Usually on Wednesdays nosotros characteristic Problems of the Week, and so today's chemical science lesson is inspired by insects.

Dr. Thomas Eisner was a very curious man. He was particularly curious almost insects, similar the beetle shown in this video (has pop-upwards 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. I of the unexpected things he establish out was that the temperature of the spray the protrude released was very hot, near 100° C. How could that be?

Endothermic and Exothermic Reactions

Sometimes chemical reactions betwixt two or more substances give off or accept in energy, oft in the form of heat. In exothermic reactions, estrus 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, and so perform them in a sink, tub, or outdoors in an area where wet spills are not a problem. Besides, scientists never eat or drinkable their experiments!

Reaction 1.

Materials:

  • About 26 g lemonade drink mix* (make sure the main ingredient is citric acid)
  • Baking soda
  • Liquid measuring cup
  • one/iv cup dry measuring cup
  • H2o (room temperature)
  • Big Styrofoam cup (to assistance insulate the reaction)
  • Container (glass or cup) to mix the potable mix and water in
  • Thermometer or temperature probe
  • Spoon

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

citric-acid-cups

Procedure 1:

  1. Measure 100 mL (approx. one/3 cup) of room temperature water and pour into in a container.
  2. Add 26 one thousand of drink mix into the water in the container. Stir until completely dissolved.
  3. Use the thermometer or probe to mensurate the temperature of the solution, taking intendance not to rest the thermometer or probe on the lesser or side of the cup.
  4. Measure 1/4 cup blistering soda into the Styrofoam cup.
  5. In a sink or like area, quickly add together the drinkable mix solution to the blistering soda in the Styrofoam cup.
  6. As the reaction starts to dull, take the temperature again. (Yous may want to permit the children touch on 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 upwardly or down?

Reaction 2:

Materials:

  • ii teaspoons active yeast
  • Liquid measuring cup
  • Measuring teaspoon
  • H2o at room temperature
  • Cup or similar container for mixing yeast
  • Big Styrofoam cup
  • Thermometer or temperature probe
  • Hydrogen peroxide (be certain to use 3 %, the kind sold for home utilize) – held at room temperature
  • Spoon

Procedure 2.

  1. Measure 100 mL of room temperature water (approx. ane/iii cup) and pour into the yeast-mix container.
  2. Mix the 2 teaspoons dry out yeast into the water. Stir until thoroughly mixed.
  3. Take the temperature of the solution, taking intendance not to residual the thermometer on the bottom or side of the cup.
  4. Add 100 mL (about 1/3 cup) 3% hydrogen peroxide to the Styrofoam loving cup.
  5. Take the temperature of the hydrogen peroxide, taking care not to residual 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 expanse, add together the yeast solution to the hydrogen peroxide in the Styrofoam loving cup.
  7. As the reaction starts to slow, take the temperature again. (Yous may want to permit the children touch the solution and compare to the room temperature water. They will demand to launder their hands later.)

Did the temperature go downward 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 Honey of Insects by Thomas Eisner

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For more than chemistry activities, check the Tabular array of Contents for Chemistry Week page.

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