A1.1 Water Flashcards
Why water is essential for living things (5)
- Many reactions in living organisms require water.
- Water helps organisms regulate their temperature.
- Water is a habitat for a lot of living organisms.
- Water is a solvent so things dissolve in it.
- Because it is a solvent, it can transport substances.
Define water
Substance in which cells first developed and life processes still occur.
Chemical structure of water
Electrons are not evenly shared between O and H; O is more electronegative because it has more protons.
Define Electronegativity
Ability of an atom to attract a shared pair of electrons which is affected by number of protons and number of outer shells.
Hydrogen bonds
Weak intermolecular force; occurs when a hydrogen atom, which is covalently bonded to a (highly) electronegative atom, is attracted to another electronegative atom in another molecule.
Define Cohesion
A property of water in which water molecules are attracted to each other by hydrogen bonding; allowing the molecules to move together.
Define Adhesion
A property of water in which water molecules are attracted to polar substances such as walls of the cells, vessels or tubes.
Define Tension
A force that tends to stretch something.
Define Hydrophobic
Molecules usually nonpolar and cannot dissolve in water; no charge.
Define Hydrophilic
Molecules usually polar and soluble in water; has charge
Water as a solvent (4)
- Makes up cytoplasm.
- Makes up fluid inside all organelles.
- Permits transport of substances in and out of cells.
- Essential component of blood and other bodily fluids.
Define Specific Heat Capacity
Amount of energy needed to heat 1kg of a liquid by 1 degree Celsius. For water it is 4.186J/°C, which is relatively high and therefore good for organisms because water can withstand large swings in temperature, keeping things relatively constant. Especially important to support the chemical reactions that happen in the body to ensure stable internal temperature is maintained.
Define Buoyancy
Force that counteracts gravity on a partially/fully submerged object. Relied on density: if density of an object is greater than density of water, this force will break and object will sink. Density of water is 997kg/m3.
Example: Green algae can float as it produces oxygen from photosynthesis, and oxygen gets trapped between algae’s filaments making it lighter and float. They also have gas vacuoles that increase its buoyancy.
Define Viscosity
Resistance to flow and is related to how much energy is needed to change the shape of a liquid. Viscosity of water is very low (1-5 cps).
Define Thermal Conductivity
Ability to transfer heat during a difference in temperature. Water’s thermal conductivity is 0.6, relatively high which means heat is more easily moved. Our body is mainly composed of water, so heat is easily transferred in body. Example: Fennec fox which live in dessert conditions have large ears with many blood vessels, helping it dissipate heat from blood to exterior environment, allowing it to cool down.
Describe the Origin of Water
When Earth was first formed 4.5 billion years ago, it was too hot to have liquid water on surface. Water was delivered by water-rich asteroids. Earth began to cool, water condensed and gravity helped retain water on the surface.
What is the Goldilocks Zone concept
Range of orbital distances around a star in which liquid water may exist on a planet.
Contrast between how physical properties of water and air have consequences for animals that live in these two habitats
Specific heat: Water - 4.186J/°C; Air -1.005J/°C
Thermal conductivity: Water - 0.6; Air - 0.024
Density: Water - 997kg/m3; Air - 1.225kg/m3
How does moderate temperature and gravity help retain water on surface of Earth.
Earth started to cool, so water became liquid and force of gravity allowed water to be retained on surface of earth.
Properties of water that affect the Ringed Seal compared to properties of air that affect the Black-Throated Loon
Water is more viscous than air so ringed seal uses more energy moving throughout the water, and fighting against buoyancy forces than the Loon does flying in the air. Water has a higher heat conductivity than air so more heat is pulled faster from the seal than the Loon. Adaptation of seal is thick coat of fur to help retain and regulate body heat, and streamlined shape to reduce drag against viscosity.
