Life is not possible without water. Many life processes are dependent on water to function, but why is that? The answer is in its chemistry; water's unique qualities and properties make it essential and fundamental to life.
Water is an excellent solvent that can dissolve nutrients in our bloodstream. It holds its temperature well due to its thermal capacity, so life in lakes and ponds doesn’t die when the air temperature drops at night. It also supports cellular structure, ensuring cells hold their shape.
Water is present in three states, i.e., water, solid, and gas. Each state has unique properties, but chemical structures (two hydrogens and one oxygen) remain the same in all forms. Learning about water and its intricacies is vital for high school students as it helps touch the base and clear route for additional complex subjects in science.
In this article, we will talk you through the snag that makes this a challenging topic, followed by practical solutions to overcome these issues.
The study of water properties at the molecular level keeps getting complicated as we continue revealing concepts of inter/intramolecular forces, polarity, surface tension, thermal capacity, etc. Let's look at some of the most prevalent reasons why water is such a tricky topic for educators and students.
The charge on water molecules is distributed unevenly due to oxygen’s ability to strongly attract or pull electrons compared to hydrogen. This tendency of an atom to attract electrons toward itself is called electronegativity. Therefore, oxygen is more electronegative than hydrogen; thus, the oxygen atom in water has a more negative charge, while hydrogen has a positive charge. The analogy of tug of war could exemplify this unequal charge distribution.
The specific geometry (due to electronegativity and hydrogen bonding) makes water a polar molecule. Water readily mixes with any other polar molecule hence the title universal solvent. Most students find it challenging to understand the intricate details behind the concept of electronegativity and the polar nature of water.
The polarity of water (Image Source)
Water reacts with several compounds and is amphoteric, meaning it has a mix of acidic and basic properties. Water undergoes a reduction reaction with electropositive elements; therefore, it is a significant source of hydrogen and electrons. Likewise, water could also be oxidized and release oxygen atoms, the phenomenon observed in photosynthesis. Thus water has a prominent role in significant redox reactions. Water hydrolysis is another essential property as it quickly breaks down into its components to dissolve ionic or covalent compounds. These content-heavy aspects of the properties of water make students apathetic toward the topic.
It is a common observation that some substances like ice float on the water, but the question here is; Why and How? The answer to this seems simple: “any object less dense than water will float,” but it is pretty challenging for teachers to explain at the high school level. The water, upon freezing, expands about 9%, but the density of ice (0.931 gm-cm-3) is less than that of water (1.0 gm-cm-3). Ice is essentially water in solid form, but the chemical bonds and cage-like structure lower the density of frozen water. Since water is denser than ice, the latter is capable of floating.
Archimedes' principle is applied here, which suggests the object floats on the water when the downward weight of the object balances the upward push of water.
To understand these details and comparisons, students need to comprehend additional terms like density, surface tension, etc., which makes the subject in hand tricky. Moreover, it creates curiosity and overwhelms students as they continue to uncover the advanced properties of water.
The properties of water do not have to be a tedious topic for students. Here are five trusted and proven strategies that would make learning about water an exciting experience.
Following are some interesting facts about water to keep students engaged and hooked during the lecture:
The amount of water on Earth is the same as when it was created. Your tap water may include substances that dinosaurs drank.
Freshwater can be found in our lakes, rivers, and streams, but don't forget about groundwater and glaciers. More than 68 percent of the world's freshwater is trapped in ice and glaciers.
The water in oceans is exceptionally salty due to the presence of sodium chloride. However, the amount of salt varies; for instance, the Atlantic is the saltiest ocean in the world.
If the layer of ice in oceans and lakes sinks, the whole water body will freeze. Therefore, ice floating on water is an essential phenomenon that sustains life in balance.
Water is strong enough to oppose gravity in plants. This is due to the plants' transpirational pull and water's unique properties (cohesion and adhesion).
Jellyfish and cucumbers are composed of 95% of water.
Some organisms, like spiders, could walk on water due to surface tension.
Drinking water regulates the body temperature during fever which explains the thermal property of water. This is also why many aquatic organisms can survive the fluctuations in hot and cold climates.
Many terms and phenomena in water chemistry are challenging to teach and understand. Therefore, before diving into the intricate details of the properties of water, take some time to discuss essential terms. Relate the definitions with examples to help students with the learning process. Here are a few terms to help you start with:
Cohesion: The water molecules hold onto each other through hydrogen bonding. It creates surface tension which prevents some organisms or substances from sinking.
Adhesion: The water molecules attach themselves or adhere to other molecules/substances. For instance, the water in plants moves to the top from the bottom by sticking to the walls of the cell.
Thermal capacity: The heat required to change the internal temperature of the substance. Water has a high thermal capacity, so it takes a lot of heat/energy to raise its temperature. That is why aquatic life thrives as the temperature fluctuation is minimum.
Evaporative cooling: Evaporation of water from the surface lowers the temperature; for instance, sweating or panting is an example of evaporative cooling.
This is the time to increase engagement rate by asking students to think outside of the box and come up with relatable examples for each term.
Students will be more interested in learning about water by including fun activities like an autobiography of water. This task could be given as a home assignment. Tell them to impersonate water and develop a story explaining water's characteristics in a narrative way. Such narrations constructed by students and their peers would increase the engagement rate in your classroom. Students would easily comprehend the complex concepts as they creatively knit or listen to stories about water properties.
Students need to memorize the science behind water to perform well in exams. The ideas mentioned above would help make the learning process fun and approachable for students, but teachers should also devise fun ways to help with memory. One such effective strategy is mnemonics (a pattern of letters or words that helps remember something). Some of the wordplays that educators could use to teach the properties of water are as follows:
The most effortless way to memorize the six main properties of water is “CAHELU” - cohesion, adhesion, high specific heat, evaporative cooling, lower density as the solid, universal solvent.
Keep track of the electronegativity trend using the mnemonic “Flaming Oxygen Nice Clear Bright I Suspect Canned Hydrogen,” which points toward the trend Fluorine > Oxygen > Nitrogen >Chlorine > Bromine > Iodine > Sulphur > Carbon > Hydrogen ≥ Phosphorus. It helps understand the hydrogen bonding in water as Oxygen is the 2nd most electronegative element, and it is capable of hydrogen bonding.
The word “therm” means “heat,” which indicates that thermal capacity is the ability of a substance to withhold heat.
Cohesion relates to “cohesiveness,” which means keeping it together/union, while adhesion relates to “adhesiveness,” which means “property of sticking or joining different surfaces.”
A virtual laboratory simulation is a great way to teach about the properties of water. At Labster, we're dedicated to delivering fully interactive advanced laboratory simulations that utilize gamification elements like storytelling and scoring systems inside an immersive and engaging 3D universe.
Check out Labster's Properties of Water Virtual Lab. In this simulation, you will build a water molecule and figure out why it behaves the way it does. Are you ready to make a splash?
Please take a look at the following snippets taken from the Labster simulations or get in touch to find out how you can start using virtual labs with your students.
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