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Maths Unit 4 (grade 10) 1. What is the value of sin 90°? A) 0 B) 1 C) -1 D) 0.5 Answer: B) 1 2. What is the value of cos 0°? A) 0 B) 1 C) -1 D) 0.5 Answer: B) 1 3. What is the value of tan 45°? A) 0 B) 1 C) -1 D) Undefined Answer: B) 1 4. Which of the following is the correct Pythagorean identity? A) B) C) D) Answer: A) 5. If , what is ? A) B) C) D) Answer: A) 6. The value of is: A) 0 B) 1 C) Undefined D) -1 Answer: C) Undefined 7. What is the value of ? A) 2 B) C) D) Answer: B) 8. What is the period of the sine function? A) B) C) D) Answer: D) 9. If , what is ? A) B) C) D) Answer: A) 10. Which quadrant contains angles where sin is positive and cos is negative? A) First B) Second C) Third D) Fourth Answer: B) Second 11. The value of is: A) 0 B) 1 C) Undefined D) -1 Answer: C) Undefined 12. The function is symmetric about: A) The x-axis B) The y-axis C) The origin D) None of these Answer: C) The origin 13. What is the value of ? A) 1 B) 0 C) -1 D) Answer: C) -1 14. The value of is: A) 0 B) C) 1 D) Answer: B) 15. If , what is ? A) B) C) D) Answer: A) #maths @knowledgebach9

History Unit 5 ✨some information about UN 🔑 Formation 👉 Founding: The UN was established on October 24, 1945, when the UN Charter was ratified by the five permanent members of the Security Council (the United States, the United Kingdom, France, China, and Russia) and a majority of other signatory nations. 👉 Predecessor: The League of Nations, formed after World War I, was the UN's predecessor but failed to prevent the outbreak of World War II. 👉 Location: The headquarters of the UN is located in New York City, USA. 🔑 Mission The primary mission of the United Nations is to maintain international peace and security. Its goals include: 👉Preventing Conflict: Through diplomacy and peacekeeping efforts. 👉Promoting Sustainable Development: Addressing economic and social issues globally. 👉 Protecting Human Rights: Advocating for fundamental freedoms and rights for all individuals. 👉Fostering International Cooperation: Encouraging collaboration among nations on various global issues. 🔑 Principles The UN operates on several core principles, including: 1. Sovereign Equality: All member states have equal rights and responsibilities. 2. Peaceful Settlement of Disputes: Encouraging resolution of conflicts through dialogue and negotiation. 3. Non-Intervention: Respecting the sovereignty of nations and non-interference in domestic affairs. 4. Collective Action: Member states agree to work together to address global challenges. 🔑 Achievements The UN has made significant contributions in various areas: 👉Peacekeeping Operations: Deployment of peacekeeping forces in conflict zones to help maintain peace and security. 👉Humanitarian Aid: Providing assistance during crises through agencies like UNICEF and the World Food Programme. 👉Health Initiatives: Eradicating diseases (e.g., smallpox) and combating others (e.g., HIV/AIDS, malaria). 👉Sustainable Development Goals (SDGs): Adoption of 17 goals aimed at addressing global challenges by 2030, including poverty, inequality, climate change, and education. 👉Human Rights Advocacy: Establishment of the Universal Declaration of Human Rights in 1948 and ongoing efforts to promote human rights worldwide. #history @knowledgebach9

Chemistry Unit 4

💎Exothermic and Endothermic Chemical Reactions Chemical reactions involve energy changes, primarily in the form of heat. 🌡 Exothermic Reactions: These reactions release energy (usually heat) into the surroundings. The reactants have more energy than the products, and the temperature of the surroundings increases. Examples include: 👉Combustion: Burning of fuels like wood or gasoline. 👉Respiration: Breakdown of glucose in cells to release energy. 👉Neutralization: Acid-base reactions that release heat. 👉Condensation and Freezing: Changes of state that release heat. 🌡 Endothermic Reactions: These reactions absorb energy from the surroundings. The reactants have less energy than the products, and the temperature of the surroundings decreases. Examples include: 👉Photosynthesis: Plants absorb sunlight to make food. 👉Melting and Evaporation: Phase changes that require heat input. 👉Thermal Decomposition: Breakdown of compounds by heating (e.g., decomposition of calcium carbonate to form lime and CO₂). 🌡 Importance of Chemical Changes Chemical changes play a crucial role in both natural and industrial processes. Their importance includes: 👉Energy Production: Fuels undergo combustion to produce heat and electricity. Cellular respiration provides energy for living organisms. 👉Manufacturing: Industries rely on chemical reactions to produce materials like plastics, medicines, fertilizers, and metals. 👉Environmental Processes: Natural cycles like the carbon and nitrogen cycles depend on chemical changes. 👉Food and Digestion: Cooking involves chemical changes that enhance food properties, while digestion breaks down food into energy. 👉Medical Applications: Chemical reactions are used in drug synthesis, sterilization, and medical treatments. 🌡 Energy Changes in Electrochemistry Electrochemistry deals with the relationship between electrical energy and chemical reactions. 👉Galvanic (Voltaic) Cells: Convert chemical energy into electrical energy. Example: batteries used in mobile phones and cars. 👉Electrolytic Cells: Use electrical energy to drive non-spontaneous reactions. Example: electrolysis of water to produce hydrogen and oxygen. 👉Corrosion and Prevention: Rusting of iron is an electrochemical process, and methods like galvanization prevent it. 👉Industrial Applications: Electrochemical processes are used in electroplating, metal refining, and water purification. Understanding these concepts is important for practical applications in energy generation, material production, and environmental conservation. #Chemistry @knowledgebach9

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Biology 1.Which organ produces bile to aid in fat digestion? a) Stomach b) Pancreas c) Liver d) Small intestine (Answer: c) Liver 2.What is the main function of the small intestine? a) Absorption of nutrients b) Storage of waste c) Production of saliva d) Breaking down proteins only (Answer: a) Absorption of nutrients 3.Which enzyme in saliva begins the digestion of carbohydrates? a) Pepsin b) Amylase c) Lipase d) Trypsin (Answer: b) Amylase 4.Where does protein digestion begin? a) Mouth b) Esophagus c) Stomach d) Large intestine (Answer: c) Stomach 5.What is the function of the large intestine? a) Absorption of water b) Digestion of fats c) Breaking down proteins d) Production of bile (Answer: a) Absorption of water 6.Which of the following is NOT part of the digestive system? a) Esophagus b) Lungs c) Pancreas d) Stomach (Answer: b) Lungs 7.What is the role of the pancreas in digestion? a) Storing bile b) Producing digestive enzymes c) Absorbing nutrients d) Producing saliva (Answer: b) Producing digestive enzymes 8.What prevents food from entering the windpipe when swallowing? a) Esophagus b) Epiglottis c) Trachea d) Liver (Answer: b) Epiglottis 9.Which part of the digestive system is responsible for breaking down food into a semi-liquid mixture called chyme? a) Small intestine b) Large intestine c) Stomach d) Liver (Answer: c) Stomach 10.Which of the following is a function of the stomach? a) Producing insulin b) Storing bile c) Breaking down food using acid and enzymes d) Absorbing most nutrients (Answer: c) Breaking down food using acid and enzymes #biology @knowledgebach9

Biology 1.Proteins are made up of amino acids. (True) 2.Lipids are soluble in water. (False) 3.Carbohydrates provide the main source of energy for the body. (True) 4.Enzymes are a type of protein. (True) 5.Lipids contain less energy per gram than carbohydrates. (False) 6.Cell membranes are primarily composed of carbohydrates. (False) 7.Starch is a complex carbohydrate found in plants. (True) 8.Proteins do not play a role in muscle building and repair. (False) 9.Lipids include fats, oils, and steroids. (True) 10.Glucose is an example of a simple carbohydrate. (True)

Chemistry 1.Acids have a pH greater than 7. (False) 2.Bases turn red litmus paper blue. (True) 3.Metal oxides react with acids to form salt and water. (True) 4.Salts are formed only by the reaction of acids with metals. (False) 5.All oxides are acidic in nature. (False) 6.A strong acid completely ionizes in water. (True) 7.Limewater (Ca(OH)₂) is an acidic solution. (False) 8.The reaction between an acid and a base is called a neutralization reaction. (True) 9.Non-metal oxides generally form acidic solutions when dissolved in water. (True) 10.Table salt (NaCl) is formed by the reaction of hydrochloric acid (HCl) with sodium hydroxide (NaOH). (True) #Chemistry https://t.me/knowledgebach9

26. Which of the following is an example of an oxide? a) NaCl b) CO₂ c) NH₃ d) HCl Answer: b) CO₂ 27. What is the chemical formula of baking soda? a) NaCl b) Na₂CO₃ c) NaHCO₃ d) NaOH Answer: c) NaHCO₃ 28. Which element is common in all acids? a) Oxygen b) Hydrogen c) Carbon d) Nitrogen Answer: b) Hydrogen 29. Which gas is used in balloons to make them float? a) Oxygen b) Helium c) Nitrogen d) Carbon dioxide Answer: b) Helium 30. What is the color of copper sulfate (CuSO₄) in its hydrated form? a) White b) Green c) Blue d) Red Answer: c) Blue 31. Which acid is found in lemons? a) Sulfuric acid b) Citric acid c) Hydrochloric acid d) Acetic acid Answer: b) Citric acid 32. Which compound is responsible for the hardness of water? a) NaCl b) CaCO₃ c) H₂O₂ d) NH₃ Answer: b) CaCO₃ 33. Which gas is produced when limestone is heated strongly? a) Hydrogen b) Carbon dioxide c) Oxygen d) Nitrogen Answer: b) Carbon dioxide 34. Which of the following is a weak acid? a) HCl b) H₂SO₄ c) CH₃COOH d) HNO₃ Answer: c) CH₃COOH 35. What is the common name for NaOH? a) Baking soda b) Bleach c) Caustic soda d) Table salt Answer: c) Caustic soda 36. Which of the following gases is used in welding? a) Oxygen b) Acetylene c) Helium d) Carbon dioxide Answer: b) Acetylene 37. Which acid is present in vinegar? a) Hydrochloric acid b) Acetic acid c) Nitric acid d) Sulfuric acid Answer: b) Acetic acid 38. Which gas has the chemical formula O₃? a) Oxygen b) Ozone c) Carbon dioxide d) Nitrogen dioxide Answer: b) Ozone 39. What is the primary use of hydrochloric acid in the stomach? a) Digestion of proteins b) Absorption of water c) Production of enzymes d) Breaking down carbohydrates Answer: a) Digestion of proteins 40. Which of the following compounds is used as a drying agent? a) H₂O b) CaCl₂ c) NH₄OH d) NaHCO₃ Answer: b) CaCl₂ 41. Which of the following is a greenhouse gas? a) Oxygen b) Carbon dioxide c) Nitrogen d) Argon Answer: b) Carbon dioxide 42. Which gas is used in light bulbs? a) Helium b) Neon c) Argon d) Oxygen Answer: c) Argon 43. What is the main component of natural gas? a) Ethane b) Propane c) Methane d) Butane Answer: c) Methane 44. What is the common name of MgSO₄? a) Epsom salt b) Table salt c) Baking soda d) Bleach Answer: a) Epsom salt 45. What happens when iron reacts with oxygen and water? a) Rusting b) Melting c) Crystallization d) Sublimation Answer: a) Rusting 46. What is the main component of acid rain? a) Sulfuric acid b) Hydrochloric acid c) Acetic acid d) Phosphoric acid Answer: a) Sulfuric acid 47. What is the chemical formula for hydrogen peroxide? a) H₂O b) H₂O₂ c) H₂SO₄ d) HCl Answer: b) H₂O₂ 48. Which of the following is NOT an example of a base? a) NaOH b) KOH c) HCl d) Ca(OH)₂ Answer: c) HCl 49. Which metal reacts with water to produce hydrogen gas? a) Copper b) Iron c) Sodium d) Gold Answer: c) Sodium 50. Which gas is used in fire extinguishers? a) Oxygen b) Carbon dioxide c) Hydrogen d) Nitrogen Answer: b) Carbon dioxide #Chemistry @knowledgebach9