Short answers, pulled from the story.
Plasma is the most common state of matter in the known universe. Liquids are the least common state of matter, existing only within a narrow window of temperature and pressure that is rare on cosmic scales.
Liquid molecules are in a constant state of flux, vibrating and shifting while maintaining close proximity. Unlike solids where particles are locked in a rigid crystalline lattice or gases where particles drift freely, liquid molecules slide past one another in a fluid motion.
Water expands as it cools between 0 degrees Celsius and 4 degrees Celsius because its molecules form a lattice when frozen that is less dense than the liquid form. This anomaly allows ice to float and protects aquatic life during winter.
Viscosity is the resistance of a liquid to flow and varies widely among different substances. It ranges from the thin, fast-moving water to the thick, slow-moving honey, and determines how precisely liquids can control machinery in engineering applications.
Helium remains liquid even at absolute zero under standard pressure due to quantum mechanical effects. The thermal de Broglie wavelength of helium atoms is comparable to the distance between them, leading to behaviors that cannot be described by classical physics.