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?
A testable hypothesis naming independent and dependent variables
An experiment that takes initial and final measurements
Controlled variables with only one varied independent variable
o Experimental data that can be recorded and analyzed

the answer to this question is 3.

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.

gas

explanation:

smoke is the matter of a gas