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Hands on Science: At Home Activity Experimenting with solutions PART 1: Making Mixtures in Water Question – Do all substances mix in water the same? Materials

• 3 medium sized glasses • tap water • 2 tablespoons salt • 2 tablespoons sand • 2 tablespoons oil • spoon • magnifying glass (optional)

Activity

1. Fill each glass half way with tap water 2. Add salt to the first glass and stir until you can’t see

the salt (approx. 2 minutes) 3. Add sand to the second glass and stir for the same

amount of time 4. Add oil to the third glass and stir for the same

amount of time. 5. Allow each glass of water to settle for 1 minute

after stirring 6. Observe the contents of the 3 glasses (use a

magnifying glass if you have one). Can you see the particles of salt, sand or oil?

Questions and Observations:

1. What happened to the particles of salt? Can you see them? How can you explain this?

2. What happened to the particles of sand? Can you see them? Why? 3. What happened to the oil? Where is it in the glass? 4. Can we separate any of the mixtures? How?

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Explanation: • When we mix sand and water, no reaction takes place. Sand and water are

composed of molecules of different types that cannot chemically combine. The sand simply settles down at the bottom of the jar. This is because sand is heavier than water and hence cannot float in water.

• The salt and water molecules do combine. The salt dissolves, or disappears in the water. Its particles (or crystals) do not fall to the bottom of the glass. This is an example of a solution. A solution is made when one substance called the solute "dissolves" into another substance called the solvent. Dissolving is when the solute breaks up from a larger crystal of molecules into much smaller groups or individual molecules.

• In the jar of oil and water the water molecules bunch up together and the oil molecules bunch up together, forming two separate layers. Water molecules pack closer together, so they sink to the bottom, leaving oil sitting on top of the water. This is a mixture of oil and water.

PART 2: Behaviour in water Question – Do solids all act the same way in water? Materials:

• 2 tablespoons flour • 2 tablespoons salt • glass • spoon • hot tap water

Activity:

1. Add flour and salt together in the glass and stir with the spoon to combine.

2. Add hot tap water to almost fill the glass. 3. Stir well and wait about 30 minutes, then reach in

with your finger and taste the water.

*Keep the mixture for Part 3.

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Questions and Observations: • How does the water at the top of the glass taste? • Did the salt dissolve in the water? How do you know? • Did the flour dissolve in the water? How do you know? • Have the salt and the flour mixed together?

Explanation:

• Salt and flour is a mixture. These substances are so different that when mixed together they can’t mix chemically in any way.

• Salt and flour behave differently in water. The flour floats and then sinks to the bottom of the glass whereas the salt dissolves into the water to form a salt solution above the flour.

PART 3: Separating a mixture Question – Can we get the salt and flour back out of the water? Materials:

1. Medium sized jar 2. Sieve lined with coffee filter or paper towel 3. Hot tap water 4. Shallow bowl 5. Salty water and flour mixture from Part 2

Activity: 1. Place the sieve lined with a coffee filter or paper towel over the top of the jar 2. Pour the salty water and flour mixture from Part 2 slowly through the sieve

filter and into the jar. 3. Very slowly add a little bit of the hot water to help the salt solution break

through the flour. Do this slowly. 4. Take the sieve off the jar 5. Pour the salt solution that has come through the sieve filter into the shallow

bowl. 6. Let the bowl stand in a warm place for 24 hours until there is no more water

left in the bowl.. 7. Observe what is left behind in the bowl.

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Questions and Observations: • What has been trapped by the filter and cannot pass through? • What has passed through the filter? • After 24 hours has all the water evaporated from the bowl? • What is left behind?

Explanations:

• The flour particles are too big to pass through the filter and have been trapped in the sieve. Only the salt water can pass through.

• The salt solution is able to pass through the filter easily. • When the water evaporated the salt is left behind in the bowl and has

reformed into salt crystals. Can you give another example of when water evaporates leaving salt behind? (Hint-is rain salty?)

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