Which of the following procedures involves a physical change in one of the substances? a. creating salt by reacting sodium metal and chlorine gas b. allowing a nail to rust c. building a model rocket propelled by mixing baking soda and vinegar d. separating a salt solution by evaporating the water

The answer is separating a salt solution by evaporating the water

A physical change can be described as a change that cannot be reversed. In a physical change, there is no creation of a new substance. Although there may be a slight change in the matter, size, color or shape of the compound that is undergoing this change. In this type of change(physical change) the physical part/appearance of the compound might change but this does not in any way affect the chemical composition of the substance.

These options listed below are not examples of a physical change;

- creating salt by reacting sodium metal and chlorine gas

- allowing a nail to rust

- building a model rocket propelled by mixing baking soda and vinegar

Hence the example of physical change in the option is;

Separating a salt solution by evaporating the water

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D. Separating a salt solution by evaporating the water

Explanation:

B. Allowing a nail to rust is a chemical change.

Becuase once the nail rust it turns into flakes and therefore is no longer a nail.

C. building a model rocket propelled by mixing baking soda and vinegar

By mixing baking soda (a powder) into vinegar ( a Acid) it causes a explosion...

the baking soda dissolve into the acid This a chemical reaction

A.creating salt by reacting sodium metal and chlorine gas

Sodium is salt but it says Sodium metal chlorine gas Changes color and it has a strong odor... chlorine gas with sodium metal turns it into salt it doesnt stay a metal or a gas it CHANGES

so therefore its a Chemical change

When A object or substance changes form or it causes a exsplosion or reaction it is a chemical change.

D. Separating a salt solution by evaporating the water

For a physical change your object may change color or shape but its still the same object.

salt in water ... The salt dont dissolve it just salty water.

So seperating salt by evaporating the water is a physical change.

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.