Page 145 - text book form physics kssm 2020

Chapter 4
Heat
Figure 4.15 shows the cooling curve when an object changes its state from gas to solid.

PQ – Gas cools to
boiling point
‡ Heat is released
‡ Temperature decreases
Temperature ‡ Kinetic energy of RS – Liquid cools to
molecules decreases freezing point
64748 ‡ Heat is released
P ‡ Temperature decreases
‡ Kinetic energy of TU – Solid cools
Gas molecules decreases ‡ Heat is released
Gas and 64748 ‡ Temperature decreases
Boiling point Q liquid R ‡ Kinetic energy of
Liquid molecules decreases
64748
S Liquid and solid T
Freezing point
Solid

U

0 64748 6447448 Time
Condensation Freezing
Gas Î Liquid Liquid Î Solid
Q – Gas starts to condense S – Liquid starts to freeze
QR – Gas is condensing ST – Liquid is freezing
R – The whole of the gas has condensed T – The whole liquid has frozen
‡ /DWHQW KHDW LV UHOHDVHG DQG PROHFXODU ‡ /DWHQW KHDW LV UHOHDVHG VR WKDW ERQG
bond is formed between molecules is strengthened
‡ 0ROHFXOHV PRYH WKURXJKRXW WKH OLTXLG ‡ 0ROHFXOHV YLEUDWH DURXQG D IL[HG SRVLWLRQ
‡ .LQHWLF HQHUJ\ RI PROHFXOHV GRHV QRW ‡ .LQHWLF HQHUJ\ RI PROHFXOHV GRHV QRW GHFUHDVH
decrease ‡ &RQVWDQW WHPSHUDWXUH
‡ &RQVWDQW WHPSHUDWXUH

Figure 4.15 Cooling curve

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4.3.2 139
4.3.2