After researching the possible effects of music, elaina proposes that if people listen to faster-paced music, their pulse rates will increase more than if they listen to slower music. her mother listens to classic rock at a high volume for 30 minutes, her younger brother listens to classical music quietly while he sleeps at night, and her grandmother listens to two hours of rap at a medium volume. elaina records each person's pulse before and after listening to the music. what is missing from elaina's scientific investigation?

Elaina's scientific investigation is missing controlled variables.

Explanation:

A good scientific investigation should vary only the factor that is studied (the speed of the music. All other factors should be kept constant.

She hasn’t controlled for volume. The volume of the music may affect the rate at which the listener’s heart rate will increase. She should have measured each person’s pulse after the same period of listening.

She hasn’t controlled for age. A grandmother may respond to loud music differently from a teenager. All her subjects should be about the same age.

She hasn’t controlled for wakefulness. A person may respond to music differently when awake than when asleep.

controled variables

Explanation:

i took the test

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.