FEEDBACK TUTORIAL LETTER

Transcription

1 FEEDBACK TUTORIAL LETTER 1 ST SEMESTER 2017 ASSIGNMENT 2 BASIC SCIENCE (BBS111S) 1

2 Dear Student Assignment Two has been marked and this serves as feedback on the assignment. Individual feedback is already included in you assignment by the tutors that marked your assignment. We hope that the answers contained in this feedback letter will guide you through finding the correct solutions more easily. The course Basic Science consists of three sections, Biology, Chemistry and Physics. These three legs of science are intertwined on so many levels and understanding how rests on many facts and rules. Study the solutions carefully. If there are still areas that are unclear, please contact the tutors. We would also like to bring under your attention a few tips on answering questions in future assignments and the examination in Basic Science: Make sure you read the question carefully. Make sure you read the WHOLE question. Try to not leave out any questions. You have enough time to answer all the questions. If you do not understand a question, ASK. Leaving out answers without any attempt costs a lot of marks. Make sure you understand what is asked. Discuss, relate, explain, estimate, calculate, determine, describe, verify, list; these are all words that have different meanings. Make sure your answer answers the question. We have found that some of your answers are unnecessarily long. Keep your answers to the point. Also observe the MARK ALLOCATION in order to decide how many facts to include in your answer. Double check your answers. Please use a dictionary, at this stage there is no excuse for spelling mistakes. 1

3 Section A Biology [40] Question Lipids(fats), carbohydrates, protein 1.2 individual sugar molecules combine to form carbohydrates 1.3 proteins 1.4 complex meaning many sugar molecules poly (many) saccharide 1.5 your knowledge of saturated and unsaturated will help here - unsaturated 1.6 there is only one clot master vitamin K 1.7 hydrolysed means breaking/splitting into building blocks, in this case it will be glucose and fructose 1.8 fats contain the most energy 1.9 Disaccharide is a sugar molecule that contain 2 monosaccharide units or 2 sugar unit Maltose = Glucose + Glucose malt sugar (Barely) Lactose = Glucose + Galactose milk and dairy product Sucrose = Glucose + Fructose sugar cane, beet sugar, table sugar Question Differentiate: Fibrous proteins are; strong water insoluble, long, narrow proteins and spirally coiled amino acids Globular proteins are; water soluble, compact and rounded shapes and the amino acids are folded upon themselves Examples of globular are haemoglobin, insulin Example of fibrous are Keratin, tendons and ligaments 2.2 Vitamin D & K D with the help of sunlight K with the intestinal bacteria 2.3 There are two classes of vitamins. Fat-soluble and water-soluble. The answer here is fat-soluble because they stay in our bodies and are stored in the 2.4 mono one meaning one double bond Poly many meaning many double bonds Mono liquid at room temperature and solidify in refrigerator Poly liquid at room temperature and in the 2

4 2.5 Complete proteins are called complete because they contain all the essential amino acids Incomplete proteins are called incomplete because they do not contain all the essential amino acids in them Question 3 Complete proteins are found in animal products Incomplete proteins are found in plant products microorganisms/bacteria convert lactose in the mild to lactic acid benefits of yogurt, in other words why is it good for us Boost immune system Help fight Candida yeast infections Rich in calcium, thus keeps bones strong and reduces the risk of osteoporosis Has anti-inflammatory properties Heals skin disorders faster Helps to keep eating disorders in check 3.2 There are 5 distinctive steps in the process. Gasohol refers to ethanol made from sugar cane Step 1: growing and cropping the sugar cane Step 2: extraction of sugars from the sugar cage and washing the cane Step 3: crystallizing out the sucrose (which is sold) leaving the molasses (a mixture of glucose and fructose) behind Step 4: molasses is fermented to produce alcohol Step 5: this alcohol is then distilled to produce a very pure ethanol and in this process the waste bagasse is used as a power source Question 4 Section B Chemistry [40] 4.1 A value is a description for a measure of quantity (how much, how long, how many etc.) that has two features: number (magnitude) and unit 4.2 Make sure you use the correct formulas for conversions. 9 F = C O R F = 1, 8 C o o o o ,15 K -227,2 o F ,75 o C 177,33 o F 3

5 4.3 these two are not related to precision and accuracy Accepted correct value based on reliable references and/or standards Experimental a value measured by an individual in a laboratory 4.4 Here you have to evaluate all the measurements taken with each other to determine precision. When looking at the results three of them are exactly the same and the other two are different by 0,001 g which is extremely small. Therefor we can say that the measurements are precise. With the true mass being 1,975 g again looking at all the measurements one is exactly the same and the other measurements differ by 0,001 g which is so small that we can say the measurements are accurate ,0 is the number expressing this with significant figures we have to use x 10 x to one significant figure 9 x to two significant figures 9.0 x When we round of there are two main rules which is determined by the operations: + and and and x These operations determine if you round off to: As many decimal places as the least accurate value (+ and -) As many total digits as the least accurate value ( and x) Least accurate value means fewest significant figures , ,16 x ,43 x Question Litmus paper is a piece of paper that changes color in order to indicate if a substance is an acid or a base concentrated acid: little water lots of acid (simply stated) dilute acid: little acid lots of water (simply stated) Concentrated and dilute is not related to strong and weak which is determines by the ph scale 4

6 5.3 the question states outline applications in other words how is ph used or useful In agriculture the soil ph must be known or monitored since plants grow in either acidic or alkaline soil In medicine the ph of blood and urine is used for the diagnosis of certain diseases 5.4 there are many answer here, but is should be limited to strong acids (ph 1-3) and common Answer may include: Hydrochloric HCl Nitric HNO 3 Sulphuric H 2 SO 4 Phosphoric H 3 PO there are many answer here, but is should be limited to strong acids (ph 1-3) and common Answer may include: Bleaching powder CaOCl 2 Sodium carbonate decahydrate NaCO 3.10H 2 O Sodium hydrogen carbonate or baking soda NaHCO 3 Sodium chloride or table salt NaCl Make sure you write the formulas correct using upper case and lower case correctly For example: NACL is not the same as NaCl 5.6 solution A the ph value is lower than 7 thus it is an acid Solution B the ph value is higher than 7 thus it is a base/alkali HCl will ionize and form the ions H + and Cl silver will displace the hydrogen and form AgSO 4 and the other product will then be H sodium will displace the hydrogen and form NaCl and the other product will then be H 2 O 5.8 Be careful of what you write. For example, ammonia is not used as a fertilizer. It is used in the production of fertilizers. Name Ammonia Sodium hydrogen carbonate (baking soda) Uses 1. Used as a cleaning agent 2. Preparation of nitric acid 3. Preparation of ammonium chloride 1. Ingredient in antacids 2. Additive in food and drinks 3. Used to make baking powder 4. Used in soda-acid fire extinguishers 5

7 Section C Physics [30] Question It is still the same element because the proton numbers are the same 6.2 mass number nucleon number 6.3 Z 6.4 Again be careful of what you write here. Food is incorrect, because by stating food you are saying all foods have radioactive substances in it. Same with plants and air. Correct answer include many rocks, cosmic rays (not atmosphere), some radioactive elements in our bodies, some buildings 6.5 extra neutrons in the nucleus 6.6 alpha reason because it is the largest particle consisting of two protons and two neutrons 6.7 gamma reason because it is electrically neutral/uncharged because an electric field can only have an effect on a particle that has a charge since the field has a positive and negative side Question The difference is in how these two devices operate since both can measure mass and the spring balance can also measure weight which the balance beam cannot do. Spring balance it works on the principle that a spring is fixed on one end and the object is attached to the other end. The distance that it is stretched is then related to the mass/weight of the object. Balance beam - A horizontal beam has two pans attached to it. The object to be measure is placed in one and a known mass is placed in the other. When the beam is in horizontal equilibrium the object is equal to the known mass in the other pan 7.2 any four correct answers here, two for pulling and two for 7.3 The spring was not damaged beyond repair OR that the spring will go back to original shape 7.4 Explain, in other words do not calculate. First assign + or signs to all forces depending on their directions. Next combine and add all the forces with the same signs. Lastly, subtract the two answers you obtained in the previous step. This will give you an answer with a magnitude and a sign. The sign will tell you the direction according to your first step. 6

8 = -75(all in direction) and then = +73(all in + direction) Add these two answers: = -2 N (remember your unit) Question In a longitudinal wave the particles vibrate in the same direction/parallel to the wave direction In a transverse wave the particles vibrate perpendicular/at right angles to the wave direction 8.2 Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency. The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency This is the exact word of many students for this answer meaning it was copied from the same source. If you want to reference please make sure you follow the rules. If you write this as your own words you will not receive any marks for it. Frequency number of waves per unit time Period time taken for one complete oscillation 8.3 On the same axis mean the two waves overlap on the same graph. Each wave has to be indicated clearly. The amplitude and period needs to be indicated/clear to see on the graph. Axes need to be labeled. 6 mm 1/ 2 B 4 mm 1/ 2 1 s 2 s 1/ 2 3 s 1/ 2-4 mm A -6 mm 7