Answer : The correct option is, Mass
Explanation :
As we know that there are 3 states of matter :
Solid state : It is a state in which the particles are closely packed and does not have any space between them. This state have a definite shape and volume.
Liquid state : It is a state in which the particles are present in random and irregular pattern. The particles are closely arranged but they can move from one place to another. This state have a definite volume but does not have a fixed shape.
Gaseous state : It is a state in which the particles are loosely arranged and have a lot of space between them. This state have indefinite volume as well as shape.
If we are taking 100 grams of ice then after melting its mass remains same but its shape, volume and temperature will be changed and after evaporation its mass remains same but its shape, volume and temperature will be changed.
Hence, the mass will stay constant, no matter if the substance is in the solid, liquid, or gas state.
Activity series of metals: K,Na,Mg,Al,Zn,Fe,Cu,Ag. Metals on the left are more reactive than metals on the right. For example Zn is more reactive than Fe and can displace him.
Reaction than can occur is: <span>CuSO4(aq) + Fe(s) → FeSO4(aq) + Cu(s).</span>
The number that represents the coefficient on the product side of the chemical reaction, 
is 7.
<h3>Coefficients of chemical equations</h3>
In equations representing chemical reactions, the coefficient of each reactant or product of a reaction is the number that comes on the left-hand side just before the chemical formula.
The coefficient of each species in a chemical reaction is obtainable when the equation of the reaction is balanced.
For example, in the following equation: 2A + B = 3C + D
The coefficients of A, B, C, and D are 2, 1, 3, and 1 respectively.
Applying this to the product side of a chemical reaction;
It means that the coefficient of the product is 7.
More on coefficients of chemical equations can be found here: brainly.com/question/28294176
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Answer: Hydrogen gas will be given off
Explanation:
Whenever a metal reacts with an acid, a salt of the metal is formed and hydrogen gas is given off.
For instance: The reaction of Zinc metal on Hydrochloric acid.
Zn(s) + 2HCl(aq) ---> ZnCl2(aq) + H2(g)
From the equation provided, hydrogen gas is given off as a by-product
