Every week, Madison (my 10-year old daughter) and I teach a 1.5-hour afterschool science club for K-2nd graders. Each week she helps plan the lesson and then write the blog about what we did.
We have provided links to the books we used to sneak in some literacy. We learned most of the science experiments and activities from Steve Spangler (awesome speaker and science guy extraordinaire). We have included links to his science supplies, experiments, and videos. We have also included links to our YouTube videos. These links take you away from the blog and to external websites.
Lesson 15 & 16
Science of Polymers
Science Standards Addressed:
- Describe the characteristics of the three states of matter (solid, liquid, gas).
- Describe what happens when substances (solid, liquid, gas) are mixed – water gel & instant snow.
- Know that materials are made of atoms and molecules – polymer science.
- Describe how heat is made and how it travels. – unburnable balloon.
- Know that living things have basic needs (food, water, air, sunlight) – radish experiment.
Plus we snuck in some speaking and listening standards like asking questions, expressing ideas, following multi-step directions, and participating in discussions.
As the children arrived we played the songs Everything Grows, by Raffi; Alligator Hedgehog, by Pete Seeger; and Cool Clear Water, by Marty Robbins.
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| Next we had a snack that once again was a hint of the science to follow. |
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Since we are working on our absorbent polymer alligator science fair project, in addition to the healthy stuff, we snacked animal crackers and a few gummy alligators! |
To sneak in some literacy standards, while they ate snack we read them
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| Zack’s Alligator, by Shirley Mozelle |
- a book about Zack, a boy who gets a key chain alligator in the mail as a gift from his uncle. The letter said to put Bridget (the alligator) in water. So he did; and the alligator grew and grew and grew! And it came to life and played with the boy. He told his mom he was going to walk his giant alligator but of course his mom did not believe him. Zack and Bridget walk around town having an adventure, but every once in a while Bridget starts to shrink and needs to take a drink from the water fountain to stay big. When Zack gets home, his dad asks to see the alligator he has been on a walk with. When the boy pulls out the alligator that is again the size of a key chain – his dad says, “That’s nice.” His parents never know that Bridget is real!
We also read
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| A Fish Out of Water, by Helen Palmer – |
- a boy who gets a pet fish and is warned to only feed it … so much. But he feeds it the whole box. The fish out grows the fishbowl, large pots, the bathtub, and eventually flows into the cellar. The boy calls a police man who helps get the fish get out of the celler and into a swimming pool.
The people that are swimming don’t appreciate that! The fish is still growing so the boy has only one option; he grabs the phone and calls the man who sold him the fish. He comes and dives right in. After a long time under water, he suddenly comes up holding the fish in a tiny bowl - the fish is small again!
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| The “stuff” that EVERYTHING is made of (matter) is composed of things that are too small to see with the naked eye – molecules, atoms, and sub-atomic particles. |
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| Some monomers (single molecular units) link with each other to form long chains of molecules – polymers. Polymers will be our focus for the next few weeks. |
Some of the polymers we will be working with are known as hydrophilic (water loving) polymers – they are super absorbents! They can absorb up to 500 times their weight in water!
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| The molecular units of these long chains have lots of sites where hydrogen bonding can occur with water molecules – they act like tiny sponges – soaking up the water and expanding in the process. |
Water Jelly Crystals
First we measured some dry polymer crystals (2-3 mm across). Then, we placed some polymer crystals in a bowl of water to hydrate. These super-absorbent polymers are fun and exciting tools for teaching about molecules and experimentation. When these particles are fully hydrated, we will measure them to compare the difference. Then we will use the hydrated polymers in our radish experiment later in the day.
Straw Paper Worms
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| You know the annoying restaurant trick where your kids (or dad) push the paper wrapper off a straw forming a scrunched up paper “worm.” |
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| Then you dunk the straw in a glass of water and cap the top of the straw with your finger. Then you lift the water from the cup and dribble it on the worm. |
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| The worm expands as the paper absorbs water. We let them all experience this as a model of how the polymers absorb water and expand. |
Growing Animals
Everyone in our science club is doing a science fair experiment that involves growing alligators that are made of super water-absorbent polymers. Te begin introducing this project we started by growing a variety of creatures: an alligator, a cobra, a lizard, a frog, and a shark.
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| First we traced the creatures on graph paper. Then we put them in water and took them home. |
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| We brought them back to science club the following week so the kids could see how much they grew – easily 3 times as big! |
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| In addition to the superabsorbent hydrophilic polymer that absorbs the water, these growing creatures also have a hydrophobic (water-fearing) polymer that helps the creatures keep their shape. |
Radish Experiment- Gardening with super-absorbent polymers
Since we know that plants need water (and sun and nutrients) to grow, and since we know how these polymers absorb water, we decided to do an experiment. We asked ourselves, “What would happen if we put these hydrated polymers in dirt for growing plants?” We thought that probably the polymer would give its water to the soil, which would give it to the plants.
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| We decided to do an experiment. |
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| In some containers we placed some hydrated polymers on the bottom, then placed some soil on top, and some radish seeds on top of that. In other containers, we started with a layer of soil, then hydrated polymers, then radish seeds. In the final container, we used soil with some seeds – no polymers. |
Then we watered them all equally and set them on a window seal to see what would happen.
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| Then we let them sit for 7 days and we saw that the one with the polymer on top sprouted the best. |
Unburnable Balloon
To engage their emotions, we did this cool demo. We blew one balloon and tied it off. We added a couple of tablespoons of water to another balloon, blew it up and tied it off. We donned our fashionable safety goggles and asked the kids what they predicted would happen if we brought the balloon close to a candle flame – unanimous POP prediction. Then we moved the first balloon closer and closer to the flame until it popped. Then we asked them to predict what they thought would happen if we brought the balloon with water in it close to the flame – it will boil, it will pop, you’ll get wet, the balloon will catch on fire, etc. Then we did the unthinkable – we held it directly in the flame. We rotated it (always keeping the water just above the flame) – nothing happened except we got black soot marks on the balloon – the kids really liked this for some reason!
The water absorbs and circulates the heat – this heat exchange works so well the balloon doesn’t pop!
School Spear-It
We learned more about polymer chemistry and really got into the school spear-it at the same time.
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| We got some quart-size freezer-strength Ziploc bags and filled them with water. |
Then we took a VERY SHARP, ROUND pencil and asked the kids what they predicted might happen if we got this extremely sharp pencil too close to the bag (poking it right at the bag to heighten the shock and horror). The kids predicted a big mess. Here’s the cool part! We held the pencil in one hand and the top of the bag in the other hand and pushed the pencil right through one side of the bag and half way out the other side without spilling a drop.
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| We gave all the kids bags and lots of pencils and we all continued to show our Children’s Choice “spear-it” by jabbing all the pencils through the bags. |
What is the science behind this cool trick? The plastic bag is made out of long chains of molecules called polymers. This gives the bag its stretchy properties. The sharpened pencil slips between the molecule strands without tearing the entire bag. Believe it or not, the long chains of molecules seal back around the pencil to prevent leaks. It is a little bit like sticking a pencil in a bowl full of cooked spaghetti – the polymer strands move out of the way but still conform to the pencil.
Diaper Chemistry
To engage their emotions and create excitement, we started this with a cool demo. We secretly put a spoonful of Water Gel in a paper cup. We filled another cup with water. The children watched as we poured a cupful of water into a seemingly (but not really) EMPTY cup. Then we asked if there was a volunteer that didn’t mind getting a little wet. Most of them volunteered! They’re so fun!
One volunteer came up and we turned the cup upside down over her head - but no water poured out! That’s because the water gel absorbed it all. We let them all examine the gel. Then we told them a secret. We told them that we would reveal where they could find this secret stuff to do this magic trick on someone else. But first they had to all swear that they would use their knowledge for good and not for evil.
The secret? A diaper. We have them all a CLEAN diaper and a Ziploc bag. They used their hands to tear into the diapers separating the plastic outer layer from the cotton batting. After shaking and separating the cotton fibers, we could see white powder granules collecting in the bottom of the bag. Then we just scooped out the cotton on top.
We carefully poured a little water into the bag with the polymer and watched it expand and turn into a gel. Dad explained that baby pee contains salt, so some of them experimented by adding some table salt to the polymer to force the water that was absorbed out of the powder. When you leave a baby in a wet diaper it starts to disintegrate. This amazing powder, called sodium polyacrylate, can absorb hundreds of times its weight in water!
We snuck in some social studies - in addition to its use in disposable diapers, sodium polyacrylate, has many uses. It is found in soil to help soil retain water. Florists use it as a dirt-free way to store water and to keep cut flowers fresh for a long time. It is used in filtration units that remove water from airplane and automobile fuels. The creatures we have been growing are made of this stuff.
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| Homeowners can spray this hydrated polymers on structures to protect them from approaching fires. |
Magic Sand – also seen as Mars Sand and Aqua Sand
As our grand finale’, we explored the strange hydrophobic properties of this crazy substance. This stuff starts out as normal sand, but it is dyed and covered with a hydrophobic (water-fearing) polymer that keeps it dry and hold its shape even UNDER WATER.
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| We had fun building structures under water, then we just scooped it out a shook out a few water droplets and put it right back in the bottle – dry again! |
Fun stuff for experimenting with hydrophobic properties! Fun way to end the day!
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