1.1 Water Flashcards
(35 cards)
What role does water play in metabolic reactions and cells?
Water is a medium for metabolic reactions and an important constituent of cells. Approximately 70% of human mass is water.
What is the structure of a water molecule?
Water consists of two hydrogen atoms covalently bonded to one oxygen atom. Each hydrogen shares a pair of electrons with oxygen.
Why are electrons not shared equally in a water molecule?
The shared electrons are not shared equally because oxygen has a greater affinity for electrons than the hydrogens, causing it to ‘pull’ the electrons closer.
What is the result of unequal electron sharing in water molecules?
This unequal sharing of electrons results in the water molecule having positive (δ+) and negative (δ-) charged ends, making it a polar molecule.
What do the symbols δ- and δ+ represent in a water molecule?
The δ- represents the slight negative charge on the oxygen atom, and the δ+ represents the slight positive charge on the hydrogen atoms.
What are hydrogen bonds in water molecules?
Hydrogen bonds are weak attractions between the slightly negative oxygen atom of one water molecule and the slightly positive hydrogen atom of another water molecule.
How do hydrogen bonds affect the properties of water?
Many properties of water are due to its ability to form hydrogen bonds. These weak bonds make it difficult to separate water molecules, contributing to water’s cohesion and surface tension.
What are the main properties of water?
Water is a polar molecule, a good solvent and reaction medium, adheres to surfaces, good for transport, has cohesion and adhesion, high surface tension, high latent heat of evaporation, high specific heat capacity, density, transparency, and acts as a metabolite.
What is cohesion in water?
Cohesion refers to the attraction between water molecules, caused by hydrogen bonds, which causes them to stick together.
What is adhesion in water?
Adhesion refers to the attraction of water molecules to other polar molecules or surfaces, such as the inside walls of plant xylem vessels.
How do cohesion and adhesion benefit plants?
Cohesion allows water to be held in a continuous column in the transpiration stream. Adhesion allows water molecules to stick to the inside walls of xylem vessels.
What is surface tension in water?
Surface tension is the force that allows water to form a ‘skin’ on the surface, enabling organisms to travel across the surface and create habitats.
What causes water’s high surface tension?
Cohesion forces between water molecules cause the high surface tension of water.
What is latent heat of evaporation?
The latent heat of evaporation is the amount of energy required to change the state of water from liquid to gas. Water has a high latent heat of evaporation, meaning it takes a large amount of energy to break hydrogen bonds.
How does latent heat of evaporation benefit organisms?
It allows organisms to carry heat away from their bodies through processes like sweating, helping to regulate body temperature.
What is the specific heat capacity of water?
Water has a high specific heat capacity, meaning it requires a large amount of energy to raise the temperature of 1 kg of water by 1°C. This helps to maintain a stable internal temperature for organisms.
Why is high specific heat capacity important for aquatic organisms?
Water absorbs large amounts of heat before its temperature rises significantly, preventing large temperature fluctuations and creating a stable environment for aquatic organisms.
Why is water considered a universal solvent?
Water is known as a universal solvent because it can dissolve a wide range of solutes due to its ability to form hydrogen bonds with ions, allowing chemical reactions to take place in solution.
How does the density of water change when it freezes?
Solid water (ice) has a lower density than liquid water because hydrogen bonds push the molecules further apart as water freezes. This causes ice to float on top of liquid water.
How does water’s density benefit aquatic life?
Ice forms an insulating layer on top of bodies of water, preventing the entire body of water from freezing and helping to keep organisms alive. Water freezes from the top down, allowing life to continue beneath the surface.
Why is water’s transparency important for aquatic plants?
Water is colorless and transparent to light, allowing sunlight to penetrate the water and reach the cells of aquatic plants, enabling photosynthesis to occur.
How does water act as a metabolite?
Water is a metabolite because it participates in many metabolic reactions. For example, in hydrolysis, water molecules are chemically inserted to break bonds.
How does water provide buoyancy and support to organisms?
Water supports organisms by providing buoyancy, such as in large aquatic animals, and helps maintain the turgidity of plant cells.
Why is water an ideal transport medium in living organisms?
Water remains liquid over a large temperature range and can act as a solvent for many chemicals. This makes it an ideal transport medium for substances, such as blood in animals.
