So Temperature Can Effect Saturation As we saw in the Supersaturation Demo, temperature is important when trying to add a solute to a solvent. This is why it is easier to make hot chocolate with powder or chocolate syrup if the milk is heated first rather than while it is cold. So if this is the effect that temperature has on liquids and solids, do you think it is the same for gases? Can you remember a solution with a gas dissolved in a liquid?
So Temperature Can Effect Saturation What do you think would happen if I opened a can of coke and let it sit on the table? What would happen to the dissolved CO 2 over time? How do you think changing the temperature would affect it? Lets do an experiment again!
So Temperature Can Effect Saturation Here we have an ice cold glass of water. What gases do you think are dissolved in this? What do you think will happen if I let it reach room temperature? What will happen to the dissolved gases?
Next topic… How do we describe how much is dissolved in something? We have gone over the descriptions of saturated, but if we were to measure the values, what words would we use? A drink that has more sugar than another is more _________ This brand of beer has a higher _________ of alcohol. Concentration! Not that kind of concentration!
How do we measure concentration?
There are many different ways that we can calculate the concentration, and they all depend on how me measure the amount of solute and solvent present. What are some ways you can quantify how much of something there is?
How do we measure concentration? First way: By Mass Lets say we are making Kool-Aid, the cherry kind …which is the best. We have: 7g of Kool-Aid powder 150g of water How do we calculate the concentration? What we want to find is the % mass of powder.
How do we measure concentration?
Lets try another one! This time we are making a salt water concentration for an oral rinse. We have: 20g of NaCl 250g of water Step 1: Find the weight of the solution Solution = Solute weight + solvent weight = 20g + 250g = 270g solution
Lets try another one!
Now you try one! Now you try one: 100g of chocolate syrup (mmm so much) 350g of milk Find the weight of solution, and % mass of chocolate syrup.
Next Concentration : By Volume This is usually for when the solute and solvent are both liquids. When we are measuring volumes of liquids, what unit do we use? The Liter! (L) When expressing the concentration of liquids we use: % Volume
Concentration by Volume
3)0.065 x 100% = 4)6.5% alcohol by volume
Concentration by Volume Lets try one backwards, and find out how much ethanol is in a bottle of vodka. This bottle of vodka is 40% alcohol by volume It is 750ml in total volume How much ethanol is in the bottle?
Concentration by Volume
Lets get you to try one: This vinegar is 600ml in volume It is a solution of acetic acid (the solute) and water (the solvent). It is 6% acetic acid by volume. How much acetic acid is within the solution?
Concentration by Volume
Molarity
Dissolved in 200ml of water.
Molarity First lets calculate the moles of Glucose: Glucose is how many grams per mole? Carbon = g/mol (x6) = 72.06g Hydrogen = g/mol (x12) = g Oxygen = g/mol (x6) = 95.94g 180.1g/mol
Molarity
= 0.2 L or 0.189M
Preparing a molar solution. Task: Create a 2L solution of 1.5M NaCl in water. You will need: NaCl (table salt) Water A scale Calculator List of atomic weights A volumetric flask
Preparing a molar solution. Task: Create a 2L solution of 1.5M NaCl in water. Step 1: Find out how many grams of NaCl you need. To do this, we need to know the molar mass of both Na, and Cl. Na = g/mol Cl = g/mol Therefore: NaCl = g/mol
Preparing a molar solution.
Ah! Ah! Ah!
Preparing a molar solution.
Task: Create a 2L solution of 1.5M NaCl in water. Step 3: Weigh out our NaCl and add it to our volumetric flask How much water do we add?
Preparing a molar solution. Task: Create a 2L solution of 1.5M NaCl in water. Step 4: Use your 2 liters of 1.5M NaCl for chemistry stuff!
Molality
= 0.3 Kg
Molality Molalit-ayyyy