Last night I had the opportunity to do another lab that I wrote with my students. It is so exciting to see something go from words on a screen to a group of students working together in a laboratory. I learned so much as I walked around the room last night. Here are a few highlights:
Students combine sodium carbonate and hydrochloric acid generating carbon dioxide gas which is allowed to escape. They measure the actual yield of carbon dioxide produced (missing mass), calculate the theoretical yield using stoichiometry, and then the percent yield. Students understand that 100% yield is the most appropriate answer (based on the Law of Conservation of Mass), so after considering the meaning of significant figures and the uncertainty of their measurements they are asked to decide if they did (or did not) get an answer that might indicate the validity of the Law.
Congratulations to Grazyna Zreda who solved the Chemical Mystery of the Mentos candies! To conduct this trick, two white Mentos candies are placed in separate beakers that both contain universal indicator.
National Chemistry week 2014 will be upon us in a little over a month.
Check out the answer to Chemical Riddle #2.
A student of mine, Anthony Shepherd, and I worked together to develop a new chemical riddle. Check out the video and see if you can come up with an answer.
In this Activity, students use citric acid and baking soda to make "bath bubblers" similar to those sold in bath and body stores. They investigate the fizzing reaction that occurs when the bubblers are added to both cold and hot water. Bringing this real world product into the classroom adds interest and can lead to creativity, while introducing both acid/base concepts and rates of reaction.
In this Activity, students extract a fluorescent substance from shavings of narra wood. The pH-dependent fluorescence can be turned on and off using household acid and base solutions. A yellow filter blocks the exciting light but not the fluorescent emission. This Activity gets students thinking about the interaction of light and molecules.
In this Activity, students gain an understanding of the importance of reading reagent labels both in chemistry class and on consumer products. Students explore the chemistry behind the directive on a package of Kool-Aid "Do not store in a metal container". The Activity illustrates properties of acids and metals.
In this Activity, students examine the effect of pH on the intensity and color of the emission of fluorescent dyes in liquid laundry detergent. They perform two titrations using vinegar to estimate the pH at which the fluorescence properties change. In the second titration, sodium bicarbonate is added to buffer the detergent solution.