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‫ال‬ ‫قوق‬ ‫ح‬ © ‫شر‬ ‫ن‬ ‫وال‬ ‫بع‬ ‫ط‬TeacherNotes4U.com. ‫محفوظة‬ ‫الحقوق‬ ‫كل‬. ‫الموضوع‬ ‫هذا‬ ‫محتويات‬ ‫نشر‬ ‫أو‬ ‫عرض‬ ‫أو‬ ‫توزيع‬ ‫أو‬ ‫إنتاج‬ ‫بإعادة‬ ‫تسمح‬ ‫ال‬
. ‫شكل‬ ‫بأي‬ ‫ًا‬‫ي‬‫جزئ‬ ‫أو‬ ‫ًا‬‫ي‬‫كل‬ ‫المحتويات‬ ‫إزالة‬ ‫أو‬ ‫بتغيير‬ ‫ًا‬‫ض‬‫أي‬ ‫تسمح‬ ‫ال‬
.
Year 7 Chemistry
1 / 2
BOILING, EVAPORATING, AND CONDENSING
Changes of State
When a substance changes from one state to another, its particles don't change.
The changes are the particles arrangement, particles movement, and particles
force of attraction.
Melting, boiling, evaporating, condensing, and freezing are all changes of state
Liquid to Gas
Evaporation or boiling is a change of state from liquid to gas. The particles move
faster and more spread out and the force of attraction between the particles become
very weak.
Evaporation happens when particles leave the surface of a liquid. It can happen at
any temperature. The particles spread out to form a gas. For example: water is
constantly evaporating from lakes, rivers and sea. Clothes dry when water evaporates
from them.
Boiling happens throughout the whole liquid. It only happens when a liquid is hot
enough, that is at boiling point. At boiling point, bubbles of liquid in the gas state form
throughout the liquid. The bubbles rise to the surface and escape.
Boiling Point
Boiling point is the temperature at which a substance boils. Every substance has its
own boiling point.
The stronger the force of attraction between particles, the higher the boiling point.
Objective:
 Recognise the changes of state
 Explain changes of state using particle
theory
solid liquid gas
ice
melting warming
water vapour
freezing cooling condensing
evaporating/
boiling
0°C
100°C
0°C
100°C
evaporation boiling
bubbles cannot form
because the vapour
pressure less than
atmospheric pressure
Bubbles can form and
rise because the vapour
pressure higher than
atmospheric pressure

2. Copyright © TeacherNotes4U.com. All rights reserved. Do not allow to reproduce, distribute, display or publish the contents of this topic. Also not allow to alter or remove the contents in whole or part, in any form.
© TeacherNotes4U.com 版权所有。未经 TeacherNotes4U 事先书面同意，任何人不得复制、发行、传播、展示、出版或广播该等内容。亦不得更改或删除该内容复制品中所包含的商标、版权或其他声明。
‫ال‬ ‫قوق‬ ‫ح‬ © ‫شر‬ ‫ن‬ ‫وال‬ ‫بع‬ ‫ط‬TeacherNotes4U.com. ‫محفوظة‬ ‫الحقوق‬ ‫كل‬. ‫الموضوع‬ ‫هذا‬ ‫محتويات‬ ‫نشر‬ ‫أو‬ ‫عرض‬ ‫أو‬ ‫توزيع‬ ‫أو‬ ‫إنتاج‬ ‫بإعادة‬ ‫تسمح‬ ‫ال‬
. ‫شكل‬ ‫بأي‬ ‫ًا‬‫ي‬‫جزئ‬ ‫أو‬ ‫ًا‬‫ي‬‫كل‬ ‫المحتويات‬ ‫إزالة‬ ‫أو‬ ‫بتغيير‬ ‫ًا‬‫ض‬‫أي‬ ‫تسمح‬ ‫ال‬
.
Year 7 Chemistry
2 / 2
When we heat up a liquid, its temperature rise until boiling point. At boiling point, the
temperature stops increasing until all the liquid changes to gas state. Then the
temperature rise again.
Gas to Liquid
Condensation is a change of state from gas to liquid. The particles move more
slowly and get closer until they touch each other. The force of attraction between
particles is much stronger in the liquid.
A substance in the gas state condenses when it is cooled to its boiling point or
below.
When we cool down a gas, its temperature drop until boiling point. At boiling point,
the temperature stops to decrease until all the gas change to liquid state. Then the
temperature drop again.
temperature
boiling point
melting point
solid
solid/liquid
mixture
liquid
liquid/gas
mixture
gas
time