Students take advantage of the natural ability of red cabbage juice to perform as a pH indicator to test the pH of seven common household liquids. Then they evaluate the accuracy of the red cabbage indicator, by testing the pH of the liquids using an engineer-designed tool, pH indicator strips. Like environmental engineers working on water remediation or water treatment projects, understanding the chemical properties (including pH) of contaminants is important for safeguarding the health of environmental water sources and systems.

Students learn about the properties of solutions—such as ion interactions, surface tension and viscosity—as they make their own soap and shampoo and then compare their properties. Working as if they are chemical engineers, they explore and compare how the two surfactants behave in tap water, as well as classroom-prepared acidic water, hard water and seawater using four tests: a “shake test” (assessing the amount of bubbles produced), a surface tension test, a viscosity test, and a pH test. Then they coalesce their findings into a recommendation for how to engineer the best soap versus shampoo. The activity may be shortened by using purchased liquid soap and shampoo from which students proceed to conduct the four tests. A lab worksheet and post-quiz are provided.

An interactive applet and associated web page that introduce the concept of a triangle. The applet shows a triangle where the user can drag the vertices to reshape it. As it is being dragged a base and altitude are shown continuously changing. Demonstrates that the altitude may require the base to be extended. The text on the page lists the properties of a triangle and lists the various triangle types, with links to a definition of each. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

La titolazione è una tecnica di analisi chimica utilizzata per determinare la concentrazione incognita di un acido o di una base in una soluzione (analita), facendola reagire con una soluzione a concentrazione (titolo) nota rispettivamente di una base o un acido (titolante).

in questa lezione cercheremo di capire come ridurre al minimo gli errori che si possono commettere durante la determinazione del titolo dell'analita.

Test the pH of things like coffee, spit, and soap to determine whether each is acidic, basic, or neutral. Visualize the relative number of hydroxide ions and hydronium ions in solution. Switch between logarithmic and linear scales. Investigate whether changing the volume or diluting with water affects the pH. Or you can design your own liquid!