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Warm-Up / EOC Prep

Warm-Up / EOC Prep. 1. Carnivorous birds that fed on organisms exposed to this chemical produced fragile eggs. The chemical is ___. A. CFC B. DDT C. DNA D. nitrogen oxide 2. An uncut lawn becomes a meadow and eventually a forest. This process is an example of ___.

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Warm-Up / EOC Prep

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  1. Warm-Up / EOC Prep 1. Carnivorous birds that fed on organisms exposed to this chemical produced fragile eggs. The chemical is ___. A. CFC B. DDT C. DNA D. nitrogen oxide 2. An uncut lawn becomes a meadow and eventually a forest. This process is an example of ___. A. Aphotic zones B. Primary succession C. Estuary D. Secondary succession

  2. Agenda • Warm-up • Notes • Acid or Base? • pH lab • Lab Questions • Clean-up • Cool-down

  3. Properties of Water and pH Guided Notes 15

  4. Why does ice float?

  5. Water expands when it freezes, thus ice is less dense than liquid water, which is why ice floats on the surface of lakes and rivers

  6. The Water Molecule • A molecule in which the charges are unevenly distributed is called a polar molecule • A water molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms

  7. The Water Molecule • The negative pole is near the oxygen atom and the positive pole is between the hydrogen atoms

  8. Hydrogen Bonds • Because of their partial positive and negative charges, polar molecules such as water can attract each other • The attraction between the hydrogen atom on one water molecule and the oxygen atom on another water molecule is an example of a hydrogen bond

  9. Hydrogen Bonds • Hydrogen bonds are not as strong as covalent or ionic bonds, but water’s ability to form multiple hydrogen bonds is responsible for many of its special properties • A single water molecule may be involved in as many as four hydrogen bonds at the same

  10. Properties of Water • Cohesion-an attraction between molecules of the same substance • Cohesion is why drops of water form beads on a smooth surface and why some insects and spiders can walk on a pond’s surface.

  11. Properties of Water • Adhesion-attraction between molecules of different substances • Adhesion is responsible for the way water dips in a graduated cylinder

  12. Solutions and Suspension • Mixture-a material composed of two or more elements or compounds that are physically mixed together but not chemically combined • Two types of mixtures include solutions and suspensions

  13. Solutions and Suspension • Solution-all the components are evenly distributed throughout the solution • Solute-the substance that is dissolved • Solvent-that substance in which the solute dissolves +

  14. Solutions and Suspension • Suspension-mixtures of water and undissolved material • Example: blood

  15. pH H2O  H+ + OH- Water  hydrogen ion + hydroxide ion Every solution has a mixture of OH- and H+ ions. The solution is classified as an acid or a base depending on how much of each ion is present.

  16. pH • pH scale-indicates the concentration of H+ ions in solution • pH scale = 0-14 • 0-7 H+ > OH- • 7H+ = OH- • 7-14 H+ < OH-

  17. pH

  18. pH • Acids • Taste sour • pH = 0-7 • The lower the pH, the stronger the acid • Examples: vinegar, tea, soda, orange juice, lemon juice

  19. pH • Bases • Feel slippery • pH = 7-14 • The higher the pH, the stronger the base • Examples: detergent, soap, ammonia, baking soda

  20. pH

  21. Acids and Bases

  22. Buffers • Buffers-weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in pH • The pH of fluids within most cells in the human body must generally be kept between 6.5 and 7.5 • If the pH is lower or higher, it will affect the chemical reactions • Therefore buffers are used to control pH, which is important for maintaining homeostasis

  23. Review

  24. What two important properties does water have?

  25. Cohesion and adhesion

  26. What pH do acids have?

  27. 1-6

  28. What pH do bases have?

  29. 8-14

  30. A pH of 7 means the substance is…

  31. Neutral, usually pure water

  32. Testing pH: Indicators • Litmus paper • Changes color based on pH of sample • Red litmus paper • Turns red in presence of an acid • Turns blue in presence of a base • Blue litmus paper • Turns red in presence of an acid • Turns blue in presence of a base • If a substance turns the red paper red and the blue paper blue, it is NEUTRAL!

  33. pH Lab • Use one red and one blue litmus paper at each station. Tear each into 3 strips- one for each sample. • Use the tweezers to dip the litmus paper into the unidentified solutions. • Place your trash on the paper plates. • Rotate among the 6 stations with your group. • Wait for time to be called before moving on to the next station. • Only talk to your group. • Keep your goggles on at all times. • No horseplay.

  34. Complete the questions about the lab on the back of the paper before you leave.

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