Nan experiment, chemists heated a solid, red substance in a test tube. vapors from the heated red substance condensed as a metallic liquid on the side of the tube. the red substance eventually disappeared, leaving only the metallic liquid and producing a gas that escaped from the tube. which statement best describes what happened to the red substance in this experiment? a. the experiment demonstrates the formation of plasma from the red substance. b. the experiment demonstrates a physical property of the red substance. c. the experiment shows that the red substance experienced a chemical change. d. the experiment shows that the red substance can be a solid, liquid, or gas. e. the experiment shows that the red substance is an element.

Answer is: C. The experiment shows that the red substance experienced a chemical change.

This is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

This is example of chemical decomposition.

Chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

Chemical decomposition is opposite of chemical synthesis.

c

Explanation:

first let us lay out the formula for potential

and kinetic energy:

pe = mgh

ke = (mv^2)/2

where: m=mass, v=velocity, g=gravitational

acceleration, h=height

calculating for mass using the known values of

pe:

340j = m (9.81 m/s^2) (50ft) (1m/3.28ft)

m = 2.27 kg

the law of conservation of energy states that

energy is neither created nor destroyed. therefore, the change in kinetic

energy from 50 ft to 35 ft would be equal to the change in potential energy

from 50 ft to 35 ft. however it would be opposite in signs since one is losing

while other is gaining.

ke(35ft) – ke(50ft) = - [ pe(35ft) – pe(50ft]

ke(50ft) = 0 since the brick is initially at rest

ke(35ft) = 340j - 2.27kg (9.81 m/s^2) (35ft)

(1m/3.28 ft)

ke(35ft)

= 102.38 j