Understanding Properties of Matter: Physical and Chemical Characteristics**

1. Properties of Matter

2. All Pure Matter has Physical Characteristics • Can observe without changing into a new substance • Examples: boiling point, freezing/melting point, hardness, color, texture, & state at room temperature (gas, liquid or solid), density, solubility • If a metal: luster, malleability, conductivity of electricity and heat, attraction to magnet

3. If matter undergoes a physical change, then it is the same substance with the same physical and chemical properties before and after the change

4. Example: an ice cube, liquid from the faucet, and steam from a boiling pot are all water. • Each state has the same chemical formula, freezing/melting and boiling points, clear color, and is the universal solvent.

5. All Pure Matter has Chemical Characteristics • Can’t be observed just by looking at it • Describes ability to turn into a new substance • To observe the property, the substance MUST react with another and form other pure substance(s), SO there must be a chemical reaction • Examples: flammability, reactivity with gas (iron to form rust, copper turns green, silver tarnishes), reactivity with metals (acids)

6. If matter undergoes a chemical reaction, a new substance with its own physical & chemical properties is produced

7. Sodium (Na) - soft, silvery metal that explodes in water • Chlorine (Cl) - a poisonous yellow-green gas.

8. Chemical Reaction: sodium chloride (NaCl) • a white solid • dissolves in water without exploding • safe to eat – table salt • melting point of 801°C (Na 97.85°C) • boiling point of 1413°C (Cl -34.6°C).

9. Mixtures

10. Compounds vs. Mixtures • A compound is a pure substance made of 2 or more elements that reacted chemically and has unique chemical properties of its own. (C6H12O6 or NH3) • All compounds are molecules, but not all molecules are compounds (some are elements like H2 or Cl2). • A mixture is made of 2 or more substances that do no react chemically, and retain their chemical properties.

11. Types of Mixtures • Heterogeneous – no matter how well mixed, you can still see the separate parts • Example – salad: lettuce, tomatoes, croutons, etc.; can pick out the cucumber slices if you don’t like • Homogeneous – parts are so evenly mixed, you can’t see the different parts; looks like one substance • Example – teaspoon of sugar stirred into hot tea; can’t see sugar but the tea tastes sweet.

12. What is another name forhomogeneous mixture? • Solution – a well-mixed mixture • At least one substance dissolves into another • Solute – substance dissolved into the 2nd substance (smaller amount) • Solvent – substance that surrounds the 1st substance (larger amount) • Solubility is a measure of how much solute goes into solvent at a given temperature – this is a physical property

14. Are all solutions a solid dissolving into a liquid? • Liquid into liquid • Gas into gas • Gas into liquid • Solid into solid • Anti-freeze: ethylene glycol into water • Oxygen in air • Oxygen in water, CO2 in soda water • Alloys: metal in metal such as bronze (Sn in Cu), brass (Zn in Cu), 14 kt gold (Ag, Cu, or Zn in Au)

15. Factors That Affect Solubility • Temperature • Pressure • Solvent compatibility

16. Temperature Affects Solubility • ↑ solid’s solubility by ↑ temperature, generally

17. Temperature Affects Solubility • ↑ gas’ solubility by ↓ temperature

18. Pressure Affects Solubility • ↑ gas’ solubility by ↑ pressure over the solvent

19. Solvent Compatibility - Like Dissolves Like • Polar solvent + polar solute • Both have + and – sides (the electrons are not distributed evenly) or are ions • Example: NaCl dissolves in H2O • Non-polar solvent + non-polar solute • The electrons are distributed evenly in the molecule (no abundance of charges in one area) • Example: Bromine will dissolve in Hexane • NaCl will not dissolve in Hexane (polar + non-polar)

20. Polar vs. Non-Polar Polar • H2O, NH3, SO2, HCl • Ethanol, methanol, vinegar, glucose Non-Polar • CO2, O2, N2, H2 • The Noble gases • Gasoline, oil, turpentine, other hydrocarbons http://www.school-for-champions.com

21. Describing Acids and Bases

22. Chemical Properties of Acids • Tastes sour (if in food) • Reacts with metals and carbonates • Turns blue litmus paper red • pH < 7 • Separate into H+ and (-) ions in water

23. Never Taste a Chemical in a Lab • Acids in foods taste sour or tart: citrus fruits, tomatoes, apples, vinegar

24. Acids React with Metals & Carbonates • Acids corrode metals • H+ react with the metal • Chemical reaction producing H2 – gas • Acids react with carbonates to produce CO2

25. Strong Acid versus Weak Acid A strong acid releases more H+ into solution. A weak acid only partially dissolves in water

26. Chemical Properties of Bases Sodium Hydroxide - NaOHPotassium Hydroxide - KOHAmmonium Hydroxide - NH4OHCalcium Hydroxide - Ca(OH)2Magnesium Hydroxide - Mg(OH)2Barium Hydroxide - Ba(OH)2Aluminum Hydroxide - Al(OH)3 • Tastes bitter (if in food) • Feels slippery • Turns red litmus paper blue • pH > 7 • Causes OH- and (+) ions in water

27. Bases in food taste bitter: radish, cabbage, Brussels sprouts, turnip, olives, coffee, unsweetened cocoa, quinine, Tums®

28. Indicator paper will tell • you if a substance is • acid (< 7), base (> 7) • or neutral (= 7) • The closer to 0, the • stronger the acid • The closer to 14, the • stronger the base (or • more alkaline) • The closer to 7, the • weaker the acid or base • Strength determines safety

29. What Happens If An Acid & Base Mix? • Neutralization = reaction between acid and base • Resulting substance is less acidic, less basic than the original substances • acid + base = a salt + water • How close to pH 7 depends on the concentrations and amounts of the originals