Science and Java pH Algorithm The lichen is an amazing plant. It is made up of two different types of plants: an alga and a fungus. They have a symbiotic relationship. The algal cells are photosynthetic and make food for the entire or- ganism. The fungal partner protects the alga by re- taining water and providing a large area for taking in mineral nutrients. Their close symbiotic rela- tionship extends the ecological range of both part- ners. Lichens commonly grow on tree bark, as shown. fibPhoto/Shutterstock.com Litmus has a useful property. It is made into paper that comes in two colors: red and blue. When a drop of a liquid is placed on litmus paper, the paper changes color. An acid, like vinegar, turns the blue litmus papers red. A base (or alkaline), like am- monia, turns the red litmus papers blue. Pure water turns both papers violet, which indicates a neutral solution. The same dye can be used to test solu- tions, as shown. chromatos/Shutterstock.com Certain species of lichens produce a dye called litmus. It was discovered in 1300 by a Spanish physician and then used more extensively in the Netherlands after the 16th century. The blue dye can be extracted from certain species found in South America, Madagascar, Norway, Sweden, and California. Assignment You are presented with an unknown clear liq- uid. The problem is to determine if the liquid is an acid, base, or neutral solution. Your task is to write an algorithm to solve this problem using litmus paper. 6 Introduction to Computer Science: Java Programming Copyright Goodheart-Willcox Co., Inc.