Discussion topic
chemical energy sources are often portable and provide large amounts of energy. fossil fuels are one kind of chemical energy source. most of the energy we use in the united states is generated by the combustion of fossil fuels. however, fossil fuel combustion adds greenhouse gases to the atmosphere, mostly co2. one measure of the total amount of greenhouse gases that are emitted into the atmosphere each year is called a carbon footprint. read this article to compare the carbon footprint of an average person in the united states to an average person around the
world. knowing that greenhouse gases are
contributing to climate change, how can we
reduce our carbon footprint, particularly in the
united states? could hydrogen fuel replace
fossil fuels in the future? why or why not? should the size of a person's carbon footprint be limited by law? why or why not?

Every compound can be represented by a chemical formula. a chemical formula is the set of symbols showing the elements that make up a compound and their proportions. water’s chemical formula is h 2 2 o. that means a molecule of water contains two atoms of hydrogen and one atom of oxygen chemically bonded. a molecule is a group of two or more atoms bonded together. molecules can range in size from two to thousands of atoms. a molecule of a compound is the smallest unit of that compound. every molecule of water has all the physical and chemical properties of water. that’s because every molecule of water is made of the same elements in the same proportions: two hydrogen atoms and one oxygen! which of the following is a true statement? a every molecule of the same compound will have different properties. b every molecule of a compound has the same proportion of elements. c molecules can be physically separated into smaller units of a compound. d molecules cannot be represented by chemical formulae.

Click an item in the list or group of pictures at the bottom of the problem and, holding the button down, drag it into the correct position in the answer box. release your mouse button when the item is place. if you change your mind, drag the item to the trashcan. click the trashcan to clear all your answers. label the following topographic map. click on a label below the map to select it, and then click on the appropriate box on the map to place the label. (increments for contour lines is 50 ft).

Factors that can increase mutation rates a. high temps b. low temps c. food additives d. uv rays