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Intro and Definitions

Solutions. Intro and Definitions. Mr. Shields Regents Chemistry U12 L01. We make or use solutions everyday in our lives. So… what are some of these everyday examples?. Making coffee / hot chocolate /tea Dissolving the flavors of spices into our foods

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Intro and Definitions

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  1. Solutions Intro and Definitions Mr. Shields Regents Chemistry U12 L01

  2. We make or use solutions everyday in our lives. So… what are some of these everyday examples? • Making coffee / hot chocolate /tea • Dissolving the flavors of spices into our foods • Putting additives into our gasoline • Adding anti-freeze to our cars cooling system • Dissolving salt or sugar in our food and drinks • Medicine dissolved in liquids to make them easier to take • Drinking liquids with dissolved Carbon dioxide • Dissolving chemicals in drinking and recreational water to • make them safe • Breathing air into our lungs • Our bodies dissolving nutrients in our blood for nourishment • AND THERE ARE MANY MANY OTHER EXAMPLES AS WELL

  3. Mixtures Recall that in the classification of matter there were 2 major categories. Do you remember what were they? - Pure Substances (elements & compounds) - Mixtures Mixtures are further divided into 2 categories. What are they? - Heterogeneous mixtures (What’s the definition? Examples?) - Homogeneous mixtures (What’s the definition? Example?) - Solutions (All kinds )

  4. Sterling silver (Cu/Ag) Solutions There are several different kinds of solutions. Can you name some? We’re going to Discuss these 4

  5. Solutions Solutions we said are homogeneous mixtures. There are Two components that make up a solution… • The Solute • & • The Solvent In solutions one substance is usually considered to be “broken down” into individual ions or molecules and dissolved into the other.

  6. Solutions The substance being dissolved is called the SOLUTE ex: NaCl is the solute when dissolved in water The substance that does the dissolving (what the solute Dissolves in) is called the SOLVENT ex: When Sugar is dissolved in water, water is the solvent

  7. Solvent vs Solute The distinction between solute and solvent is not Always so clear. For example consider the following… A solution that is 5% ethanol& 95% water. If you said water you would be correct … But now consider what happens if I kept increasing the ethanol until the solution contained 60% ethanoland40% water. Which is the solvent? Which one is the solvent?

  8. Some rules 1) If the solute and solvent are present in the Same Physical state then the Solvent is considered to be the one present in the larger amount. Ex: Ethanol Water 35% 65% water is the solvent 55% 45% ethanol is the solvent 2) If the solute being dissolved in a solvent is present in a Different Physical State from the solventit is always considered the solute no matter how much of each is present. Ex: 5g or 120g of KNO3(s) in 100ml of H2O; KNO3 is always the solute

  9. Solution Concentration The Words UNSATURATED, SATURATED and SUPERSATURATED can be used to describe the amount of solute in the solvent. A SATURATED solution is one in which the solvent can no longer Dissolve any additional solute. An UNSATURATED solution is the opposite. It is one in which More solute can be dissolved in the solvent.

  10. Unsat & Saturated solutions Sol’n can’t dissolve any More solute Sol’n can dissolve more solute Solubility of Sucrose in 100ml Of water at 20º C If I add 50 g to a sat. Sol’n It just sits at the bottom

  11. Supersaturated Besides saturated and unsaturated there are also SUPERSATURATEDSOLUTIONS A supersaturated solution is a solution that contains MORE SOLUTE in solution than the SOLVENT can normally dissolve At a given temperature. So how do we put more solute into solution than the solvent Can dissolve??? In other words how is a supersaturated solution formed?

  12. Making a supersaturated sol’n • The solute is dissolved at some high temperature • The sol’n is then very slowly cooled • As the sol’n cools it has more solute in it than it can normally • dissolve at that temperature • - Decreasing temperature decreases solubility • 4. The solute concentration does not • decrease so we end up • with an unstable situation • 5.If a single crystal is added • to the supersaturated solution…

  13. Supersaturated The addition of a small crystal will cause excess solute to crystallize out of a supersaturated solution immediately! The solution remaining behind is SATURATED!

  14. Liquid Sol’n terms Two other terms used when both solute and solvent are Liquids – Miscible and Immiscible A liquid is MISCIBLE in another liquid if it is… SOLUABLE in one another IN ALL PROPORTIONS Example: Alcohol in Water A liquid is IMMISCIBLE in another liquid if it is… NOT SOLUBLE in one another IN ANY PROPORTION Example: Oil in Water

  15. Liquid Solubility The general rule of thumb is the following: “LIKE DISSOLVES LIKE” So What does this mean in terms of solubility? 1- Polar liquids will dissolve polar liquids 2- Non-polar liquids will dissolve Non-polar liquids 3- But Polar and non-polar liquids tend to be immiscible Remember Polar and non-polar?

  16. Measuring Concentration All the terms we’ve used so far to discuss solution concentrations Are subjective terms. We’ll next discuss ways to specify solution concentrations in More objectiveterms The methods we’ll look at for specifying the concentration of solutions are: 1- Molarity (M) – most common method 2- Percent (%) - mass/mass & volume/volume 3- Parts per Million (ppm) – Used for very dilute solutions

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