Question

If solid iron pellets and sulfur powder are poured into a container at room temperature, a simple ___ has been made. If the iron and sulfur are heated until a chemical reaction takes place between them, a(n) ___ will form.

Short answer

A simple heterogenous mixture has been made (before heating). A compound, iron(II) sulfide, will form (after heating).

Step-by-step solution

Identify the initial mixture

When solid iron pellets and sulfur powder are poured into a container at room temperature, the two substances just get mixed physically, without undergoing any chemical reaction. This type of mixture is called a heterogenous mixture, as the substances can be visually distinguished.

Recognize the effect of heating on iron and sulfur

When iron and sulfur are heated together, they undergo a chemical reaction which completely changes their properties. The resulting product is a compound named iron(II) sulfide (FeS) which is a homogeneous mixture at the molecular level, ie, one cannot visually distinguish iron and sulfur in it. Putting these results, the final answers are: 1. A simple heterogenous mixture has been made (before heating). 2. A compound, iron(II) sulfide, will form (after heating).

Key concepts

Heterogeneous Mixture

In chemistry, a heterogeneous mixture is a combination of two or more substances where each element retains its own individual properties. In such mixtures, the components do not blend completely, hence, they remain discernible from each other. For example, consider pouring solid iron pellets and sulfur powder into a container; these two substances will mix but remain separate and visible to the naked eye. This means you can still see and differentiate the iron from the sulfur.

The heterogeneity in these mixtures is due to the lack of uniformity. The substances are not evenly distributed. As a result, each part of the mixture can have different compositions and properties.

• Components can be easily separated by physical methods such as filtration or sieving.
• Examples include sand in water, iron filings in salt, or trail mix.

Understanding heterogeneous mixtures is important because they show how different substances can coexist without changing each other chemically.

Homogeneous Mixture

Unlike heterogeneous mixtures, homogeneous mixtures appear uniform throughout. In these mixtures, the different components are mixed at the molecular level and cannot be distinguished from each other. When iron and sulfur are heated and react to form iron(II) sulfide, the result is a homogeneous mixture. This is because, at the molecular level, the composition is consistent and uniform.

Homogeneous mixtures are often referred to as solutions. These solutions can be solids, liquids, or gases. The key feature is their uniformity in terms of appearance and composition.

• Components cannot be easily separated by physical means.
• Examples include salt dissolved in water, air, or an alloy like bronze.

Studying homogeneous mixtures helps in understanding solutions and the nature of substances mixed at the atomic or molecular level.

Iron(II) Sulfide

Iron(II) sulfide is a compound that forms when iron and sulfur react chemically. This reaction requires heating and signifies a transformation from a simple mixture to a new substance. The chemical formula for iron(II) sulfide is \(FeS\), indicating each molecule consists of one iron atom bonded to one sulfur atom.

This transformation process underlines an important aspect of chemical reactions, where original substances lose their individual properties. Instead, a new compound with distinct properties emerges.

• Iron (Fe) and sulfur (S) are elements, but once reacted, they form iron(II) sulfide, which is a compound.
• The properties of iron(II) sulfide, such as its appearance and reactivity, differ significantly from its constituent elements.

Iron(II) sulfide exemplifies how chemical reactions can create substances with new properties, and how such compounds cannot be broken down into their initial elements by physical separation methods.