Answer:
Matter is anything that has mass and takes up space. Matter can change form through physical and chemical changes, but through any of these changes, matter is conserved. The same amount of matter exists before and after the change none is created or destroyed.
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repartExiplanation:cionde atomos
The chemical compound sodium sulfide has the formula Na2S. It is written as
. It has a crystalline state. Na is followed by a two or 2. this indicates that the molecule has two of the specified element's atoms.
There is just one of these because there is no number following the S.
In all, this molecule consists of one sulfur atom and two sodium atoms.
A compound's chemical formula, which uses symbols for combining atoms, reveals the composition of the complex. We require the valency of the combining parts in order to write the formula.
The sodium sulfide chemical formula must be written down. So sodium and sulfur make up the two elements in the chemical. Sodium has a valency of +1, while sulfur has a +2.
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Reaction 3 is the double displacement reaction.
Double displacement reaction occurs when the negatively and the positively charged ions of the compounds interchange their position when the new compound in the product is formed.
<h3>Which is a double displacement reaction?</h3>
In the <u>first reaction</u>, the element lead (Pb) is not an ion and no exchange of the cations or the anions occurs hence it is not a double displacement reaction.
In the <u>second reaction</u>, one compound is getting split into two new compounds and is a decomposition reaction.
In the <u>third reaction</u>,
in
and
in
are anions and cations and exchanges their places to produce two new compounds 
In the <u>fourth reaction</u>, a single compound is generated as the result of the combination reaction and hence, it is not the double displacement reaction.
Therefore,
is the double displacement reaction.
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Answer:
12,375 cm³
Explanation:
v=l×w×h
Since there are 3 books the equation would then be
v=3(l×w×h)
v=3(25×15×11)
v=3(4,125)
v=12,375 cm³