Water is life – you've probably heard this saying more than once. And it's hard to disagree, considering that water provides us and many other organisms with the nutrients necessary for proper functioning. And because it's so important, as aquarists also know, we've decided to devote a separate article to it. Today, we'll talk about water – its physical and chemical properties.
A few words of introduction. What is water?
H₂O – probably the most popular chemical formula in the world. It stands for water, whose chemical synonym is hydrogen oxide. Under standard conditions, it exists in a liquid state. However, it has the ability to change its state of matter – into gas (water vapor) and solid (ice). It is the queen of substances in the Universe. It is one of the building blocks of the planets, present in the atmosphere and the waters covering the Earth. In nature, it occurs in the form of gases and salt solutions – seawater contains the most of these, and atmospheric precipitation the least. Are you familiar with the division into soft and hard water? It is simply a measure of the amount of minerals (hard water contains many, soft water contains few).
Where did the water come from?
It's not entirely clear. There are several hypotheses, the most popular of which is that water, both free and in chemical compounds, was already present on Earth at the time of the planet's formation.
According to the solar hypothesis, water appeared on our blue planet thanks to… the solar wind, which delivered hydrogen atoms, which, reacting with the oxygen already present, created the H₂O we all know.
In turn, supporters of another popular hypothesis – geochemical – believe that water was born in the Earth's mantle, together with silicon hydride as a side effect of the reaction of silicon dioxide with hydrogen.
Physical properties of water – those that are very and less important for aquarists
There are many physical properties of water. We'll try to list them all, but we'll also describe in more detail those that are most important in aquariums.
- High specific heat and heat capacity
The specific heat capacity of water is high (4.19 J/g*K), which explains the liquid's considerable thermal inertia and its role in regulating Earth's temperature. Oceans—a kind of water reservoir—store vast amounts of heat, which is transported by ocean currents. Water evaporation absorbs energy from the aquatic environment, regulating its temperature. Through the process of vapor condensation and condensation, this heat is returned to the atmosphere.
High specific heat and heat capacity translate into the fact that raising water temperature requires a significant amount of energy. What significance does this have in the biological world? Water, thanks to its temperature-regulating properties, creates stable living conditions for living organisms and protects against dangerous and unexpected temperature fluctuations.
- Ability to adhere and cohese
Adhesion refers to the ability of a liquid to attract water molecules to electrically charged surfaces. Cohesion, on the other hand, is the mutual attraction of water molecules. The former phenomenon is evident when water molecules adhere to vessels or instruments placed in an aquarium, while the latter allows, for example, small animals to move across the water surface.
- Low compressibility – low ability to change volume
Occurring in response to changes in pressure, it allows cells to maintain their shape, straighten certain body parts (legs or antennae), and maintain the firmness of plant cells.
- Very good solvent
Each water molecule creates a water envelope around the electrically charged substance. This property is responsible for the fluid's "vital" properties – the fact that it transports valuable substances (micro- and macroelements) and serves as the site for all chemical reactions in cells.
- Density greater than air
This allows fish, and especially much larger organisms (e.g., dolphins and whales), to stay afloat in water. Density is the close, mutual contact of water molecules achieved through hydrogen bonds.
- Reactivity
Water is referred to as a substrate (a chemical compound that is transformed as a result of a chemical reaction): for example, in the process of photosynthesis, and as a product of biochemical reactions: for example, aerobic respiration.
The physical and chemical properties of water are not the easiest topics. Most of us encounter them primarily in chemistry and biology classes, and then don't have the opportunity to expand our knowledge in this field. We hope that this text – briefly and concisely – has presented the most important ones and allowed us to organize our knowledge. Were you particularly interested in any of the points and would like to see them elaborated on? Be sure to let us know – in a comment or via private message.
Bibliography:
- S. Kwok: Physics And Chemistry of the Interstellar Medium, University Science Books, 2007.
- P. Dyches, F. Chou, The Solar System and Beyond is Awash in Water, NASA/Jet Propulsion Laboratory.
- Planet Earth makes its own water from scratch deep in the mantle, "New Scientist".
- J. Fuerst, Biology. Vademecum for high school and technical school, GREG Publishing House, Cracow 2008.
- J. Fuerst., A. Jakubowska, I. Król, Tables. Biology. Chemistry, GREG Publishing House, Cracow 2018.
- J. Holeczek, B. Januszewska-Hasiec, J. Kobyłecka, J. Stawarz, R. Stencel, Teraz Matura. Biologia Vademecum, Nowa Era, Warsaw 2015.