Unit 5.1 – Thermal Energy

8/17/2019 Unit 5.1 – Thermal Energy

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[UNIT 5 – PHYSICS FROM CREATION TO COLLAPSE – 5.1] 1

5.1 Thermal Energy

1. Δ E = mc Δ θ2. Internal Energy3. Absolute Zero4. ½m = 3/2k!. E"uat#on o$ state $or an I%eal &as

1. Δ E = mc Δ θ

• Energy trans$erre% to a mater#al' Δ E' #s g#(en by)

Δ E = mc Δ θ

*+ere m #s t+e mass o$ t+e mater#al' kgc #s t+e s,ec#$#c +eat ca,ac#ty' - kg1 1

Δ θ #s t+e c+ange #n tem,erature' • 0,ec#$#c +eat ca,ac#ty' c t+e amount o$ energy re"u#re% to

ra#se t+e tem,erature o$ 1kg o$ a substance by 1.•

#gure !.1 E5,er#ment to %eterm#ne s,ec#$#c +eat ca,ac#ty o$l#"u#%s


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#gure !.2 E5,er#ment to %eterm#ne s,ec#$#c +eat ca,ac#ty o$sol#%s.

2. Internal Energy• #s t+e sum o$ t+e k#net#c an% ,otent#al energ#es o$ all

molecules *#t+#n a g#(en mass.•

Eac+ molecule *#ll conta#n bot+ energ#es.• +e #nternal energy #s ran%omly %#str#bute% as ,er 6a5*ell7olt8mann %#str#but#on.

• As tem,erature r#ses' t+e range o$ %#str#but#on *#ll be s,rea%$urt+er an% t+e #ts ,eak *#ll also mo(e to*ar%s +#g+erenerg#es.

• 0#nce masses o$ t+e same molecules are t+e same' t+e k#net#cenergy #s %e,en%ent on #ts s,ee%.

#gure !.3 6a5*ell7olt8mann %#str#but#on

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[UNIT 5 – PHYSICS FROM CREATION TO COLLAPSE – 5.1] 3

•

3. Absolute Zero

•

• 0#nce k#net#c energy #s ,ro,ort#onal to tem,erature' t+eremust be a ,o#nt *+ere k#net#c energy #s 98ero: an% +encel#ke*#se to tem,erature.

• At t+at tem,erature' molecules sto, (#brat#ng.

4. ½m = 3/2k

• ;oot mean s"uare s,ee% ' *+ere c #s t+e s,ee% o$ t+e ,art#cle

• +e a(erage k#net#c energy o$ any molecule #n a gaseoussam,le #s ,ro,ort#onal to t+e absolute tem,erature o$ t+e gas.

1

2m =

3

2kT

*+ere 7olt8mann constant' k = 1.3 5 123 - 1

•

!. E"uat#on o$ state $or an I%eal &as• 7oyle:s la*

o P∝1

V @ T, m constant

• +arles: la*o V ∝T @ P, m constant

• +e ,ressure la*o P∝T @ T, m constant

•


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Unit 5.1 – Thermal Energy

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