Question

Which substance cannot be broken down by a chemical change?

A) butanal
B) propene
C) gold
D) water

Answer 1

Answer: C) Gold

Explanation:

Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions.Example: Gold $Au$

Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass. It can be decomposed into simpler constituents using chemical reactions. Example: water $H_2O$ , butanal $CH_3CH_2CH_2CHO$, and propene $CH_3CH=CH_2$

For example: $2H_2O\rightarrow 2H_2+O_2$

Thus the element gold can not be broken down by a chemical change.

Answer 2

The substance that cannot be broken down by chemical change is $\boxed{{\text{C) gold}}}$.

Further Explanation:

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

A) Butanal $\left( {{{\text{C}}_4}{{\text{H}}_8}{\text{O}}} \right)$ is made up of four carbon atoms, eight hydrogen atoms, and an oxygen atom so it is a compound. Therefore it can be broken down by chemical change.

B) Propene $\left( {{{\text{C}}_{\text{3}}}{{\text{H}}_{\text{6}}}} \right)$ is made up of three carbon atoms and six hydrogen atoms so it is a compound. Therefore it can be broken down by chemical change.

C) Gold $\left( {{\text{Au}}} \right)$ is an element so it is present in its simplest form. Therefore it cannot be broken down by chemical change.

D) Water $\left( {{{\text{H}}_{\text{2}}}{\text{O}}} \right)$ is made up of one oxygen and two hydrogen atoms so it is a compound. Therefore it can be broken down by chemical change.

Learn more:

1. How to classify brass? https://brainly.com/question/9053565
2. Which must be a mixture of substances? https://brainly.com/question/637791

Answer details:

Grade: High School

Subject: Chemistry

Chapter: Elements, compounds, and mixtures

Keywords: substance, butanal, propene, gold, water, element, compound, chemical change, decomposed, simplest form, NaCl, CH4, carbon, sulfur, cobalt.