Which of the following is a physical property of a substance? a. hardness b. flammability c. reactivity d. toxicity

The physical property of a substance among the options is; Choice A: Hardness

The physical properties of a substance include properties which can be assessed about a substance without the substance going through any change.

On the other hand, chemical properties of a substance are properties which can only be assessed after the substance undergoes a chemical change..

Hence, Hardness is the only physical property of a substance among the options above.

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A. Hardness

Explanation:

Physical property is those that can be observed without changing the substance directly. This includes hardness, color, volume, etc.

Chemical property is observed by changing the chemical identity of the substance, for example, corrosion, oxidation, etc. Flammability, Reactivity, and Toxicity all fall under this category.

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-

c (diamond),

sio2 (quartz)