When solid sodium hydroxide is dissolved in water, the temperature of the soution formed rapidly increases. a) compare the total energy of the solid NaOH with that of the solution and state which is greater.

NaOH is greater

Explanation:

 In a perfectly isolated system, the total energy is the same.

Explanation:  The conservation laws for mass and energy hold in a system that is isolated from its surroundings.  The enegy released by the dissolution of solid NaOH in water is absorbed by the water.  So the total energy of the syetm remains the same.  It is simply converted from lattice energy of the NaOH into heat energy as measured by the temperature of the water.  As long as it is operfectly isolated, the total energy remains the same.

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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