Resolving Dissolving

1. Resolving Dissolving p. 119

2. Resolving Dissolving • Create a new title/thread “Resolving Dissolving” and date:11/19/13 • Learning Target: I can explain why some substances dissolve in water and others do not. • Update your Table of Contents!

3. Resolving Dissolving • Read the intro on p. 119 • Put your work under Process & Procedure p. 119

4. Resolving Dissolving Process and Procedures • 1. Read Solvation Process (p. 120-122) • Work within your table group to answer any of your questions in your T-table. Create a T-Table to take notes on the reading assignment • “Fact or Idea” on one side • “Questions I have about the fact or idea” on the other side • Make sure to update your vocab section with new vocabulary words that you find in the reading • 2. Using your knowledge of covalent and polar molecules from the reading, draw a series of sketches that show why water does not dissolve paraffin. • Include + and - symbols where appropriate. • Explain each sketch with a caption. • 3. Read the Passage Other Polar Covalent Molecules: • Repeat 1-2. • Use sketches to explain why molecules such as sugar are soluble in water

5. Resolving Dissolving • All matter demonstrates electrical properties • Means that all matter is made up of plus and minus charges • But… not all matter demonstrates electrical properties in the same way! • Why do certain substances dissolve in water? • Because they have similar electrical properties

6. Resolving Dissolving • From particular properties, the salts (hard crystalline solids with high melting points and high conductivity in solution) dissolve in water. • They dissolve in water because they have similar electrical properties. • Oils and wax have low melting points and do not conduct electricity. • They do not dissolve in water because they have different electrical properties.

7. Resolving Dissolving • Ions are charged particles. • Solids made of ions are called ionic compounds.

8. Resolving Dissolving • Solid sodium chloride is made up of ions. • Positive Sodium Ions (Na+) and negative Cloride Ions (Cl-) • Because the ions have opposite charges, they are attracted to each other. • This attraction keeps them locked in place – the structure is called a crystal lattice. • Since the ions in a solid are not free to move around, a solid ionic compound cannot conduct electricity.

9. Resolving Dissolving • Ionic compounds can dissolve in water because water is polar • Water has a dipole (a positive end and a negative end in the same molecule). • The negative end of a water molecule will attract Na+ • The positive end of a water molecule will attract Cl- • This attraction is enough to pull the ions free from the crystal lattice.

10. Resolving Dissolving • Once the ions are free of the crystal lattice, they are surrounded by water molecules. • The process of water interacting with ions and dissolving an ionic compound is called solvation. • The ions (charged particles) can move freely, which is why ionic compounds can conduct electricity in solution 

11. Resolving Dissolving • General rule: substances with similar electrical properties to water molecules will dissolve in water. • “Like dissolves like”

12. Resolving Dissolving • Why doesn’t baby oil and wax dissolve in water? • Because they have different electrical properties than water! • There are no dipoles in wax or baby oil (no sections of plus and minus charge). • These are non-polarmolecules. • Baby oil and wax are covalent molecules • The plus and minus charges are equally distributed over the whole molecule, so there are no dipoles.

13. Resolving Dissolving • Ionic compounds: • Polar molecules: • Non-polar molecules:

14. Resolving Dissolving • P&P #2: Why does paraffin (wax) NOT dissolve in water?

15. Resolving Dissolving • Read “Other Polar Covalent Molecules” p.123-124 • Take notes • Remember to include a summary at the end! • Do R&C #1-3 on page 124 - 125!

16. Other Polar Covalent Molecules • Dipoles are the result of differences in the plus-minus nature of atoms. • The strength of the dipole is determined by the electrical properties of the atoms that make up the molecule. • Molecules that contain dipoles can attract each other. • The strength of attraction depends on the strength of the dipoles involved.

17. Other Polar Covalent Molecules • Molecules with dipoles interact because of their plus and minus parts. • Molecules with dipoles will dissolve in each other (because their plus and minus parts interact).

18. Other Polar Covalent Molecules • Sugar dissolves in water because parts of the molecule have a dipole.

19. Other Polar Covalent Molecules • Most organic compounds are made of carbon rings. • They contain dipoles (of different strengths) because there are “stronger” atoms bonded to the carbon. • The dipoles make it so that these organic compounds are soluble in water.