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Chemistry TAKS Rotation 2011

Chemistry TAKS Rotation 2011. Physical vs. Chemical Changes. 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.

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Chemistry TAKS Rotation 2011

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  1. Chemistry TAKS Rotation2011

  2. Physical vs. Chemical Changes • 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. H2 + O2 H2O • Reactant + Reactant  Product • C. Reactant- what goes into a reaction • D. Product- what is produced by the reaction

  3. Be sure to know the “terms” that can give you the answer to a physical/chemical change question… 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. Burning a piece of paper- (chemical change) a piece of iron that rusts in the rain (chemical change) Boiling a pan of water (physical change) A silver tea set that has tarnished (chemical change) THE CORRECT ANSWER IS C!

  4. Density • 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 cm3 • m= mass measured in kg or g • V= volume measured In mL or cm3 • 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. Viscosity • 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. Buoyancy Force • 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. Elements, Compounds & Mixtures • 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. Know how to classify…. • 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. The Periodic Table • 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 1st! (over picking a “next door neighbor” element).

  11. Valence Electrons and Charges/Oxidation #’s • 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. Examples….. • Which of these are composed of two or more different substances that are chemically combined in a definite ratio? • Compounds • Mixtures • Elements • Solution • Oxygen (O2) is an example of • An alloy • A molecule • A salt • A mixture

  13. Structure of an Atom • 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

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