Chapter 2

Energy and Matter

Energy is the capacity to do work.Work is the capacity to move an object over a distance against a resisting force.Three categories of energyKinetic: applies to objects in motionPotential: energy that applies to an objects position, ex. Gravitational, electrical, chemical.Radiant: Light energy

MeasurementUnits: Calorie, jouleCalorie (cal): the amount of heat needed to raise 1 g of water by 1 OC. This is known as the specific heat of water.Calorie (Cal): in food the Cal is equal to 1000 cal or 1kcal.Joule: Named for James Joule, 4.184 J = 1 cal. The joule is an SI unit.4.184 J will raise 1 g of water by 1OC.

TemperatureGalileo Galilei (1564-1642) invented the first thermometer.Gabriel Fahrenheit (1686-1736) thermometer maker, designed his own scale.Anders Celsius (1701-1744) designed around water. 0 OC = freezing, 100 OC = boiling.William Thomson, Lord Kelvin (1824-1907)Absolute scale, absolute zero = 0K or -273.15 OC.1 OC = 1K

TemperatureCentigrade Fahrenheit1.8 x OC + 32 = OFCentigrade KelvinOC + 273.15 = KFahrenheit Centigrade???Which scale is the SI unit?

HEAT CAPACITY AND CALORIMETRY

SPECIFIC HEAT CAPACITYThe heat capacity : the amount of heat energy required to raise the temperature of a substance by 1 o C or 1 K.(Unit : J K-1 or Jo C-1)The specific heat capacity : the amount of heat required to raise the temperature of 1 gram of the substance by 1 o C or 1 K.( unit : J g-1 K-1)

The relationship between the amount of heat (Q) and the specific heat (c) is given by:

Q = mct

m = mass of the substance in gram t = change in temperature]

The specific heat capacity of some substance is given in the following table

SubstanceSpecific heat capacity (J g-1 K-1)Aluminium0.900Methanol2.530Ethanoic acid2.170Water4.180

Example:

Calculate the heat capacity of 60 g of waterThe heat capacity of 60 g water = (60g)(4.180 J g-1 K-1)(1K) = 250.8 J

This means that 250.8 J is required to increase the temperature of 60 g of water by 1 K or 1o C

Calculate the heat required to raise the temperature of 250 g of water from 28 o C to 58 o C.

Using the equation : Q = mcT

Q = mcT = (250g)(4.180 J g-1 K-1)(30K) = 31350 J

TUTORIALCalculate the heat involved when a 5.5g iron nail is cooled from 37 C to 25 C. (c = 0.449 J / g C)

A 774g sample of water at 93.4 C loses 51.83 kJ of heat. Calculate the temperature of the water after losing this amount of heat. (c = 4.184 J / g C)

MatterDefinition: Anything that has mass and takes up space.Examples?What cannot be classified as matter?States:Solid: high density, fixed shape and volume.Liquid: high density, fixed volume, indefinite shape.Gas: low density, indefinite shape and volume.Plasma: low density, indefinite shape and volume. Exists at very high temps.

Phase Change Diagram

Properties and Changes of MatterPhysical properties characteristics that are observed w/o changing the substance. Ex. Density, color, melting/boiling points.Chemical properties characteristics that are observed by altering a substance. Reactivity is the primary example.Like energy, matter is neither created nor destroyed. Law of Conservation of Matter

Elements and CompoundsElement: any substance that cannot be separated into simpler substances by a chemical change.Compound: a substance that contains two or more elements combined in a fixed proportion.Elements and compounds are pure substances.

MixturesA blend of two or more substances.Homogeneous vs. HeterogeneousMethods of separating mixtures: filtration, chromatography, distillation (evaporation), crystallization.

Theory of MatterIs made up of very small particlesIt is always in a continual state of motionHas empty spaces in between particlesUnique for each substancesHeld together by strong attractive forcesEnergy in each particle is affected by temperature

Examples of ParticlesAtomSmallest component element that still retain chemical properties of that element and it is generally made up of a nucleus containing a combination of protons and neutrons and one or more electrons that is bound to the nucleus by electrical attractionSmallest componentretain chemical properties

MoleculeThe smallest particle of a substance that still retains the physical and chemical properties of that substance and is generally made up of two or more atoms.smallest particleretains the physical andchemical properties

IonAn atom or a molecule which has lost or gain one or more electrons resulting in either a net positive or negative charge.

Substance and MixtureElementA pure chemical substance that is made up of only one type of atom. It cannot be broken down further into simpler type of matter by either chemical or physical methods.

Compound - substances that is made up of two or more types of elements bound to one another and can only be separated into simpler particles by chemical means - chemical and physical properties may differ from its component elements - component elements is always in the same ratio

Mixtures - composed of two or more elements and/or molecules that are intermingled hence it is possible to separate them into their different components by physical means - retains many of the properties of its different component

Heterogeneous MixtureMixtures made up of two or more phases

Homogeneous MixtureMixtures are in the same single phase only

Physical & Chemical Properties of Matter

Physical propertiesSolidsVolume and shape is fixedParticles are densely packed together and is held by strong attractive forcesTends to vibrate insteadHigh densityExpansion and compression is very minute

Crystalline solidVery orderly and in 3D arrangement of particlesPattern is repeatingDiamond, iceAmorphous solidArrangement and pattern is randomGlass, wax

LiquidDefinite volume but no definite shape. Takes the shape of containerForce of attraction is slight weaker than that in solidsAbility to flow when poured and spread when spilledHigh densityDifficult to expand and compress

GasNo definite volume and shapeForces of attraction is weakestLarge amount of empty space between particlesNot capable of flowingLow density so easy to compress and expand

PropertiesSolidLiquidGasShapeFixedTakes the shape of the containerTakes the shape of the container

VolumeDefinitedefiniteFills entire containerAbility to flowNoYesYesCompressibleVery slightlyVery slightlyYesVolume change during heatingVery smallSmallLarge

Chemical propertiesChemical properties is determined by subjecting a substance to a change in compositionExamples:Is it acidic or basic?Is it corrosive or not?

Physical & Chemical Changes

Physical ChangeChemical ChangeDefinition No new substances producedRemains the same despite change in physical stateMay require energyRelease of energy may occurFinal substance is different from the initial substanceEnergy released but would require energy to jumpstartPropertiesOutside may look different but inside is still the sameParticles rearrangedForces of attraction could be weaker or strongerNew substance producedParticles of new substance is different from the old substance

ExamplesSugar + waterIce -> waterSolid wax -> liquid waxVinegar + baking soda = CO22HCl + Mg -> H2 + MgCL2

Changes of states of matter

Endothermic when matter gain heat

Exothermic when matter losses heat

Change FromTo HeatExamplesSublimationSolidGas/VapourEndothermicDry iceDepositionGas/VapourSolidExothermicSnowFrostMeltingSolidLiquidEndothermicIce meltingFreezingLiquidSolidExothermicIce freezingEvaporationLiquidGas/VapourEndothermicWater drying under the sunCondensationGas/VapourLiquidExothermicWater droplets breathing on cold mirror

Degree of motion depends on the particular particle interaction with other particles and the amount of energy it possess.Solids : space is smaller. Liquid: larger space. Gas: Huge spaceForces: Ionic, covalent, hydrophobic, hydrophillicHigher temperature = faster movement = higher collision = more space = object expand

**Monotomic gas: NeonDiatomic: N2, CO*Na+, Cl-, H+,Mg2+Positively charged: CationsNegatively charged: Anions*Examples: Na, C, Cl, O2, H2, Cl2*Vibrate due to their internal energy. Cannot move from one place to another*Particles do move but not fast enough or strong enough to overcome the strong attractive forces between particles*Weaker forces compared to solidsBump into the sides of the container = translational energyParticles capable of moving fast and strong enough to overcome the attractive forces between particles*Particles move very fast and strong so as to break away from one another.*Physical properties of each state of matter*