Chemistry for Kids, Part 4: Polymers

Class 4/Week 4: Polymers  

B/N: I missed a week in-between posting Chemistry lesson plans I thought I had posted it already (oops!). Enjoy!

Review/Introduction

Remember we talked about solids, liquids and gases and how they are all made up of tiny things called atoms. Remember also that elements are the type of atoms we can have and that when atoms join together, they make molecules.

Today we are going to talk about Solids and Liquids that behave in a funny way when we do certain things to them. Specifically, we are going to talk about something called a Polymer.

What is a Polymer?

• A Polymer is a long chain of made of up many molecules. How a polymer will act when you do things to it depends on how its atoms are connected, as well as which atoms or elements it's made up of in the first place.

  

  Teflon Molecule

  • Some are rubbery like a bouncy ball, some are sticky and gooey, and some are hard and durable like a skateboard.
• Polymers can bend and twist and get tangled up. The longer a polymer chain is the more likely it is that it will get tangled up, just like a jumprope or some string. Since the chains are hard to pull apart once they get all tangled up, a polymer ends up being very strong. So, things made out of polymers are hard to break.
• Polymers can stick together. Some polymers don't get tangled up, though, but they are made up of very neat, straight chains. They are still very strong, though. For example: cellulose is a natural polymer found in wood, which makes trees and wood very very strong and tough to break apart.
• Polymers are lightweight, strong, durable, recyclable- some are easier than others to recycle. However, they last a very long time and this can be bad for the environment when they are thrown away. We should try to recycle the polymers that we can.

Source: http://www.pslc.ws/macrog/kidsmac/atoms.htm

Viscosity

• The longer it takes a fluid to flow, the more viscous it is.
• Polymers are very viscous- they move slower because they're so big. The longer the chains, the slower the flow.

Activity: Explain & Observe Viscosity Using Honey (Teacher-Demonstrated)

• Explain viscosity and demonstrate using honey. Show how honey moves more slowly and becomes more viscous when it's cold and less when it's hot/warm (put some honey in a container on ice and then have some at room temp so they can observe the difference in how it flows or behaves.
• Press on each to show that pressure has no effect on it. It is a Newtonian fluid.

Activity: Show kids this video of people running across a pool of Oobleck: http://www.youtube.com/watch?v=yHlAcASsf6U&feature=player_embedded

• Ask them to watch what happens when they run vs. when they stand still.
• Explain that Oobleck is a Polymer. It changes viscosity because of pressure, not because of temperature. 

Activity: Observe Oobleck, a Non-Newtonian Fluid (Teacher-Demonstrated)

• Make Oobleck ahead of time, using 2 parts Cornstarch: 1 part water. Place it in a plastic dish that is large enough for your entire hand to fit in if pushed flat into the dish. Cover with a lid until ready to use. A plastic baggie is also great for observing how this fluid behaves- it's very neat and contained but the kids can still press on it then allow it flow inside the bag.
  • Allow the kids to observe how it behaves: gently swirl or shake it, press on the liquid firmly to see what happens, pour it to see what happens. Allow kids to take turns pressing on it to feel how it responds to pressure.

• Contrast it with honey in terms of flow, and water (in another dish) in terms of how it behaves when pushed. Water does not clump together and separate from the dish cleanly when stirred with a fork.

Activity: Observe and Play with something like Silly Putty (Silly Putty is a brand name but that's not what we're calling it here)

Make putty Ahead of time using the recipe below and place in individual snack-sized ziploc bags until ready to use. Or, if you have a smaller class, you can allow the kids to make it in class. Be sure to provide plastic snack baggies for them to take their creation home.

Putty Recipe

This will bounce and pick up pictures from the paper just like the name-brand stuff.

• Add: 1/2 cup water to 1/2 cup Elmer's glue (Not School Glue!)
• Mix and add 3 drops of food coloring (optional)
• Make Borax solution: Take 2 tablespoons borax (You can buy this at a grocery store or online) and add to 1 cup of water and stir.
• Add 1/2 cup of Borax solution to water and glue mixture
• Stir and store in a plastic bag

Mix well. Add food coloring if you wish. Let it dry about an hour. When ready, it will be smooth and rubber-like. Store in an airtight container.

Source: http://homeschooling.gomilpitas.com/extras/Gak.htm

Activity: Make Fake Snow

• Give each child sodium polyacrylate beads in a small, snack-sized ziploc bag and allow them to add a small amount of water to it. Encourage them to observe how super-absorbent it is by watching it expand and change appearance with the addition of water.
• Explain that it's used for many things, but the most common we'd recognize is for fake snow in the movies or in baby diapers to keep them from leaking.
• Emphasize that they can play with it but that they must wash their hands and never, never put it in their mouths or swallow it. It's safe on your hands but not in your mouth!!!!

All Images taken from http://www.publicdomainpictures.net/

Chemistry for Kids, Part 3: Crystals

Amethyst

Diamond

Ice Crystals

Lesson 3/Week 3: Crystals

Review/Introduction

Establish what a pattern is: draw a series of three (or more) incomplete patterns on the white board and ask the kids to finish each one. You can either invite the kids up to finish each pattern or you can poll them and then fill it in yourself.

All Images from PublicDomainPictures.net

Activity: Using M & M's, separate them into colors ahead of time and place them in individual plastic ziploc bags. Hand them out in class, along with a napkin or white paper for the kids to lay the candy out on. Have kids mix up candy to show how the molecules of solids normally arrange themselves randomly. Then ask them to arrange the candy into a repeating pattern to show how the same molecules will line up to form a crystal. Their reward if they get the concept and do it right is to eat the candy.


"Remember in our first class we talked about how lots of molecules together make up things that we can see and we talked about solids, liquids and gases. Well today we're going to talk about solids whose molecules form a pattern, or crystals. Not all solids have a pattern, their molecules are scattered all about randomly, but crystals follow a regular, repeating pattern".


"It's possible to "grow" crystals, and when we grow then, we are separating all the building block molecules into individual little pieces in water, and letting them falling into their natural repetitive pattern once the water evaporates, or "dries up"."
Source: http://www.chemistry.co.nz/crystals_defined.htm


Types of Crystals:

• Ionic (salt)
• Molecular (sugar, ice), where the molecule's actual shape can be seen once the crystal has formed; we were lucky enough to still have snow on the ground, so I also used this as an example.
• Covalent (diamond and other gems), Some elements can make more than one crystalline form. For example, Carbon has different forms can be graphite like in a pencil or added to steel to make it stronger, OR it can be diamond like in jewelry
• Metallic (atoms of metals)

Crystals have different shapes and properties.
Activity: Show different pictures on laptop of crystals and of salt, water, salt + water molecules.


Crystals can only grow from a saturated solution. When a liquid is saturated, nothing more of what you add to it will dissolve. For example, you can dissolve sugar by adding it to a cup of hot tea. If you stir it well, the sugar crystals will disappear and you won't see them anymore. BUT if you keep adding huge amounts of sugar, after awhile no more will dissolve and all you'll see is crystals from the extra sugar you added. That is when the solution/liquid/tea has become what is called saturated.

Experiments

Experiment: Growing Glow-In-The-Dark Crystals:

1. While stirring a cup of boiling water, slowly pour in Epsom Salts, adding about 1/4 cup at a time. It will hold quite a lot. As soon as the solution won't turn clear with stirring, it is time to stop.
2. Take one or two pretty, colorful pipe cleaners. Bend it into some shape at one end, leaving the other end for a "hanger."
3. Paint it with GITD paint and allow to dry for 15-30min.
4. Hang it over a pencil suspended over a STRAIGHT SIDED container, or you won't be able to get your crystal out.
5. Pour the Epsom Salt solution over the pipe cleaner in the container. Set it in the warmest room in your home where it won't be disturbed. In about 3 weeks, the water will have evaporated, leaving long, lovely crystals behind on the pipe cleaner.

 Source: http://homeschooling.gomilpitas.com/explore/crystals.htm
  http://chemistry.about.com/od/holidayhowtos/a/glowsnowflake.htm


Experiment: Making Rock Candy***
Explanation: When growing sugar crystals, the sugar in solution is not "happy" so it comes out of the water-sugar solution because there's too much sugar and not enough water to balance it out. When it comes out of the solution, it's called a precipitate. The more water that evaporates or dries up out of the cup/solution, the more sugar will come out, too, making the crystals grow, because there's already not enough water to make the sugar "happy".

1. Heat 2 cups of water to boiling.
2. Completely dissolve 4 cups of sugar and stir using a wooden spoon until solution is clear.
3. Pour the cooled solution into a glass jar & cover the jar with a paper towel.
4. Wrap a pipe cleaner around a bamboo skewer, with the tip removed, leaving about 1 inch in between the bottom of the cup and the pipe cleaner. It should not touch the bottom.
5. Dip the pipe cleaner into the sugar solution, remove it, lay it on a piece of waxed paper, straighten it out, and let it dry for a few days.
6. Gently suspend the pipe cleaner in the solution and let it sit for about 7 days. Be careful not to move or touch it during this time, except to observe daily crystal growth.

 Source: http://www.exploratorium.edu/cooking/candy/recipe-rockcandy.html#


***I prepared a kit ahead of time for each student and handed it out at the end of class for them to take home. It consisted of a plastic ziploc sandwich bag 1/3 of the way full of sugar-saturated and colored (with food coloring) solution I made ahead of time at home, a 9oz plastic cup, a half of a bamboo skewer and a white pipe cleaner cut in half.


I placed the bagged solution inside of the cup to avoid leakage, then tucked the skewer and the pipe cleaner in the cup next to it. I placed each kit into a brown paper bag and stapled an instruction sheet for parents to the outside of each bag. I made sure to demonstrate the process for the kids in class so that they could guide their parents on how to assemble the kit at home, if they were unsure or got stuck.***


Last, show them the video at this link so they can see what their crystals will look like at home. http://www.youtube.com/watch?v=WQdXbf8huuQ

Chemistry for Kids, Part 2: Acids and Bases

 Lesson 2/Week 2: Acids and Bases

Review/Introduction

"Matter, the stuff around us, is used to create atoms. Atoms are used to create the elements. Elements are used to create molecules. It just goes on. Everything you see is built by using something else."  Source: http://www.chem4kids.com/files/atom_intro.html

Molecules- Show pics at this link and explain what each is/does: http://www.nyhallsci.org/marvelousmolecules/marveloussub.html

Water Molecule is made up of 2H's and 1O (draw on whiteboard)
Demonstrate in drawing how acids and bases "take" from water: H goes to acid/OH goes to base.
Split water molecule in drawing on white board. Compare split to a matching game: if you were to play matching with a split-up water molecule, the match would be OH-H, not OH-OH or H-H.

Acids & Bases

Acids
Common acids: Fruit juice, battery acid, vinegar (pH 4), lemon juice, shampoos
Acids taste sour & Acids are corrosive (they eat away at things)
 ex. soda will dissolve a nail or a coin over time bc of the citric acid in it
Acids lose their acidity when mixed with bases

Bases
Common bases: bleach, soap, hair conditioner, drain cleaner, baking soda (pH 8)
Bases are slippery and taste bitter
Bases lose their basicity when mixed with acids

Strong acids and strong bases can be dangerous- never touch, taste, swallow, or smell them because they can burn you or make you sick!!
Source: http://schooldownthelane.wordpress.com/2008/02/04/science-class-4-acids-and-bases/

Why they interact with each other and weaker acids/bases: They share/swap OH's & H's until each one is "happy" or neutral. Show pH scale how neutral is in the middle.
Activity: Use M&M's and ask them to swap in groups of 2 until everyone is happy with the amount they have.

• Scientists use the pH (parts Hydrogen) scale to tell if an acid or base is weak or strong. Water is neutral.
• "Knowing whether something is acidic or basic can be very useful. For example, wasp stings are alkaline but bee stings are acidic. So if you get stung you need to put bicarbonate of soda on a bee sting and vinegar on a wasp sting. Hair conditioner is slightly alkaline as shampoo tends to be slightly acidic, so any traces of shampoo can be neutralised by the conditioner." 

 Source: http://www.york.ac.uk/res/sots/activities/acidtest.htm

Experiments/Activities

Knowing what we now know about acids and bases, we're going to do a series of experiments to help us try and guess whether something is an acid or base and/or see how they react/what they do.

Pre-make the following 7 solutions for use in the Experiments below:
2qts Water + 2 cups baking soda 1qt Water + 1 cup sugar 1qt Water + 1/2 cup salt
1qt Water + 1/4 cup citric acid 1qt Vinegar 1/2 qt lemon juice
Red Cabbage Solution*

* Add chopped Red Cabbage to boiling water, allow to simmer until water is a deep purple, then allow to cool, separate the cabbage leaves from the water using a colander, refrigerate when not in use.



Experiment: Have some fizzy fun!
....by adding several of our proven acids (lemon juice, citric acid solution, vinegar) to some baking soda and seeing if a stronger acid reacts more strongly. The kids then checked some of our bases (soap, baking soda, borax) to see if anything happened (nope) and the neutrals (water, sugar water, salt water) as well (ditto).
Source: http://schooldownthelane.wordpress.com/2008/02/04/science-class-4-acids-and-bases/


Experiment: Does an acid or base clean pennies better?
Split into groups of 2, give each group 6 dixie cups, 6 dirty pennies.
Cleaning solutions we're using: lemon juice, vinegar, citric acid solution, soapy water, baking soda water, borax water) Drop a penny into each cup of cleaning solution and wait a few minutes before examining the penny to see if it's shiny.
Source: http://www.miamisci.org/ph/lpexpand1.html


Experiment: Let's see if we're right!
 Red cabbage water is an indicator of pH. Although it can't be used to determine exact pH, it can distinguish between acid (pH of 0 to 6), neutral (pH near 7), and base (pH of 8 to 14).

acid                     neutral                       base

0   1   2   3   4   5   6   7   8   9   10  11  12  13  14

In this activity:

• If the indicator turns the solution red or pink, the solution is an acid.
• A purple solution indicates that it is neutral, neither an acid nor a base.
• If the indicator turns the solution blue or green, the solution is a base.

Activity: Invisible Ink Writing.
You can even use the power of acid and base chemistry to write secret messages! You can write a message in invisible ink by doing this: Dip a Q-tip in baking soda solution and write a message on white paper- careful not to use too much liquid! Once the paper dries, rub a red grape over the message OR spray the message with a spray bottle filled with Red Cabbage Indicator. Handy hint: using a hair dryer speeds things up.

Sources: http://www.york.ac.uk/res/sots/activities/acidtest.htm & http://www.miamisci.org/ph/lpexcite3.html

Activity: Magic Liquids
Materials: 1 cup water, 1 cup baking soda solution (above), 1 cup water + vinegar, Red Cabbage Indicator, 3 glasses/clear cups
-Fill each of the three cups with one of the first three liquids above.
-Take turns adding the Red Cabbage Indicator to each, ask children to predict what color each will turn.
Source: http://www.miamisci.org/ph/lpexcite2.html



Activity: Blow up a balloon using baking soda and vinegar.
Pour vinegar into a bottle with a narrow neck (soda or water bottle, cleaned out, no label) until it is about 1/4 of the way full. Use a funnel to put a small amount of baking soda in a deflated balloon. Place lip of balloon over rim of bottle and shake the baking soda out, then watch it inflate. Explain that the reaction between the acidic vinegar and the basic baking soda gives off gas that causes the balloon to inflate.

Chemistry for Kids, Part 1: The Fun Stuff

The Fun Stuff for Lesson 1/Week 1 is below, as promised:

Activity: Make a 1-D model of water H2O using construction paper cutouts, above. (Cut them out ahead of time,  label them with H's and O's, put pieces in a snack-sized Ziploc bag for easy classroom distribution, and have kids glue them together- glue sticks are quick and not so messy). 

The ability of elements to form molecules gives us many different types of matter, such as water. Explain if you could see the tiniest parts of water, this is what it would look like, made up of three atoms and O gets 2 H's because it's so big, it wants to bond with 2 friends, 2 H's. When all these little molecules come together, you see water- hold up some water, a just, a cup, a glass, whatever you have.

Explain a bond in everyday terms: it's when you're close to someone, like your mom or dad or a best friend, and you just want to be with them. In the same way, elements like to hang out with one another and "bond" as well.

  

Activity: Show how Carbon forms chains and bonds similarly to the parts of the water molecule- stand in a straight line using long end-pieces from foamy puzzles (or just have kids join hands) and explain how Carbon/elements want to "share" their electrons, have kids share their foamy pieces, "electrons", by having each hold one end, or explain that their hands are the electrons that Carbon wants to share.

Activity: Properties of matter-Point to different objects in the room and have kids describe it, hard, soft, color, texture, shape, smell, hollow, etc.. Write the words on the white board. Give examples: glass is see-through, Aluminum is lightweight, Honey is viscous (thick), rubber is flexible, water is generally cold. Visuals are always great.

Activity:States of matter- Have kids stand around in a group to do demonstrations:

Solid- stand close together and move around very slowly

Liquid- stand a little farther apart and move a little faster, floating your arms like waves

Gas- stand way apart and move around, jump around like crazy, bounce gently into walls

Plasma- (just discuss, no demo) most common form of matter, Lighting, flame, stars; the particles of plasma usually have an electric charge.

Activity: You will need 3 Ziploc sandwich bags, water something solid that will fit in the Ziploc bag (I used a building block), a clear glass or cup, and paper towels for clean-up. Fill one bag with the water, one with the solid, and the third. air, and seal up tight. Let the kids examine the bags. Then with the solid ask them if it takes up space. Take it out of the bag ask them if it changes shape. Put it in the cup ask if it changed shape to fit the cup. Have them hold it. Then ask does it have weight? Ask them if you were to drop it on the table would it pass through the table? Do it, and then ask them why it didn't. They should respond because they are both solid. 

Holding up the water bag ask them if it takes up space. Hand them the bag and ask if it has weight. Does it have a shape? Now open the bag and pour some of it into the cup. Did it change its shape to fit the cup? Ask them what would happen if you poured some on the table. Pour a little on the table and ask them what happened- they'll love this part; spilling on purpose?! *gasp*. 

Holding up the bag of air ask them if it takes up space. Hand them the bag and ask if it has weight. Not much but there is some. Ask them if it has shape. Ask what would happen if you opened the bag. Open the bag and let some out. Did it change shape? Where did it go? Explain that it couldn't wait to get out and spread out, filling the room.

Experiments/Craft(Do whatever time allows)

1. Have kids make a collage of solids, liquids & gases from mag clippings. If you can find plasmas, great! If not, having them draw a star, or some lightning will do, or, just leave it out- your call.

2. Fill a glass jar with sand- I borrowed from our sandbox. Ask the children if there is still any space in the jar. Now fill a measuring cup with water and allow the kids to take supervised turns adding what they can to the jar. Ask the children how much water was added to the jar by asking them to subtract the quantity left in the measuring cup from the original amount. Watch for bubbles coming up and out near the lip of the jar, this is the water pushing the air out as it fills the space. Also, watch for the seepage of water as it travels down the jar, making the sand a darker shade. The amount of water added represents the amount of space left in the jar. Discuss with the students the idea that there is always space around particles. There is space around each atom or molecule of any substance/anything. Also, think: Solid (sand), Liquid (water added), Gas (the air being pushed out as bubbles).

http://www.sciencetech.technomuses.ca/english/schoolzone/matter3.cfm

3. Make a Lava Lamp:

 A glass or plastic bottle with a cap

Water

Vegetable Oil

Alka-Seltzer (store brand) broken into several pieces

 A funnel

Do these steps in the exact order as laid out, or it won't come out right. First fill the empty bottle ¼ full of water using the funnel to keep from making a total mess. Next add food coloring. (An added fun step here...on the back of most food coloring boxes there is a chart that shows you how to mix the colors to make even more colors like purple, orange, lime green, etc. You can take this opportunity with your kids to learn about mixing colors and have some fun with it!) Fill the remaining ¾ of the bottle with vegetable oil, leaving about 1" empty from the top of the bottle. The kids will be tempted, but tell them DON'T SHAKE! Add Alka-Seltzer piece- Kids can do this part, just emphasize that they are not to put it in their mouths!! I gave their parents a packet of Alka-Seltzer to take home so they could do the demo again at home. Again, think: Solid (Alka-Seltzer), Liquid (oil and water), Gas (the bubbles created from Alka-Seltzer being dropped into oil/water mixture, causing the "lava" blobs to float).

http://www.associatedcontent.com/article/2804354/homemade_lava_lamp_craft_for_kids.html?c

at=24