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Usually on Wednesdays we feature Bug of the Week, so today's chemistry lesson is inspired by insects.

Dr. Thomas Eisner was a very curious man. He was particularly curious about insects, like the beetle shown in this video (has pop-up ad).

When he discovered these particular beetles, Dr. Eisner began to experiment with them because he wanted to know what and how they were squirting. One of the unexpected things he found out was that the temperature of the spray the beetle released was very hot, nearly 100° C. How could that be?

Endothermic and Exothermic Reactions

Sometimes chemical reactions between two or more substances give off or take in energy, often in the form of heat. In exothermic reactions, heat energy is given off during the reaction and the temperature increases. In endothermic reactions heat energy is removed by the reaction ("taken in") and the temperature of the reactants decreases.

Below are two chemical reactions that use household products. Find out whether they are exothermic or endothermic.

Notes:  These activities are messy fun, so perform them in a sink, tub, or outdoors in an area where wet spills are not a problem. Also, scientists never eat or drink their experiments!

Reaction 1.

Materials:

  • About 26 g lemonade drink mix* (make sure the primary ingredient is citric acid)
  • Baking soda
  • Liquid measuring cup
  • 1/4 cup dry measuring cup
  • Water (room temperature)
  • Large Styrofoam cup (to help insulate the reaction)
  • Container (glass or cup) to mix the drink mix and water in
  • Thermometer or temperature probe
  • Spoon

* Math alert:  Originally I used Crystal Light pink lemonade mix, which came in 3.68 g packets (see the serving size information for the number of grams per packet). I used 7 packets for about 28 g. Then I switched to an off brand, and the packets were 2.6 g each (10 packets for 26 g). It worked just as well. Also, check the amount of vitamin C information on the labels. The raspberry-flavored lemonade mix contained significantly more citric acid for some reason.

citric-acid-cups

Procedure 1:

  1. Measure 100 mL (approx. 1/3 cup) of room temperature water and pour into in a container.
  2. Add 26 g of drink mix into the water in the container. Stir until completely dissolved.
  3. Use the thermometer or probe to measure the temperature of the solution, taking care not to rest the thermometer or probe on the bottom or side of the cup.
  4. Measure 1/4 cup baking soda into the Styrofoam cup.
  5. In a sink or similar area, quickly add the drink mix solution to the baking soda in the Styrofoam cup.
  6. As the reaction starts to slow, take the temperature again. (You may want to let the children touch the solution and compare to the room temperature water. They will need to wash their hands afterwards.)

reaction 1 citric acid

Did the temperature of the contents of the Styrofoam cup  go up or down?

Reaction 2:

Materials:

  • 2 teaspoons active yeast
  • Liquid measuring cup
  • Measuring teaspoon
  • Water at room temperature
  • Cup or similar container for mixing yeast
  • Large Styrofoam cup
  • Thermometer or temperature probe
  • Hydrogen peroxide (be sure to use 3 %, the kind sold for home use) - held at room temperature
  • Spoon

Procedure 2.

  1. Measure 100 mL of room temperature water (approx. 1/3 cup) and pour into the yeast-mix container.
  2. Mix the 2 teaspoons dry yeast into the water. Stir until thoroughly mixed.
  3. Take the temperature of the solution, taking care not to rest the thermometer on the bottom or side of the cup.
  4. Add 100 mL (about 1/3 cup) 3% hydrogen peroxide to the Styrofoam cup.
  5. Take the temperature of the hydrogen peroxide, taking care not to rest the thermometer on the bottom or side of the cup. The two solutions should be roughly the same temperature.
  6. In a sink or similar area, add the yeast solution to the hydrogen peroxide in the Styrofoam cup.
  7. As the reaction starts to slow, take the temperature again. (You may want to let the children touch the solution and compare to the room temperature water. They will need to wash their hands afterwards.)

Did the temperature go down or up?

reaction-2-hydrogen-peroxide

 

Which reaction was endothermic? Which reaction was exothermic? Let us know what you find out.

 

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If you are interested in learning more about the beetles, read the first chapter in:

For Love of Insects by Thomas Eisner

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For more chemistry activities, check the Table of Contents for Chemistry Week page.

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What are elements, atoms and molecules? How do we study them?

Chemistry Vocabulary:

Elements- Chemists have identified substances that can not be broken down further using chemical means. These are called the elements. Examples of elements are oxygen, carbon and gold. Jefferson Lab has a list of the 10 Most abundant elements in the universe.

Atoms- Atoms are the smallest units of elements. They are also what makes up all the matter in the universe.

Molecules- Many elements are found in nature as two or more atoms interacting together. When two or more atoms interact together or bond, then the result is called a molecule.

Atoms from different elements can also form molecules. An example of a molecule of this type is water, which is formed of hydrogen and oxygen atoms.

A friend used to ask me, “Has anyone ever seen an atom?” Recently scientists have developed technology that allows us to do just that. It is called an atomic force microscope/scanning tunneling microscope. They use extremely cold conditions to hold the atoms or molecules still enough to visualize. Want to see what they look like?

A Boy And His Atom: The World's Smallest Movie

This is a stop motion animated movie created using images from a scanning tunneling microscope. Note: This should really be called a boy and his molecule, because the researchers moved carbon monoxide (CO) molecules to create the images.


Moving Atoms: Making The World's Smallest Movie

In the video below you can see how researchers made A Boy and His Atom. You can also see how excited the researchers are to be doing this creative project and how it has practical applications. It is well worth watching.

 

Related activity:

Make An Element Collection

One great way to make chemistry more concrete is to have have experience with the pure form of different elements.

Gather:

  • A periodic table of the elements (About.com has some to download for free)
  • Box for holding the collection
  • Paper and pen or computer for generating labels
  • Tape or glue (for attaching labels)
  • Small vials for holding samples (optional)
  • Elements

Caution:  Some elements are gases at room temperature, and would be hard to hold in a collection. Some elements, such as mercury, beryllium, and arsenic, are toxic and should not be collected by children.

Elements that you can find at home, hardware supply stores, department stores, rock shops, etc.

  • Carbon:  coal, charcoal
  • Copper:  plumbing supplies
  • Aluminum:  foil, pots and pans
  • Iron:  nails, some magnets
  • Magnesium:  Campfire starters (warning:  highly flammable!)
  • Tin:  new lead-free fishing sinkers
  • Lead:  older fishing sinkers (handle with rubber gloves and wash hands afterwards)
  • Silicon:  computer chips
  • Platinum, gold, silver:  jewelry, small amounts available at bead stores
  • Lithium:  specialized batteries
  • Sulfur:  rock and mineral shops
  • Zinc:  Galvanized nails, electrodes in lemon battery kits (can be toxic if sufficient amounts are swallowed)
  • Tungsten:  Light bulb filaments
  • Neodymium:  Magnets (very powerful, handle with care)
  • Nickel:  Many neodymium magnets are nickel-plated
  • Titanium:  bicycle parts

Always label the items in your collection with the name of the element, and when and where you collected it. That way you won't forget what it is and you can tell your friends where you found it.

You might also want to include elements in common compounds (not in pure form):

  • Sodium:  Table salt (Sodium Chloride)
  • Iodine:  Iodized table salt
  • Calcium:  Chalk, antacids (Calcium carbonate)
  • Magnesium:  Epsom salts (Magnesium sulfate)

Collecting elements can tie in nicely with a rock and mineral collection. For example, look for rocks with copper, sulfur or iron. Panning for gold is fun, too.

copper-mineralsCopper is found in many minerals including azurite and malachite.

Looking for more information? Try:

The Elements: A Visual Exploration of Every Known Atom in the Universe by Theodore Gray, with photographs by Nick Mann

To get an idea what the book is like, Theodore Gray has his periodic table of element photographs at http://periodictable.com. To look at each element, click on the photograph.

Paperback: 240 pages
Publisher: Black Dog & Leventhal Publishers; Reprint edition (April 3, 2012)
Language: English
ISBN-10: 1579128955
ISBN-13: 978-1579128951

 

Slide1Check our Chemistry Week Table of  Contents page for links to all our activities.

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Every once in awhile we have a week of related themed posts here at Growing with Science (see for example, Children's Garden Week and Ocean Science Week.) This week we are excited to pull together a full week chemistry experiments and activities for kids.

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Learning about chemistry is important because in many ways it is central to all other fields of science. Anyone who wants to study science will need to understand chemistry.

Chemistry-central-science

Chemistry experiments are thrilling for kids because the results usually appear quickly. They can also be performed with common household items or those available at your local pharmacy.

This post will be the Table of Contents for the week, where I will add links as they go live (Some of these may be modified throughout the week).

Monday - Elements, Atoms and Molecules

Tuesday - Using chemicals from plants to study pH (for Seed of the Week)

Wednesday - Easy endothermic and exothermic reactions to explore

Thursday - Chemistry resources for young adults

Friday- Chemistry Experiments for Kids using Table Salt

 

As always, you are welcome to join in our party. Please share your related links or questions in the comments.

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popular-chemistry-books-for-kidsYou may want to visit our list of popular chemistry books for kids for more ideas.