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 are presented with a short lesson on the difference between cohesive forces (the forces that hold water molecules together and create surface tension) and adhesive forces (the forces that causes water to "stick" to solid surfaces. The interaction between cohesive forces and adhesive forces causes the well-known capillary action. Students are also introduced to examples of capillary action found in nature and in our day-to-day lives.

As part of a (hypothetical) challenge to help a city find the most affordable and environmentally friendly way to clean up an oil spill, students design and conduct controlled experiments to quantify capillary action in sand. Like engineers and entrepreneurs, student teams use affordable materials to design and construct models to measure the rate of capillary action in four types of sand: coarse, medium, fine and mixed. After observing and learning from a teacher-conducted capillary tube demonstration, teams are given a selection of possible materials and a budget to work within as they design their own experimental setups. After the construction of their designs, they take measurements to quantify the rate of capillary action, create graphs to analyze the data, and make concluding recommendations. Groups compare data and discuss as a class the pros and cons of their designs. Pre- and post-evaluations and two worksheets are provided.

Students gain a basic understanding of the properties of media soil, sand, compost, gravel and how these materials affect the movement of water (infiltration/percolation) into and below the surface of the ground. They learn about permeability, porosity, particle size, surface area, capillary action, storage capacity and field capacity, and how the characteristics of the materials that compose the media layer ultimately affect the recharging of groundwater tables. They test each type of material, determining storage capacity, field capacity and infiltration rates, seeing the effect of media size on infiltration rate and storage. Then teams apply the testing results to the design their own material mixes that best meet the design requirements. To conclude, they talk about how engineers apply what students learned in the activity about the infiltration rates of different soil materials to the design of stormwater management systems.

Students observe multiple examples of capillary action. First they observe the shape of a glass-water meniscus and explain its shape in terms of the adhesive attraction of the water to the glass. Then they study capillary tubes and observe water climbing due to capillary action in the glass tubes. Finally, students experience a real-world application of capillary action by designing and using "capillary siphons" to filter water.

Imagine this challenge: You have two glasses of water -- one empty and one full. You want to pour half of the full glass into the empty one. The twist? You aren't allowed to pick up either glass! Can you get the water to "walk" between the glasses using nothing but a paper towel? Try this activity to find out!

Students observe capillary action in glass tubes of varying sizes. Then they use the capillary action to calculate the surface tension in each tube. They find the average surface tensions and calculate the statistical errors.

This pathway explores the properties of water that make it essential for life. Key properties of water discussed in this pathway include water as a solvent, hydrogen bonding, specific heat and cohesion.

This lesson will provide an understanding of the chemical and physical nature of water. It is 1 of 4 in the series titled "The Properties of Water."

Student teams are challenged to evaluate the design of several liquid soaps to answer the question, “Which soap is the best?” Through two simple teacher class demonstrations and the activity investigation, students learn about surface tension and how it is measured, the properties of surfactants (soaps), and how surfactants change the surface properties of liquids. As they evaluate the engineering design of real-world products (different liquid dish washing soap brands), students see the range of design constraints such as cost, reliability, effectiveness and environmental impact. By investigating the critical micelle concentration of various soaps, students determine which requires less volume to be an effective cleaning agent, factors related to both the cost and environmental impact of the surfactant. By investigating the minimum surface tension of the soap, students determine which dissolves dirt and oil most effectively and thus cleans with the least effort. Students evaluate these competing criteria and make their own determination as to which of five liquid soaps make the “best” soap, giving their own evidence and scientific reasoning. They make the connection between gathered data and the real-world experience in using these liquid soaps.

In an activity that integrates science and art, students see, experience and harness the phenomenon of surface tension as they create beautiful works of art. Students conduct two experiments related to surface tension floating objects on the surface of water and creating original artwork using floating inks. They also learn historical and cultural information through an introduction to the ancient Japanese art form of suminagashi. They take the topic a step further by discussing how an understanding of surface tension can be applied to solve real-world engineering problems and create useful inventions.

This pathway provides an introduction to the structure of water and properties of water, such as hydrogen bonding, that make it essential for life. For a deeper look at this topic, we recommend the pathway The Chemical Foundation of Life from the OpenStax textbook Biology for AP® Courses.