Learning About Elements: The Earth's Building Blocks (page 2)
Try New Approaches
- The most abundant elements in the atmosphere (gaseous envelope surrounding the Earth) are nitrogen (78%), oxygen (21%), and other elements (1%). Use these percentages and the procedure in the original experiment to construct a pie chart representing the elements in the atmosphere.
- The abundant elements in the hydrosphere (total watery part of the Earth) are oxygen (86%) and hydrogen (11%). Other elements make up the remaining 3%. Construct a pie chart showing the elements in the hydrosphere.
Design Your Own Experiment
Within the lithosphere, most elements are joined together to form minerals (natural substances with specific chemical compositions and distinct atomic structures). A few minerals occur as just one element, such as when carbon atoms join to form the mineral graphite. Make a model of graphite using clay balls for atoms and toothpicks for chemical bonds. Start by using six clay balls and six toothpicks to form a hexagon to represent a carbon atom. Add four more clay balls and toothpicks to form a single layer made up of two hexagons joined together. Make another layer of two hexagons and stack the second layer on top of the first one using five 6-inch (15-cm) pieces of spaghetti (see Figure 9.2).
In graphite layers, covalent bonds (strong attractions between atoms that share electrons) hold the carbon atoms within the layers together. In this experiment, toothpicks represent covalent bonds. One layer of graphite is held to another graphite layer by van der Waals bonds (weak electrostatic attractions between atoms that are easily broken). The spaghetti represents these weak bonds. What is the difference between these types of bonds? For information, see Brian J. Skinner and Stephen C. Porter, The Dynamic Earth (New York: Wiley, 1992), pp. 47-48.
Get the Facts
Matter exists in three basic phases: solid, liquid, and gas. The atoms in a solid vibrate but are held in relatively fixed positions. A solid has a definite shape and volume. Use a chemistry or earth science textbook to discover the movement, shape, and volume of the atoms of liquids and gases. What causes matter to change from one phase to another? Use this information to model and explain phase changes in the Earth's lithosphere, hydrosphere, and atmosphere, such as the evaporation of water from the hydrosphere and the condensation of water in the atmosphere in the formation of clouds and precipitation. Display models showing the bonding between the three phases of matter.
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