Do Now. Take out your notes packet Identify the solute, solvent and solution for hot chocolate. Solution: What is a solution? Solute, solvent and solution.
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Do Now • Take out your notes packet • Identify the solute, solvent and solution for hot chocolate
Solution: What is a solution? Solute, solvent and solution • The term ‘solution’ may be one you are familiar with outside of chemistry, but the definition for it in chemistry may be different than what you thought. In chemistry a solution is defined as “A homogeneous mixture formed from a solute dissolved into a solvent”. Remember that ‘homogenous’ means that it has the same consistency throughout the mixture. Solute and solvent may be new terms for you as well. A solute is what is being dissolved, and the solvent is the one that is doing the dissolving. Most of the time in class water will be our solvent.
2. Identify the solute, solvent and the solution for a pitcher of kool-aid • Solute:____________ • Solvent:________________ • Solution:____________
What is happening when something is dissolving? • Using an example to answer this question will be helpful. Let’s take a look at dissolving Sodium Chloride (NaCl), table salt. Salt in the crystal form is really organized and the ions are locked into place because of their opposite charges. When these crystals are introduced to water, which is polar, they begin to interact. The positive ends of the polar water molecule are attracted to the negative chloride ion. The negative ends of the water are attracted to the positive sodium ions. The water molecules begin to surround the individual ions and tear them away from the other ions in the crystal. These ions are kept separated from each other by the water molecules
Simulator • This may help • Online version
Use the image on the previous page to answer the following questions • 1. How is the left and right image different from each other? • 2. What is the difference between how the water molecules surround the Na+ ions and how they surround the Cl- ions? • 3. Let’s say all the water molecules were ‘busy’ separating the ions from each other. What would happen if you added more salt?
c) How much ‘stuff’ is dissolved: Saturated, unsaturated and supersaturated • There is a limit to how much solute (‘stuff’) a certain amount of solvent (usually water) can dissolve. At a certain point the solution becomes saturated. An analogy may help make sense of the term ‘saturated’. A sponge, like a solution, can only hold so much ‘stuff’ before it cannot hold any more. When a sponge is saturated, it can no longer hold any more water. When a solution becomes saturated, it can no longer ‘hold’ (dissolve) any more ‘stuff’ (solute). If you were to add more solute it would simply sink to the bottom of the solution as an undissolved solid. This undissolved solute is called the precipitate, hence the saying: “If you aren’t part of the solution, then you’re part of the precipitate!” (lol). If a solution has dissolved as much solute as it can possibly hold, it is described as saturated. If it can still dissolve more solute, then it is described as unsaturated. Sometimes solutions can be ‘tricked’ into dissolving more solute than it should be able too. This is a special condition referred to as supersaturated. Rock candy is made from making use of a supersaturated solution of sugar and water. Carbonated water is another example. The closed bottle forces more CO2 to dissolve in the water by increasing the pressure. Once it is opened the CO2 slowly escapes as bubbles. This process can be sped up by the addition of a nucleation site (such as ones found on a Mentos candy). Remember, if it is supersaturated, all the ‘extra’ solute is actually dissolved, and not sitting at the bottom of the solution.
Cool demo • Supersaturated solution used as a heat pack • Neat experiments using them • What happens when salt water starts to evaporate?
Do Now • Pick up a copy of the lab (for later) (due Tuesday when we return) • Take out your notes packet • Try and come up with a way to remove the permanent marker on the board with…
Factors affecting solubility; How can we make more stuff dissolve? • ‘Like dissolves like’: Why doesn’t water and oil mix? • The first factor to be examined for how to make more stuff dissolve can be remembered with the simple phrase ‘like dissolves like’. It refers to the polarity of a the solute and the solvent. If both are polar or if both are nonpolar, then the solvent will dissolve the solute. If they are different (one polar and the other nonpolar) then the solvent will not dissolve the solute. An example of this can be seen when you mix oil with water. Water is polar, and oil is nonpolar. This will result in neither dissolving into the other. You may have previously believed that oil and water didn’t mix because of their different densities, but YOU WERE WRONG! They do not mix because they have different polarities! The reason why the oil sits on top of the water is because it is the less dense of the two, but the reason they don’t mix is because of the difference in polarities. PLEASE, correct your friends and strangers alike from this point forth if they have this misunderstanding. • The idea of ‘like dissolves like’ can also be applied to permanent markers. They are considered ‘permanent’ because you would probably try to clean them with water. The pigments in the marker are nonpolar, and water is polar. This means that when you try to clean the marker with water, the water will not be able to dissolve it! If you were a clever science student, you would try a different, nonpolar, solvent to clean it with (benzene or ethyl acetate AKA nail polish remover). PLEASE NOTE, before you go marking stuff up, it works best on clean, non-porous surfaces. Also, using these nonpolar solvents may also damage the thing you are trying to clean, so be careful…don’t ruin anything!
Let me show you • Water and oil in slow-mo
Temperature and pressure: Why does soda go flat? • Other factors that affect how much solute can dissolve in a solution are temperature and pressure. Temperature can have different effects on different types of solutes. For solid solutes, generally speaking, the higher the temperature, the more solute can be dissolved. This can be seen with salt and water. If you had some salt water with salt sitting undissolved at the bottom, you could heat the water up and more salt would dissolve. For gases, generally speaking, as temperature increases its solubility decreases. Think about what happens to soda once it gets warm…it goes flat. The water cannot hold as much carbon dioxide gas and it loses its fizz! • - Pressure only affects gaseous solutes, and has no effect on solids. Gases become more soluble with an increase in pressure. You can think of it as the pressure is pushing more of the gas into the liquid. This is also why, once you open the pressurized soda bottle, the gases start to bubble out, there is now less pressure! • On the axis to the side, draw a solid line showing the relationship between temperature and solubility for solids, and a dashed line for gas.
Solid line = solids Dashed = gases
Practice problems • 1. Nuclear power plants produce a lot of uncontaminated warm water which gets dumped into rivers. Why would this be a concern for the fishes that live in the water?
2. Scuba divers use pressurized tanks to store air so that they can dive deep underwater and still breath. The further down they go, the greater the pressure there is on their body. How would this affect the amount of air that would dissolve into the divers body?
2b. OH NO! AN EMERGENCY! RISE! RISE! RISE! A scuba diver experiences a problem and must immediately surface after spending a bit of time swimming very deep. What would happen to the amount of gas that could be dissolved in their blood when they surfaced?
Do Now • Take out the quarterly review you picked up on Friday • Work on it • Questions? Throw a hand up
Major Topics • -Periodic table • Organization of periodic table (atomic number, groups vs. periods, principle energy levels, valence electrons) • Chemical properties based on location on periodic table • Classifying elements on the PT (metals, nonmetals, metalloids, noble gases) (you wont have your PT for the quarterly) • Calculating parts of the atoms (protons, neutrons, electrons, mass etc..) • Various models of the atom (Dalton, Bohr, etc..)
Major Topics • Bonding: • Determining types of bonds (END, metals and nonmetals, etc.) • Determine bond polarity • Determining molecular polarity • Calculating: gfm, converting to and from moles, %composition
Major Topics • Equations • Balancing chemical equations • Determining type of reaction based on equation • Stoichiometry: using balanced equations to solve stoichiometry problems
How Mr. Donohue Would Study • Read through each notes packet as a refresher • Came across stuff I totally didn’t remember: • Rewrite it out “Periods go across = PEL” • Redo the homework problems • Cover the answers, check them • Not sure what the answer is… • Do some research and find out the right answer • Retake the test(s) and see how I did
For right now • I’ve put together some practice problems • Do them, check the answers, consult a friend then me if you can not figure out the right answer • Finished? Read over the notes packets, redo the homework packets/tests. Keep studying (20% of your grade is kind of a big deal)
Do now • Pick up a copy of the lab and read it over • Homework: Finish the lab • Read the next topic in the notes • C. Solubility Curves • TEST Friday after regents week (start reading the rest of the packet) • DIDN’T TAKE LAST UNITS TEST: itll be a zero if you don’t make it up…
Safety • Goggles • Pretty safe lab…don’t do anything silly • No rough housing • No squirting each other with water…
The Story • Someone stole my Pez Dispenser! • Luckily they left a ransom note • The ink from the note will be analyzed and compared to the pens found in the 4 suspects offices
Big Idea • Markers are a mixture of different pigments, some of which are really polar and some of which are really nonpolar • This difference will be used to separate the pigments • Polar pigments will dissolve in and travel with the water • Nonpolar pigments will stick to the nonpolar filter paper • This will allow us to examine the pigments in different pens and ID the pen used to write the ransom note
GO DO IT! • Homework: Finish the lab • Read the Rest of the notes packet over the next 9 days…
Do Now • A bit-o-review • Solute – Solvent – Solution… • To increase solubility of a solid solute you _________ temperature • To increase solubility of a gaseous solute you can ___________ temperature OR __________ ______________ • CSI Lab due tomorrow
c) Solubility curves Go Ahead and take out your RT + Notes packet
c) Solubility curves • Solubility curves show the solubility of different solutes in water at different temperatures. The lines represent how much of that solute can dissolve in 100. grams of water at the given temperatures. Don’t let the unit ‘g solute/100.g H2O’ throw it off. Remember, if we used more water we could dissolve more solute, therefore we need to pick a specific amount of water used to dissolve the solute. 100. Grams is a nice round number. If you used 200. grams of water instead, you would be able to dissolve twice as much solute. If you used 50. g instead of 100 g, then you could only dissolve half of the solute indicated on the graph. • You also need to be able to use this chart to determine if a solution is saturated, unsaturated or supersaturate. Remember, the lines represent saturation, so if you were given a point and it fell directly on the line, then that solution is saturated. If your point fell below the line, that means more solute could be dissolved in the solution, making it unsaturated. If your point fell above your line, then that solution is holding more solute than it is supposed to be able to hold and is supersaturated.
Example: • How many grams of NaNO3 are required to make a saturated solution in 100 g of water at 30oC? • Start at 30oC, move up to the NaNO3 line. Scoot across to Solute (g). • 96 grams can be dissolved in 100 g of water at 30oC.
How many grams of NaNO3 are required to make a saturated solution in 50 g of water at 30oC? • Since in the last question, it was determined that 96 grams of NaNO3 can be dissolved in 100 g H2O, since 50 g is half as much water, only half as much NaNO3 can be dissolved. Therefore, 96/2 = 48 g of NaNO3 can be dissolved in 50 g H2O.
What is the solubility of HCl in 100 g of water at 70oC? • Start at 70oC, up to HCl and across: 52 g HCl in 100 g H2O @ 70oC
What kind of solution do you have if 80 grams of KClO3 are dissolved in 100 g of water at 40oC? • Start at 80 grams, and 40oC. See where the lines intersect with respect to the KClO3 line. They intersect far above the KClO3 line. At 40oC, the solubility of KClO3 is only 16 grams in 100 g of water. This solution is supersaturated.
For the above solution, what can you do with temperature and amount of KClO3 to make the solution saturated? • If you want to dissolve 80 g of KClO3 in 100 grams of water, the table says you need to heat the solution to 75oC (adding an additional 35oC to the current temperature of 40oC).
Practice in the notes • Your turn!
1) As the temperature decreases, the solubility of gases • 2) As the temperature decreases, the solubility of solids in liquids
3) Which of the salts on Table G is the least soluble at 90oC • 4) Which gas on Table G is most soluble at 60oC? • 5) Which salt on Table G shows the least change in solubility between 30oC and 70oC?
6) 108 g of KNO3 at 60oC • 7) 20 g of NH4Cl at 30oC
9) What is the solubility of NaNO3 in 100 grams of water at 40oC? • 10) How many grams of KClO3 can be dissolved in 1000 g of water at 30oC? • 11) What is the solubility of NaCl in 50 grams of water at 70oC?
How many grams of solute must be added to a solution containing 30 g of NH4Cl in 100 g of H2O at 90oC in order to make it a saturated solution?
A solution contains 80 g of KNO3 in 100 g of H2O at 80oC. To what temperature must the solution be lowered in order to make it a saturated solution?
Consider a saturated solution of NaNO3 in 100 g of H2O at 70oC. If the solution is cooled to 20oC, how many grams of solute will precipitate?