p19_020.pdf

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Chapter 19 - 19.20
20. (a) We use ρ = m/V and ∆ ρ =∆( m/V )= m ∆(1 /V )
m V/V 2 =
ρ (∆ V/V )=
3 ρ (∆ L/L ) .
The percent change in density is
ρ
ρ =
L =
3(0 . 23%)=
0 . 69% .
(b) Since α =∆ L/ ( L T )=0 . 23
×
10 2 / (100 C
0 . 0 C) = 23
×
10 6 / C , the metal is aluminum
(using Table 19-2).
3 L
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