View source for Specific Latent Heat of Vaporisation

==Key Stage 4==
===Meaning===
'''Specific Latent Heat of Vaporisation''' is the [[energy]] required to [[State Change|change the state]] of 1kg of a [[substance]] from [[liquid]] to [[gas]].

===About Specific Latent Heat of Vaporisation===
: The [[SI Unit]] of '''specific latent heat of vaporisation''' is the J/kg.
: Different [[material]]s have a different '''specific latent heat of vaporisation'''.
: '''Specific latent heat of vaporisation''' depends on the strength of the [[bond]]s holding the [[particle]]s to each other in the [[liquid]].
: The '''specific latent heat of vaporisation''' of a [[material]] can be found by [[measuring]] the [[energy]] needed to [[boiling|boil]] 1kg of the [[material]].

{| class="wikitable"
|[[File:BoilingGraph.png|center|500px]]
|-
| style="height:20px; width:500px; text-align:left;" |The increase [[Internal Energy|internal energy]] during the [[time]] when the [[temperature]] remains constant is the [[energy]] required to [[boil|vaporise]] the [[material]]. This can be used to calculate the [[Specific Latent Heat of Vaporisation|'''specific latent heat''' of vaporisation]].
|}

===Equation===
''NB: You do not need to remember this equation but you need to be able to use it.''

Specific Latent Heat = (Energy Transferred)/(Mass)

<math>L_v = \frac{E}{m}</math>

Where:

<math>L_v</math> = The [[Specific Latent Heat of Vaporisation]] of the [[material]].

<math>E</math> = The [[Energy]] [[Energy Transfer|transferred]] to the [[material]] while [[boiling]].

<math>m</math> = The [[mass]] of the [[material]].

===Example Calculations===
{| class="wikitable"
| style="height:20px; width:300px; text-align:center;" |15g of [[Mercury (Element)|Mercury]] requires 4.1kJ of [[energy]] to vaporise at its [[Boiling Point|boiling point]]. Calculate the [[Specific Latent Heat of Vaporisation|'''specific latent heat''' of vaporisation]] of the [[Mercury (Element)|Mercury]] correct to two [[Significant Figures|significant figures]].
| style="height:20px; width:300px; text-align:center;" |A pan containing 500g of [[water]] at 100°C is [[heat]]ed with an [[energy]] of 1.13kJ until all of the [[water]] has been vaporised. Calculate the [[Specific Latent Heat of Vaporisation|'''specific latent heat''' of vaporisation]] of the [[water]] [[steam]] correct to two [[Significant Figures|significant figures]].
|-
| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities in [[SI Unit]]s'''

E = 4.1kJ = 4.1x10<sup>3</sup>J

m = 15g = 15x10<sup>-3</sup>kg
| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities in [[SI Unit]]s'''

E = 1.13kJ = 1.13x10<sup>3</sup>J

m = 500g = 0.5kg
|-
| style="height:20px; width:300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''

<math>L_v = \frac{E}{m}</math>

<math>L_v = \frac{4.1 \times 10^3}{15 \times 10^{-3}}</math>

<math>L_v = 2.733 \times 10^5 J/kg</math>

<math>L_v \approx 2.7 \times 10^5 J/kg</math>
| style="height:20px; width:300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''

<math>L_v = \frac{E}{m}</math>

<math>L_v = \frac{1.13 \times 10^3}{0.5}</math>

<math>L_v = 2260 J/kg</math>

<math>L_v \approx 2300 J/kg</math>
|}