Which substance can be broken down by chemical means?
(1) co (3) ca
(2) ce (4) cu

The substance that can be broken down by chemical means from the choices given is CO  (Carbon monoxide).

Carbon monoxide is a compound made up of carbon and oxygen and can therefore be broken by chemical means.

Further Explanation Pure substances  Pure substances are substances that have a constant composition and also cannot broken down into simpler substances using physical means. Pure substances are classified as either elements or compounds. Elements Elements are a type of pure substances that are made up of one type of atom and cannot be broken down into simpler substances by both chemical and physical means. Atoms making up a certain element are similar or identical in properties. Examples of elements are, Oxygen, sodium, calcium, etc. Periodic table shows an arrangement of all known elements. Compound  A compound is a pure substance that is made up of than one type of atoms of different elements and can be broken down into individual elements making it using chemical means. Compounds cannot be broken down into simpler substances by physical means but only using chemical means. Compounds have constant composition and therefore they have a constant ratio of elements. For example the ratio of elements making up carbon dioxide is always 27% Carbon and 73% Oxygen. Examples of compounds include, water, Ammonia, calcium sulfate, carbon dioxide, etc. In our case, Carbon monoxide, (CO) is a compound made up of a carbon atom and an oxygen atom. Other choices, Ca, Ce, and Cu are all elements.

Keywords: Compound, elements, pure substances  

Learn more about: Compounds: link Pure substances: link Elements: link

Level: High school

Subject: Chemistry  

Topic: Atoms, elements, compounds and mixtures