1/9/09

Post date: Jan 09, 2009 1:40:47 AM

Bell Activity: What types of mixtures are there?

  • Extra Credit Opportunity

      • Write a paper about an event or observation you've made in your life that you understand better because of one of your science classes

      • Explain the event (example: I saw a rainbow. It looked like ... )

      • Explain the science behind it ( example: Light enters tiny droplets of water in the sky when it rains ... )

      • Minimum of 1 page long

      • Graded on how thorough your paper is and how accurate the science portion is. (hint: being thorough will probably mean writing more than 1 page)

      • Use books or internet resources to research your topic, and include a bibliography

      • Any papers copied from a web site will receive no credit

      • Due at the time of your final (Wednesday for 2nd block, Thursday for 3rd block). No late papers will be accepted, so consider turning your paper in early so you don't forget on the day of your final!

      • Can earn a MAXIMUM of 10% of your overall grade for the class ... only exceptionally well done papers will earn that much.

    • Finished with Chapter 6, covering part of chapter 8.

    • No unit test over this material, but will be on the final.

    • We've already discussed mixtures

      • parts of a mixture are not bonded together

    • mixtures are divided by how well they are mixed

      • heterogeneous - no fixed composition, possibly "chunky"

        • Suspension - a mixture in which particles of a material are more or less evenly distributed throughout a liquid or gas

          • Particle in a suspension eventually settle to the bottom, forming layers like orange juice

          • "shake well before opening"

          • Particles in a suspension can be filtered out

        • Immiscible mixtures - two or more liquids that do not mix, will eventually form layers

        • Colloids - Mixture with smaller particles spread throughout a liquid or gas

          • particles are too small to settle out or filter

          • particles are smaller than those in suspensions, but larger than those in solutions

      • homogeneous - same composition throughout

        • Solution - a homogeneous mixture where two or more substances are uniformly dispersed

          • Smallest particles, mixes at the molecular level

          • Parts of a solution

            • Solute - the substance that gets dissolved (e.g. salt in salt water)

            • Solvent - the substance that the solute dissolves in (e.g. water in salt water)

          • Miscible liquids can mix together to form solutions

            • Can be separated by distillation (heating until one substance turns to a gas but the other stays liquid)

          • Can be formed with various states of matter

            • solid in liquid - salt in water

            • liquid in liquid - vinegar (acetic acid in water)

            • gas in gas - air (nitrogen, oxygen, argon, carbon dioxide, and others)

            • solid in solid - brass (zinc in copper)

              • these are called alloys, used to make materials with different properties than any single element has

    • Read chapter 8, section 1 (pages 259-266) and do the section 1 review (page 266: 1-7)