bright-line spectrum Planetary Model electrons move in circular orbits within specific energy levels

4.04 – Atomic Theory Erwin Schrödinger (1926) Quantum mechanics electrons can only exist in specified energy states Electron cloud model orbital: region around the nucleus where e- are likely to be found

Electron Cloud Model (orbital) 4.04 – Atomic Theory Erwin Schrödinger (1926) Electron Cloud Model (orbital) dots represent probability of finding an e- not actual electrons

4.04 – Atomic Theory James Chadwick (1932) Discovered neutrons neutral particles in the nucleus of an atom Joliot-Curie Experiments based his theory on their experimental evidence

revision of Rutherford’s Nuclear Model 4.04 – Atomic Theory James Chadwick (1932) Neutron Model revision of Rutherford’s Nuclear Model

4.05 – Properties of Atoms An atom refresher Matter is anything that takes up space and has mass. All matter is made of atoms Atoms are the building blocks of matter, sort of how bricks are the building blocks of houses.

4.05 – Properties of Atoms An atom refresher An atom has three parts: Proton = positive Neutron = no charge Electron = negative The proton & neutron are found in the center of the atom, a place called the nucleus. The electrons orbit the nucleus. Picture from http://education.jlab.org/qa/atom_model_03.gif

4.05 – Properties of Atoms What are elements? Elements are the alphabet to the language of molecules. To make molecules, you must have elements. Elements are made of atoms. While the atoms may have different weights and organization, they are all built in the same way.

4.05 – Properties of Atoms

4.05 – Properties of Atoms More about Elements.. Elements are the building blocks of all matter. The periodic table is a list of all of the elements that can build matter. It’s a little like the alphabet of chemistry. The periodic table tells us several things…

O 4.05 – Properties of Atoms Oxygen 8 16 Atomic Number: Number of protons and it is also the number of electrons in an atom of an element. 8 O Element’s Symbol: An abbreviation for the element. Oxygen Elements Name Atomic Mass/Weight: Number of protons + neutrons. 16

4.05 – Properties of Atoms Atom Models There are two models of the atoms we will be using in class. Bohr Model Lewis Dot Structure

4.05 – Properties of Atoms Bohr Model - The Bohr Model shows all of the particles in the atom. In the center is circles. Each circle represents a single neutron or proton. Protons should have a plus or P written on them. Neutrons should be blank or have an N. In a circle around the nucleus are the electrons. Electrons should have a minus sign or an e. + + -

Electrons have special rules…. 4.05 – Properties of Atoms Electrons have special rules…. You can’t just shove all of the electrons into the first orbit of an electron. Electrons live in something called shells or energy levels. Only so many can be in any certain shell.

4.05 – Properties of Atoms Nucleus 1st shell 2nd shell 3rd shell Adapted from http://www.sciencespot.net/Media/atomsfam.pdf

Electrons have special rules…. 4.05 – Properties of Atoms Electrons have special rules…. You can’t just shove all of the electrons into the first orbit of an electron. Electrons live in something called shells or energy levels. Only so many can be in any certain shell. The electrons in the outer most shell of any element are called valance electrons.

So let’s try it…. 3 Li Lithium 7

So let’s try it…. Li Lithium Protons = 3 3 7 Neutrons = 4 (7-3=4) - + Electrons = 3 2 in the 1st shell, 1 in the 2nd shell Neutrons = 4 (7-3=4)

O 4.05 – Properties of Atoms Lewis Dot Structure + - The Lewis Dot Structure is a bit different from the Bohr model. It only shows the element symbol and it’s outer most electron shell. • O • • • • •

4.05 – Properties of Atoms How to… Write the symbol. Start on the right hand side, working your way clockwise around the symbol. Try Lithium

4.06 – The Periodic Table of Elements 1869, Dmitri Mendeleev, a Russian chemist, set out to organize the 63 known elements. He started by organizing the elements by their mass in ascending order. When elements were arranged in order of their mass, he noticed that their physical properties repeated

4.06 – The Periodic Table of Elements To group elements by similar properties, Mendeleev had to arrange a few elements out of order by mass. the periodic trends did not fit perfectly with the elements’ masses. When atomic numbers became known, scientists organized the chart of elements using the number of protons in each element instead of the atomic mass.

4.06 – The Periodic Table of Elements The modern periodic table of elements is a valuable resource. Check out the wealth of information contained in the periodic table:

4.06 – The Periodic Table of Elements Element name and symbol Atomic number (number of protons in each atom) Average atomic mass

4.06 – The Periodic Table of Elements Physical Properties: metal, non-metal, or metalloid

4.06 – The Periodic Table of Elements Electronegativity – ability to attract electrons Bigger the number, the greater the ability to attract electrons and bond to other atoms Increases as you go left to right and move up

4.06 – The Periodic Table of Elements Ionization Energy – energy needed to release an electron Think, opposite of electronegativity Increases as you go left to right and up

4.06 – The Periodic Table of Elements Atomic Radius Relates to number of energy levels = quantum number Increases as you go down and to the left

4.06 – The Periodic Table of Elements Valence Electrons – outermost electrons Elements in the same group have similar valence electrons

4.06 – The Periodic Table of Elements Oxidation Number – number of electrons the atom uses or receives + when atom loses electrons, - when atom gains electrons

4.06 – The Periodic Table of Elements Representative Elements Columns 1-2 and 13-18 Follow trends and behave more predicatibly than other groups

4.06 – The Periodic Table of Elements Exceptions to the Rules Hydrogen Placed with metals even though it is a gas Placed in 1st column to reflect the properties of its electrons