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Objective: describe how a substance can dissolve in water by dissociation, dispersion, or ionization. . DO NOW . List all the facts you know about solutions. . How do shaking and heating affect a carbonated beverage? . Are solutions only a solid and water?

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DO NOW

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  1. Objective: describe how a substance can dissolve in water by dissociation, dispersion, or ionization. DO NOW List all the facts you know about solutions.

  2. How do shaking and heating affect a carbonated beverage? • Are solutions only a solid and water? • What happens when we take the cap off of the soda bottle? • Why does the balloon expand when we put it on the bottle and shake? • How does shaking affect the rate of the change in the beverage? • How does temperature affect what happens when the cap is removed?

  3. Dissolving • A solute is a substance whose particles are dissolved in a solution. • The substance in which the solute dissolves is called the solvent. • Example: Sea water- salt is the solute and water is the solvent • Substances can dissolve in water in three ways: dissociation, dispersion, and ionization.

  4. Dissociation of Ionic Compounds • For a solute to dissolve in water the solute and solvent particles must attract one another. • Before a solution can form, the attractions that hold the solute together and the solvent together must be overcome. • The polar molecules of the water are attracted to the ions of the solute • Crystal of the salt dissolves as the sodium and chlorine ions get pulled into the solution • The process in which ionic compound separates into ions as it dissolves is called dissociation.

  5. Dispersion of Molecular Compounds • Dispersion: Breaking into small pieces that spread throughout the water. • Both sugar and water are polar, so they attract each other. • Water molecules move constantly so as they attract the sugar, they are moving it around.

  6. Ionization of Molecular Compounds • Ionization: neutral molecules gain or lose electrons • Dissolving by ionization is the only chemical change. • The resulting solution has different properties than the original substances. • Example: hydrogen chloride and water it forms a chloride ion and a hydronium ion.

  7. Recap • What is a solution? • What are the two parts of a solution? • What three ways allows substances to dissolve into water? • Which of the three ways is the only one to cause a chemical change?

  8. Homework • Prepare for the vocabulary quiz on Wednesday.

  9. DO NOW • Take out your homework • List the three ways that substances can dissolve in water. • Which one of these three ways involves a chemical change? • What are some factors that may affect how fast a substance dissolves? Objective: describe how the physical properties of a solution can differ from those of the solute and solvent. Identify energy changes that occur during the formation of a solution.

  10. Properties of Liquid Solutions • Three physical properties that can be different from those of its solute and solvent are conductivity, freezing point, and boiling point.

  11. Conductivity • Often times substances that are poor conductors of electricity are able to conduct electricity when dissolved in water because the ions are free to move around in the water.

  12. Freezing and Boiling Point • Solutes added to water can either lower the freezing point or raise the boiling point. • There are many uses for this property change; some examples are the salt that is spread to melt ice (when mixed with the water on the ice, the freezing point becomes lower and therefore the water does not freeze) and coolant in cars (to prevent the water in an engine from boiling).

  13. Heat of Solution • During the formation of a solution energy is either absorbed or released. • This can be described as either exothermic or endothermic. • In order for a solution to form the attraction among the solute and solvent particles must be broken and breaking attractions requires energy. • The amount of energy required to break the attractions is called the heat of solution.

  14. Factors Affecting Rates of Dissolving • Surface area • The greater the surface area the more often collisions occur and the faster the substance will dissolve • Stirring • Moves dissolved particles away from the surface and increase the rate of dissolving • Temperature • Increasing temperature usually increases the motion of the particles which increases the number of collisions in a given time resulting in an increase in rate of dissolving.

  15. Homework • Complete worksheet • Prepare for vocabulary quiz on Wednesday

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