Question

Which of the following is true for compounds?
They can be separated into their component elements through physical means.
They can be created by chemical reactions.
They can consist of no more than two types of elements.
They all have the same properties regardless of their elemental composition.

Answer 1

They can be created by chemical reactions.

Compounds have varying properties, depending on the compounds they are made from, and are created by chemical reactions.

Answer 2

Answer: The correct option is that the compounds are created by chemical reactions.

Explanation:  

Option 1: Elements combine chemically in a specific ratio to form compounds. They can't be separated by physical methods like filtration. For example, $H_2O$ is made up 2 H-atoms and 1 O-atom. When we filter water through normal filtration, we do not obtain H-atom and O-atom separately, but we get combined form of hydrogen and oxygen atom that is $H_2O$.

Option 2: Compounds are formed when two or more elements combine chemically.

$2H_2(g)+O_2(g)\rightarrow 2H_2O(l)$

Option 3: Compounds can have more than two types of elements. For example, In $CaCO_3$, 3 elements are present - Calcium(Ca), Carbon(C), Oxygen(O).

Option 4: Compounds formed have different properties from one another. There can be difference in physical properties as well as chemical properties. For example, $H_2O$ (water) and $CaCO_3$ (calcium carbonate) are two compounds. Water is present in liquid state and calcium carbonate is present in solid state. Hence, it showed that all the compounds cannot have same properties.