Focus Question: What happens if you keep adding salt to water? Investigation 2-1 Mixtures and Solutions
What is a Solution?• How would you test a mixture to find out if it is a solution?• We made a salt solution by dissolving a spoon of salt in 50 ml of water. What do you think would happen if we put two spoons of salt in 50 ml of water?• Would it dissolve to make a solution?• How about three spoons?• Will salt keep dissolving forever?
Investigation Question• How can we find out what might happen if you keep adding salt to 50 ml of water?
Available Materials• Bottle - keep solution from spilling• Funnel - use to direct salt into the bottle• Sticky note - mark the water level at the beginning• Syringe• Water• Salt• Measuring scoop
Challenge• Question: “How much salt can you dissolve in 50 ml of water?”How much water will you put in the bottle at the start?How much water will you add later?Why would you not add any water later?
Getting Started• Put 50 ml of water into your bottle• Put a sticky note to mark the beginning water level• Add one spoon of salt to bottle. Shake the bottle until the salt dissolves.• Add another spoon of salt.• Repeat above until salt stops dissolving• Keep track of the spoons of salt added
Review• What happened to the salt when you put it in the water?• Where is the salt now?• What happened to the level of the liquid?• Why did the level go up?
Saturation• You made a solution by dissolving solid material in a liquid. When solid material is added to a solution until no more will dissolve, the solution is a saturated solution. You all made saturated salt solutions.• How do you know you have a saturated salt solution?
How much salt dissolved?• You have a saturated solution. How much salt did it take to saturate 50 ml of water?• More precise: How many grams of salt are dissolved in your saturated salt solution?• Is the undissolved salt at the bottom of the bottle part of the saturated solution?• What is the mass of 50 ml of water?
Plan - Worksheet• Place labeled cup under the funnel• Filter the solution using a wet filter paper. Saturated solution will pass through the filter; the undissolved salt won’t• Place saturated salt solution on one side of the balance and 50 ml of plain water on the other side• Add gram weights to the plain water to achieve balance. The mass added to the 50 ml of water is equal to the mass of salt dissolved into the 50 ml of water used to make the saturated solution• Record the number of grams of salt it takes to saturate 50 ml of water on your worksheet.
• A salt solution is made of two parts: the water and the salt. These two parts of a solution are called the solvent and the solute.• The solvent is the liquid into which the solid material goes. The solute is the material that dissolves.• A solution is always made of a solvent with some kind of solute dissolved in it.
Vocabulary• Solvent – The liquid part of a solution• Solute – The solid that dissolves in the solvent (liquid)• Saturated Solution – A solution in which no more solute will dissolve in the solvent
Content• Is there a limit to the amount of salt that will dissolve in water?• How can you determine the amount of salt present in a saturated volume of water?• Your questions?Homework: Read Solutions Up Close, pg 16-19 and answer questions