Presentation on theme: "Physical & Chemical Changes"— Presentation transcript:
1Physical & Chemical Changes Chapter 3Physical & Chemical Changes
2Properties of MatterPhysical Properties are characteristics of a substance that can be observed without changing the identity of the substance.Ex. Wood is wood whether it is in a house, a toothpick or a baseball bat.Physical Properties that you already learned about:MassVolumeDensityWeightAlso, color, texture, hardness, shape, etc.
3Section 1 - Another Important Physical Property of Matter that we need to study is the… Phases of MatterThere are 4 phases of matter:SolidLiquidGasPlasma
4Section 1 - Solids Have a definite shape and a definite volume Particles (molecules) are packed very close together so no movement can occur except vibrations.2 typesCrystalline solids have particles arranged in regular repeating patterns, ex table salt, quartzAmorphous solids have particles that aren’t arranged in a rigid way, so they can flow slowly, ex – candle wax, silicone rubber.
5Section 1 - LiquidsDo not have definite shape, but do have a definite volumeParticles are close together, but not as close together as a solid.The particles can move past one another, thus allowing it to flow.They take the shape of the container they are in.One important Property of liquids is viscosityViscosity – the resistance of a liquid to flow; ex honey has a higher viscosity than water.
6Do not have definite shapes or volumes. Section 1 - GasesDo not have definite shapes or volumes.Particles are very far apart and move very freely.
7NOTE: Plasma TV’s ARE NOT made of Plasma!!!! Section 1 - PlasmaExtremely high in energy and temperature.Matter becomes so hot that the electrons separate from the nucleus.Plasma is rare on earth (ex. lightning & parts of flames), but is the most common form of matter in the universe because….Stars are made of plasma and stars are quite common.NOTE: Plasma TV’s ARE NOT made of Plasma!!!!
8Section 1 – More About Gases 2 scientists studied how gases behave in relation to pressure and temperature.Boyle’s Law – pressure & volume are inversely (indirectly) relatedThe higher the pressure, the lower the volume.The lower the pressure, the higher the volumeCharles’ Law – temperature & volume are directly relatedThe higher the temperature, the higher the volumeThe lower the temperature, the lower the volume
9Section 1 – Gas LawsBoyle’s Law – pressure & volume are inversely (indirectly) relatedP1 = V2P2 V1Charles’ Law – temperature & volume are directly relatedV1 = V2T1 T2
10Section 1 – Using the Gas Laws If 50 mL of oxygen gas is compressed from 20 atm of pressure to 40 atm of pressure, what is the new volume? (assume constant temp)GIVEN:V1 = 50 mLV2=?P1 = 20 atmP2 = 40 atmWORK:P1 = V2P2 V120 atm = V240 atm mL1000 atm mL = 40 atm (V2)40 atm atmV2 = 25 mL
11Section 1 - Using the Gas Laws A gas occupies a volume of 100 mL at 300° C. At what temperature will the gas have a volume of 200 mL?GIVEN:V1 = 100 mLV2= 200 mLT1 = 300° CT2 = ?WORK:V1 = V2T1 T2100 mL = 200 mL300° C T2100 mL (T2) = 60,000° C mL100 mL mLT2 = 600° C
12Section 2 - Phase Changes Phase changes are caused by adding or taking away thermal energyThermal energy is fancy schmancy word for HEAT!!!!!!Phase changes of matter are called:MeltingFreezingVaporizationCondensationSublimation
13Section 2 - Phase Changes cont’d Phase changes are Physical ChangesThis is because the substance is changes its form, but it is not changing the kind of substance it is chemically.Ex – water (H2O) is still water whether it is in an ice cube, liquid water or water vapor)
14Section 2 - Solid – Liquid Phase Changes Melting - Solid to LiquidMelting point – temperature at which a substance will meltFreezing – Liquid to SolidFreezing Point – temperature at which a substance will freeze.The melting point of a substance is the same temperature as its freezing point!!
15Section 2 - Liquid - Gas Phase Changes Vaporization – Liquid to Gas2 kinds:Evaporation – Liquid to Gas only at the surface of liquidBoiling – Liquid to Gas in the entire liquidTemperature at which a substance boils is the boiling point
16Section 2 - Gas - Liquid Phase Changes Condensation – Gas to LiquidThe gas molecules lose thermal energy (heat) and slow down. Then, as they come together, they join to form a liquid.
17Section 2 - Solid - Gas Phase Changes Sublimation – Solid directly to GasExamplesSolid carbon dioxide (dry ice) changes directly into a gasMoth balls
18As you move to the right, is heat being added to or given off by the substance?
19As you move to the right, what is happening to the space between the molecules?
20As you move to the left, is heat being added to or given off by the substance?
21As you move to the left, what is happening to the space between the molecules?
22What temperature is this if this substance is water?
23What temperature is this if this substance is water?
24Let’s Review for a Moment… Phase of matter, color, shape, hardness, mass, volume, density were all what kind of properties of matter?PHYSICAL PROPERTIES!!! Right……
25Section 3 - Physical Properties - Definition Physical Properties – properties of matter that can be observed using the senses without changing the identity of a substance.What kind of property would describe a change of matter into another substance?
26Section 3 - Chemical Properties and Changes Chemical Properties – the properties that describe the ability of a substance to change into a different substance.Flammability – the ability to burnEx wood is flammableSupporting burning – the ability of a substance to be used during burning.Ex – oxygen is needed for wood to burn but the oxygen itself doesn’t burn.
27Section 3 - Chemical Properties and Changes Chemical changes (aka chemical reaction) – the process by which a substance changes into another substance by chemical means.Ex: cars rusting, wood burning, yeast changing sugar into gas in bread, cheese aging, leaves changing color…
28Classify the following as either a physical or chemical change…. An ice cube crackingCarving a piece of marble into a statueBurning woodWax meltingSugar dissolving in tea or coffeePop rocks releasing carbon dioxide into your mouthLeaves changing colors in the fall