If the enthalpy value for a reaction is negative, what does that indicate about the reaction? explain how you got your answer
a) it’s endothermic and heat is absorbed by the system.
b) it’s exothermic and heat is absorbed by the system.
c) it’s endothermic and heat is released to the surroundings.
d) it’s exothermic and heat is released to the surroundings.

The answer is; D

Enthalpy is the system’s internal energy ( considering the product of its pressure and volume). When the enthalpy is negative, it means that the products have a lower energy level than the reactants - meaning the system has dispensed some energy into the environment.

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.

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