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Natural sciences

Matter, measuring and reactions

Educator section


Examples of physical change: a pan that is heated; tea that cools down

Examples of chemical change: burning match; toasting bread


  • Yes, it tastes slightly different after being toasted
  • Yes, it became black and powdery
  • Chemical change. It is permanent - the chemical reaction changed the sugar to carbon.

Leaner Section


Activity: to investigate and discuss physical and chemical changes in substances [lo 2.3]

People make use of different natural substances and change them into something else. To achieve this change, substances are mixed with other substances, heated, separated, dissolved or treated with electricity. Some changes are not permanent, while other changes cannot be reversed. We also distinguish between physical and chemical changes.

Physical Change

When crystallised honey is heated in a pot it becomes fluid again. But when it cools down and is exposed to air, it will crystallise once more. No new substances are formed and the properties of the honey remain exactly what they were. The change is a physical change. In the previous experiment, the orange/red mercuric oxide became black when it cooled down (physical change).

Chemical change

When you pour pancake batter into warm oil, something happens: the appearance of the batter changes. It is not runny any more, but stiff. The change that occurs is permanent. A change that is permanent and results in something new is a chemical change. The properties of the new substance differ from those of the original substances. The mercuric oxide also experienced a chemical change when it was decompounded into mercury and oxygen.

Name two further examples of physical and two examples of chemical change:





Try the following:

Bring some marshmallows to school. Push them onto the prongs of a fork and heat them over a flame. Answer the questions that follow.

  • Taste a marshmallow (when it has cooled down). Has the taste changed?
  • Has the appearance changed? Describe what you observe.
  • Did this involve a physical or a chemical change? Motivate your findings.






Learning Outcome 2: The learner will know and be able to interpret and apply scientific, technological and environmental knowledge.

Assessment Standard 2.3: We know this when the learner interprets information by identifying key ideas in text, finding patterns in recorded data, and making inferences from information in various forms (e.g. pictures, diagrams, text).

Questions & Answers

Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Natural sciences grade 7. OpenStax CNX. Sep 16, 2009 Download for free at http://cnx.org/content/col11077/1.1
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