2.  I. Physical Change- a change in the physical properties of a substance.  A. This includes mostly phase changes. Ex. Ice to water  II. Chemical Change- a change that alters the chemical composition of a substance.  A. If a chemical reaction occurs, a new substance will be produced.  B. A chemical equation uses the following format.  Ex. H 2 + O 2  H 2 O  Reactant + Reactant  Product  C. Reactant- what goes into a reaction  D. Product- what is produced by the reaction

3. Physical ChangesChemical Changes MeltRust EvaporateCorrode Condensation/condensateBurn BoilingTarnish ShredProduces DissolveCombust These are a few of the common words that you might see in a TAKS question. Just by Knowing these key words you can identify the examples as physical or chemical changes. Ex. Which listed below is an example of a physical change. a.Burning a piece of paper- (chemical change) b.a piece of iron that rusts in the rain (chemical change) c.Boiling a pan of water (physical change) d.A silver tea set that has tarnished (chemical change) THE CORRECT ANSWER IS C!

4.  I. Density- DEF- Measures how compact molecules are within a substance.  A. Formula: D=m/V where  D= density measured in kg or g/mL or cm 3  m= mass measured in kg or g  V= volume measured In mL or cm 3  II. Things to remember…..  A. The density of water is 1.0 g/mL  B. If an object is MORE dense than the liquid it is in…it will sink.  C. If an object is LESS dense than the liquid it is in….it will float.  D. The formula on the formula sheet is D=m/V however, be prepared to rearrange the formula to be able to solve for m or V.

5.  I. Viscosity- DEF- a measure of a fluid’s resistance to flow.  Ex. Compare pancake syrup to water….which one will flow faster?  Water! SO…..water has a lower viscosity than pancake syrup. The longer something takes to flow, the greater the viscosity.  A. By increasing the temperature of a substance, you can DECREASE the viscosity.  Ex. Compare warm pancake syrup to cold pancake syrup

6.  I. Buoyancy Force- DEF- Buoyant force is the upward force exerted by a fluid on an object.  II. Buoyancy- Buoyancy is the ability of a liquid (such as water) to support or hold up other liquids or objects.  A. This helps to explain how a large cruise ship floats even when the ship is more dense than the water it is in.  1. As the ship is pushing down (gravity), the water pushes up and supports the boat by this buoyancy force.  *** The TAKS tests loves to use the example of the boat in water so be sure you understand this concept!*

7.  This is about classification…..  I. Elements- 1 type of matter that cannot be separated by physical means Ex. Fe, N, Cl  II. Compound- more than 1 type of matter that cannot be separated by physical means Ex. NaCl  III. Mixtures  1. Homogeneous- matter that CAN be separated by physical means with uniform composition. Ex. Milk  2. Heterogeneous- matter that CAN be separated by physical means that does not have uniform composition. Ex. Chex mix

8.  Ex. Chicken noodle soup would be an example of a  A. element  B. compound  C. homogeneous mixture  D. heterogeneous mixture  ???Think…..can the substance be separated?  YES!  So….is it a homogeneous mixture of a heterogeneous mixture?  (When you look at c.n. soup….does it look the same? )  **** TERM TO KNOW******  Alloy- a mixture of 2 or more metals

9.  Quick Review  I. Groups- vertical columns- 18 total  1. Group 1- most reactive metals, alkali metal  2. Group 2-alkaline earth metals  3. Group 17- Halogens, most reactive non- metals, 7 valence electrons  4. Group 18- noble gases, 8 valence electrons, stable due to full octet, will NOT be involved in bonding  II. Metals vs Non-metals  1. Metals- left of staircase  2. Non-metals- right of staircase

10.  3. Metals will Give AWAY electrons  4. Non metals will GAIN electrons.  5. Metalloids- elements that touch the staircase on the periodic table. Have properties of both metals and non-metals.  III. WOAH important!!!  A. All elements bond in order to have 8 valence electrons.  B. Elements in the same GROUP will have similar chemical properties.  *** If you are asked a question that deals with elements having things in common….go with the GROUP answer 1 st ! (over picking a “next door neighbor” element).

11.  I. Valence Electrons-DEF- atoms electrons in the outermost energy level/orbital.  Group 1-1  Group 2-2  Group 13-3, 14-4, 15-5, 16-6, 17-7, 18-8  II. Charges  When elements transfer electrons (ionic bond- M + NM) in order to be stable (have 8 valence electrons) they will GAIN or LOSE electrons. This causes them to have a charge (they will have MORE or LESS electrons compared to protons.)  More electrons than protons- negative charge  Less electrons than protons- positive charge  Group 18-0 charge since they wont gain or lose electrons.

12. 1. Which of these are composed of two or more different substances that are chemically combined in a definite ratio? a. Compounds b. Mixtures c. Elements d. Solution 2. Oxygen (O 2 ) is an example of a. An alloy b. A molecule c. A salt d. A mixture

13.  I. An atom is made up of protons, neutrons and electrons.  II. Remember these 3 rules!  1. atomic #= # protons  2. # protons= # electrons  3. atomic mass= # protons + # neutrons