In this activity, students explore the effect of chemical erosion on statues and monuments. They use chalk to see what happens when limestone is placed in liquids with different pH values. They also learn several things that engineers are doing to reduce the effects of acid rain.

Students are introduced to the differences between acids and bases and how to use indicators, such as pH paper and red cabbage juice, to distinguish between them.

Acids and bases are substances that are able to give and receive hydrogen ions respectively. This seemingly insignificant ability gives rise to a wide range of reactions and is essential for many biological processes. This pathway provides resources related to acids and bases, the types of reactions they undergo, and the pH scale which is used to measure the concentration of hydrogen ions in a solution.

In this video segment, the ZOOM cast demonstrates how to use cabbage juice to find out if a solution is an acid or a base.

In this video segment adapted from ZOOM, two cast members demonstrate what happens when vinegar is added to baking soda inside a container. The resulting chemical reaction produces enough carbon dioxide to launch their paper rocket skyward.
Recommended for: Grades K-5

It would seem that bottles of lemon juice and rockets have only their basic shape in common. However, as two cast members from ZOOM demonstrate in this adapted video segment, when baking soda is added to the mix, a plastic bottle can act very much like a real rocket. Grades 3-8.

Students watch a video lesson that demonstrates how to solve exponential equations using logarithms. The tutorial includes two detailed examples. [2:38]

This lesson presents the idea that the area of any triangle is exactly half of a certain parallelogram -- thus we get the familiar formula of multiplying the base and the altitude and taking half of that. The lesson contains varied exercises for students.

Video tutorial uses problems to reinforce understanding that the angles in a triangle always add up to 180 degrees. (Part 1) [3:55]

Video tutorial uses problems to reinforce understanding of angles in a triangle. (Part 2) [6:23]

Learn about the autoionization of water into hydronium and hydroxide ions. [10:55]

Khan Academy learning modules include a Community space where users can ask questions and seek help from community members. Educators should consult with their Technology administrators to determine the use of Khan Academy learning modules in their classroom. Please review materials from external sites before sharing with students.

Students hypothesize whether vinegar and ammonia-based glass cleaner are acids or bases. They create designs on index cards using these substances as invisible inks. After the index cards have dried, they apply red cabbage juice as an indicator to reveal the designs.

Students learn the basics of acid/base chemistry in a fun, interactive way by studying instances of acid/base chemistry found in popular films such as Harry Potter and the Prisoner of Azkaban and National Treasure. Students learn what acids, bases and indicators are and how they can be used, including invisible ink. They also learn how engineers use acids and bases every day to better our quality of life. Students' interest is piqued by the use of popular culture in the classroom.

Biology 2e is designed to cover the scope and sequence requirements of a typical two-semester biology course for science majors. The text provides comprehensive coverage of foundational research and core biology concepts through an evolutionary lens. Biology includes rich features that engage students in scientific inquiry, highlight careers in the biological sciences, and offer everyday applications. The book also includes various types of practice and homework questions that help students understand—and apply—key concepts. The 2nd edition has been revised to incorporate clearer, more current, and more dynamic explanations, while maintaining the same organization as the first edition. Art and illustrations have been substantially improved, and the textbook features additional assessments and related resources.

By the end of this section, you will be able to do the following:

Describe the properties of water that are critical to maintaining life
Explain why water is an excellent solvent
Provide examples of water’s cohesive and adhesive properties
Discuss the role of acids, bases, and buffers in homeostasis

Students use a simple pH indicator to measure how much CO2 is produced during respiration, at rest and after exercising. They begin by comparing some common household solutions in order to determine the color change of the indicator. They review the concepts of pH and respiration and extend their knowledge to measuring the effectiveness of bioremediation in the environment.

A video tutorial demonstrating how to calculate the pH of a solution given the hydrogen ion concentration. [3:44]

This video lesson demonstrates how to calculate the area of a triangle. It includes detailed examples including ones that use the Pythagorean Theorem. Students can check their understanding with an assessment. [10:43]