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Properties of Matter

Properties of Matter. All Pure Matter has Physical Characteristics. Can observe without the substance changing into a new substance Examples: boiling point, freezing/melting point, hardness, color, texture, & state at room temperature (gas, liquid or solid), density, solubility

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Properties of Matter

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  1. Properties of Matter

  2. All Pure Matter has Physical Characteristics • Can observe without the substance 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 cubemelts into liquid water and then can be boiled to make steam. • Each state has the same chemical formula (H2O), boiling and freezing/melting 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 a substance’s 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 other elements and compounds (in the air iron forms rust, copper turns green, silver tarnishes)

  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) • Na + Cl NaCl (table salt) • a white solid • dissolves in water without exploding • safe to eat • melting point of 801°C (Na 97.85°C) • boiling point of 1413°C (Cl -34.6°C).

  9. Mixtures

  10. Compounds vs. Mixtures • Molecules are substances with 2 or more atoms chemically combined. • A compound is a molecule made up of atoms from 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 (examples: salad, lemonade).

  11. Describing Acids and Bases

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

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

  14. 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 (this is what happens in the reaction of baking soda and vinegar)

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

  16. 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 litmuspaper blue • pH > 7 (also called alkaline) • Causes OH- and (+) ions in water

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

  18. pH = 7 • A substance with a pH of 7 is neutral • Closer to 7 = weak acids or bases • Closer to 0 – stronger acid (more acidic) • Closer to 14 = stronger base (more alkaline)

  19. What Happens If An Acid & Base Mix? • The reaction between an acid and a base is called a Neutralization or oxidation-reduction reaction (redox) • Resulting substance has a pH closer to neutral (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

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