91Ó°ÊÓ

(a) The pure substance silicon chip as an element or a compound.

(a) Silicon is a pure substance which may not be separated into further simpler substance by using chemical methods. Silicon ($Si$) is used as chips in various equipments. Chips consist of small crystals of Silicon ($Si$). It's composed of just one kind of material.
Therefore, a silicon ($Si$) chip isan element.

(b) The pure substance hydrogen peroxide as an element or a compound.

(b)Hydrogen peroxide (H₂O₂)has a single covalent bond between the two oxygen atoms, which is called the peroxy (O-O) bond. Since the Hydrogen and oxygen atoms are chemically combined to form Hydrogen peroxide, it is a compound. Hydrogen peroxide can be further broken down into simpler substances, proving that it is a compound.It is a strong oxidizing agent.

(c) The pure substance oxygen gas as an element or a compound.

(c)

Pure Oxygen gas (O₂) is made up of only one type of element: oxygen. The symbol represents this idea. Since it is made up of atoms of only one element (oxygen atoms), it is an element and not a compound.

Therefore, Pure oxygen gas is an element.

(d) The pure substance rust as an element or a compound.

(d) Rust $\left({\mathrm{Fe}}_2{\mathrm{O}}_3\right)$ is that the common name for iron oxide. Rust is a product of corrosion, which occurs when oxygen combines with metal ($Fe$) in the presence of moisture (H₂O). Since, it is formed by the chemical combination of two or more atoms of different elements, it is a compound. It can be broken down into simpler substances when treated with chemicals.
Therefore, rust $\left({\mathrm{Fe}}_2{\mathrm{O}}_3\right)$ is a compound.

(e) The pure substance methane as an element or a compound.

(e)

Methane (CH₄)is a colourless, odourless gas. It is formed by the chemical combination of atoms of carbon and hydrogen(a hydrocarbon), making it a compound. It is the simplest alkane.

Since methane has atoms of different elements (C & H), it is a compound.