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Focus on basic properties of matter!
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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
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Properties that describe the chemical behavior of matter. Formation of cations (+) or anions (-). Combines with oxygen or burns in air. Anything related to reactivity.
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WWhat’s the difference between density and weight? Which changes if you suddenly land on the moon? WWeight! Density is a ratio of your mass to volume which shouldn’t change if you made it safely. IIf a block of wood is cut in half, how does that change the density? IIt doesn’t!!
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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.
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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.
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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.
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Heat = - 510 kilojoules Heat = +510 kilojoules If Heat is +, it’s endothermic (Temp. drops) If Heat is -, it’s exothermic(Temp. increases
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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. 4 th Pd = 4 th outer level.
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TTransition metals/Alkali metals HHalogens NNoble gases; what’s special about them? CCalcium will form what kind of ion with what magnitude of charge? 22+ CChlorine ? 11- FFormula?? CaCl 2
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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.
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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.
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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 - = MgCl 2 magnesium chloride Mg +2 + PO 4 -3 Mg 3 (PO 4 ) 2 magnesium phosphate
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KClO 3 KCl + O 2 22,2,3 H 2 + O 2 H 2 O 22,1,2
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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?
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MMass of Reactants = Mass of Products 2H 2 + O 2 2 H 2 O 11 g. ? 23 g. 111 + ? = 23 then ? = 12 grams!
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Elements Elements: the purest form of matter. * Check the periodic table. Compounds 2 Compounds: combinations of elements in a specific ratio ( water is H 2 0, not H 2 0 2 ). Mixtures Mixtures: compounds and elements tossed together in any proportion.
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Homogenous: the mixture looks the same throughout. - kool aid, salt water, milk.. Heterogeneous: mixture maintains separate parts. - rocks and water, dirt.
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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.
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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
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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.
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Acids are made of Hydronium ions (H 3 O+) in water. Bases are made of Hydroxide ions (OH-) in water. Water is neutral, a pH of 7, because the number or concentration of H 3 O + s = OH - s. H 3 O + + OH - 2 H 2 O (neutral) acid base
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