Chemistry - States of Matter - Quick Guides

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Study GuideChemistry–States of Matter1. Quiz: Solids, Liquids, and Gases1.QuestionWhich of the following isnota common state of matter under ambient conditions?Answer Choices•Solid•Liquid•PlasmaCorrect AnswerPlasmaWhy This is CorrectUnder normal or ambient conditions (room temperature and normal pressure), matter usually existsas asolid,liquid, orgas.Plasmais a high-energy state of matter that forms only at very high temperatures, such as in stars orlightning. It isnot commonly found under everyday conditions.For Example•Ice is asolid•Water is aliquid•The Sun containsplasma2.QuestionThe term “fluids” collectively refers to

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Study GuideAnswer Choices•Liquids and gases•Solids and liquids•Solids and gasesCorrect AnswerLiquids and gasesWhy This is CorrectFluids are substances that can flow and do not have a fixed shape. Bothliquidsandgasescan flowand take the shape of their container, so they are called fluids.For ExampleWater (a liquid) and air (a gas) can both flow, but solids like stone cannot.3.QuestionA solid can be referred to as havingAnswer Choices•indefinite volume and definite shape•definite shape and definite volume•indefinite shape and definite volumeCorrect AnswerDefinite shape and definite volumeWhy This is CorrectA solid has particles that are tightly packed and fixed in position. Because of this, a solid keeps itsown shapeanddoes not change its volumeregardless of the container.For ExampleA stone or a book keeps the same shape and size wherever it is placed.

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Study Guide4.QuestionSolids that have an organized, regular repeating structure areAnswer Choices•amorphous•crystalline•colloidalCorrect AnswercrystallineWhy This is CorrectCrystalline solids have particles arranged in a fixed, orderly, and repeating pattern throughout thesolid. This regular arrangement gives them definite shapes and characteristic properties.For ExampleCommon salt and sugar are crystalline solids because their particles are arranged in a regular latticestructure.5.QuestionMolecules of a liquid haveAnswer Choices•Strong intermolecular forces of attraction and are in a fixed position•Weak intermolecular forces of attraction and are randomly placed•Moderate to strong intermolecular forces of attraction and are able to shift positionsCorrect AnswerModerate to strong intermolecular forces of attraction and are able to shift positions

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Study GuideWhy This is CorrectIn liquids, the molecules attract each other more strongly than in gases but not as strongly as insolids. Because of thismoderate to strong intermolecular attraction, the molecules stay closetogether but arenot fixed in one place. They can move and slide past one another, which allowsliquids to flow and take the shape of their container.For ExampleWater molecules stay close together in a glass but can move freely, allowing the water to flow whenpoured.6.QuestionMolecules of a gas haveAnswer Choices•very weak intermolecular forces of attraction between the molecules•strong intermolecular forces of attraction between molecules yet are able to shift positions•weak intermolecular forces of attraction between molecules yet are set in fixed positionsCorrect Answervery weak intermolecular forces of attraction between the moleculesWhy This is CorrectIn gases, the molecules are far apart from each other. Because of this large distance, theintermolecular forces of attraction arevery weak, allowing gas molecules to move freely andrandomly in all directions.For ExampleAir spreads out to fill the entire room because gas molecules are not strongly attracted to oneanother.7.QuestionWhat determines the physical state of a substance?

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Study GuideAnswer Choices•the number of moles present in the sample•the pressure placed on it and the temperature•the volume occupied at the time of investigationCorrect Answerthe pressure placed on it and the temperatureWhy This is CorrectThe physical state of a substance (solid, liquid, or gas) depends mainly ontemperature andpressure.•Temperature affects the kinetic energy of particles.•Pressure affects how closely the particles are packed.Together, these two factors determine whether particles stay tightly packed (solid), move past eachother (liquid), or move freely (gas).For ExampleWater becomes ice at low temperature and steam at high temperature, even though the amount ofsubstance remains the same.8.QuestionAt room temperature (22°C) and normal atmospheric pressure, water exists as aAnswer Choices•solid•liquid•gas

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Study GuideCorrect AnswerliquidWhy This is CorrectAt 22 °C and normal atmospheric pressure, water has enough energy for its molecules to move freelywhile still remaining close together. This behavior is characteristic of a liquid state.9.QuestionDuring any phase change, heat energy isAnswer Choices•either absorbed or released•held constant always•not a consideration in a physical changeCorrect Answereither absorbed or releasedWhy This is CorrectDuring a phase change (such as melting, freezing, boiling, or condensation), heat energy is eitherabsorbed or released to change the state of matter. The temperature remains constant during thephase change, but energy is still involved in breaking or forming intermolecular forces.For ExampleIce absorbs heat to melt into water, and water releases heat to freeze into ice.10.QuestionDuring any phase change, attractive forces between molecules areAnswer Choices•unchanged•not a consideration in a physical change•being broken or being formed

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Study GuideCorrect Answerbeing broken or being formedWhy This is CorrectDuring a phase change (such as melting, freezing, boiling, or condensation), the substance does notchange its chemical identity. Instead, energy is used tobreak or form intermolecular attractiveforcesbetween molecules. These changes in attraction allow molecules to move closer together orfarther apart, resulting in a change of state.For ExampleWhen ice melts into water, energy breaks some of the attractive forces holding water molecules tightlyin place, allowing them to move more freely.11.QuestionIn which physical change is heat energy absorbed?Answer Choices•Melting•Freezing•CondensingCorrect AnswerMeltingWhy This is CorrectHeat energy is absorbed duringmeltingbecause particles gain energy to overcome the attractiveforces holding them in a solid structure.For ExampleWhen ice melts into water, it absorbs heat from the surroundings to change from a solid to a liquid.

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Study Guide12.QuestionAt a pressure of 1.0 atm, when water is heated to 100°C itAnswer Choices•freezes•condenses•vaporizesCorrect AnswervaporizesWhy This is CorrectAt normal atmospheric pressure (1.0 atm), 100°C is the boiling point of water. At this temperature,liquid water changes into water vapor. This process is called vaporization.For ExampleWhen water is boiled in an open pot, it turns into steam and escapes into the air.13.QuestionIn which physical change is heat energy released?Answer Choices•Melting•Vaporizing•FreezingCorrect AnswerFreezing

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Study GuideWhy This is CorrectHeat energy is released when a substance changes from a liquid to a solid. During freezing, particleslose energy, move more slowly, and come closer together. The excess energy is given off to thesurroundings as heat.For ExampleWhen water freezes to form ice, it releases heat energy into the surrounding environment.2. Phase DiagramsEarlier, you learned that changingtemperaturecan cause water to melt, freeze, or boil. However,pressurecan also cause changes of state.In laboratory experiments,temperature and pressure can be changed independentlyor keptconstant. Because scientists control them separately, they are calledindependent variables.In a graph, these two variables are placed on axes:•Thehorizontal axisshowstemperature•Thevertical axisshowspressure, measured inatmospheres (atm)2.1What Is a Phase Diagram?Aphase diagramis a graph that showswhich physical state (or phase) of a substance is stableat different temperatures and pressures.The wordphasemeans asingle, uniform physical state, such as:•Solid•Liquid•GasIn the phase diagram for water, all three phases have thesame composition (H₂O)but exist indifferent physical states.

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Study Guide2.2Reading the Phase Diagram of WaterFigure 1. The phase diagram for water.•Whether water will be solid, liquid, or gas•How changing temperature or pressure affects its stateMost combinations of temperature and pressure fall inside regions whereonly one phase is stable.Thelinesbetween regions show conditions wheretwo phases can exist together.2.3Changing the Phase of Solid Water (Ice)Figure 2. Changing the phase of solid water.

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