Question

Suppose you let a sugar solution evaporate, leaving sugar crystals behind. Are these crystals minerals? Explain.

Short answer

No, sugar crystals are not minerals because they are organic and not naturally occurring.

Step-by-step solution

Understanding Minerals

Minerals are naturally occurring, inorganic solids with a definite chemical composition and crystal structure. To determine if the sugar crystals are minerals, we need to evaluate these characteristics against the properties of sugar crystals.

Evaluate Natural Occurrence

For a substance to be a mineral, it must occur naturally. Sugar crystals, in the form discussed in this exercise, originate from a sugar solution that is human-made, and thus they do not meet this criterion.

Assess Inorganic Nature

Minerals must be inorganic. Since sugar is derived from plants, it is organic. Therefore, sugar crystals do not qualify as inorganic substances.

Chemical Composition and Crystal Structure

A mineral has a specific chemical composition and crystal structure. While sugar crystals do possess a definite structure and composition, this alone does not make them minerals without satisfying previous criteria.

Key concepts

Chemical Composition

When we talk about minerals, one of the defining characteristics is their chemical composition. This means that minerals maintain a specific chemistry that is consistent throughout every sample of that mineral.
For instance, table salt is a mineral known as halite, with the chemical formula \( \text{NaCl} \).
This formula indicates that every molecule of halite consists of one sodium atom and one chlorine atom, arranged in a set ratio.
Chemical composition is crucial because it directly influences the mineral's properties, such as hardness, color, and crystal structure.

• If two substances have the same elements but in different ratios, they are considered different substances.
• Sugar, primarily composed of carbon, hydrogen, and oxygen, follows the formula \( \text{C}_6\text{H}_{12}\text{O}_6 \) which distinguishes it from minerals.
• This composition derives from sugarcane or beets, making it organic and non-mineral by nature.

Crystal Structure

Minerals are recognized not only by their specific composition but also by their definite crystal structure. This refers to the orderly and repetitive arrangement of atoms in a mineral.
Such structures are what give minerals their shape, and they repeat at a microscopic level, forming a solid that often results in distinctive crystal forms.

• A great example of crystal structure is quartz, which consistently forms hexagonal crystals.
• The crystal structure is crucial for identifying minerals, as it influences their appearance and physical properties.

Sugar crystals do have a characteristic structure and are often observed taking a certain form during crystallization.
However, because they originate from an organic process, unlike inorganic minerals, their structure does not qualify them as minerals.

Inorganic Substances

One key characteristic that minerals share is their inorganic nature. Inorganic substances are made of materials that are not derived from living organisms and do not contain carbon-hydrogen bonds.
Minerals, in their natural state, are found within the Earth or as precipitates from mineral-rich waters, and they do not consist of organic substances.

• Sugar, extracted from plants such as sugarcane or sugar beet, is organic due to its biological origin.
• The presence of carbon-hydrogen bonds in sugar confirms its organic nature, disqualifying it from being a mineral.

Hence, regardless of having a crystal structure or specific chemical composition, sugar cannot be classified as a mineral because it is not inorganic.