5. Which sentence best describes the runner whose distance-time graph is shown? 40
30
Distance from starting line (meters)
8
10
1
2
3
Time (seconds)
O A The runner ran forward for 2 seconds, and then backward for 2 seconds
O B. The runner ran forward for 2 seconds, and then stood still for 2 seconds.
O C. The runner ran forward for 2 seconds, and then ran forward more slowly for 2 seconds.
O D. The runner ran forward for 2 seconds, and then turned right and continued forward at the same speed for 2 seconds.
I’m

c. electrical charges of ionic bonds.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.