Final answer:
The most common liquid on Earth is water, which is a compound consisting of hydrogen and oxygen. Earth's surface is about 70% covered with water, mostly in liquid form, and the molecule's polar nature is essential for many of its life-supporting properties.
Step-by-step explanation:
The most common liquid on planet Earth is water. While hydrogen is the most abundant element in the universe and is a major component of many compounds, including water, it is not commonly found in its elemental form on Earth due to its low density and high reactivity. On Earth, hydrogen is primarily found combined with oxygen in the form of water (H₂O). Water is not only the most abundant compound of hydrogen on Earth, but it also covers about 70% of the planet's surface, existing mainly in its liquid state, but also as a solid (ice) and as a gas (water vapor).
Water is a simple molecule consisting of one oxygen atom bonded to two different hydrogen atoms. The molecule has a bent structure, which is crucial because it makes the molecule polar. This polar nature of water molecules is significant and critical for many of the life-sustaining properties that water has on Earth.