I don't know about 14, but 15 is (4), because a liquid draws in heat to turn into a gas. 16 is (2), because to turn into a cold solid, something has to release heat.
<h3><u>Answer;</u></h3>
B) a system is a group of objects analyzed as one unit
C) energy they moves across system boundaries is conserved
<h3><u>Explanation;</u></h3>
- System is a group of objects analyzed as one unit
.
- An open system is a system that freely exchanges energy and matter with its surroundings.
- A closed system is a system that exchanges only energy with its surroundings, not matter. An isolated system does not exchange energy or matter with its surroundings.
Answer:The correct answer is option(C).
Explanation:
Compound is a substance made up of two or more elements which are chemically joined together.
When the iron and sulfur heated together in the test tube a chemical reaction reaction took place between the iron and sulfur which lead to the formation of iron sulfur compound (here black mass).And this compound will differ in chemical proprieties with respect to its constituting pure element.
When the magnet was brought near to it , it doesn't attracted the black mass towards itself.This is because the 'The black mass is a compound and no longer retains the properties of iron'.
In this case, according to the given information about the oxidation numbers anf the compounds given, it turns out possible to figure out the oxidation number of manganese in both MnI2, manganese (II) iodide and MnO2, manganese (IV) oxide, by using the concept of charge balance.
Thus, we can define the oxidation state of iodine and oxygen as -1 and -2, respectively, since the former needs one electron to complete the octet and the latter, two of them.
Next, we can write the following 
, since manganese has five oxidation states, and it is necessary to calculate the appropriate ones:
Next, we multiply each anion's oxidation number by the subscript, to obtain the following:
Thus, the correct choice is Manganese has an oxidation number of +2 in Mnl2 and +4 in MnO2.
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The answer is A mutualism
