# Teacher Activities

A partial listing of the teacher activities is contained here.

 The Floating Cork The Liquid that Disappears Floating Things A Full Glass? Drops that Don't Move A Mixture or a Solution? Separating Objects by Physical Means Invisible Gas A Molecular Model - Can the Beaker Hold More? Solubility and Temperature

### 1) The Floating Cork

Material: small cork and glass (or beaker) of water.
1. Fill the beaker about half full of water and place the cork on the water surface. Observe what happens.
2. Give the cork a small push in different directions and watch each time where it comes to rest.
3. Fill the beaker full of water to the extent that it overflows a little. Now place the cork on the water surface and observe what happens.
4. What happens when you try to move the cork around now?

QUESTIONS/CONCLUSIONS

1. Where is the water the highest when the beaker is half full? Why?
2. Why does the cork tend to go the side of the beaker and stay there when the beaker is half full?
3. Where is the water level the highest when the beaker is full? Why?
4. Where does the cork float in the full beaker? Why?

### 3) Floating Things

Material: several glasses or beakers, food coloring, various liquids like water, vegetable oil, honey or syrup; various items like plastic, pasta, metal objects, etc.
1. Fill glasses or beakers with the various liquids you have - one per glass, do not mix liquids. Add food coloring and stir.
2. Try floating the various objects you have on each of the liquids. Find which ones float and which don't.
3. Now pour honey or syrup into the glass (wide if possible) about a quarter full. Then slowly pour the same amount of vegetable oil over the syrup, and on top of that the water. Observe what happens.
4. Now carefully place the objects on top of the water and observe what happens.

QUESTIONS/CONCLUSIONS

1. What do you note about the items which float on the various liquids? How do you distinguish the ones that only float on water?
2. What happens when the liquids are in the same container and the objects are added?
3. How can you explain the phenomena you have observed?

### 5) Drops that Don't Move

Material: beaker, water, alcohol, vegetable oil, medicine dropper.
1. Mix and stir 2/3 volume of alcohol and 1/3 volume water in a beaker.
2. Fill a medicine dropper with vegetable oil and place a few drops of oil down in the liquid. What happens to the oil drops?

QUESTIONS/CONCLUSIONS

1. What shapes do the oil drops have?
2. What happens to the oil drops? Do they move?
3. Explain what is happening to the oil drops. What could you do to keep the drops suspended if they move up or down. Try it!
4. Why are the oil drops spherical?

### 6) Separating Objects by Physical Means

Material: various objects like sand, sugar, iron filings, BBs and other requested objects like a magnet, beaker and water, coffee filter, cheesecloth.
1. Mix together the objects in a beaker.
2. Figure out ways to separate the objects physically.

QUESTIONS/CONCLUSIONS

1. Which objects might you remove first? How would you do that?
2. How many ways can you think of to remove the BBs?
3. After the BBs and iron filings are removed, how would you separate the sugar from the sand?

### 7) A Mixture or a Solution?

Material: BBs, sugar, water, two beakers or glasses, paper clips, toothpicks, bits of paper.
1. Fill the two beakers about half full with water.
2. Put a spoonful of sugar in one beaker and the BBs, paper clips, toothpicks, and bits of paper in the other beaker.
3. Stir both beakers. What do you observe?
4. One of these beakers is a mixture and the other beaker contains a solution. Identify them.

QUESTIONS/CONCLUSIONS

1. Which beaker contains a mixture? Why?
2. Which beaker contains a solution? Why?
3. If you mix the following substances individually into a beaker of water, would you have a mixture or a solution? Sand, salt, chocolate powdered milk.
4. Give your best definition of a mixture and a solution.

### 8) The Liquid Disappears

Material: rubbing alcohol, medicine dropper.
1. Place 4 drops of alcohol on your open palm held horizontally using a medicine dropper. Time how long it takes to disappear. The teacher can also drop the alcohol on several students' palm.
2. You can do this experiment with students by having each one using a medicine dropper to place 4 drops on their own hand or by having the teacher do it. Starting together let the students try to get rid of the liquid as fast as possible. They can not rub it off on absorbent material, but can rub it on their skin. Do not tell the students what the liquid is. They can blow on it, spread it on their palm, wave their hand in the air, etc.

QUESTIONS/CONCLUSIONS

1. What happened to the liquid?
2. Do you feel anything on your palm while the liquid was disappearing?
3. How long did it take for the four drops to disappear?
4. What can you do to make the liquid disappear faster?

### 9) A Full Glass?

Material: Three glasses or clear plastic cups, water, paper towels, eyedropper, food coloring, pennies, liquid detergent.
1. Place a glass on several layers of paper towels. Fill it almost full with water and then place a few drops of food coloring in the water and stir.
2. Using another glass or cup, pour some more water into the glass until you think it is full. Do not let it overfill and spill over.
3. Now the fun begins. Place your bets. How much more water do you think can be placed in the glass until it spills over the rim?
4. Using a medicine dropper, add water one drop at a time until the water spills.
5. A variation of this is to add pennies, one at a time, instead of adding drops from a medicine dropper. The pennies should be dropped in vertically!
6. Now do the experiment again with a full glass of water in which a few drops of liquid detergent has been added, but don't tell anyone you added the liquid detergent!

QUESTIONS/CONCLUSIONS

1. How many drops of water could you add? Pennies?
2. Why does the water not overflow easily for the first glass?
3. Why does the water overflow so easily for the glass with liquid detergent?
4. What shape does the meniscus have in the two cases?

### 10) A Molecular Model - Can The Beaker Hold More?

Material: clear beaker or container, marbles, sand, water, graduated cylinder or beaker.
1. Fill the beaker to the top with as marbles.
2. Now (using the graduated cylinder or beaker) carefully add as much sand as you can to the beaker. Make sure you measure the amount of sand that you put in. You should shake the beaker to allow the sand to settle to the bottom and go among the marbles. DRAW A DIAGRAM.
3. Now carefully add as much water as you can to the beaker. Again measure the amount of water you use.

QUESTIONS/CONCLUSIONS

1. How can the already filled container hold sand and then water when it was apparently full?
2. What would have happened if we had started with water, then added sand, then the marbles?
3. What can you infer from this experiment about the sizes of the objects?
4. What relationship does this experiment have with the molecular model?

### 11) Invisible Gas

Material: steam kettle for boiling water, candle or flame source.
1. Put water in the steam kettle and start it boiling.
2. Observe steam coming out of the kettle after the water is boiling.
3. Light the candle or heat source and place it under the path of the steam, so the steam passes over the flame. What do you observe? DRAW A DIAGRAM.
4. Move the candle around under the steam. What do you observe?

QUESTIONS/CONCLUSIONS

1. Where did you observe and not observe steam?
2. How are we able to see steam?
3. Where else where we see water vapor?
4. What conditions are necessary for fog to form?

### 15) Solubility and Temperature

Material: Two 600 mL beakers, hot and cold water, sugar.
1. Put 200 mL of hot water in one beaker and 200 mL of cold water in the other beaker. Carefully note exactly how much water you have in each beaker. It does not need to be precisely 200 mL.
2. Place 5 mL of sugar into each beaker and stir well until the water dissolves.
3. Place another 5 mL of sugar into each beaker and stir well until the water dissolves.
4. Continue adding 5 mL of sugar into each beaker until the sugar no longer dissolves in that beaker. Note the amount of sugar that dissolved in both the hot and cold water.

QUESTIONS/CONCLUSIONS

1. Which beaker held the most sugar?
2. Why did the hot water hold more sugar?
3. Do you think a sugar cube would dissolve faster in hot or cold water? If you are not sure, then do the experiment and time it.
4. Do you think salt would behave the same way as sugar? Explain.