Focus Question:How do you separate a salt

solution?

Mixtures and Solutions

Separating Mixtures 1-2

Mixtures Review

• What is a mixture? How can a mixture be separated?

• All mixtures can be separated. We used a metal screen and filter paper to separate two of our mixtures.

• Salt and water make a special kind of mixture, called a solution.

Separating a Salt Solution

• Can you separate a solution with a screen? With a paper filter?

• How might you separate the ingredients in a solution?

• Today we’ll be putting together and taking apart salt solutions.

Weighing Water

• Put two empty cups on the balance and zero the balance

• Use a syringe to add 50 ml of water to one cup

• Add 1-gram pieces to the empty cup until it balances again

• Count the gram pieces

• What is the mass of 50 ml of water?

Salt Solution• If you put a spoon of salt in 50 ml of

water and stir until the salt dissolves, will the solution have the same mass as 50 ml of plain water? More mass? Less mass? (Mass is the amount of matter in an object)

• How can you find out?

• Discuss with your group to decide how to answer this question.

Determining the Mass of Salt• Did the salt and water mixture have the

same mass as plain water? More mass? Less mass?

• How can you determine the mass (number of grams) of salt you put in the water to make the solution?

• 50 ml of water = 50 gr• Mass of the salt is the difference

between the solution mass and 50 gr.

Separating the Salt Solution

• Mixtures can be separated

• Separated gravel and water, and powder and water with filters.

• How can you separate the salt from the water? How can you get the salt back?

Evaporating the Salt Solution• Set up two evaporating dishes

• Use two pieces of scratch paper to label with room # and group #

• Place scratch paper and empty dishes in evaporating tray

• Then pour a small amount of solution from the cup into each dish, just enough to cover the bottom of the dish

• Clean up. Throw out remaining solution, rinse cups and replace all equipment in bin.

Results Observations• We set up evaporating dishes to try to

separate the salt from the water in our saltwater solution.

• What happened when the saltwater solution evaporated?

• What is the material in the dish?• What happened to the water that was in

the mixture?• Does the salt look the same as it did

originally?

Evaporation Results

• Use the hand lenses to help complete Evaporation Results worksheet.

• Draw and label a picture of the crystals in the dish.

• Zoom in on one crystal; draw and label the crystal.

• Answer the questions on the page.

Crystals• Observing sodium chloride (salt)

crystals– A crystal is the solid form of a material that

can be identified by its properties, such as shape, color, and pattern.

– The salt crystal looks square and sometimes has lines corner to corner, making an X.

• Replace dishes for use in later investigation.

Separation Review

• In your group, describe how you would separate the following mixtures:– Gravel-and-water mixture– Powder-and water mixture– Salt-and-water solution

• Write your descriptions in your science notebook.

Response Sheet

• Complete Response Sheet - Separating Mixtures.

• Turn to Vocabulary when you are finished.

Vocabulary• Mass - a measure of the amount of matter in

an object. It can be determined by weighing an object with a balance.

• Evaporation - the process of a liquid drying up. The liquid turns to a gas and goes into the air.

• Crystal - the solid form of a material that can be identified by its properties, such as shape, color, and pattern

Content

• How can you separate a solution?• When a solution evaporates, it leaves the

dissolved solid material behind.• How can you identify the material left behind

by evaporation?• If the evaporation material forms a crystal, it

can be identified by its properties, such as shape and pattern.

• Your questions?