3.3
3.3.1
Ice, Water, Steam
Introduction
In this section we look at the transition from one phase to another, paying particular attention to the amount of energy required to change from solid to liquid to gas
hjhjhhj
Terms
Be able toBy the end of this section you should be familiar with terms such as:
Phase change
Latent heat of fusion
Latent heat of vapourisation
Use latent heats in an energy calculation
3.3.2
Ice, Water, Steam
Wood Gasification Boilers
Have you ever heard of wet wood, or for that matter dry wood?
With the current fashion in wood fuelled stoves perhaps you have noticed logs piled up outside a house.
This video provides some surprising results about heating with wood fuel and how important it is to dry the wood before burning
3.3.3
Ice, Water, Steam
Pause for thought
Solid
Liquid
Gas
In the video we learnt about heating with wood fuel and how important it is to dry the wood before burning.
The video suggested that dry wood contains 45% more energy than wet wood! Can this be true?
To understand this we need to learn more about the energy required to change the phase of a substance.
We need to know
The energy required to change a solid into a liquid
The energy required to change a liquid into a vapour
We will discover the concept of latent heat and will learn why so-called ‘condensing’ gas boilers are more efficient than traditional designs.
3.3.4
Ice, Water, Steam
Screencast
Outline
In this unit we will again look at the transition from one phase to another, paying particular attention to the amount of energy required to change from a solid to a liquid and finally to a gas. We will review the concept of phase change and explore the energy required for phase change to occur. We will conclude by investigating a practical, real world consequence.
3.3.5
Ice, Water, Steam
Review Questions
-
Referring to the material presented in this section, can you answer the following questions -
How does volume of a liquid change when it is heated at constant pressure?
-
Referring to the material presented in this section, can you answer the following questions -
What does the term ‘Latent heat of Fusion’ refer to?
-
Referring to the material presented in this section, can you answer the following questions -
What does the term ‘Latent heat of vapourisation’ refer to?
-
Referring to the material presented in this section, can you answer the following questions -
Why should wood be dried before burning in a wood burner?
-
Referring to the material presented in this section, can you answer the following questions -
What does the term ‘condensing’ refer to with respect to gas boilers?
-
Referring to the material presented in this section, can you answer the following questions -
Why are condensing boilers more efficient than traditional gas boilers?
