Question

Which substance cannot be broken down by a chemical change?(1) ammonia (2) mercury (3) propane (4) water

Answer 1

The substance that cannot be broken down by chemical change is $\boxed{\left( 2 \right){\text{ mercury}}}$.

Further Explanation:

Substance is the pure form of matter while a combination of atoms or molecules is termed as mixture.

Types of substances:

1. Element

The simplest form of substance that cannot be further decomposed by any chemical means is called an element. Carbon, sulfur, and cobalt are some of the examples of elements.

2. Compound

When two or more different elements are held together by chemical methods, compounds are formed. These can further be decomposed into their corresponding constituents. The properties of compounds are very different from those of their constituent elements. NaCl, ${\text{C}}{{\text{H}}_{\text{4}}}$ and ${{\text{H}}_{\text{2}}}{\text{O}}$ are examples of compounds.

(1) Ammonia is composed of one nitrogen and three hydrogen atoms so it is a compound. Therefore it can be broken down by chemical change.

(2) Mercury is an element so it is the simplest form in which it can exist. Therefore it cannot be broken down by chemical change.

(3) Propane is composed of three carbon and eight hydrogen atoms so it a compound. Therefore it can be broken down by chemical change.

(4) Water is composed of one oxygen and two hydrogen atoms so it is a compound. Therefore it can be broken down by chemical change.

Learn more:

1. Which sample is a pure substance? brainly.com/question/2227438
2.  Which must be a mixture of substances? brainly.com/question/637791

Answer details:

Grade: High School

Subject: Chemistry

Chapter: Elements, compounds, and mixtures

Keywords: substance, mercury, propane, water, ammonia, element, compound, chemical change, decomposed, simplest form, NaCl, CH4, carbon, sulfur, cobalt.

Answer 2

Mercury is the correct answer. Mercury is an element, meaning it's the smallest piece of a substance that is still that substance. Ammonia, propane, and water are all compounds/molecules, which can be broken down into elements.