Question

On Earth, oxygen usually exists as which of the following? A) solid C) liquid B) gas D) plasma

Short answer

Oxygen usually exists as a gas on Earth, so the correct answer is B) gas.

Step-by-step solution

Understanding the Question

The question is asking about the most common state in which oxygen is found on Earth. We need to identify if oxygen is typically found as a solid, liquid, gas, or plasma.

Recognizing Common State of Oxygen

On Earth, oxygen is most commonly found in its gaseous state. This is the form of oxygen that humans breathe and is the second most abundant gas in the Earth's atmosphere.

Identifying the Correct Option

Based on the information that oxygen is found predominantly as a gas, we can match this with the options provided in the exercise. The correct answer is option B: gas.

Key concepts

Oxygen

Oxygen is a fundamental element that is vital for life on Earth. It is represented by the symbol \( O_2 \) when referring to its diatomic gaseous form, which is the most stable and common form of oxygen. This element is crucial for various biological processes, including cellular respiration, where organisms convert oxygen and glucose into energy. Without oxygen, most life forms, including humans, would not be able to survive.

• Atomic number: 8
• Atomic weight: approximately 16.00 g/mol
• Oxygen is a highly reactive non-metal

Its reactivity makes it abundant in various compounds, including water \((H_2O)\) and carbon dioxide \((CO_2)\). Oxygen's reactive nature leads to oxidation, which plays a key role in combustion and rusting processes.

Gaseous State

The gaseous state is one of the four fundamental states of matter, alongside solid, liquid, and plasma. In the gaseous state, particles move freely at high speeds and can fill any container, taking its shape and volume. This high kinetic energy of particles allows gases to spread and mix easily in the air, which is observed as diffusion.

• Characteristics of gases include compressibility and fluidity
• They have no definite shape or fixed volume
• Gases expand to fill their containers due to particle movement

Oxygen in its gaseous form is essential for respiration and combustion. Because it is less dense than solids or liquids, it is easily transported and diffused throughout Earth's atmosphere.

Earth's Atmosphere

Earth's atmosphere is a mixture of gases that surround the planet, essential for supporting life and protecting it from harmful solar radiation. It is composed of multiple layers, each with unique characteristics, such as the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. These layers contribute to Earth's climate and weather patterns.

• Major components: nitrogen \( (N_2) \) 78%, oxygen \( (O_2) \) 21%
• Minor components include argon, carbon dioxide, and trace gases
• Oxygen is crucial for life and combustion processes

Oxygen's presence as a significant component emphasizes its importance in maintaining life as we know it. Its interaction with other elements and compounds within the atmosphere also plays a role in the biosphere, hydrosphere, and other environmental systems.

Elemental Composition

Elemental composition refers to the proportion of different elements in a substance, material, or environment. On Earth, the elemental composition of the atmosphere, crust, and even living organisms is crucial for understanding biological and physical processes. In the context of oxygen, it contributes significantly to the composition of several environments:

• Atmosphere: Oxygen is about 21% of Earth’s atmosphere
• Water: Each water molecule contains one oxygen atom \((H_2O)\)
• Human body: Oxygen makes up about 65% of human body mass, being essential in water, proteins, and DNA

Understanding elemental composition helps scientists and researchers study ecological systems, mineral resources, and biological processes effectively. It highlights how oxygen, as an element, interacts within various systems and maintains its role as a critical life-supporting factor.