Problem 39 - Chemistry and Chemical Reactivity

Question

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

Step-by-Step Solution

Answer

Sterling silver: Mixture; Carbonated mineral water: Mixture; Tungsten: Element; Aspirin: Compound.

Step 1: Understanding the Classification

To categorize the given substances, we need to understand the definitions: - An **element** is a pure substance that cannot be broken down into simpler substances by chemical means. - A **compound** is a pure substance composed of two or more different elements chemically bonded together. - A **mixture** consists of two or more substances physically blended but not chemically combined.

Step 2: Analyze Sterling Silver

Sterling silver is a **mixture** because it is an alloy, generally composed of 92.5% silver and 7.5% other metals like copper. It does not meet the criteria of a pure substance since it involves physical blending of silver with another metal.

Step 3: Analyze Carbonated Mineral Water

Carbonated mineral water is a **mixture**. It contains water (H2O) and carbon dioxide gas (CO2) physically mixed, along with various dissolved minerals. The components do not chemically combine, which makes it a mixture.

Step 4: Analyze Tungsten

Tungsten is an **element** with the chemical symbol W. It exists on the periodic table and cannot be broken down into simpler substances by chemical means, thus it is an element.

Step 5: Analyze Aspirin

Aspirin is a **compound**. It has the chemical formula C9H8O4 and is created by chemically bonding carbon, hydrogen, and oxygen atoms. This makes it a pure substance with consistent properties.

Key Concepts

Elements

Elements are the simplest form of matter that cannot be broken down by ordinary chemical processes. Each element is made of one type of atom. These are the building blocks of all substances. For instance, when you refer to tungsten with the symbol W, you are talking about an element.
Elements are neatly organized in the periodic table and each one has a unique atomic number. This atomic number represents the number of protons in the nucleus of an atom.
Some common characteristics of elements include:

• They cannot be separated into simpler substances by chemical reactions.
• They are pure substances.
• Their properties are uniform throughout.

In practical terms, elements like tungsten have applications in industries due to specific properties, such as high melting points, that result from their atomic structures.

Compounds

Compounds are pure substances like elements but consist of two or more different elements chemically bonded together. A good example is aspirin, which has a chemical formula C9H8O4.
When elements combine to form compounds, they do so in fixed ratios and create a substance with different properties from the original elements.
Key characteristics of compounds include:

• They have fixed proportions of elements.
• Their physical and chemical properties differ from the constituent elements.
• They can be broken down into simpler substances by chemical means, such as electrolysis.

For example, aspirin is not just a blend of carbon, hydrogen, and oxygen. It is a carefully structured compound that alleviates pain by affecting biochemical pathways in our body.

Mixtures

Mixtures are physical combinations of two or more substances. Unlike compounds, the components of a mixture retain their individual properties and can be separated by physical means.
Sterling silver and carbonated mineral water are excellent examples of mixtures. Sterling silver comprises metals like silver and copper blended without chemical bonds, while carbonated mineral water contains dissolved gases and minerals mixed with water.
Characteristics of mixtures include:

• They do not have fixed compositions. The ratio of substances can vary.
• The properties of the mixture are a mix of the properties of its components.
• They can be separated through physical techniques like filtration or distillation.

This means mixtures are highly adaptable and used in a variety of everyday applications, from jewelry making with alloys like sterling silver to culinary arts using mineral waters.