Solutions and Concentration

Transcription

1 Solutions and Concentration

2 Review: Organization of Matter Pure substance A substance made of all the same types of atoms or molecules Only one type of particle Mixture Two or more substances that are NOT chemically combined

3 Mixture or Pure Substance? Pure substance Mixture Pure substance

4 Mixture or Pure Substance? Mixture Mixture Pure substance

5 Review: Organization of Matter Heterogeneous mixture A mixture where you can clearly see the different particles Homogeneous mixture A mixture of substances that looks uniform You cannot see the difference between the particles

6 Heterogeneous Mixtures A mixture of substances where you can clearly see the different particles

7 Homogeneous Mixtures A mixture of substances that looks uniform You cannot see the difference between the particles

8 Review: Organization of Matter Solution A homogeneous mixture where the parts cannot be distinguished from each other even under magnification Colloid A homogeneous mixture where the parts cannot be distinguished from each other to the naked eye But the particles CAN be distinguished under magnification

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10 What is a solution? Homogeneous mixture of solute and solvent Solute: substance dissolved Often a solid Solvent: usually a liquid in which the solute is dissolved Solution = solute + solvent

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12 Example of a solution I take a spoonful of Nesquik powder and mix it into my milk to make chocolate milk. What is the solute? Nesquik powder What is the solvent? Milk What is the solution? Chocolate Milk

13 Solubility The solubility of a substance is a characteristic property. It is a measure of how much solute can be dissolved into a liquid (usually water)

14 Solubility Eventually, so much solute can be added that it no longer dissolves We call this the saturation point

15 Solubility For a solid solute, increasing the temperature of the solution will increase its solubility Why it s easier to dissolve sugar in a hot beverage as compared to a cold one

16 Solubility We have 3 types of solutions: Unsaturated solutions Saturated solutions Supersaturated solutions

17 Solubility Unsaturated solutions: Able to have more solute dissolved into them

18 Solubility Saturated solutions: NOT able to have more solute dissolved into them If you added any more solute, it would stay solid and not dissolve

19 Solubility Supersaturated solutions: A solution that contains more dissolved solute than would be possible under normal circumstances This is often achieved through heating the solution

20 Solubility If a substance cannot be dissolved, it is insoluble Ex: sand in water

21 Dissolution Is this a chemical or physical change?

22 Dissolution Dissolution (dissolving a solute into a solvent) is a physical change We are simply mixing everything together so that it is uniform

23 Dissolution Why is it easier to dissolve something in warm water rather than cold water?

24 Dissolution Think back to particle model As you increase the heat, you give the particles more energy With more energy, they move more freely

25 What is concentration? The amount of solute within a given volume C = M V C: concentration (g/l) m: mass of solute (grams) V: volume of solution (litres) Remember: 1 L = 1000 ml

26 More/less concentrated What does it mean when something is more concentrated than something else? Example

27 More/less concentrated? 1L m=8g V=4L m=2g V=1L 4L C= m/v C=8g/4L C=2g/L C=2g/1L C=2g/L

28 Practice Problem Calculating Concentration 1. Ashley made herself 50ml of Kool-Aid by dissolving 2.5g of the powder into water. What is the concentration of the Kool-Aid in g/l? V= 50ml = 0.050L M = 2.5g C=m/V C=2.5g/0.05L = 50g/L

29 Practice Problem Calculating Concentration 2. Devin is having a party and is making Minute Made juice. He mixes in 100g of the concentrate with some water to produce 2000mL of juice. What is the final concentration (g/l) of the juice? V= 2000ml = 2L M = 100g C=m/V C=100g/2L = 50g/L