Question

Categorize each of the following as an element, a compound, or a mixture. (a) sterling silver (b) carbonated mineral water (c) tungsten (d) aspirin

Short answer

(a) Mixture, (b) Mixture, (c) Element, (d) Compound.

Step-by-step solution

Understanding Elements

An element is a pure substance that cannot be broken down into simpler substances by chemical means. Each element is made up of atoms with the same number of protons. On the periodic table, tungsten is a listed element.

Understanding Compounds

A compound is a substance formed when two or more elements are chemically bonded together. Compounds have a fixed composition and can be broken down into simpler substances. Aspirin, a chemical compound, is made up of carbon, oxygen, and hydrogen atoms bonded together.

Understanding Mixtures

A mixture is a combination of two or more substances that are not chemically bonded, allowing for the separation of its components by physical means. Mixtures do not have a fixed composition. Sterling silver is an alloy (mixture) of silver and another metal, often copper. Carbonated mineral water is a mixture of water with dissolved gases and minerals.

Categorize Each Substance

(a) Sterling silver: Mixture because it is an alloy. (b) Carbonated mineral water: Mixture due to the presence of water, gases, and minerals. (c) Tungsten: Element as it is found in the periodic table. (d) Aspirin: Compound because it is made from chemically bonded elements.

Key concepts

Elements

Elements are the building blocks of matter. They are pure substances that consist entirely of one type of atom. Each element is defined by its atomic number, which is the number of protons in its nucleus.
This uniqueness is why elements cannot be broken down into a simpler form by chemical means.
Examples of elements include gold, oxygen, and as mentioned in the exercise, tungsten.

• Each element has specific physical and chemical properties.
• Elements are represented by symbols on the periodic table, such as "W" for tungsten.
• Understanding elements is essential, as they combine to form compounds and mixtures.

Scientists organize elements on the periodic table, which classifies them by similar characteristics and behaviors.

Compounds

Compounds are substances formed when two or more elements are chemically bonded together. This bond changes the properties of the elements to form a new substance entirely.
Unlike mixtures, compounds have a fixed, definite composition.
Aspirin, highlighted in the exercise, is a well-known example of a compound, consisting of carbon, oxygen, and hydrogen atoms bonded in a specific way.

• Compounds have distinct characteristics from the elements that form them.
• They can be broken down into their constituent elements through chemical reactions.
• Examples of compounds apart from aspirin include water ( \( H_2O \) ) and sodium chloride ( \( NaCl \) ).

This understanding of compounds underscores their role in forming myriad materials and products used in daily life.

Mixtures

Mixtures result from the physical combination of two or more substances. What’s unique about mixtures is that they do not involve chemical bonds, meaning their components remain separate at the atomic level.
Mixtures can vary in composition and properties.
For example, sterling silver, a mixture, or more accurately, an alloy, typically involves silver and another metal like copper. Similarly, carbonated mineral water consists of water, dissolved gases, and minerals.

• Mixtures can be homogeneous or heterogeneous.
• Homogeneous mixtures have uniform composition, like saltwater, whereas heterogeneous mixtures have distinct phases or parts.
• The components of mixtures can usually be separated by physical processes, such as evaporation or filtration.

Recognizing mixtures helps distinguish between substances that involve chemical versus physical combinations.

Alloys

Alloys are a special type of mixture where two or more metals, or a metal and another element, are blended together. This blend creates a material with enhanced properties, such as increased strength or corrosion resistance, compared to the individual components.
Sterling silver is a classic example, as it combines silver with a base metal, often copper, to craft a more robust substance.

• Alloys retain the metallic properties of their components while improving certain features.
• They are of great importance in industries for making items ranging from coins to aircraft parts.
• Some popular alloys include bronze (copper and tin) and stainless steel (iron, chromium, and nickel).

The concept of alloys is essential for understanding advancements in material science and engineering.