Physical or Chemical?
Ice melts into liquid water. Is this a physical or chemical change?
Physical change
What is the substance that gets dissolved called?
Solute
What does it mean when a solution is concentrated?
It has a larger amount of solute compared with the amount of solvent.
What are the three factors we studied that affect the rate of dissolution?
Temperature, surface area, and agitation
True or False: Dissolving sugar in water creates a new substance.
True
A nail rusts after being left outside. Is this a physical or chemical change?
Chemical Change
What is the substance that does the dissolving called?
Solvent
What does it mean when a solution is dilute?
It has a smaller amount of solute compared with the amount of solvent.
Which will dissolve sugar faster: hot water or cold water?
Hot Water
Salt is stirred into water until you can no longer see it. Did the salt disappear?
No, the salt dissolved and is still present in the solution.
A student cuts a sheet of paper into small pieces. Why is this a physical change?
No new substance forms
In salt water, what is the solute?
Salt
What happens to the concentration of lemonade when you add more water?
The concentration decreases/the lemonade becomes more dilute.
What does agitation mean when talking about dissolving?
Stirring
A student adds more drink mix powder to a pitcher without adding more water. What happens to the concentration?
It increases/becomes more concentrated.
A piece of wood burns and produces smoke and ash. What type of change occurred?
Chemical Change
In an aqueous solution, what substance is always the solvent?
Water
Two cups contain the same amount of water. Cup A has 1 spoonful of sugar, and Cup B has 4 spoonfuls. Which is more concentrated?
Cup B
Which dissolves faster in water: a sugar cube or the same amount of crushed sugar? Why?
Crushed sugar because it has greater surface area exposed to the water.
Two students dissolve identical amounts of sugar. Student A uses hot water and stirs. Student B uses cold water and does not stir. Who should dissolve the sugar faster?
Student
A substance changes color, releases gas, and gets warmer after two substances are mixed. What type of change most likely occurred, and why?
Chemical Change because there is evidence that a new substance formed.
A student mixes 10 grams of sugar into 100 mL of water. Identify the solute and solvent.
Solute=Salt, Solvent=Water
A student says, “Adding water to salt water removes some of the salt.” Is the student correct? Explain.
No. The amount of salt stays the same; adding water dilutes the solution.
You have a large sugar cube in cold water. Name three changes you could make to help it dissolve faster.
Increase the temperature, crush the sugar cube, and stir/shake the solution.
A student crushes a solid tablet, places it in warm water, and stirs it. Explain how surface area, temperature, and agitation each help increase the rate of dissolution.
Crushing increases surface area, warm water increases particle movement, and stirring increases contact between the solute and solvent.