Biosphere 2 was an attempt to have humans live within a perfectly closed system, as a model for living on other planets. The first attempt
failed because the system began losing CO2, which was chemically reacting with
the exposed concrete walls. How would you go about designing a habitat that is a
closed system? Explain how matter and energy would flow within the system.

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. 75.7

i think that is the right

acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.

the product of the pressure and volume is also constant