Author: HJM Teacher

Properties of Water Lab

Name _________________________

Read all instructions first
Follow all instructions unless otherwise told.
Do not play during labs
Encourage others to follow the rules

Date: 03/27/15

K—What you know about water. List everything you know about water and its properties.

W— what you want to know. What things do you wan to learn about water?

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An investigation of the Liquid that Makes all Life Possible: WATER!

Background: Water has some peculiar properties, but because it is the most common liquid on Earth, we typically do not recognize how truly peculiar water really is. Water is everywhere. It's in the air we breathe. It's in our sink faucets, and it's in every cell of our body. Water is an unusual substance with special properties. Just think about the wonder of water:
How does water rise from the roots of a redwood tree to the very top?
How do insects walk on water?
Why does ice float rather than sink?
Why do people become seriously ill, or die, if they go without liquid for a week or so?
How would life in a lake be affected if ice sank and lakes froze from the bottom up?
When it is your turn to run your station: read aloud the information and instructions to your group.
Perform any necessary activity & clean-up…get help from lab table-mates when you need it. Then, lead the discussion of what happened. Run one test at a time with everyone in your group paying attention.
What to write down: the number of the station, the title of the station, the data from the station (i.e. what you observe (qualitative data), any quantitative data, & answer any question(s) for that section.
Clean-up – it is imperative that you clean up each station so that the next class will be ready to go!
Get your teacher’s initials on your paper before ANYONE leaves your lab table.

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Make Predictions here: ( the four questions on previous page)
1.
2.
3.
4.
Watch this video: https://www.youtube.com/watch?v=HVT3Y3_gHGg

You will need:
salt
2 spoons
Beaker with water
beaker with salt & oil

Station 1:
Solubility - Water the Super Solvent –
The Universal Solvent!
Solubility is the ability of one substance to dissolve another substance. (Remember: the chemical being dissolved is the solute and the chemical doing the dissolving is the solvent!). Water is a good solvent, especially for ionic compounds – salt is an ionic compound.
Ions have to be able to dissolve quickly in cell fluids for cellular metabolism (the energy pathways of a cell) to work properly! As a matter of fact, water is called the UNIVERSAL SOLVENT….Do you remember what this term means? If not, Look at your Chem notes!
1. Put a pinch of salt in the water that is already in the beaker.
2. Stir vigorously for 1 minute. Record what happens?
3. The beaker with oil already has salt in it. Stir vigorously for 1 minute. Record what happens?
4. Which is a better solvent for an ionic substance like salt …. water? or oil?
( i.e. is it the non-polar oil?, or is it the polar water?)
& Why might this be?

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Answer here:
2.
3.
4.
Clean-up – Leave the oil and salt as you found it. Pour the beaker of salty water into the sink. Rinse it and dry it (and dry the lab table), and fill the beaker with the same volume of water as there is oil in the beaker. Re-set the station as you found it…beakers, stir rods, salt, etc…
***As ALWAYS Clean-up - Return your station to the condition in which you found it! ...or cleaner!

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Station 2: Surface Tension – Adhesion and Cohesion

Adhesion (water other) and Cohesion (waterwater)
Because each water molecule is polar, the water molecules are highly attracted to one another. This is especially true at the surface, where the water is much more attracted to itself than it is attracted to the air…It almost seems like water can form a skin on the surface…this is called surface tension…
Surface tension is really a combination of:
the attraction between molecules of water
= cohesion = water sticks to water = think: “water attracted to water”
& the molecular attraction between water molecules and other substances
= adhesion = water sticking to something else…think: “adhesive tape”!
1. Pour a small amount of water on a Petri dish, sprinkle the surface with some pepper…. 2. Observe the pepper floating on the surface of the Petri dish.
3. Take the Q-tip from the soapy water and barely touch it to the center of the surface of the peppery water in the center of the dish.
4. Record what happened to the pepper? & 5. Why do you think this happened?
Leave lots of space here after your explanation…later, we will discuss all the cool things that were really happening and you’ll want to take notes here!
****As ALWAYS Clean-up - Return your station to the condition in which you found it! ...or cleaner!

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Station 3 Surface Tension & Adhesion Drop Behavior - Water on Penny Part A

1. Obtain a medicine dropper and a small (10 ml) graduated cylinder. Make sure the dropper is clean.
2. Drop water into the graduated cylinder with the dropper, counting each drop.
3. How many drops, of the size produced by your medicine dropper, are in each cubic centimeter (cc) of water? (1 cubic centimeter = 1 milliliter)? __________ drops
4. Conversely, how much water is in each drop? (divide 1cc by the number of drops) __________ cc.
per drop, average.
****As ALWAYS Clean-up - Return your station to the condition in which you found it! ...or cleaner!

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Answer questions from previous page here:
4.
5.
Notes:

Station 3 Surface Tension & Adhesion Drop Behavior - Water on Penny Part B

1 How many drops of water can pile on a penny before it overflows? Predict in a table like below:

Name	Prediction # of Drops
Total

6. Now, let's see how many drops of water you can you place on the surface of a penny before it overflows. Drop water from the dropper onto a penny, keeping careful count of each drop. Draw a diagram like the one below, showing the shape of the water on the penny after one drop, when the penny is about half full, and just before it overflows.
Figure 1. Drawing of Drops on a Penny

Single Drop

Half Full
_____Drops

Near Overflowing
______Drops

7. How many drops were you able to place on the surface of the penny before it overflowed?
__________ drops
8. How is the number of drops different from your prediction, explain what accounts for any difference.
Explain your results in terms of cohesion .

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Answer number 8 here:

Station 3 Surface Tension & Adhesion Drop Behavior - Water on Penny
Part C Effects of Detergent

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Table 2. Prediction of # of Drops of Water on a Penny with Detergent

Name	Prediction # of Drops
Total

4. Using the same dropper as before, add drops of water to the penny surface. Keep careful count of the number of drops, and draw the water on the penny after one drop, about half full, and just before overflowing.
Figure 2. Drawing of Drops on a Penny with Detergent
5. How many drops were you able to place on the penny before it overflowed this time?
__________ drops
6. Did the detergent make a difference? Describe the effect of the detergent.
****As ALWAYS Clean-up - Return your station to the condition in which you found it! ...or cleaner!

Half Full
_____Drops

Near Overflowing
______Drops

Single Drop

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Station 4: Surface Tension - Floating Paperclip

Using a steady hand and a piece of string, see if you can get the paper clip to rest on the surface of the water in such a way that it will not sink. After you succeed, answer the question below:
What property(ies) of water allows the paperclip to rest on the surface of the water?
****As ALWAYS Clean-up - Return your station to the condition in which you found it! ...or cleaner!
Question to investigate
Do different amounts of water have the same density?
Materials for each group
Graduated cylinder, 100 mL
Water
Balance that measures in grams (able to measure over 100 g)
Dropper
Procedure
Find the mass of an empty graduated cylinder. Record the mass in grams in the chart on the activity sheet.
Pour 100 mL of water into the graduated cylinder. Try to be as accurate as possible by

Station 5: Density

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checking that the meniscus is right at the 100 mL mark. Use a
dropper to add or remove small amounts of water.
Weigh the graduated cylinder with the water in it. Record the mass in grams.
Find the mass of only the water by subtracting the mass of the empty graduated cylinder. Record the mass of 100 mL of water in the chart.
Use the mass and volume of the water to calculate density. Record the density in g/cm3 in the chart.
Pour off water until you have 50 mL of water in the graduated cylinder. If you accidentally pour out a little too much, add water until you get as close as you can to 50 mL.
Find the mass of 50 mL of water. Record the mass in the activity sheet. Calculate and record the density.
Next, pour off water until you have 25 mL of water in the graduated cylinder. Find the mass of 25 mL of water and record it in the chart. Calculate and record the density.

Finding the density of different volumes of water
Volume of water	100 milliliters	50 milliliters	25 milliliters
Mass of graduated cylinder + water(g)
Mass of empty graduated cylinder(g)
Mass of water (g)
Density of water (g/cm3)

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Finding the density of different volumes of water Volume of water 100 milliliters 50 milliliters 25 milliliters Mass of graduated cylinder + water (g) Mass of empty graduated cylinder (g) Mass of water (g) Density of water (g/cm3 )
Look at your values for density in your chart. Does the density of the different volumes of water seem to be about the same?
What do you think is the density of water in g/cm3 ?
Using the data from your chart, graph the volume and mass for 100 mL, 50 mL, and 25 mL.
Look at the graph you made. If you measured 40 milliliters of water, what do you think its mass would be? What would its density be?
Volume: 40 mL Mass ___________ Density _________
Choose any volume of water between 1 and 100 milliliters. Based on the graph, what would its mass be? What would its density be?
Volume ________ Mass ___________ Density _________
Density is a “characteristic property” of a substance. This means that the substance will have the same density no matter how big or small the sample is. Would you say that density is a characteristic property of water? Why or why not?
****As ALWAYS Clean-up - Return your station to the condition in which you found it! ...or cleaner!

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L—What did you learn? As the conclusion for this lab list all the things you learned about water that you didn’t previously know.

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1. With your finger, spread one small drop of detergent on the surface of a dry penny.
2. How many drops do you think this penny will hold after being smeared with detergent, more, less, or the same as before?
Why?
3. Exactly how many drops do you think it will hold?
Table 2 is on the next page.