Saturday, January 18, 2020

Anaerobic respiration in yeast Essay

AIM: See the effect of temperature in anaerobic respiration of yeast by counting carbon dioxide bubbles. HYPHOTESIS: Anaerobic respiration in yeast will decrease as temperature increases. VARIABLES: Independent: Temperature Dependent: Rate of anaerobic respiration in yeast Fix: Volume of sugar solution (40ml) , Concentration of sugar solution, yeast mass (2g), volume of solution of yeast & sugar all together (20ml) MATERIALS: Delivering tube 2 test tubes 2 beakers Bunsen Burner Tap Water Thermometer ( ±0.1 °) Electronic Balance Spatula Sugar Solution Yeast Water Measuring Cylinder PROCEDURE: 1. Measure 40 ml of sugar solution with the measuring tube. Place the 40 ml on the big beaker 2. Measure 2 g of yeast using the electric balance. Place the 2 g on the beaker with the sugar solution 3. Stir the yeast-sugar solution (Solution A) using the glass stick until the yeast has completely dissolved 4. Separate Solution A into two 20 ml solutions (Solution A1 and Solution A2). To do so, measure 20 ml with the measuring tube and place them on a small beaker. Repeat the procedure with the other 20 ml. 5. Prepare a water bath on the Styrofoam cup. Using the thermomether, make sure the water bath has a temperature of 45 °C. 6. Light the Bunsen burner. Heat solution A1 to a temperature of 40 °C 7. Using the measuring cylinder, measure 15 ml of Solution A1 and place them on one of the boiling tubes. Cover the boiling tube with the delivery tube and place the other end of the delivery tube into a test tube which contains tap water 8. Count the number of CO2 bubbles  coming out of the delivery tube. Record the number of bubbles which came out each minute (checking time with the stopwatch) 9. Repeat from step 5 with Solution A2, but this time heat the solution up to a temperature of 100 °C instead of 40 °C. CONCLUSION: We may realize that our aim was successfully achieved because we  were able to know the effect of anaerobic respiration in yeast in 2 temperatures: 40 ° & a boiling temperature (90 °-100 °). If we see our results we may see that in test tube B, the one with the boiling water, hasn?t produced CO2 bubbles, there is no bubbles because yeast is boiled, so yeast don’t breath because when it was boiled it was killed, that causes yeast to not to breath. By looking at the formula of anaerobic respiration in fungi (yeast) & bacteria: We can see that yeast contains glucose, because if the product is CO2 , the have to contain glucose. If we see graph 1 we can see that the line that indicates de results for water at 40 ° is increasing as time passes. As I already mentioned, at a boiling temperature yeast don’t breath so we can say that as temperature increases less CO2 bubbles are produced, so less respiration is done by yeast. EVALUATION: One way in which we may improve the experiment is by doing different ranges of temperatures, & changing the volume of yeast it would be interesting for another experiment. One of the main source of uncertainty in this experiment is the observer because if you confuse the number of bubbles the results may be different, in another way the observer could be the source of uncertainty is by when reading the thermometer placed into the water, you may confuse and the results will not be the same because yeast will be placed in another temperature.

Friday, January 10, 2020

“Once More to the Lake” by E.B. White Essay

1.In paragraphs two, ten, and twelve of â€Å"Once More to the Lake,† White’s brilliant use of metaphors, similes, and personification illustrates a lucid image of the speaker’s intertwining past and present for the reader. White starts paragraph ten with a fragment, â€Å"Peace and goodness and jollity,† and creates a great emphasis on his past and current feelings. He continues to illustrate his past memories with a personification of the vocal senses as he explains the sound of the motorboats; â€Å"the one-lungers throbbed and fluttered, and the twin-cylinder ones purred and purred, and that was a quiet sound too.† He then compares this beautiful memory of the past to his current experience of the outboard powerboats, and exclaims, â€Å"These motors †¦ whined about one’s ears like mosquitoes.† This contrasting simile outlines the speaker’s transition from one point of time to another within his illusion. He continues to use a metaphor to describe the behavior of the old boats, and explains, â€Å"The boat would leap ahead, charging bull-fashion at the dock.† After a thunderstorm passes, White describes his son as he is entering the water; â€Å"As he buckled the swollen belt suddenly my groin felt the chill of death.† The â€Å"chill of death† is a metaphor for the truth White finds himself a part of, even though he is experiencing both his past and present. He realizes that the life course that leads to death starts with birth, and that his son’s maturity also means that the end of White is approaching. This, along with his allusion between past and present, allow White to develop his universal truth within his text. At first, while his illusion from the similar shape of the outdoors gives the false perception that time has not past, his pinpointing of the different identities of the son and father serves as testimony that the cycle from birth to death is universal. 2.In â€Å"Once More to the Lake,† White utilizes connotative words and phrases to establish the illusion that is the connection between childhood and adulthood. In his return to the lake, many years after his childhood, White confronts multiple changes as he struggles with the illusion that the peaceful world of his childhood, and his present existence within it, remain the same. In paragraph one, White describes the things that remind him of past memories with the words, â€Å"Restlessness of the tides and the fearful cold of the sea water and the incessant wind.† These words all have negative  connotations, and let the reader know that the speaker’s present experiences make him wish to go back â€Å"to revisit old haunts.† These words and their negative connotations are crucial to the nature of the illusion the speaker is describing. It provides the pretext of why he wishes for memories of his past. White says, while fishing with his son; â€Å"I looked at the boy who was silently watching his fly, and it was my hands that held his rod, my eyes watching. I felt dizzy and didn’t know which rod I was at the end of.† These connotative words allow White to establish a connection between young and old, past and present, then and now. These linked ideas blur the line between birth and death, and serve to establish the truth that the cycle from creation and mortality is universal. 3.White employs many descriptive details throughout his story. He creates contrasting symbols, almost placed as an antithesis, to illustrate his realization of age, and the universality of life to death. Taking his son fishing is the event that convinces him â€Å"beyond any doubt that everything was as it always had been, that the years were a mirage and that there had been no years.† A dragonfly that lands on the tip of his son’s fishing rod ignites this feeling that the two, both son and father, are the same individual. When he lowered the tip of his rod â€Å"into the water, tentatively, pensively dislodging the fly, which darted two feet away, poised, darted two feet back, and came to rest again a little farther up the rod,† he asserts that â€Å"there had been no years between the ducking of this dragonfly and the other one – the one that was part of memory.† Here, White’s language has bulls-eye precision, and the dragon fly is transformed into a representation of the continuous cycle of life and death. The present mixing with his past experience is again validated with details of the lake that â€Å"had never been what you would call a wild lake.† It is a calm, tranquil, and bounded place where youth is apparent. Here, the lake represents the familiarity of one’s past. This description is contrasted with the sea, as it comes right after the description of the endless body of water. The sea has the remnant memories of â€Å"restlessness of the tides and the fearful cold of the sea water and the incessant wind.† The sea symbolizes the harshness of aging, while the lake symbolizes the familiarity and safety of youth and the past.

Thursday, January 2, 2020

Ionization Energy Definition and Trend

Ionization energy is the energy required to remove an electron from a gaseous atom or ion. The first or initial ionization energy or Ei of an atom or molecule is the energy required to remove one mole of electrons from one mole of isolated gaseous atoms or ions. You may think of ionization energy as a measure of the difficulty of removing electron or the strength by which an electron is bound. The higher the ionization energy, the more difficult it is to remove an electron. Therefore, ionization energy is in indicator of reactivity. Ionization energy is important because it can be used to help predict the strength of chemical bonds. Also Known As: ionization potential, IE, IP, ΔH ° Units: Ionization energy is reported in units of kilojoule per mole (kJ/mol) or electron volts (eV). Ionization Energy Trend in the Periodic Table Ionization, together with atomic and ionic radius, electronegativity, electron affinity, and metallicity, follows a trend on the periodic table of elements. Ionization energy generally increases moving from left to right across an element period (row). This is because the atomic radius generally decreases moving across a period, so there is a greater effective attraction between the negatively charged electrons and positively-charged nucleus. Ionization is at its minimum value for the alkali metal on the left side of the table and a maximum for the noble gas on the far right side of a period. The noble gas has a filled valence shell, so it resists electron removal.Ionization decreases moving top to bottom down an element group (column). This is because the principal quantum number of the outermost electron increases moving down a group. There are more protons in atoms moving down a group (greater positive charge), yet the effect is to pull in the electron shells, making them smaller and screening outer electrons from the attractive force of the nucleus. More electron shells are added moving down a group, so the outermost electron becomes increasingly distance from the nucleus. First, Second, and Subsequent Ionization Energies The energy required to remove the outermost valence electron from a neutral atom is the first ionization energy. The second ionization energy is that required to remove the next electron, and so on. The second ionization energy is always higher than the first ionization energy. Take, for example, an alkali metal atom. Removing the first electron is relatively easy because its loss gives the atom a stable electron shell. Removing the second electron involves a new electron shell that is closer and more tightly bound to the atomic nucleus. The first ionization energy of hydrogen may be represented by the following equation: H(g) → H(g) e- ΔH °Ã‚   -1312.0 kJ/mol Exceptions to the Ionization Energy Trend If you look at a chart of first ionization energies, two exceptions to the trend are readily apparent. The first ionization energy of boron is less than that of beryllium and the first ionization energy of oxygen is less than that of nitrogen. The reason for the discrepancy is due to the electron configuration of these elements and Hunds rule. For beryllium, the first ionization potential electron comes from the 2s orbital, although ionization of boron involves a 2p electron. For both nitrogen and oxygen, the electron comes from the 2p orbital, but the spin is the same for all 2p nitrogen electrons, while there is a set of paired electrons in one of the 2p oxygen orbitals. Key Points Ionization energy is the minimum energy required to remove an electron from an atom or ion in the gas phase.The most common units of ionization energy are kilojoules per mole (kJ/M) or electron volts (eV).Ionization energy exhibits periodicity on the periodic table.The general trend is for ionization energy to increase moving from left to right across an element period. Moving left to right across a period, atomic radius decreases, so electrons are more attracted to the (closer) nucleus.The general trend is for ionization energy to decrease moving from top to bottom down a periodic table group. Moving down a group, a valence shell is added. The outermost electrons are further from the positive-charged nucleus, so they are easier to remove. References F. Albert Cotton and Geoffrey Wilkinson, Advanced Inorganic Chemistry (5th ed., John Wiley 1988) p.1381.Lang, Peter F.; Smith, Barry C. Ionization Energies of Atoms and Atomic Ions. Journal of Chemical Education. 80 (8).