Nutrition and Growth of Bacteria (page 4) (This chapter has 6 pages) Â© Kenneth Todar, PhD Physical and Environmental Requirements for Microbial Growth The procaryotes exist in nature under an enormous range of physical conditions such as O2 concentration, Hydrogen ion concentration (pH) and temperature.
In a double replacement reaction parts of two compounds switch places to form two new compounds. Two reactants yield two products. For example when silver nitrate combines with sodium chloride, two new compounds--silver chloride and sodium nitrate are formed because the sodium and silver switched places.
In simplest terms, a chemical change (or chemical reaction) occurs when two substances are mixed together and transform into a third substance. Not all substances react chemically when mixed together, however. For example, some substances, when mixed together, remain simply a mixture of those two substances. In this lesson, students observe chemical reactions that produce obvious effects (as opposed to reactions in which the substances appear not to change at all). They begin by exploring a different substance every day for one week. They compare the substances and learn that substances can be solids, liquids, or gases.