S1-Mid Term Biology Answer Key PDF

INPS School Shakhbout – Middle & High Section Science Department (2024-2025) Biology Mid Exam Answer Key - Semester 1 Lesson 1 : Elements and compounds Choose the correct answer 1. Which of the following is a trace element?...

INPS School Shakhbout – Middle & High Section Science Department (2024-2025) Biology Mid Exam Answer Key - Semester 1 Lesson 1 : Elements and compounds Choose the correct answer 1. Which of the following is a trace element? a. Oxygen b. Hydrogen c. Copper d. Nitrogen 2. What are the four most abundant elements found in living systems? a. Nitrogen, carbon, sulfur, and oxygen b. Hydrogen, oxygen, calcium, and nitrogen c. Hydrogen, oxygen, nitrogen, and carbon dioxide d. Hydrogen, oxygen, nitrogen, and carbon 3. Which of the following has negligible mass? a. Neutron b. Proton c. Electron d. Atom 4. An element has eight protons, nine neutrons, and eight electrons. Its atomic number and mass number, respectively, are __________ a. 9 and 16 b. 8 and 17 c. 9 and 17 d. 8 and 16 5. Which of the following are compounds? a. H2O, O2, and CH4 b. H2O and O2 c. O2 and CH4 d. H2O and CH4, but not O2 6. Which of the following atoms has the smallest number of neutrons? a. nitrogen-14 b. carbon-14 c. oxygen-16 d. neon-20 Answer the following questions 7. What is the difference between an element and a compound in the context of substances? o An element is a pure substance that cannot be broken down into simpler substances by chemical means (e.g., gold Au), (has one type of atom) o A compound is a pure substance made up of two or more elements chemically combined in a fixed ratio (e.g., water H2O). (has MORE one type of atom) 8. Classify the following substances into elements or compounds by placing them in the correct column of the table: Hydrogen (H₂) - Carbon dioxide (CO₂) - Sodium (Na) - Water (H₂O) - Oxygen (O₂) - Sodium chloride (NaCl) - Iron (Fe) - Glucose (C₆H₁₂O₆) 9. 10. What are trace elements, and why are they essential for human health? Trace elements are tiny amounts of minerals found in your body, like iron, zinc, and iodine. These elements help with important functions like making red blood cells, supporting your immune system, and regulating hormones. Without enough trace elements, your body can't function properly, leading to health problems. 11. Where is the most of atomic mass can be found? Why? Most of the mass of an atom is found in the nucleus, because nucleus has protons and neutrons inside. 12. Use the periodic table to answer some of the following questions: a. An atom of Neon has an atomic number of 10 and a mass number of 20. How many protons, neutrons, and electrons does it have? Number of protons = Number of electrons =10 Number of neutrons = Mass number -Atomic number = 20-10 =10 13. Use the information in the element below to find , atomic number, number of protons , electrons ,and neutrons Number of protons = Number of electrons =15 Number of neutrons = Mass number -Atomic number = 31-15 =15 Lesson 2 : Isotopes Choose the correct answer: 14- Which of the following best describes isotopes? A) Atoms of the same element with the same number of protons and the same number of neutrons. B) Atoms of different elements with the same number of protons but different numbers of neutrons. C) Atoms of the same element with the same number of protons but different numbers of neutrons. D) Atoms of different elements with the same number of protons and neutrons. 15- How many neutrons does a Flourine-14 isotope have? A) 4 B) 5 C) 9 D) 14 16- Which part of the atom changes in different isotopes? A) Protons B) Electrons C) Neutrons D) Energy levels 17- How do the atomic number and mass number of isotopes differ? A) The atomic number differs, but the mass number stays the same B) The atomic number stays the same, but the mass number differs C) Both the atomic number and mass number differ D) Both the atomic number and mass number stay the same 18. - Given two isotopes of carbon, C-12 and C-14, how do their neutron numbers differ? A) C-12 has 6 neutrons, and C-14 has 8 neutrons. B) C-12 has 6 neutrons, and C-14 has 7 neutrons. C) C-12 has 7 neutrons, and C-14 has 8 neutrons D) C-12 has 8 neutrons, and C-14 has 10 neutrons  19. Which of the pairs below are isotopes of the same element? answer B 20. Fill the blanks in tables (you need to use the periodic table) Radioactive Isotopes Choose the correct answer 21. Phosphorus-32 (radioactive) has __________ than phosphorus-35 (normal). a. three more neutrons b. three more protons c. three fewer protons d. three fewer neutrons 22. Why are radioactive isotopes useful in scientific research? a. Because they decay spontaneously and give off energy and subatomic particles b. Because they are not readily incorporated into biological reactions c. Because they are difficult to detect in small amounts but living cells cannot distinguish them from the corresponding stable isotopes d. Because they can be used as tracers to follow particular atoms and molecules through metabolic pathways Ionic, Covalent, and Hydrogen Bonds Choose the correct answer 23. Which of the below elements will most likely form an Ionic Bond? a) P and O b) Ca and O (Ca is metal O is nonmetal) c) Li and Mg d) Ne and Cl 24. Which of the below elements will most likely form a Covalent Bond? a) K and Cl b) H and O (H and O both are nonmetals) c) Al and Mg d) K and Na 25. A covalent bond is likely to be polar under which of the following conditions? a) one of the atoms sharing electrons is more electronegative than the other atom b) the two atoms sharing electrons are equally electronegative c) carbon is one of the two atoms sharing electrons d) the two atoms sharing electrons are of the same elements 26 When do hydrogen bonds occur?. Hydrogen bonds occur when a hydrogen atom that is covalently bonded to a highly electronegative atom, such as oxygen, nitrogen, or fluorine, interacts with another electronegative atom nearby. 27. Explain briefly why carbon dioxide considered non-polar molecule but water considered polar molecule. Water: Bent shape causes an uneven pull of electrons → Polar. Carbon dioxide: Straight shape causes equal pull on both sides →Nonpolar 28. Why does water have a positive and negative side? Because of unequal sharing of electrons between oxygen and hydrogen, give water a positive side (near the hydrogens) and a negative side (near the oxygen). 29. Label the water molecule using the following 30. Look at the given molecular formula. Can this compound form hydrogen bonds? Identify the atoms involved and explain your answer Compound Contains Hydrogen (Explanation) Bond? (Yes/No) Water ( H2O) H attached with O Yes Methane ( CH4) No Ammonia (NH3) H attached with N Yes Carbon Dioxide (CO2) No Hydrofluoric Acid (HF) H attached with F Yes Hydrogen Sulfide ( H2S) No Lesson 3: Properties of Water 31. How are the hydrogen bonds formed between water molecules? A) by the attraction between the positive end of one water molecule with the negative end of the other B) by sharing of electrons between two water molecules C) by the transfer of electrons from one water molecule to the other D) by sharing protons between two water molecules 32. The partial negative charge in a molecule of water occurs because ________. A) the oxygen atom donates an electron to each of the hydrogen atoms B) the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus C) the oxygen atom has two pairs of electrons in its valence shell that are not neutralized by hydrogen atoms D) one of the hydrogen atoms donates an electron to the oxygen atom 33. Which of the following properties of water is responsible for the formation of raindrops? A) cohesion property B) adhesion property C) high thermal energy D) high kinetic energy 34. Which of the following can be attributed to water's high specific heat? A) Oil and water do not mix well. B) A lake heats up more slowly than the air around it. C) Ice floats on water. D) Sugar dissolves in hot tea faster than in iced tea. 35. Which of the following effects can occur because of the high surface tension of water? A) Lakes cannot freeze solid in winter, despite low temperatures. B) A raft spider can walk across the surface of a small pond. C) Organisms can resist temperature changes, although they give off heat due to chemical reactions. D) Sweat can evaporate from the skin, helping to keep people from overheating. Answer the following questions: 36. How does the polarity of water allow it to dissolve substances like salt? Water’s polarity allows it to dissolve ionic substances like salt (NaCl) because the partial positive charge of the hydrogen atoms in water attracts the negatively charged chloride ions (Cl⁻), and the partial negative charge of the oxygen atom attracts the positively charged sodium ions (Na⁺). This process is called hydration. 37. Explain how water's polarity contributes to hydrogen bonding and its impact on the physical properties of water, such as boiling point. Water’s polarity leads to hydrogen bonding. As a result, water has a higher boiling point compared to other molecules of similar size because it requires more energy to break these hydrogen bonds during the state transition from liquid to gas. 38. Imagine you’re in the kitchen, about to make a cup of tea. You fill a pot with water and set it on the stove. As the heat is turned up, you notice the water takes a while to boil, even though the burner is very hot. Meanwhile, you spill a little cooking oil on the stove, and it quickly starts to sizzle and evaporate. Why do you think water takes so much longer to boil compared to other liquids, like cooking oil? Water takes longer to boil compared to liquids like cooking oil primarily because of its strong hydrogen bonds. In water, the molecules are held together by hydrogen bonds, which require a significant amount of energy to break. These bonds must be overcome for water molecules to escape into the gas phase (boil), which increases the time it takes to reach boiling point. In contrast, cooking oil molecules are held together by weaker forces. Since less energy is needed to break these weaker interactions, cooking oil heats up and boils faster than water. 39. Imagine you accidentally spill a glass of water on the kitchen counter. You quickly grab a paper towel to clean it up. As you press the paper towel against the spill, you notice that the water is being absorbed into the towel, leaving the surface dry. The towel soaks up the water disappears. How does the paper towel manage to soak up and hold the water from the surface so effectively? A paper towel soaks up and holds water effectively due to two forces: cohesion and adhesion. Adhesion is when water molecules stick to the paper towel's fibers. The paper towel is made of materials (like cellulose) that water easily clings to. This makes water spread out and soak into the towel. Cohesion is when water molecules stick to each other. As some water molecules are absorbed by the towel, they pull other water molecules along with them, helping more water get soaked up. Together, adhesion helps water stick to the paper towel, and cohesion helps the water pull in more of itself, allowing the paper towel to absorb and hold a lot of water. These strong properties due to the Hydrogen bonds between water molecules 40. Imagine it’s a bright, sunny day at the beach. You decide to take a stroll along the shoreline. As you step on the dry sand, you immediately feel how hot it is under your feet, and you quickly hop towards the water. When your feet hit the water, it feels much cooler, even though the sand and the water have been under the same sun all day. Explain Why is the sand so hot, but the water feels cooler? The sand feels hot, but the water feels cooler because sand and water heat up differently due to their specific heat capacity. Sand has a low specific heat capacity, which means it heats up quickly with just a little energy from the sun. As a result, sand can become very hot in a short amount of time. Water, on the other hand, has a high specific heat capacity, which means it takes much more energy to raise its temperature due to the Hydrogen bonds between water molecules. Because of this, water absorbs a lot of heat without getting very hot, making it feel cooler compared to sand even under the same sunlight. Lesson 4: Biological Macromolecules 41. Which of the following is an organic molecule? a. Ne b. CH4 c. O2 d. NaCl 42. Which of the following characteristics is responsible for the complexity and variety of organic molecules? a. the chemical versatility of carbon atoms b. the variety of rare elements in organic molecules c. the diverse bonding patterns of nitrogen d. their interaction with water. 43. Which of the following unique feature of carbon allows it to support life on Earth? a. Carbon is hydrophobic in nature. b. Carbon is the most abundant element on earth. c. Carbon can form a variety of bonds in nature. d. Carbon is the most electronegative element in the periodic table. 44. Which of the following best compares dehydration reactions and hydrolysis? a. Dehydration reactions assemble polymers; hydrolysis reactions break polymers apart. b. Dehydration reactions eliminate water from membranes; hydrolysis reactions add water to membranes. c. Dehydration reactions and hydrolysis reactions assemble polymers from monomers. d. Hydrolysis reactions assemble polymers; dehydration reactions break polymers apart. 45. Which of the following terms does not describe a molecule of glucose? a. an isomer of fructose b. an aldose c. a hexose d. a disaccharide 46.Which of the following statements is correct regarding starch and cellulose? a. They are polymers of glucose. b. They are cis and trans isomers of each other. c. They are used for energy storage in plants and animals. d. They are structural components of the plant cell wall. Answer the following questions 47. Compare monosaccharides, disaccharides, and polysaccharides. Monosaccharides are single sugars, disaccharides are two linked sugars, and polysaccharides are complex chains of many sugars. Monosaccharides and disaccharides provide quick energy, while polysaccharides are used for longer-term energy storage or structural purposes.  48. What is the role of water in hydrolysis? Water is added in hydrolysis to break down polymers 49. What happens to a polymer during hydrolysis? The polymer is broken down into smaller parts, called monomers. 50. What is the role of water in dehydration synthesis? Water is removed in dehydration synthesis when monomers join together 51. How are dehydration synthesis and hydrolysis different? Dehydration synthesis builds polymers by removing water, and hydrolysis breaks down polymers by adding water. 52. Why are hydrolysis and dehydration synthesis important in biological systems? Give one example of each in the human body. Hydrolysis is important for digestion, such as breaking down starch into glucose. Dehydration synthesis helps build proteins from amino acids. Both are essential for maintaining and processing biological molecules. 53. How does the body use dehydration synthesis and hydrolysis to maintain energy balance? Dehydration synthesis helps store energy and build essential molecules like proteins and glycogen. Hydrolysis helps release stored energy by breaking down these polymers during digestion. Together, these processes balance the building and breakdown of molecules, maintaining homeostasis (Energy balance ) 54. Imagine a scenario where a person’s cells could not perform hydrolysis. Predict the effects on the person’s ability to digest and utilize nutrients. If cells could not perform hydrolysis, the person would be unable to break down complex polymers like proteins, carbohydrates, and fats into their monomer components, such as amino acids and glucose. This would prevent the body from absorbing and utilizing essential nutrients, leading to malnutrition and energy deficiency. 55. How are monomers and polymers related, and what role do dehydration and hydrolysis reactions play in forming and breaking down these molecules?” Monomers form polymers through dehydration synthesis, which removes water to link them together. Polymers are broken down into monomers through hydrolysis, where water is added to break the bonds. 56. List three foods that are high in carbohydrates? a. Rice: A staple food in many cultures, rice is rich in starch. b. Bread: Made from wheat or other grains, bread is a common source of carbohydrates. c. Fruits: Foods like bananas and apples contain natural sugars and fiber, making them high in carbohydrate 57. What is the difference between simple and complex carbohydrates? Can you give examples of each? 1. Simple Carbohydrates: These are composed of one or two sugar molecules and are quickly absorbed by the body, leading to rapid spikes in blood sugar levels. Examples include: Glucose: Found in fruits and honey. Fructose: The sugar found in fruits. Sucrose: Common table sugar. Complex Carbohydrates: These consist of longer chains of sugar molecules and take more time to digest, providing a more sustained energy release. Examples include: Starches: Found in foods like potatoes, pasta, and whole grains.  Fiber: Present in fruits, vegetables, legumes, and whole grains, which aids digestion and helps maintain steady blood sugar levels. 58. How do different types of carbohydrates impact blood sugar levels, and why is this important for people with diabetes? Different types of carbohydrates impact blood sugar levels in varying ways: Simple Carbohydrates: Foods high in simple sugars (like candies or sugary drinks) can cause rapid spikes in blood sugar levels. This can lead to a quick burst of energy followed by a crash, which is particularly problematic for individuals with diabetes, as it can complicate blood sugar management. Complex Carbohydrates: Foods rich in complex carbohydrates (like whole grains and legumes) are digested more slowly, leading to a gradual increase in blood sugar levels. This is important for people with diabetes, as maintaining stable blood sugar levels helps prevent complications and supports overall health. 59. Analyze the impact of a high-carbohydrate diet on athletic performance A high-carbohydrate diet can greatly improve athletic performance because carbohydrates are the main source of energy for our muscles. When athletes eat enough carbs, they can train harder and recover faster, helping them perform better in their sports. Carbs also help maintain stamina during long workouts or competitions, so athletes can keep going without getting tired too quickly. 60. Compare dehydration and hydrolysis reactions. Dehydration: Stores energy, reactants are monomers and energy, products are polymers and water. Hydrolysis: Releases energy, reactants are polymers and water, products are monomers and energy 61.The following diagram shows different types of carbohydrates. A B C a. Which one is Glucose ? Explain A because glucose is monosaccharide which is made of one simple sugar. b. Which one is Maltose? Explain B because maltose is disaccharide. c. Which one is Glycogen? Explain C because Glycogen is polysaccharide