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TAKS Review: Chemistry

TAKS Review: Chemistry. Focus on basic properties of matter!. Physical Properties. Describe the physical nature of matter, not its chemical behavior. Examples: Melting point, boiling point, freezing points, color, viscosity, density . . .

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TAKS Review: Chemistry

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  1. TAKS Review: Chemistry Focus on basic properties of matter!

  2. Physical Properties • Describe the physical nature of matter, not its chemical behavior. • Examples: • Melting point, boiling point, freezing points, color, viscosity, density . . . • Melting and boiling points along with density are ways of identifying unknown substances

  3. Chemical Properties • Properties that describe the chemical behavior of matter. • Formation of cations (+) or anions (-). • Combines with oxygen or burns in air. • Anything related to reactivity.

  4. Physical and Chemical Changes • Rotting, burning, cutting in half, vaporizing, rusting, explodes ….. • So, which of the above are physical changes and which are chemical? • Ask, which of the above changes the essence of the matter? • Exploding is chemical, why? It’s a reaction! • Cutting in half? Physical; it’s still the same stuff.

  5. Evidences of a chemical change! • Precipitates = solids formed when 2 clear liquids mix. • Gas given off • Color change (be careful, can be physical only, but a color change often accompanies a chemical one). • Heat (exothermic or endothermic). • Light.

  6. Exo or Endo • Heat = - 510 kilojoules • Heat = +510 kilojoules • If Heat is +, it’s endothermic (Temp. drops) • If Heat is -, it’s exothermic(Temp. increases

  7. Density vs. Weight • What’s the difference between density and weight? Which changes if you suddenly land on the moon? • Weight! Density is a ratio of your mass to volume which shouldn’t change if you made it safely. • If a block of wood is cut in half, how does that change the density? • It doesn’t!!

  8. Viscosity • Thickness of a liquid based on bonding. • Syrup is more viscous than water because of the cohesive bonding of the molecules. • How would you measure the viscosity of a liquid? Drop a marble in it and time it. • I know, it sounds stupid, but we’re trying to pass the test. • The longer it takes for the marble to reach the bottom in equal amts., the more viscous.

  9. Review Your Periodic Table • Know the difference between a Group and a Period. • Groups, vertical. Group I has Li and Na which have similar properties because they have 1 valence electron and form +1 ions to achieve a stable octet. • Periods, horizontal. Have same outer energy levels. 4th Pd = 4th outer level.

  10. Parts of the Table • Transition metals/Alkali metals • Halogens • Noble gases; what’s special about them? • Calcium will form what kind of ion with what magnitude of charge? • 2+ • Chlorine ? • 1- • Formula?? CaCl2

  11. 3 states of Matter • Solids • Liquids • Gases • Describe the molecular motion for each state. • What is the relationship between the strength of the bonding and matter’s physical state? • Stronger bonds tend to form solids.

  12. Types of Bonds • Ionic = metal and non-metal • Na+ + Cl-  NaCl • Covalent = sharing e’s; non-metals. • H – Cl share 1 pr. of e’s. • Ionic – crystals • Covalent – some solids, liquids and gases. • Gases tend to be non-polar covalent.

  13. Balancing Equations • First, write the correct “formula” for a compound if it’s not given. • Ca + O  CaO Ca+2 + O-2 = CaO so the charges =0 • Mg+2 + Cl- = MgCl2 magnesium chloride • Mg+2 + PO4-3 Mg3(PO4)2magnesium phosphate

  14. So, put it together • KClO3 KCl + O2 • 2,2,3 • H2 + O2  H2O • 2,1,2

  15. Kinetic Energy and atoms • The More KE atoms have, the more they move. • Bonding holds them together • Gases have little bonding, so adding more heat (Kinetic Energy) causes them to move a lot. • Gas molecules moving around eventually cause collisions which create gas “pressure” inside a container. • Increase the temperature (KE) and the gas pressure increases. Why?

  16. Law of Conservation of Mass • Mass of Reactants = Mass of Products • 2H2 + O2 2 H2O 11 g. ? 23 g. • 11 + ? = 23 then ? = 12 grams!

  17. 3 forms of Matter • Elements: the purest form of matter. * Check the periodic table. • Compounds: combinations of elements in a specific ratio ( water is H20, not H202). • Mixtures: compounds and elements tossed together in any proportion.

  18. Mixtures: types of. • Homogenous: the mixture looks the same throughout. - kool aid, salt water, milk . . • Heterogeneous: mixture maintains separate parts. - rocks and water, dirt.

  19. Solutions: a type of mixture • Made of a solute (what gets dissolved) and a solvent (what does the dissolving). • Homogeneous and Heterogeneous solutions. See last slide. • Water is always the solvent, salt is a solute. • Unsaturated, saturated and super-saturated solutions.

  20. Acids & Bases • Solutions can be acidic or basic. • Acid solutions taste sour, Basic solutions taste bitter. Lemon vs. Soap. • pH is a scale used to identify weak solutions as either acidic or basic. 7(neutral) 0 Acidic Basic 14

  21. Types of Acids/Bases • Acids: hydrochloric acid (HCl) is a Strong acid • Organic acids like citric or vinegar are weak acids. • Strong base solutions are often called alkaline or caustic. • If a solution has a pH of 10, it’s basic and would require vinegar, maybe, added to it to bring the pH down. That’s why they put citric acid in your shampoo which is normally basic because it’s a soap down to 5.5 which is the pH of your hair.

  22. Water • Acids are made of Hydronium ions (H3O+) in water. • Bases are made of Hydroxide ions (OH-) in water. • Water is neutral, a pH of 7, because the number or concentration of H3O+s = OH-s. • H3O+ + OH- 2 H2O (neutral) acid base

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