Hot and Cold Water: Mixing

Tried this demonstration at home before I try it in the classroom. It shows how hot and cold water can both mix or not mix together.  I used blue food coloring for cold water and yellow food coloring for hot water (didn’t have red handy at home, but will use red at school).  It also demonstrates a great surface tension trick with the upside down jar of water and a playing card. I use playing cards b/c the waxy surface works best for either demo. (I used old glass jelly jars, we go through a  lot of jelly at my house. I run them in the dishwasher and save them for science experiments.)

For this demo, I am not going to tell the kids that I am using cold and hot water. Want to see if they can figure it out .

When the cold blue water is on the top, and the hot yellow water in on the bottom, as soon as you pull the card away, they mix and the water turns green in both jars. (purple if you use red). When the cold water is on the bottom, and the hot water is on the top, when you take the card away, it does NOT mix like before. there may be a small zone of mixing where the two meet. Great discussion about density and the effects of temperature on the movement of the water particles.

It is a pretty cool trick and I think the kids will love it when they see it, only b/c it is so unexpected for them .

For more information, check out this website: http://www.exploratorium.edu/science_explorer/watertrick.html

Water – Polarity Demo

One of my students recently sent this video clip to me. (Thanks James!) It demonstrates the polarity of water by doing a rather simple experiment, I had never seen this before and can now add this to my bag of tricks!  My unofficial theme for this year has been water. Everything we have studied so far this year, relates to water in some way. I tease my students and say that if they don’t remember anything else from 5th grade, they will know the formula for water! =) Enjoy!

Dunkin’ 4 Density Activity

We completed the “Dunkin’ for Density” activity today, collected our data, entered it into excel, and discussed our findings. 

For this lesson, the kids had to make 1 film canister float, 1 film canister suspend, and 1 film canister sink in water by changing their densities.  We used white/clear plastic film canisters and I calculated the volume as 39 ml or cm3 by using water displacement and a large graduated cylinder.  (The film canisters hold about 35 mL of water, in case you were wondering!)

Supplies: plastic tray, 3 film canisters per set of two lab partners, a bowl or large beaker filled with water, pennies, rubber stoppers, cork stoppers, paper clips, and bits of clay. I also had a really large/deep bowl as the “official suspend testing tank”.  Once the kids tested their suspending canister, they brought it over to be officially checked by me.

Using whatever combination they like, they place the items into the film canisters to complete the task. I only have two rules: you must have at least one item in the canister (which I forgot to tell the 1st class!) and it must be able to close and seal tightly so no water enters the film canister. The floaters and sinkers are the easiest to do and the kids figure those out pretty quickly. But I am very picky about my definition of suspend and it drives them nutty!  In order to qualify as a suspender, the film canister has to touch the bottom of the bowl when I tap it, and then float up slowly until it is near the surface of the water. Only a small part, if any, may rise above the water line. This is a great problem solving activity and after a few tries, they usually get just the right combination of stuff inside their film canisters to make the density very close to 1 g/cm3. (For this to happen, the mass ends up being close to 39 g,)

Once they have completed all three tasks, they use the TBB to find and record the mass into their notebooks. (Tip – make sure the film canisters are dry before they use the TBB) (Tip #2 – have them find the mass of an empty film cansiter before they begin dunking.)  Using the formula for density (D=m/v), they find and record those densities into their notebooks.  Once everyone is done, each group reports their data and we enter it into the excel spreadsheet, displaying the data on the SmartBoard. We then discuss the data and I ask the kids if they notice any patterns in the data. (Sometimes I’ll show the data from previous classes so they can compare their results to older experiments.)

After we have discussed the data, they answer the analysis questions and write a conclusion on page 41, the right side of their notebook. The one misconception that some kids may have is that the film canisters sank because they became heavier.   We talk about how yes, they did get heavier, but they sank because they became denser.

Notebook:

pg. 40 – Dunkin’ for Density

pg. 41 – Analysis: Dunkin’ for Density

Excel Spread Sheet Template to enter data  (This is a very old template, it won’t graph for some reason. If I can, I will update it.)

 

If you have completed this activity, I would love to hear from you and see your results!

Density Bottles

As an introduction to density, I do a demonstration/discussion/group activity using density bottles. They are small sports drink bottles that I estimated to have a volume of approximately 400 mL.  There are 5 bottles, each  filled with a different item: cotton, air, sand, rice, and colored water.

These are some of the questions I used for our discussion:

• “Do these bottles have the same volume?” There is some uncertainty at first, but then they quickly say “yes”.
• “Do these bottles have the same mass?” No
• “Why don’t they have the same masses?” Variety of answers
• “Which one do you think is the heaviest?” We do a survey with a show of hands then have the kids give some reasons for their answers
• “Which one do you think has the most ‘stuff’ crammed into the bottle?” It’s interesting, there is a wide variety of answers and it usually doesn’t match the answer to the question of which is the heaviest

I tell them that they will find out the answers in a minute! We watch the BrainPOP movie for Measuring Matter. After the movie, I give the analogy of standing and waiting for an elevator.  Two identical elevators open up: one has 2 people in it and the other has 15 people in it.  “Which elevator would you choose and why?” Naturally, they say the one with only two people, there is more room in that one. I ask them, which elevator is denser? The one with 15 people, of course. We then discuss that there is less empty space available in the elevator with 15 people in it.  I then relate molecules to the people in the elevator, matter that has a lot of molecules, or atoms, crammed into a given space are denser than objects whose molecules or atoms have a lot of empty space between them.

I hand one bottle to each group and have them find the mass.  We collect the data and I write it on the board. I re-ask the following questions:

• Which one is the heaviest?
• Which one has the most ‘stuff’ crammed into the bottle? (Variety of responses)
• Which one is the densest? (Variety of responses)

Now that we have the mass and the volume, we calculate the densities for each bottle.  After we collect the data, I have the kids come over to the dunk tank.  One at a time, we predict which bottles will float. We do a survey and raise our hands if we think the bottle will float.  I have one student place the bottle into the tank and we see if it floats or not. We continue until all 5 are in the tank.

The cotton, rice, water, and air filled bottles floated, the bottle with the sand, sank to the bottom. I then ask the kids “Why did the bottle of sand sink?” They usually say it was the heaviest. I then say, “But a cruise ship is a lot heavier, and it doesn’t sink? Why?”  I give them a hint, “Look at our data, what do the bottles that floated have in common?” After a while, they figure out that the bottles that floated, all had numbers that were decimals, or less than one.  The sand was over 1, and sank. I tell them the density of water is 1, so objects with a density greater than 1 will sink.

We talked about how the bottle of sand is the densest b/c it has the most amount of “stuff” crammed into the same space, and that there is less empty space between the atoms.  I tell them that the density of gold is 19.3 g/cm3, and that if this bottle was filled with gold, it would be about 19 times denser, meaning that there would be 19 times more “stuff” crammed into the same space. The next day we talked about the story of Archimedes.  We calculated how much mass the same bottle would have if it was filled with pure gold - it would be 7,720 grams!! 

After the dunk tank, we did a small group acitivty using the graphic organizer from BrainPOP.  It shows a ring, balloon, yo-yo, and pillow.  We have to categorize them according to mass, volume, and density, from highest to lowest.  We do one category at a time and I give them a minute  for each, going over the answers between each category. I liked this graphic organizer b/c it really made them think about each item and their properties.

pg. 34 - BrainPOP – Archimedes

pg. 35 - BrainPOP – Mass, Volume, Density Graphic Organzier

Volume Labs- Regular and Irregular

Over the period of about 3 days, we covered finding the volume of a rectangular prism using the formula length x width x height and finding the volume of irregularly shaped objects using water displacement.  I usually do these labs as stations labs, but decided to have the kids do the activities at their tables.

For finding the volume of rectangular prisms, I placed some everyday objects onto a tray as well as some scrap wood from our woodworking shop. Students could choose what they wanted to measure in whichever order they like.  We then compared our results.  I usually allow a  +/- 2 mm window for their measurements.

I made up some hand signals and we practiced them as a class so that the students could remember the three dimensions when taking their measurements.  It helped a lot and I saw the kids use it to orientate themselves for the 3 dimensions.

• hold your hand flat and straight on the table = length
• hold your hand sideways with your wrist bent at a 90 degree angle = width
• hold your hand straight up in front of you, fingers towards the ceiling, with your wrist at a 90 degree angle = height

What happens sometimes is that they forget which side they already measured or have trouble choosing which side will be their length, which side is their width, and which is the height. I have them lay the object flat on the table in front of them and have the longest side be their length and pointing towards them to get them started.

For the irregular volume, I kept it simple and the kids really liked it.  I placed an assortment of rubber stoppers and marbles on their try.  Some stoppers were solid, some had one hole, some had 2 holes, some were skinny, some were wider. They could place whatever combination they wanted into the graduated cylinder and they recorded what they tried. They also asked questions like “Does the stopper with 2 holes have a smaller volume than a stopper with no holes if they are the same size?” and they tried it out.

They also figured out that if they fill up the graduated cylinder with too many stoppers, they couldn’t find the volume b/c it was more than 100 mL or items were no longer in the water, they were stacked above the water line.

The spoon is there to prevent the items from falling into the beaker, they cover the top of the graduated cylinder, drain the water, and then place the objects back on the try.  Keeps everyone dry!

See below for my notebook pages:

pg. 20 – Volume Lab: Pre-Lab,  Length, Width, & Height

pg. 21 – Practice: Measuring in cm & mm

pg. 22 – Irregular Volume Lab: Pre-Lab,Water Displacement

pg. 23 – Practice: Reading a graduated cylinder, water displacement, volume (page 1)

pg. 24 – Practice Reading a Ruler pg 1

pg. 25 – Practice Using a Ruler cm #1-10, mm #1-10

pg. 26 – Practice using the formula L x W x H  pg.1

pg. 27 – Practice: Reading a graduated cylinder, water displacement, volume (page 2)

Drops of Water on a Penny Lab

Last week we completed the Drops of Water on a Penny Lab.  In this lab, we learned about surface tension, how to use a pipette, how to collect data, how to use a stem and leaf plot, how to do an experiment, and what variables are.  Our question was: Does soapy water make a difference?

Each set of lab partners completed 3 trials each for clean water and soapy water, then calculated an average for each.  We posted our averages onto the stem and leaf plot. What I like about the stem and leaf plot is that it allows you see how the numbers are grouped- it’s a visual representation that allows you to see patterns and ranges quickly.

One of the things we talked about was that if we all completed the same experiment, why didn’t we all get the same results?  Some ideas were that some people used smaller or bigger drops of water, some held  the pipette really close to the penny while some held the pipette higher above the penny. Some pennies were newer and smoother while others were older and rougher. One other idea is that some cups of soapy water were soapier than others.

So, did soapy water make a difference? Did soap affect the surface tension of the water? What do you think?

Volume: Water Displacement

After we are done with the volume of regular objects lab, we will determine volume using water displacement. This is a lab where setting up the equipment on a lunch tray really comes in handy, its pretty messy! Whenever we use water, I always add a few drops of blue or green food coloring to it. The food coloring makes its easier to read the water levels in the graduated cylinders. Yellow is light, and red tends to stain more than the other colors. I use a large beaker as my stock of colored water then fill smaller beakers with it. A few drops per 100 mL is plenty.

This will be a stations lab with 10 stations. On each tray, there will be a beaker (200 – 250 mL) of colored water, graduated cylinders (10 mL, 25 mL, and 50 mL), two items to measure (rocks, small rubber stoppers, marbles, pennies, etc..) and a plastic spoon. The plastic spoon is a must have for this lab. How so? Lets say the kids are finding the volume of a small rock, they drop the rock into the graduated cylinder, find the volume, now they have to get it out. I show them how to tilt the graduated cylinder to pour the water back into the beaker while using the spoon to cover the opening of the graduated cylinder. Water pours out while the rock is stopped by the spoon. They can easily take the rock and place it back on the lunch tray.

If that doesn’t work, and the rock (or whatever object they are finding the volume for) falls into the beaker, they can use the spoon to fish out the rock from the bottom of the beaker. Otherwise, the kids are putting their whole hand into the beaker to fish out the rock and their hand will displace the water in the beaker = spills. Another reason to use the spoon is that some objects, like metal cylinders or marbles, can crack the beaker when it falls out of the graduated cylinder. (also, to prevent the grad. cylinder from breaking when an object is placed in it, place a small rubber stopper inside the grad. cylinder)

I usually remind the students that when they fill up the graduated cylinders to only fill it about half way with water. This allows room for the object to be placed into the graduated cylinder without the water running over. I also remind them to record the starting volume, drop the object in, record the final volume, and to subtract the final volume from the stating volume to calculate the volume of the object. (1 mL = 1 cubic cm)

Prior to starting the lab, we will talk about Archimedes, how to read a graduated cylinder, what a meniscus is, what displacement is and how to use it to calculate volume, and how to determine the increments to read the volume. We will also do a few practice problems as a pre-lab.

Left Side:

• Pre-Lab- reading a graduated cylinder
• Lab Sheet- water displacement activity

Right Side:

• Practice: Reading a Graduated Cylinder and determining volume by displacement (page 1)

Surface Tension Demonstration

I do this lesson as an observation with the students gathered around the table. We talk about surface tension and most kids have a general idea of what it is.

I fill up a glass with water, but not all the way to the top. I ask the kids “Can this paper clip float on top of the water?” Kids usually say no. I add a little drama and try really hard to get the paper clip to float on top of the water and act really disappointed when it drops to the bottom each time. Then I “remember” how to do it the right way.

I slowly add more water to the glass and the kids watch as the water rises over the top but does not run down the side of the glass. It forms a dome. We talk about surface tension again.

I then take a paper clip (the smaller ones work really well) and hold it horizontally. I place one edge on the lip of the glass and slowly slide the paper clip onto the dome of water. I give it a slight tap and the paper clip slides across the top of the dome to the other side. The kids think its such a neat trick. We then make observations of how the paperclip is slightly indented into the surface of the water and that the surface tension is holding it up.

I then add another paperclip and we make more observations. Sometimes the paper clips bump into each other and float around the top. We keep going until I can no longer place anymore on top. I think we had 15 floating at once as our highest count.

After we discuss this demo and wrap it up, I show the kids how to use a pipette and have them practice using it so they are ready for our surface tension lab the next class. Using a pipette is a fine motor skill and takes practice so all the water doesn’t gush out at once or come out in uneven large drops. I show them how to hold it with their thumb and first two fingers on the bulb end and to keep the pipette on a slight angle. You don’t want to hold it perfectly horizontal because you want the water to be near the opening and reduce air bubbles. Holding it vertically doesn’t give you as much control. You want to hold the pipette steadily and have good control.

One other key point is not to the have the tip of the pipette touch anything or submerge into the water. When they do the real lab, I remind them that the pipette tip should not touch the penny or any drops of water on the surface of the penny. I bring up that whenever I watch crime shows and they show some kind of testing liquid from a dropper touching the item they are testing it drives me nutty because they just contaminated the bottle they were using and its not using proper “CSI” techniques. =)

The kids then practice with different amounts of pressure and experiment on how to get a good even flow of drops of water, and to practice counting them. The kids really get into it and we see how many drops of water they can get in a row.

Using Publisher, I made a tri-fold brochure for this demonstration, here is the pdf.