Both the study of the pH scale and life offer a few ways to approach the subject.
Two major topics in school science lessons are the pH scale -- used to measure the acidity of a particular substance -- and life, a broad subject which can include everything from examining definitions of what it is to be alive to cellular activity. These topics can crop up more than once as students progress through the school system, and so teachers can benefit from employing a range of interesting activities to teach these two subjects.
Cabbage Juice Test
This activity demonstrates a method of testing the acidity of a variety of substances. Each group of students is handed a beaker of red cabbage juice, six empty containers, and plastic cups containing liquids such as sugar, vinegar and baking soda. To begin, a small amount of each solution is poured into each empty container; each one is then labeled numerically. A tablespoon of the cabbage juice is then added to each container. The resulting color change in the liquid will indicate the acidity and pH scale number of the solution, as shown on the chart on the Middle School Science website. For example, if the liquid turns purple, this indicates a low pH value and thus a strongly acidic substance.
Taste Observations
Students can observe both acid and base solutions to learn the differences between each. Each student should taste an acidic substance, such as lemon juice, and record anything she notices; then, she should do the same with a base substance such as quinine water. The teacher should then explain where each substance falls on the pH scale, and students can record the characteristics they've noticed under a chart of the scale in their exercise books.
Life Definition Discussion
A powerful tool for teaching concepts of living things is a class or group discussion on the nature of life, followed by a research activity. The teacher should begin by introducing the idea that there are certain characteristics which define a living thing; for example, a living thing must use energy. Then the teacher should ask the class to research -- using library books or the Internet -- the answers to a few dilemmas around these definitions. For example, as the Exploratorium website suggests, the teacher could ask students to find out whether scientists consider a virus to be alive.
Food Chain Yarn Game
This activity is based around exploring the food chains which connect each species of animal and plant, and uses a ball of yarn to illustrate these links. Each student is given a hole-punched name tag labelled with a type of flora or fauna. One student's card instead says the sun; this child begins play by keeping one end of the yarn and then rolling the rest to a student carrying a plant tag. Play continues with each student threading the yarn through her card and handing the rest to a classmate whose card is next highest in the food chain. Once one food chain can go no further, play returns to the sun and a new chain is begun, until a food web is created. Colored yarn can be used to avoid confusion between food chains.
Tags: teacher should, acidic substance, cabbage juice, Each student, food chain, food chains, living thing
