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Exam Questions 5. In the potassium chlorate and gummy bear lab, what happens when potassium chlorate is heated? ○ A) It produces oxygen gas ○ B) It changes color ○ C) It forms salt crystals ○ D) It absorbs water 7. What does the pH scale measure?...

Exam Questions 5. In the potassium chlorate and gummy bear lab, what happens when potassium chlorate is heated? ○ A) It produces oxygen gas ○ B) It changes color ○ C) It forms salt crystals ○ D) It absorbs water 7. What does the pH scale measure? ○ A) Temperature ○ B) Acidity or basicity ○ C) Density ○ D) Concentration of salts 8. What is the main purpose of a nuclear reactor in a power plant? ○ A) To produce electricity by burning coal ○ B) To create energy through nuclear fission ○ C) To use the sun’s energy for power ○ D) To produce wind energy 9. When rounding to 2 significant figures, what is 4.756? ○ A) 4.8 ○ B) 4.75 ○ C) 4.76 ○ D) 4.7 10. In an atom, where are protons located? A) In the nucleus B) In the electron cloud C) In the outer shell D) In the bonds between atoms 13. In a crystal growth lab, which of the following factors affects the size of the crystals?  A) The amount of light in the room B) The temperature of the solution C) The volume of the solution D) The shape of the container 14. What does the term "oxidation" mean in the rust lab? A) The absorption of water B) The loss of electrons from a substance C) The release of hydrogen gas D) The formation of ice 15. In the sodium nitrate and water lab, what happens when sodium nitrate dissolves in water? A) It turns into a gas B) It releases energy C) It breaks into sodium ions and nitrate ions D) It evaporates 21. What does the term "current" refer to in an electrical circuit? A) The amount of heat produced B) The flow of electric charge C) The resistance in the circuit D) The amount of power consumed 22. Voltage is often described as: A) The speed of electrons B) The pressure that pushes electrons through a circuit C) The size of the battery D) The number of wires in the circuit 24. When two solutions are mixed and a solid forms, the solid is called a: A) Supersaturated solution B) Catalyst C) Precipitate D) Gas 25. What does it mean for a solution to be supersaturated? A) It has dissolved more solute than it can normally hold B) It has too much solvent C) It cannot dissolve any more solute D) It has completely crystallized 26. Which of the following terms describes the arrangement of atoms in a crystal structure? A) Random B) Ordered and repeating pattern C) Single-layered D) Irregular 27. What is the SI unit for mass? A) Meter B) Kilogram C) Mole D) Second 28. Gravity is best defined as: A) A force that pushes objects upwards B) A force that pulls objects toward the center of the Earth C) The mass of an object D) The speed of falling objects 29. If you increase both the mass and the volume of an object equally, what happens to its density? A) It increases B) It decreases C) It stays the same D) It becomes zero 30. What is the role of a catalyst in a chemical reaction? A) It speeds up the reaction without being consumed  B) It slows down the reaction C) It gets consumed in the reaction D) It produces energy for the reaction 31. An exothermic reaction: A) Absorbs heat B) Releases heat C) Stays at room temperature D) Produces electricity 32. When a compound decomposes, it: A) Combines with oxygen B) Breaks down into simpler substances C) Releases water D) Turns into a gas 35. After a chemical reaction, the solid material left behind is called: A) Precipitate B) Catalyst C) Residue D) Anion 37. Static electricity occurs when: A) There is a steady flow of electrons in a conductor B) Electric charges accumulate on the surface of a material C) Electric charges move through an insulator D) Objects generate light 38. Which of the following is an example of static discharge? A) A battery powering a lightbulb B) A lightning bolt C) A circuit breaking D) A neon sign turning off 39. A conductor allows electricity to pass through it. Which of the following is an example of a conductor? A) Glass B) Rubber C) Copper D) Wood 40. The SI unit for measuring electric current is: A) Volt B) Ampere C) Kelvin D) Candela 41. pH importance in daily life? A) pH is used to measure electricity in some situations B) pH can help identify dangerous substances in food and water C) pH measures how well materials conduct heat D) pH is mostly used in testing for gases 42. Difference in mass despite same size in a density lab? A) The objects are made of different materials, so their densities differ B) The larger object must have less mass per unit volume C) The objects likely have the same density because they are the same size D) One object is probably hollow inside 48. Why don't noble gases react easily with other elements? A) Noble gases are stable because they have full electron shells B) Noble gases are too heavy to bond with smaller atoms C) Noble gases lose electrons too easily to form bonds D) Noble gases only bond with metals, so reactions are rare 52. Why does oxidation happen to metals like iron when exposed to air and moisture? A) Oxygen from the air removes electrons from the metal B) The moisture adds heat to the metal, causing it to break down C) The metal gains electrons, forming rust D) Air evaporates water from the metal, causing rust to appear 53. Why does the gummy bear burn so vigorously after being added to the heated potassium chlorate? A) Potassium chlorate reacts with the sugar in the gummy bear, producing heat and oxygen B) The gummy bear is made of combustible rubber C) The potassium chlorate evaporates the water in the gummy bear D) The gummy bear absorbs the oxygen from the air 54. Why is static electricity a concern in industrial settings? A) Static electricity can damage equipment by creating heat B) Static discharges can ignite flammable materials C) Static electricity builds up when materials are too cold D) Static electricity slows down production in factories 55. Why does neon gas glow when exposed to electricity? A) Neon atoms emit light when their electrons return to lower energy levels B) Neon produces light because it conducts heat C) Neon glows because it is unstable when exposed to electricity D) Neon only glows when it becomes a solid at low temperatures 58. Difference between solutions and mixtures? A) Solutions have solutes dissolved in solvents, while mixtures have components that can be separated easily B) Solutions are solid, while mixtures are always liquid C) Solutions form when liquids are mixed with gases, while mixtures are solids D) Solutions and mixtures are basically the same thing, so there’s no difference 71. Is the reaction 2 H₂ + O₂ → 2 H₂O balanced as written? A) Yes B) No C) Sometimes D) It depends 74. Is the reaction 2 KClO₃ → 2 KCl + 3 O₂ balanced as written?  A) Yes B) No C) Only with a catalyst D) Only under high pressure 84. A stone has a mass of 300 g and a volume of 150 cm³. What is its density? A) 1 g/cm³ B) 2 g/cm³ C) 3 g/cm³ D) 0.5 g/cm³ 85. An object has a density of 1.2 g/cm³ and a volume of 500 cm³. What is its mass? A) 600 g B) 550 g C) 450 g D) 500 g 86. A liquid has a density of 0.8 g/cm³ and a mass of 400 g. What is its volume? A) 320 cm³ B) 500 cm³ C) 450 cm³ D) 250 cm³ 91. In a simple electrical circuit, what happens if the circuit is open? A) The current flows continuously B) The current stops flowing C) The voltage increases D) The resistance decreases 92. Gunpowder contains sulfur, charcoal, and potassium nitrate. When ignited, it produces heat, light, and gases. This reaction is an example of: A) An endothermic reaction B) A combustion reaction C) A decomposition reaction D) An acid-base neutralization 93. What process can help form larger crystals from a saturated solution? A) Rapid cooling of the solution B) Gradual cooling of the solution C) Adding more solute immediately D) Stirring the solution continuously 94. Cations are positively charged ions, while anions are negatively charged. Which of the following statements is correct? A) Cations form when an atom gains electrons B) Anions form when an atom loses electrons C) Cations form when an atom loses electrons D) Anions form when an atom gains protons 95. Which of the following numbers is written correctly with three significant figures? A) 0.0450 B) 6.02 C) 4500 D) 12.30 96. In a lava lamp, why do the oil and water not mix? A) The oil is less dense than the water B) The oil is denser than the water C) Oil and water have different boiling points D) Oil and water are immiscible due to their molecular structures 97. Which of the following describes an exothermic reaction? A) Energy is absorbed from the surroundings B) Energy is released to the surroundings C) The temperature of the surroundings decreases D) No energy is exchanged with the surroundings 99. Which of the following is an example of a chemical reaction? A) Water boiling B) Dissolving sugar in water  C) Rust forming on iron D) Ice melting 102. Why does the gummy bear burn so vigorously after being added to the heated potassium chlorate? A) Potassium chlorate reacts with the sugar in the gummy bear, producing heat and oxygen B) The gummy bear is made of combustible rubber C) The potassium chlorate evaporates the water in the gummy bear D) The gummy bear absorbs the oxygen from the air 106. What residue is left over after the gummy bear has been completely combusted in the presence of potassium chlorate? A) Potassium nitrate B) Water and carbon dioxide C) Potassium chloride D) Potassium carbonate ### **Restated Questions:** --- 111. **What is the main role of potassium nitrate (KNO₃) in the black powder used in model rocket engines?** - A) It acts as a fuel source - B) It provides oxygen for the combustion of charcoal - C) It lowers the ignition temperature - D) It absorbs heat during the combustion process --- 113. **In the combustion of black powder, what role does charcoal (carbon) play?** - A) It acts as the oxidizer - B) It is the primary fuel, providing energy for the reaction - C) It reacts with sulfur to produce sulfur dioxide - D) It decomposes into water and carbon dioxide --- 117. **Which type of reaction describes the breakdown of potassium nitrate (KNO₃) when black powder is ignited?** - A) Synthesis reaction - B) Endothermic reaction - C) Decomposition reaction - D) Double displacement reaction --- 5. **A** – Potassium chlorate decomposes when heated, releasing oxygen gas, which fuels the combustion of the gummy bear. --- 7. **B** – The pH scale measures how acidic or basic a substance is. --- 8. **B** – A nuclear reactor produces energy through the process of nuclear fission, not by burning coal. --- 9. **A** – When rounding to two significant figures, 4.756 rounds to 4.8. --- 10. **A** – Protons are located in the nucleus of an atom, along with neutrons. --- 13. **B** – Temperature is the most significant factor affecting crystal size, especially when solutions are cooled gradually. --- 14. **B** – Oxidation refers to the loss of electrons from a substance, commonly leading to rust formation. --- 15. **C** – Sodium nitrate dissociates into sodium and nitrate ions when it dissolves in water. --- 21. **B** – Current refers to the flow of electric charge in a circuit. --- 22. **B** – Voltage is often described as the "pressure" that pushes electrons through a circuit. --- 24. **C** – When two solutions are mixed and a solid forms, the solid is called a precipitate. --- 25. **A** – A supersaturated solution contains more solute than the solvent can typically hold at a given temperature. --- 26. **B** – A crystal structure has an ordered and repeating pattern of atoms. --- 27. **B** – The SI unit for mass is the kilogram (kg). --- 28. **B** – Gravity is the force that pulls objects toward the center of the Earth. --- 29. **C** – If mass and volume increase proportionally, the density stays the same because density is mass divided by volume. --- 30. **A** – A catalyst speeds up a chemical reaction without being consumed in the process. --- 31. **B** – Exothermic reactions release heat into the surroundings. --- 32. **B** – When a compound decomposes, it breaks down into simpler substances. --- 35. **C** – The solid material left after a chemical reaction is called residue. --- 37. **B** – Static electricity occurs when electric charges accumulate on the surface of a material. --- 38. **B** – A lightning bolt is an example of static discharge, where built-up charges are suddenly released. --- 39. **C** – Copper is an example of a conductor, which allows electricity to pass through it. --- 40. **B** – The SI unit for measuring electric current is the ampere (A). --- 41. **B** – pH is important for identifying dangerous substances in food and water. --- 42. **A** – If objects of the same size have different masses, they must have different densities due to the material they are made of. --- 48. **A** – Noble gases do not react easily because they have full electron shells, making them stable. --- 52. **A** – Oxidation happens when oxygen from the air removes electrons from the metal, leading to rust. --- 53. **A** – Potassium chlorate reacts with the sugar in the gummy bear, releasing heat and oxygen, fueling the combustion. --- 54. **B** – Static discharges in industrial settings can ignite flammable materials, posing a safety hazard. --- 55. **A** – Neon atoms emit light when their electrons return to lower energy levels after being excited by electricity. --- 58. **A** – Solutions have solutes dissolved in solvents, while mixtures have components that can be easily separated physically. --- 71. **A** – The reaction 2 H₂ + O₂ → 2 H₂O is balanced because the number of hydrogen and oxygen atoms is equal on both sides. --- 74. **A** – The reaction 2 KClO₃ → 2 KCl + 3 O₂ is balanced because the number of potassium, chlorine, and oxygen atoms are equal on both sides. --- 84. **B** – The density of a stone with a mass of 300 g and a volume of 150 cm³ is calculated as 2 g/cm³ using the formula Density = Mass ÷ Volume. --- 85. **A** – An object with a density of 1.2 g/cm³ and a volume of 500 cm³ has a mass of 600 g (Mass = Density × Volume). --- 86. **B** – A liquid with a density of 0.8 g/cm³ and a mass of 400 g has a volume of 500 cm³ (Volume = Mass ÷ Density). --- 91. **B** – In a simple electrical circuit, if the circuit is open, the current stops flowing. --- 92. **B** – Gunpowder undergoes a combustion reaction, releasing heat, light, and gases when ignited. --- 93. **B** – Gradual cooling of a saturated solution allows larger crystals to form. --- 94. **C** – Cations form when an atom loses electrons, while anions form when an atom gains electrons. --- 95. **A** – The number 0.0450 is correctly written with three significant figures. --- 96. **D** – Oil and water are immiscible due to their molecular structures, which prevents them from mixing. --- 97. **B** – An exothermic reaction releases energy to the surroundings, often in the form of heat. --- 99. **C** – Rust forming on iron is an example of a chemical reaction because it involves a change in the composition of the metal. --- 102. **A** – The gummy bear burns vigorously because potassium chlorate reacts with the sugar, producing heat and oxygen. --- 106. **C** – After the combustion of the gummy bear in potassium chlorate, the residue left is potassium chloride (KCl). --- --- ### **Restated Questions with Answers and Explanations:** --- 111. **What is the main role of potassium nitrate (KNO₃) in the black powder used in model rocket engines?** - **Answer: B) It provides oxygen for the combustion of charcoal** **Explanation:** Potassium nitrate (KNO₃) serves as the **oxidizer** in black powder, releasing oxygen when it decomposes. This oxygen is essential for the combustion of the fuel (charcoal), allowing the fuel to burn even in the absence of atmospheric oxygen. --- 113. **In the combustion of black powder, what role does charcoal (carbon) play?** - **Answer: B) It is the primary fuel, providing energy for the reaction** **Explanation:** Charcoal, which is mostly carbon, acts as the **fuel** in the reaction. When it reacts with oxygen from the decomposed potassium nitrate, it burns and releases energy in the form of heat and gases, which contribute to the thrust of the rocket. --- 117. **Which type of reaction describes the breakdown of potassium nitrate (KNO₃) when black powder is ignited?** - **Answer: C) Decomposition reaction** **Explanation:** The breakdown of potassium nitrate (KNO₃) during combustion is a **decomposition reaction**. It splits into oxygen and potassium compounds (like potassium carbonate), releasing the oxygen needed for the fuel (charcoal) to combust. --- These restated questions with explanations highlight the critical chemical roles of the components in the black powder used in model rocket engines.