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Natural sciences

Grade 8

Matter: classification

Module 15

Phase changes of matter

Prior Knowledge:

  • Matter has three phases: solid substances, liquid substances and gases

Class activity: reading skill

In the heart of a Cape winter

Adventurers went camping in the Cedar Mountains.

The night brought a fall of snow that

Glistened in the early morning light.

Slowly, surely, the ice was melted by the wintry sun

And water ran in rivulets to the riverbed.

A camper scooped up a billycan of the stream’s water

He struck a match to light his fire

And soon steam billowed from his billycan!

1. Name all the phases of water mentioned in the text – list all the descriptive words.

2. Name the source of energy that causes:

a. the ice to melt

b. the water to steam

3. a. In which phase do particles of water have the greatest freedom of movement?

b. Which phase presents the strongest attraction between particles of water?

4. The phases of water are also an important part of nature, as the WATER CYCLE becomes possible because of it. Fill in the following:

The Water Cycle

6. The following illustrations represent phase changes. Explain what happens to the water in each instance:

Assessment of reading skills

Were you able to make the correct deductions from the text?

[LO 2.3]


Find out the following:

(You could use the given web addresses or any other source for research.)

Why ice floats on water.– www.geocities.com (iceberg+ float)

How snowflakes are formed.– google.com (snowflakes)– www.edu.pe.ca/rural/chemist

Why alcohol (as in Schnapps or Witblits) does not freeze in the freezer.

What the boiling point of fluids like cooking oil and alcohol is.– www.ucc.ie – (boiling points)

Paste or write the information on the facing page.

Assessment for assignment

Has the information been collected and recorded?

[LO 1.3]

7. Each substance has its own boiling and freezing point.

Water freezes at

Water boils at

 Do you know the following? 

A fourth phase of matter has been discovered – it is known as PLASMA.

It only occurs at excessively high temperatures and in stars.

Read more about PLASMA!



Learning outcomes 1: Scientific investigations

The learner will be able to act confidently on curiosity about natural phenomena, and to investigate relationships and solve problems in scientific, technological and environmental contexts.

We know this when the learner

1.3 is able to evaluate data and communicate findings.

Learning outcomes 2: Constructing science knowledge

The learner will know and be able to interpret and apply scientific, technological and environmental knowledge.

We know this when the learner

2.3 is able to interpret information.


1. snow; ice (solid substance) – water; river water (liquid) – steam (gas)

2. a) sun b) fire

3. a) steam (gas) b) snow/ice

4. spaces smaller in solid substances

5. 1 – evaporation; 2 – transpiration; 3 – cloud formation / condensation

4 – precipitation (rain, snow, etc.)

6. condenses; melts; freezes (crystallises); evaporates

Questions & Answers

Would you expect the kinked demand curve to be more extreme (like a right angle) or less extreme (like a normal demand curve) if each firm in the cartel produces a near-identical product like OPEC and petroleum? What if each firm produces a somewhat different product?
James Reply
what is supply
Mizta Reply
what is opportunity cost
The opportunity gained interms of opportunity lost is known as opportunity cost Or The second best alternative use of resources
forgone alternative: like forgoing Something our of two to buy one
what is macro economic s
Addo Reply
macroeconomics is the study of economic as a whole level.
meaning of positive science
Sumit Reply
positive science it is focused on facts and cause and effect and behavioural relationship and include developmental testing in economic theoreis.
what is inflation
Sama Reply
inflation is the general price increase of goods and services in an economy.
Inflation is the persistent rise in the general price level
inflation is characterized by increase in the general price of goods and services. when there is too much money in circulation. increase in demand of goods pursuing fewer goods. when purchasing power of money decreases .
inflation is the persistent rise general price level
inflation is the persistent increase in price
how are you
increase in the general level of price...
what is deflation
is the gradual decrease of currency exchange in a country.
why ecnomics important ? give answer plz
Because is a field of science study that reflects on our day to day activities with human behavior.
different between demand and quantity demand
Farhan Reply
No difference
demand is the overall demand for it
actually theres no difference
quantity demanded is used in Equilibrium of d and s
for evrything else u use deman
the difference of it is that when demand simply denotes the willingness and a person's ability to purchase. And as against quantity demand represent the amount of an economic good or services desire by a consumer at a fixed price .☺
how to calculate inflation
Richard Reply
Explain the factors that have led to high quantity demanded
Ogwang Reply
price of the product increase of price substitute product as people shift to cheap one
what are the methods used by trade union to increase wages of their members?
Black Reply
the size of the commodity
increase demand of labour decrease supply of labour
I do support your answer Jackel.
but how do they do it?
by increasing more labour and reduced the suppliers
they can not increase labour, they increase demand of labour.
how do they increase demand for labor?
by analyzing the market equilibrium , cost reduction and cost control , savings in time .
decreasing supply of labour are achieved through training and certification that require for you to employed, you must have certificate, also trade union encouraged government to restrict migration into the country causing shortage of labour supply. Note that the aim of union is to enhance life
objective of union: better working conditions, liveable wage, protect member from unfair treatment which are done through negotiations betweens representative and management. known as collective bargaining.
what is the nature of economics?
Tyscar Reply
economics is a social science since it seeks to solve social problem of scarcity
main concerns is the decision individuals make on the allocation of scarce resources among the competing wants
in the short run firm produce a positive as long as the price is larger than what?
yoel Reply
what is economic
Bah Reply
economics is the study of managing the resources in order to maximize the needs and satisfy the wants to a great extent in a regulated set-up..
One explanation for deviation when there is no impact on balance of trade
economic s is a social science that deals with human behavior as a relationship between ends and scarce means which has alternative uses
economic is a study of mankind in ordinary business of life
economics it is the study of social science that deals with human behaviour as relationship between ends and scarce means which have alternative uses
Economic is the use of scarce recourses to attain economic dough effectively and efficiently.
economics is the study of how humans make decisions in the face of scarcity. Eg. family decision, individual decision, and societal decision.
what is diminishing returns
Blessed Reply
what is the difference between calculus linear equation and derivative?
whats inferior goods?
jaamac Reply
Good having low quality , also known as giffin goods. When income increases people shift to better quality goods . Hence having a negative effect on inferior goods rather than positive relation ( ie when income increases demand increases but not in case of inferior goods ) example wheat and bajra .
What do u understand by the word ENDS in professor Lord L C Robinson definition of Economics?
Kaba Reply
I understand that ENDS is the unlimited needs of human. But we have limited resources to achieve our unlimited needs/wants. Thank you.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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While the American heart association suggests that meditation might be used in conjunction with more traditional treatments as a way to manage hypertension
Beverly Reply
Researchers demonstrated that the hippocampus functions in memory processing by creating lesions in the hippocampi of rats, which resulted in ________.
Mapo Reply
The formulation of new memories is sometimes called ________, and the process of bringing up old memories is called ________.
Mapo Reply
Berger describes sociologists as concerned with
Mueller Reply
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Source:  OpenStax, Natural sciences grade 8. OpenStax CNX. Sep 12, 2009 Download for free at http://cnx.org/content/col11050/1.1
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