Concentration
What is concentration?
The amount of solute for a given amount of solvent
What is density?
The ratio of something's mass to it's volume
What is solubility?
How much of a substance can dissolve in a given amount of solvent
In an experiment, what is the independent variable?
The variable that the researcher manipulates or changes
Oil floats on top of water. What is true about the densities of the oil and water? How do you know?
The oil is less dense than the water. Less dense objects/liquids will float on top of more dense liquids.
How can we make a solution more concentrated?
Add more solute
Use more water
What is the equation to solve for density?
density - mass/volume
Which is more soluble? Table salt or Epsom salt?
Epsom salts
In an experiment, what is the dependent variable?
The variable that is affected due to a change by the researcher
A solution with 75 g of solute and 100 mL of water is saturated. Write how much of substance would be required to make a saturated solution with 200 mL of water.
150g
How can we make a solution less concentrated?
Use more water
Use less solute
What is the density of an object with a mass of 5 grams and a volume of 25 grams?
5 g/mL
What is the word used to describe when a solvent can not dissolve any more solute?
Saturation
How many dependent and independent variables should you have in an experiment?
1 independent and 1 dependent
A student makes a solution using 100 mL of water and two spoons of solid. One spoon of solid has a mass of 5 g. The student lets the solution sit until all the water evaporates. What is the mass after all the water has evaporated?
10g
If a solution is more dilute, what is true about its mass and density?
Mass is less, and density is less
What is the density of an object with a mass of 35 grams and a volume of 5 mL?
7g/mL
How do we know a solution is saturated?
When a layer of the solute begins to form on the bottom
Explain concentration and how it changes as each spoon of salt is added to water until saturation is reached. Then describe what happens to the salt and concentration of the solution after saturation is reached.
As each spoon of salt is added to a solution, the solution becomes more concentrated.
Once saturation is reached, the concentration is the highest it can be and doesn't change after that (as long as the temperature remains constant).
Even though you may add more salt, the concentration remains the same, because no more can dissolve. Instead, the solid sinks to the bottom of the container.
Imagine a bathtub with 5 cm of water in a room that is completely sealed. No air can get in or out. Now imagine you weigh the air in the room (while the water is still in the bathtub). Then you weigh the air after all the water in the tub evaporates. What happens to the weight of the air?
The weight would increase because the water has evaporated and added particles to the air.
What is the concentration of a solution made with 100mL of water and 25 grams of salt?
25/100 OR 1/4
In solution A, I mixed 20g of salt and 100mL of water. In solution B, I mixed 15g of salt and 50mL of water. Which solution is more dense?
Solution B
How can we increase the saturation point in a solution?
Heat up the solution
A class had four unknown substances in cups labeled A, B, C, D. They wondered whether different substances have different solubilities. One student said,“I think they will all be the same.” Write a procedure for an investigation to determine whether the student’s idea about solubility is true. Include what evidence would support the student’s idea and what evidence would challenge it
1. Pour an equal amount of water into each cup.
2. Measure a spoonful (or other equal measure by weight or volume) of each substance, and mix them with water, each in a different cup.
3. Stir until all of the substances have dissolve
4. Add measures of substance until you see significant amounts of undissolved substance.
5. After all solutions are saturated, filter each solution into another set of labeled cups.
6. Weigh each solution; subtract the weight of the water to determine how much substance dissolved.
7. Compare the weights. If the student is correct, the weights will all be the same. If the weights are different, that indicates substances have different solubilities (and the student was not correct
A class had four unknown substances in cups labeled A, B, C, D. They wondered whether different substances have different solubilities. One student said, “I think they will all be the same.” Write a procedure for an investigation to determine whether the student’s idea about solubility is true. Include what evidence would support the student’s idea and what evidence would challenge it.
1. Pour an equal amount of water into each cup.
2. Measure a spoonful (or other equal measure by weight or volume) of each substance, and mix them with water, each in a different cup.
3. Stir until all of the substances have dissolve
4. Add measures of substance until you see significant amounts of undissolved substance.
5. After all solutions are saturated, filter each solution into another set of labeled cups.
6. Weigh each solution; subtract the weight of the water to determine how much substance dissolved.
7. Compare the weights. If the student is correct, the weights will all be the same. If the weights are different, that indicates substances have different solubilities (and the student was not correct