Science T1 Final - Past Paper PDF

1. Define chemical change. A chemical change is a change in which one or more new substances are formed. 2. Give three examples of a chemical change. Burning: Carbon dioxide and water form when methane burns in a stove. The wick and wax of a candle, wood, and gasoline all undergo c...

1. Define chemical change. A chemical change is a change in which one or more new substances are formed. 2. Give three examples of a chemical change. Burning: Carbon dioxide and water form when methane burns in a stove. The wick and wax of a candle, wood, and gasoline all undergo chemical changes to form new substances when they burn. Cooking food [roasting, grilling, frying…]: Chemical changes cause vegetables to change color when they are roasted. 3. Define chemical reaction. A chemical reaction is the process that rearranges the atoms in substances into new substances. 4. Define reactant. A reactant is a starting substance that undergoes a chemical change in a chemical reaction. 5. Define product. A product is a substance that results from a chemical reaction. 6. How many reactants and products can be involved in one chemical reaction? Chemical reactions may involve more than one or two reactants and may produce more than one or two products. 7. Is energy needed or released when you break or form a bond during a chemical reaction? Energy is needed to break bonds, and is released when chemical bonds form. 8. How can you detect the change of heat energy during a chemical reaction? We detect the change in heat by measuring temperature (using a thermometer). 9. Give two examples of reactions that involve temperature changes. The reaction that takes place when paper burns gives off heat and warms the surrounding air. The reaction between iron and oxygen to form iron oxide, or rust, also releases heat. 10. What are some examples that provide evidence of a chemical reaction? Change of state: Solid baking soda with liquid vinegar react producing carbon dioxide gas. Change of color: White paper burns to become black ash. Silvery-gray iron rusts to become a characteristic orange color. Light Production: Some chemical reactions give off energy in the form of light (Light sticks glow because of a chemical reaction that gives off light). 11. Define precipitate. A precipitate is a solid that forms when two solutions are mixed together. 12. Give an example of a chemical reaction where the reactants and products have similar physical properties but different chemical properties. A chemical reaction happens when methane burns. Yet, the products and reactants are all colorless gases. 13. In which form are substances found in nature? Give an example. Very few of the substances in nature are pure elements. Almost all of the substances around us are compounds. 14. Give an example of a substance: a. Extracted from nature. Humans extract substances like metals and minerals from nature. b. Invented by chemists. Chemists have invented substances like plastic. 15. Write the word equation for the reaction of decomposition of water into hydrogen and oxygen. The word equation is: water → hydrogen + oxygen 16. Write the chemical equation for the reaction of decomposition of water into hydrogen and oxygen. Water, 𝐻2 𝑂, decomposes to give hydrogen, 𝐻2 and oxygen, 𝑂2. The balanced reaction is: 2𝐻2 𝑂 → 2𝐻2 + 𝑂2 17. Why do scientists use chemical formulas to write chemical equations? Support your answer with an example. The formulas are useful because they show the elements involved in the reaction. The formulas also help to more simply represent long chemical names. Example: The chemical formula for silver nitrate is 𝐴𝑔𝑁𝑂3. This formula tells you that silver nitrate is made up of one silver ion, 𝐴𝑔+ , and one nitrate ion, 𝑁𝑂3−1. 18. What information does reading a chemical equation provide? Reading a chemical equation provides information about the elements involved in the reaction, the reactants, the products, and the states of the reactants and products. 19. How are the states of the reactants and products indicated in chemical reactions? The states of the reactants and products State Symbol are shown by letters in parentheses Solid (s) which are added after the Liquid (l) chemical formula, usually in italic. Gas (g) Dissolved in water (aqueous) (aq) 20. What does the abbreviation “aq” refer to in a chemical equation? The letters aq stand for “aqueous”, meaning the substance is dissolved in water. 21. Write the ionic equation of the following reaction: Zn(s) + CuO(aq) → Cu(s) + ZnO(aq) 𝑍𝑛(𝑠) + 𝐶𝑢+2 (𝑎𝑞) + 𝑂−2 (𝑎𝑞) → 𝐶𝑢(𝑠) + 𝑍𝑛+2 (𝑎𝑞) + 𝑂−2 (𝑎𝑞) 22. Define coefficient. In a chemical equation the coefficients are numbers used to indicate the number of molecules of each substance involved in the reaction. 23. Define balanced equation. In a balanced equation, the number of atoms of each element is the same in the reactants and the products. 24. State the law of conservation of mass. The conservation of mass states that physical or chemical changes do not create or destroy mass (in any reaction the total mass of products must equal the total mass of reactants). 25. How can you balance a chemical equation? Coefficients are placed in front of formulas to balance equations. Subscripts should not be changed because each formula represents a specific substance. Add coefficients one at a time to balance each element. 26. Calculate the total number of each kind of atoms involved in the following chemical reactions: 2𝐻2 𝑂 → 2𝐻2 + 𝑂2 2 atoms Oxygen – 4 atoms Hydrogen 27. What is the ratio of hydrogen to oxygen molecules in the following reaction? 2𝐻2 𝑂 → 2𝐻2 + 𝑂2 The ratio is 2:1. 28. Why are the smallest whole numbers used to balance chemical equations? Scientists use the smallest whole numbers to write balanced equations. Fractions could be used to balance the numbers of atoms of each element, but they would not accurately represent what happens to the molecules. For example, half of a molecule of methane cannot react with one molecule of oxygen. 29. Define chemical energy. Chemical energy is energy that is stored in chemical bonds. 30. What does the chemical energy stored in a molecule depend on? The chemical energy stored in molecule depends on the energy of all of the bonds it contains. 31. What causes the energy exchange in a chemical reactions? All chemical reactions involve changes in energy because bonds are broken and new bonds are formed. 32. Relate energy to breaking and forming chemical bonds. Energy is required to break chemical bonds in the reactants so that atoms can be rearranged. Energy is released when new chemical bonds form between atoms to make products. 33. What is the relationship between the energy of a chemical reaction and the energies of the substances involved in that reaction? The energy released or gained by a chemical reaction is the difference between the energies of the bonds that form and the energies of the bonds that break. 34. Define exothermic reaction. An exothermic reaction is a reaction that gives off heat. 35. What is the evidence of an exothermic reaction? An increase in the temperature of the surroundings is evidence of an exothermic reaction. 36. Define endothermic reaction. An endothermic reaction is a reaction that takes in heat. 37. What is the evidence of an endothermic reaction? Reactions cause a decrease in the temperature of their surroundings. 38. Define reaction rate. A reaction rate is a measure of how fast a reaction occurs. 39. Define concentration. The concentration of a substance in a mixture is defined as the amount of that substance in a given volume of solution. (A dilute solution is a solution with low concentration of solute, while a concentrated solution is a solution with high concentration of solute.) 40.Give an example of a) a fast chemical reaction b) a slow chemical reaction. a) The reaction between methane and oxygen is a fast chemical reaction. b) The reaction between iron and oxygen (rust) is a slow chemical reaction. 41. Are all exothermic reactions faster than endothermic reactions? Explain. Reaction rates vary widely, but they do not depend on whether a reaction is exothermic or endothermic. Both exothermic and endothermic reactions may be fast or slow. 42. List three factors that increase the rate of a reaction. These factors include temperature, particle size, the concentration of reactants, and agitation. 43. How does the temperature affect the rate of a reaction? Give an example. The rate of a chemical reaction usually increases as the temperature increases. Example: When cooking, increasing the temperature makes the food cook faster, and decreasing the temperature makes the food cook slower. 44. How does the contact surface area affect the rate of a reaction? Give an example. Reactions tend to be faster when the size of the reactant pieces is smaller. Crushing and cutting a reactant will decrease the particle size and increase the area of the contact surface between the reactants. Example: a large log will burn slowly because much of the wood is on the inside but chopping the log into smaller pieces will make it burn faster because more of the wood is in contact with the oxygen in air. 45. How does increasing the amount of reactants in a fixed volume affect the rate of a reaction? Give an example. Increasing the concentration of reactants tends to increase the reaction rate. Example: Many fruits give off the gas ethylene, which they need to ripen. Placing the fruits in a closed paper bag makes them ripen faster. The ethylene gas is trapped in the bag, increasing the concentration of the gas around the fruit 46. How does stirring affect the rate of a reaction? Give an example. When you stir or shake a mixture, you are agitating it. Agitation increases reaction rates. Example: Rock collectors use agitation to clean rock samples. Stirring the rocks in the cleaning solution cleans the rocks more quickly than letting the rocks sit in the solution. 47. How does a catalyst affect the rate of a reaction? Give an example. A catalyst is a substance that speeds up a reaction, but is neither a reactant nor a product. Example: Catalysts are used in our bodies, many of the reactions in your body would be too slow to help your body keep functioning. Catalysts that speed up reactions in living organisms are called enzymes. 48. How does grouping chemical reactions into categories help scientists? Grouping chemical reactions into categories helps scientists predict the products of reactions. 49. Give two examples of how scientists classify chemical reactions. The reactions can be classified as exothermic or endothermic based on whether they release or absorb heat. Another simple way to classify reactions is to compare the number of reactants and products to determine if the reactant combined or broke apart into simpler substances. 50. Define synthesis reaction and give examples. A synthesis reaction is a reaction in which two or more reactants combine to make a single product. Examples: Synthesis of (i) sodium chloride, (ii) ammonia, and (iii) carbonic acid. Reactants Product (i) 2Na(s) +𝐶𝑙2(g) → 2NaCl (s) (ii) 𝑁2 (g)+ 3𝐻2 (g) → 2𝑁𝐻3 (g) (iii) 𝐶𝑂2(g)+ 𝐻2 𝑂(l) → 𝐻2 𝐶𝑂3(aq) 51. Why do scientists use synthesis reactions? Give an example. Chemists use synthesis reactions to make large, complex molecules. Chemists used more than 30 steps to make Taxol, a drug used to treat cancer. 52. Define decomposition reaction and give examples. A decomposition reaction is a reaction in which a compound breaks apart into two or more simpler substances. Examples: Decomposition of (i) ammonia, (ii) carbonic acid, and (iii) water. Reactant Products (i) 2𝑁𝐻3 (g) → 𝑁2 (g)+ 3𝐻2 (g) (ii) 𝐻2 𝐶𝑂3(aq) → 𝐶𝑂2(g)+ 𝐻2 𝑂(l) (iii) 2𝐻2 𝑂(l) → 2𝐻2 (g)+ 𝑂2(g) 53. Compare decomposition reaction to synthesis reaction. Support your answer with an example. A decomposition reaction is the reverse of a synthesis reaction. If a reaction releases energy, the reverse reaction will require energy to occur. For example, energy is needed for water to decompose into hydrogen and oxygen. Passing an electric current through water can provide the energy needed to break down water. 54. Give an example of a decomposition reaction that occurs without added energy. Some decomposition reactions occur without added energy. For example, heat is released when hydrogen peroxide, 𝐻2 𝑂2, breaks down into water, 𝐻2 𝑂, and oxygen, 𝑂2. 55. Define combustion reaction and give examples. A combustion reaction is any reaction where a substance combines with oxygen. Examples: Combustion of (i) methane, (ii) propane, (iii) hydrogen, and (iv) magnesium. Reactants Product (i) 𝐶𝐻4 (g)+ 2𝑂2 (g) → 2𝐻2 𝑂(g) + 𝐶𝑂2(g) (ii) 𝐶3 𝐻8 (g) + 5𝑂2 (g) → 4𝐻2 𝑂(g) + 3𝐶𝑂2 (g) (iii) 2𝐻2 (g)+ )+ 𝑂2(g) → 2𝐻2 𝑂(𝑙) (iv) 2𝑀𝑔(s)+ )+ 𝑂2(g) → 2𝑀𝑔𝑂(s) 56. Define hydrocarbons and give examples. Compounds that are made of only carbon and hydrogen are called hydrocarbons. Methane, propane, and the compounds in gasoline are hydrocarbons. 57. What are the products of a combustion reaction between a hydrocarbon and oxygen? The combustion reaction of any hydrocarbon produces the same products—water, 𝐻2 𝑂, and carbon dioxide, 𝐶𝑂2. 58.What does the amount of water and carbon dioxide produced during the combustion of a hydrocarbon depend on? The amount of water and carbon dioxide produced during a reaction depends on the number of carbon and hydrogen atoms in the molecule. [Because the molecules in gasoline contain many carbon and hydrogen atoms, a large amount of carbon dioxide and water is produced during a reaction.] 59. How do living organisms get the energy they need to survive? Living organisms get the energy they need from the energy released by chemical reactions through a process called cellular respiration. 60. What is the overall reaction for cellular respiration? 𝐶6 𝐻12 𝑂6 (𝑠) + 6 𝑂2 (𝑔) → 6 𝐶𝑂2 (𝑔) + 6 𝐻2 𝑂 (𝑔) 61. To what type of reaction does cellular respiration belong? The overall reaction for cellular respiration is the combustion of glucose, 𝐶6 𝐻12 𝑂6. 62. Compare the overall reactions of photosynthesis to that of cellular respiration. The overall reaction for photosynthesis is the reverse of the reaction for cellular respiration. 63. Define replacement reaction. In a replacement reaction, one element replaces another in a compound. Replacement reactions are sometimes called displacement reactions. 64. Define single-replacement reaction and give examples. The reaction between zinc and copper chloride is a single-replacement reaction because one element replaces another in a compound. 65. Define double-replacement reaction and give an example. In a double-replacement reaction, two elements switch places to form two new compounds. The reaction between silver nitrate, 𝐴𝑔𝑁𝑂3 , and sodium chloride, NaCl, is a double-replacement reaction. 66. What causes the energy emitted by uranium? The energy given off by uranium is released because of changes taking place in the nucleus of uranium atoms. 67. Define nuclear reaction. A nuclear reaction is a reaction that changes the nucleus of an atom. 68. Define nuclear radiation. The energy and particles given off during a nuclear reaction are called nuclear radiation. 69. Does the law of conservation of mass always apply to nuclear reactions? Explain. Mass can change during a nuclear change. The mass of the nucleus is slightly less than the total mass of the individual protons and neutrons that make it up. 70. How did Einstein relate mass to energy? In 1905, Albert Einstein published a short article in which he reasoned that mass can change into energy. He stated that energy, E, is mass, m, times the speed of light, c, squared. 𝐸 = 𝑚𝑐 2 71. What does the stability of the nucleus depend on? The stability of a nucleus depends on the number of its protons and neutrons. 72. Define radioactive decay. Radioactive decay is the process by which a nucleus emits, or releases, particles and/or energy. 73. What elements undergo radioactive decay? Give an example. Radioactive elements, such as all elements that have an atomic number greater than 83, undergo radioactive decay. In addition to other elements that have radioactive isotopes such as carbon (carbon-14). 74. Define alpha particle. An alpha particle is made of two protons and two neutrons. 75. What is meant by alpha decay? Alpha decay is the emission of an alpha particle. 76. Define beta particle. A beta particle is simply an electron. But a nucleus contains only neutrons and protons—no electrons. 77. What is meant by beta decay? The emission of a beta particle involves the transformation of a neutron into a proton and an electron. In fact, a neutron detached from its nucleus is very unstable and decays into a proton by emitting an electron—a beta particle. 78. How does beta decay affect the nucleus? Beta decay does not change the mass number because the total number of particles in the nucleus stays the same. However, it does increase the atomic number by one, so the nucleus of a new element is formed. 79. Define gamma ray. A gamma ray is a form of high-energy electromagnetic radiation. 80. What is meant by gamma decay? A gamma decay is the third main type of radioactive decay that does not involve particle emission. It is often given off during alpha or beta decay. Giving off this energy in the form of gamma rays makes the nucleus more stable. 81. Define nuclear fission. Nuclear fission is the process in which a large nucleus splits into two smaller nuclei. Nuclear fission releases neutrons and a large amount of energy. 82. How can the nuclei of uranium-235 be broken apart through nuclear fission? The nuclei of uranium-235 can break apart by hitting them with a neutron. 83. What is the effect of nuclear fission on the total number of protons and neutrons? The total number of protons and neutrons is the same before and after the fission reaction. 84. What is meant by chain reactions? A series of fission reactions is called a chain reaction. In a nuclear chain reaction, the neutrons that are released by one fission reaction hit other nuclei. These nuclei split apart and release more neutrons. 85. Define nuclear fusion. During nuclear fusion, two small nuclei combine to form a larger nucleus. 86. What is the source of energy of the sun? Most of the energy Earth receives comes from the sun, which is powered by nuclear fusion. 87. How do nuclear fusion reactions occur on the sun? The temperature at the center of the sun is about 15 million degrees Celsius, which is hot enough for hydrogen nuclei to undergo nuclear fusion. 1. What were the first signs in early history? The roots of science go back to before recorded history, when people observed the natural world and discovered patterns and correlations in nature. 2. Describe scientific inquiry. The scientific inquiry describes the different ways in which scientists study the natural world and comprises the vast knowledge gained by studying the natural world. 3. What are the two main branches of science? List some areas of study in each branch. Two main branches of science are life sciences, the study of living things, and physical sciences, the study of nonliving things. Life sciences include areas such as anatomy, zoology, botany, and taxonomy; while physical sciences include areas such as geology, astronomy, physics, and chemistry. 4. List some branches of physics Physics includes many topics from which you will investigate in the next years’ mechanics, thermodynamics, vibrations and waves, optics, electricity and electromagnetism, and quantum mechanics. 5. How is mathematics used in science? What is its advantage? Scientists realized that nature can be observed, analyzed, and modeled or described mathematically. By using mathematical models, scientists were able to eliminate any ambiguity that usually occurs by using common language. 6. List the main steps of the method used for scientific inquiry. 7. Identify and explain the first step of scientific inquiry. Give an example. The first step of scientific inquiry is observation. Observation does not only rely on the sense of sight; it also requires the senses of hearing, touch, smell, and taste.Suppose you have crickets in your yard. You notice that the crickets chirp faster on some nights than on others. 8. Identify and explain the second step of scientific inquiry. Give an example. The second step of the scientific inquiry is asking Checkpoints related to your observations. In your attempt to explain what causes crickets to chirp very fast, you ask yourself several Checkpoints: “Does the chirping of crickets depend on their mating season?” 9. What is inference? When you try to find a logical interpretation based on your observations and previous knowledge, you are applying the skill of inference. 10. What is a hypothesis? Give an example. A hypothesis is a reasonable explanation of an observation that can be repeatedly tested by an experiment. EX: The statement “crickets chirp faster when it is warmer” is called a hypothesis. 11. What test groups are needed to perform a controlled experiment? Controlled experiments use two test groups: the control group and the experimental group. 12. What is meant by control group in an experiment? The control group is a standard for comparison. 13. What is meant by experimental group in an experiment? In the experimental group, all factors are kept the same as with the control group, except one 14. What is a variable in an experiment? The factor that we change is called the variable. 15.What is a scientific data? Scientific data includes facts, figures, and other evidence you collect through observation. 16. What are qualitative and quantitative data? Qualitative data are descriptions, such as color, sound, or shape. Quantitative data involve measurements and numbers. 17. How do scientists draw conclusions? Interpreting your data leads you to conclude that the warmer the temperature, the faster the cricket chirps. 18. Why do scientists communicate their results with other scientists? This process allows other scientists to test, challenge, or disprove hypotheses. 19. What do all chemical changes have in common? All chemical changes result in the formation of new substances. 20. What does the energy change during a chemical reaction depend on? When heat is released during a chemical reaction, the temperature of the surroundings increases. When heat is taken in, the temperature of the surroundings decreases. 21. Why is energy in the form of light evidence of a chemical reaction? Some chemical reactions release energy in the form of light. 22. How do changes in state and colour provide evidence of a chemical reaction? The products of a reaction may be in a different state or have a different colour than the reactants have. Therefore, observing these changes is evidence of a chemical reaction. 23. How do the chemical and physical properties of reactants compare to those of the products? The reactants and products may have some similar physical properties. The chemical properties of the reactants are different from those of the products and indicate whether a chemical reaction has occurred or not. 24. What is one example of how chemists have increased the diversity of matter? Chemists have increased the diversity of matter by making new substances, such as plastics, that do not exist in nature. 25. [G] Define chemical change. A chemical change is a change in which one or more new substances are formed. 26. [G] Define chemical reaction. A chemical reaction is the process in which atoms in given substances rearrange into new substances. 27. [G] Define reactant. A reactant is a starting substance that undergoes a chemical change in a chemical reaction. 28. [G] Define product. A product is a substance that results from a chemical reaction. 29. [G] What are some examples that provide evidence of a chemical reaction? Evidence of a chemical reaction include temperature changes, light production, change of state, change of color, and change in chemical properties. 30. How does a chemical equation show the reactants and products of a reaction? A chemical equation uses chemical formulas. The reactants are on the left side of the equation, and the products are on the right side. 31. When can ionic equations be used to represent a reaction? Ionic equations can be used when at least one of the reactants or products is an ionic compound that is dissolved in water. 32. How can you tell that a chemical equation is balanced? For each element, the number of atoms in the reactants equals their number in the products. 33. How can you show that mass is conserved in a reaction? Comparing the total mass of all of the reactants to the total mass of all of the products will show that the mass does not change in a reaction. 35. Why are whole numbers used to balance chemical equations? Chemical equations represent what happens to the particles during a chemical reaction. Since a fraction of a molecule will not react, only whole numbers must be used. 36. [G] Write the chemical equation for the reaction of decomposition of water into hydrogen and oxygen. 2𝐻2 𝑂 → 2𝐻2 + 𝑂2 37. [G] What information does reading a chemical equation provide? the elements involved in the reaction, the reactants, the products, the states of the reactants and products 38. [G] How are the states of the reactants and products indicated in chemical reactions? State Symbol Solid (s) Liquid (l) Gas (g) Dissolved in water (aqueous) (aq) 39. [G] Write the ionic equation of the following reaction: Zn(s) + Cu𝑆𝑂4 (aq) → Cu(s) + Zn𝑆𝑂4 (aq) 𝑍𝑛(𝑠) + 𝐶𝑢+2 (𝑎𝑞) + 𝑆𝑂4−2 (𝑎𝑞) → 𝐶𝑢(𝑠) + 𝑍𝑛+2 (𝑎𝑞) + 𝑆𝑂4−2 (𝑎𝑞) 40. [G] Define balanced equation. A balanced equation is a chemical equation where the number of atoms of each element is the same in the reactants and the products. 41. [G] Compare the mass of products to that of reactants in a balanced chemical equation. In a balanced chemical equation, the total mass of the products equals the total mass of the reactants. 42. [G] How can you balance a chemical equation? Add coefficients one at a time to balance each element. 43. What is the source of energy that is released by rotting leaves? The energy is released by the chemical reactions that cause the leaves to rot. 44. How can you tell if a reaction is exothermic or endothermic? A reaction is exothermic when it releases heat, making its surroundings warmer. It is endothermic when it takes in heat, making its surroundings cooler. 45. How does the concentration of reactants change over time for a reaction that has a fast reaction rate? The amount of reactants will decrease quickly as they change into products. 46. Why are catalysts not reactants? Catalysts are not used up during reactions. 47. [G] Define chemical energy. Chemical energy is energy that is stored in chemical bonds. 48. [G] What causes the energy exchange in a chemical reaction? The breaking of bonds and the formation of new ones 49. [G] Define exothermic reaction. An exothermic reaction is a reaction that gives off heat. 50. [G] Define endothermic reaction. An endothermic reaction is a reaction that takes in heat. 51. [G] Define reaction rate. A reaction rate is a measure of how fast a reaction occurs. 52. [G] List three factors that increase the rate of a reaction. increasing the temperature, increasing the concentration of the reactants, agitation, using a catalyst 53. Why is reaction of sodium and chlorine a synthesis reaction? Sodium and chlorine react to form sodium chloride, so two reactants combine to form one product. 54. Can an element be a reactant in a decomposition reaction? Explain. An element cannot be a reactant in a decomposition reaction because it cannot break down into simpler substances. 55. How are the reactants similar in all combustion reactions? The common reactant is oxygen. 56. How does the combustion of glucose in living organisms differ from burning glucose? The combustion of glucose in living organisms happens in a series of steps so that the energy is released more gradually than when glucose is burned. 57. What happens during a single-replacement reaction? During a single-replacement reaction, one element replaces another in a compound. 58. [G] Define synthesis reaction and give examples. A synthesis reaction is a reaction in which two or more reactants combine to make one product. 59. [G] Define decomposition reaction and give examples. A decomposition reaction is a reaction in which a compound breaks apart into two or more simpler substances. 60. [G] Define combustion reaction and give examples. A combustion reaction is a reaction in which a substance combines with oxygen. 61. [G] Define replacement reaction. A replacement reaction is a reaction in which an element replaces another in a compound. 62. How is a nuclear reaction different from a chemical reaction? A nuclear reaction involves changes to the atomic nucleus, not merely the valence electrons. 63. How does the equation 𝐸 = 𝑚𝑐 2 help explain the change in mass during a nuclear reaction? The equation shows that the mass lost in a nuclear reaction is changed into energy. 64. Why does alpha decay result in the formation of a different element? Alpha decay decreases the number of protons in the nucleus by two, which results in a new element. 65. How does a nucleus change during beta decay? During beta decay, one neutron changes into a proton and a beta particle is released. Therefore, the number of neutrons decreases by one and the number of protons increases by one. 66. Why do fission reactions release a large amount of energy? Some of the mass of the large nucleus changes to energy when it splits apart. 67. Why do fusion reactions occur in the sun but not on Earth? The temperatures in the sun are hot enough for nuclei to collide. Temperatures on Earth are not hot enough for fusion to occur. 68. [G] Define nuclear reaction. nuclear reaction is a reaction that changes the nucleus of an atom. 69. [G] Define nuclear radiation. The energy and particles given off during a nuclear reaction are called nuclear radiation. 70. [G] Define radioactive decay. Radioactive decay is the process by which a nucleus emits, or releases, particles or energy. 71. [G] Define alpha particle. An alpha particle is formed of two protons and two neutrons. 72. [G] Define beta particle. A beta particle is an electron that is released from the nucleus during radioactive decay. 73. [G] Define gamma ray. A gamma ray is a form of high-energy electromagnetic radiation. 74. List some topics of physics. Some topics of physics include optics, mechanics, electricity, electromagnetism, and quantum mechanics. 75. [G] What are the two main branches of science? List some areas of study in each branch. The two main branches of science are physical sciences and life sciences. Life sciences include areas such as anatomy, zoology, botany, and taxonomy; while physical sciences include areas such as geology, astronomy, physics, and chemistry. 76. [G] List the main steps of the method used for scientific inquiry. 1. Make observations. 2. Ask a question. 3. Hypothesize. 4. Do an experiment. 5. Draw conclusions. 6. Communicate your results.