[ 407 ] Physical Science GED ® TEST SCIENCE FLASH REVIEW • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • While hiking in a deep canyon, a lost hiker yells out loud. He hears the echo 0.86 seconds after the yell. The speed of the sound wave in the air is 342 m/s. Calculate the distance to the nearest canyon wall. Here are two formulas that will help. Velocity = distance/time Distance = velocity · time HINT: Remember, the echo represents sound traveling to the wall and back. Classify each substance as an element, compound, or mixture. Water (H 2 O): ___________ Hydrogen (H): ___________ Salt (NaCl): ___________ Glucose (C 6 ): ___________ H 12 O 6 Oxygen (O 2 ): ___________ Saltwater: ___________ Fill in the blanks in the following sentence using the choices that follow. Within a system, energy can be ______, but can neither be ______ nor ______. • created • transformed • destroyed