Looking for a Tutor Near You?

Post Learning Requirement »
x

Choose Country Code

x

Direction

x

Ask a Question

x

Hire a Tutor
Dubai

A1.1 Water

Loading...

Published in: Biology | Science
136 Views

Please find attached notes which go with the accompanying PowerPoint slides

Saoirse M / Dubai

0 year of teaching experience

Qualification: BSc. Science Education

Teaches: Biology, Science, ESS Environmental Systems And Societies, Environmental Science

Contact this Tutor
  1. A 1.1 Water Learning objectives and guiding questions: "What physical and chemical properties of water make it essential for life?" "What are the challenges and opportunities of water as a habitat?" Al.l.l Al.1.2 Al.1.3 Al.1.4 Al.1.5 Al.1.6 Al. 1.7 AHL Al. 1.8 AHL Water as the medium for life Hydrogen bonds as a consequence Of the polar covalent bonds within water molecules Cohesion of water molecules due to hydrogen bonding and consequences for orgamsms Adhesion Of water to materials that are polar or charged and impacts for organisms Solvent properties Of water linked to its role as a medium for metabolism and for transport in Physical properties Of water and the consequences for animals in aquatic habitats Extraplanetary origin of water on Earth and reasons for its retention Relationship between the search for extraterrestrial life and the presence Of water Students should appreciate that the first cells Originated in water ard that water remains the medium jn which most processes of life occur. Students should understand that polarity of covalent bonding within water nwlecules js due to unequal sharing Of electrons and that hydrogen bonding due to this polarity occurs between water molecules. Students should be able to represent two or more 'voter molecules and hydrogen bonds between them with the notation shown below to indicate polarity. Include transport of water under tension in xylem and the use of water surfaces as habitats due to the effect known as surface tension. Include capillary action in soil and in plant cell walls. Emphasize that a wide variety of hydrophilic molecules dissolve jn water and that most enzymes catalyse reactions in aqueous solution, "Students should also understand that the functions of some molecules in cells depend on them being hydrophobic and insoluble. Include buoyancy, viscosity, thermal conductivity and specific heat. Contrast the physical properties of water with those of air and illustrate the consequences using examples of animals that live in water and in air or on Ion", such as the black-throated loon (Gavia arctica) and the ringed seal (Pusa hispida). The abundance of water over billions of years of Earth's history has allowed I,ife to evolve. limit hypotheses for the origin of water on Earth to asteroids and reasons for retention to gravity and temperatures low enough to condense Include the idea of the "Goldilocks zone". Il
  2. Water as the medium of life Life has originated in the water, with first cells enclosing a small volume Of it in a membrane, where solutes dissolved, and chemical reactions occurred. The interaction Of molecules in water is the basis Of all life. Atmosphere Living t h mgs Freiwater 2.5% ther saline 96.5% Hal global 1.2% f reshwater Ground- 30.1% G læiers Freshwater 3.0% 20.9% Ground ice and permaf rost 69.0% Surface water and 026% 0.49% moisture Over 70% of Earth's surface is water, with most Of the water found in oceans. Water forms a large proportion of living organisms. Look at the graph to the left. Where is most of the Earth's freshwater stored? Where is most of the surface water and Other freshwater stored? Most Of a cell and its organelles are made up from water, forming the cytoplasm. What makes water so useful for cells? RNA Phospholilid membrane Membranes enclose an aqueous medium. This is used for a number Of different cellular processes. Ph0SPh01iPid head group tail Early cells evolved membranes to separate their insides (cytoplasm) from the ocean water. Cell membranes (phospholipid bilayers) naturally form in aquaeous medium 21
  3. Water chemistry: Water has some unusual properties, which are crucial for living things and to understand these we first need to look at the structure of water. Draw a molecule of water showing bonding and non-bonding electrons, and highlight the polar covalent bond: Water has a defined polarity — this is due to the unequal attraction of electrons towards the nuclei of the respective atoms. The oxygen atom has a larger nucleus (8 protons) than hydrogen (1 proton) and has therefore a stronger pull towards shared and unshared electrons. This causes an uneven charge distribution. Name the type of bond which is formed between the atoms in a water molecule: Why is the bond in a water molecule said to be polar? Draw hydrogen bonds between 2 — 3 water molecules: What is a hydrogen bond? Explain. 31
  4. Cohesion of water molecules due to hydrogen bonding and consequences for organisms A single hydrogen bond is not very strong. This large number of hydrogen bonds is very strong. Each water molecule bonds with four others in a tetrahedral arrangement. This is because of hydrogen bonds which makes water "stick together". Water is therefore cohesive. The cohesive property of water leads to important consequences for living organism: What is surface tension? How is surface tension of importance for living organism? Give examples: MeSO#.yu s Air space within leaf rat ion Xyle m Cohesion and cells in the Cohesion , by hydrogen How does cohesion allow the transport of water under tension in plants? Root hair Soil particle Water uptake from so" 41
  5. Adhesive properties of water: What are adhesive properties and how are they brought about? The effect of adhesive forces can be observed when water forms a meniscus inside test tubes or capillary tubes. Since the polar water molecules adhere to the polar glass, a meniscus is established. This contrasts with nonpolar mercury, which does not form a meniscus. polar or Charged Object What is capillary action and what is its impact for organism? BLOTTING PAPER OR FILTER PAPER WATER Capillary action is also happening in porous solids due to the large amount of (polar) surface area (soil, paper, cellulose fibers in plant cell walls). This helps water to rise up from an underground source. 080 WATER MOLECULE on polar surfaces of stkkirw to withmt Wing Off TRANSPORT IN XYLEM XYLEM VESSEL WATER MOVING up PAPER TO CoæS10N BETWEEN WATER MOLECULES AND ADHE SION OF WA MOLECULES TO PAPER WATER MOVING up XYLEM VESSEL Oue TO COHESION BETWEEN WATER MOLECULES ANO ADHESION OF WATER MOLECULES TO XYLEM CELL WALLS 00 XYLEM CELLS o 0 o WATER ADHESION BY HYDROGEN BONDING CELL WALL COHESION BY HYDROGEN BONDING 51
  6. Solvent properties of water: Water is a good solvent because it is a polar molecule, and it will therefore dissolve polar solutes easily. An ionic solid such as Sodium chloride (NaCl) will break into its ions in water since polar attractions cause the water molecules to surround and isolate the solute molecules. 00 000 oo Explain how NaCl (Sodiumchloride) dissolves in water by referring to the polarity of water, charges on ions and hydration shells: Because water is a good solvent, it is a medium for metabolic reactions. Dissolved particles can move around easily in the cytoplasm of cells and blood stream of organisms. Solutes such as amino acids, salts, sugar, and ions needed for cell processes are dissolved in the plasma of blood. All metabolic reactions in living things occur in solutions. WHOLE BLOOD by me) CENTRIFUGED SAMPLE OF BLOOD fluids Bury wat TOTAL BODY WEIGHT by we •t) 42—6-2 mill FORMED ELEMENTS (number cubic mm) PROTEINS Albumins Globulins 38% Prothrorrbin 1% OTHER SOLUTES Regula LEUKOCYTES MonoMös 91% of the plasma of blood is composed of water. The solubility of substances in blood is therefore important for an effective transport around the circulatory system.
  7. Hydrophilic & hydrophobic properties of water: Hydrophilic "Water-lovi ng" Proteins are composed of polypeptides, which are long chain of amino acids joined together. Ode the outside CON of the molecule can fom hydro"n to Their respective variable side groups orientate themselves towards or away from the water, depending on their associated polarity or charge. This then determines the specific 3D shape of a polypeptide or protein. Hydrophobic "Water-hating" Substances such as the phospholipid bilayer of cell membranes have hydrophobic (water hating) and hydrophilic (water loving) features. Water Hydrophilic "heads" Hydrophobic fatty acid -tails" Hydrophilic This is important; as the membrane forms a protective, partially permeable barrier around the cell's content and allows for the separation of metabolic reaction. Into the space provided, draw a diagram of a small section of the cell membrane (phospholipid bilayer) and water molecules on either side. Clearly show the orientation and interaction Of the water molecules: 71 Page
  8. Summarizing the solubility of some important biological molecules: Molecule & structure Glucose Fats & lipids c-CH Chemical features Glucose as an example for a simple sugar is polar and hydrophilic due to the many -OH (hydroxyl) groups which are found on his molecule. Amino acids are the building blocks of proteins. There are 20 common amino acid, each is characterized by a different chemical side group. The side chain (R- group) can be charged, polar or nonpolar . Oxygen is entirely nonpolar and hydrophobic. Fat molecules are entirely nonpolar due to the long fatty acid tails which do not have any polarity. Soluble or insoluble in water? 81
  9. Phvsical properties of water: Buoyancy is the ability of any fluid (liquid or gas) to provide vertical upwards force on an object placed in or on it. When the (buoyant) force which water exerts on a body is equal to the weight of the object, it floats. Swim bladder filled with oxygen fish becomes lighter. floats up Swim bladder Slightly deflated and smaller. fish remains at the same depth Swim bladder with Very less oxygen, fish sinks to the bottom The images above show a cyanobacteria with gas filled vesicles inside their cells, a bird midair, and fish with swim bladders. How do these organism use buoyancy as an adaptation to life? Buonyancy depends on object density. Living organisms have an overall density close to water and tend to float, making water a suitable habitat. Obi"t Obi«t a, Ice is less dense than water and floats at the surface, becoming the barrier that protects the liquid water below from the colder air. This way, invertebrates can survive the cold winter months. In ice, the maximum number of hydrogen bonds form. the to be spread far In liquid Water, bonds t ly and reform. enabling a more dense spacing than in ice. 91
  10. 2. Viscosity What is viscosity? What is viscosity caused by? The viscosity of substances changes with the amount Of solute dissolved in it. Difference in viscosity between water and air Compare and explain the viscosity in water and air at increasing temperatures by looking at the graph: Air 3. Specific heat capacitv of water It takes a lot of energy for the temperature of water to change, while the temperature of air changes much faster. This is expressed through the specific heat capacity. Specific heat capacity is the amount Of energy needed to change the temperature of lg water by IOC is 4.18 Joule (J). Explain why the specific heat capacity for water is so high: SPECFIC HEAT CAPACITY 390 SPECIFIC HEAT CAPACITY = 940 J,'k9'C SPEC"C æAT CAPACITY OF WATER - 4200 .'/kgt LOWER SPECIFIC HEAT CAPACITY- WARMS up AND COOLS DOWN AS IT TAKES *JCH ENERGY TO CHANGE ITS TEMPERATURE HIGHER SPECIFIC HEAT CAPACITY - up AND COOLS DOWN SLOWLY AS IT TAKES MUCH MORE ENERGY TO CHANGE ITS TEMPERATURE 10 |
  11. Gas •Gas - Liquid Liquid 1 Liquid- Solid Heat Added Water is a liquid over a wide range of temperatures. This is a consequence Of the high specific heat capacity. To change the temperature of water, the kinetic energy and molecular motion must be increased. During phase changes, the molecular motion does not increase. Instead, the energy is going into breaking hydrogen bonds. solid The temperature of large bodies of water remains therefore relatively stable, which makes it an ideal habitat for a lot of organisms, which only tolerate a narrow range Of conditions. The graph on the right shows the temperature changes in water and air on a summer day. Comparing air and water temperature changes on a summer day: 18:00 water 24:00 Explain why there is such a big difference in temperatures between water and air: It takes a lot of energy for water to change temperature. This means that, when water evaporates, a lot of energy is required in order to break the hydrogen bonds between water molecules. Why does this (The high specific heat capacity of water) make water an effective coolant? 11 |
  12. 4. Thermal conductivity What is thermal conductivity? The rate at which heat passes through water is relatively high. Fats and oils conduct heat ca. 25% as quickly as water, air only ca. 5% as quickly. These materials are therefore insulators of heat. area A Heat flow The speed at which heat passes through materials depends on the collision of particles and electrons. Why are gases usually insulators and poor conductors of heat? thin gas (low pressure) dense gas (high pressure) •t The physical properties of air and water are different — mostly because of their differing densities (air has a much higher density Of 998.21 kg/m 3 compared to water with 1.204 kg/m•3). Summarize the physical properties for air and water: Air Buoyancy Viscosity Thermal conductivity Specific heat capacity Water 12 |
  13. Comparing the adaptations to physical properties of animals: The ringed seal (Pusa hispida) lives almost exclusively in the cold seas and on the ice of the Arctic Basin. The black-throated loon (Gavia arctica) also lives in the cold Arctic, spending time in the water, on land and in the air. These two animals have physical and behavioural adaptations to the physical properties of both air and water in respect to viscosity, buoyancy, thermal conductivity and specific heat capacity. Complete the table to compare animal adaptations to the physical properties of air and water The mammal: Ringed seal (Pusa hispida) Buoyancy Viscosity Thermal conductivity Specific heat capacity Extraplanetary origin of water on Earth There is a lot of water on Earth — where does it have its origin? Scientists believe that water sources on Earth are a consequence of asteroid collision, which have taken place in the first few 100 million years after Earth's formation. These asteriods most likely also contained a lot Of water in the form of hydrated minerals. The bird: Arctic loon (Gavia artica) 13 |
  14. Watch the film and answer the questions: When was the Earth formed? What is the most widely supported hypothesis for the origin of the vast amounts of water on Earth? For a long time, scientists thought that comets, which contain far more water than asteroids, were thought to have delivered water to Earth Why has this idea been refuted? Asteroids only collide with Earth about once every 20 million years and usually do not contain much water. Larger bombardment in the history of the Earth seems to have taken place even after the moons formed. Pieces Of evidence which seem to support the idea of asteroid bombardment are found within two 4.5-million-year- old meteorites containing water which were found on Earth. The "molecular fingerprint" in terms of its isotope ratio matches the ones Of our oceans. The Earth's crust also contains a remarkable amount Of gold. How does this further support the hypothesis that asteroid brought the water to the Earth? After its delivery by asteroids, how was the water retained on the Earth's surface rather than evaporating and being lost back into space? Comment on: Distance of Earth from the sun (Goldilock zone): Size Of the Earth and resulting gravity and magnetic field: Extraplanetary origin of water on Earth For water to stay on Earth (or any planet) after its appearance, it must be at the right temperature, as if the temperature is to high water would evaporate. If it were too low, all the water would freeze. The right temperature is therefore the one which allows water to stay at a liquid zone. The temperature is determined by the distance of a planet away from a star. Habitable Zone just r&ht 14 | Page

Need a Tutor or Coaching Class?

Post an enquiry and get instant responses from qualified and experienced tutors.

Post Requirement

Related Study Notes

Upload Study Notes

If you have your own Study Notes which you think can benefit others, please upload on MyPrivateTutor. For each approved Study Note you will get 100 Credit Points and 100 Activity Score which will increase your profile visibility.

Upload Now
Home > Study Notes > A1.1 Water