<< Chapter < Page Chapter >> Page >

Natural sciences

Energy transfers and forces

Educator section


(i) Refrigerator; kettle; toaster

(ii) Convection heater; fan heater; iron

(iii) Refrigerator; kettle; vacuum cleaner or toaster

(iv) Food mixer; convection heater; fan heater; filter

E.g. heaters can be replaced by isolating ceilings, carpets on cement floors, properly sealed panes, etc.

Leaner section


Activity 10: to compare the energy consumption of a variety of electrical appliances [lo 3.2]

a. Study the following and answer the questions that follow:

With one unit of electricity ______________________________________________

The above illustrates the working costs of some household appliances with reference to their consumption per unit of electricity.

(i) Which three appliances use the least energy?


(ii) Which three appliances are the most expensive to operate?


(iii) Which appliances are used most frequently in households?


(iv) Which appliances would you regard as unnecessary and replaceable with other appliances that do not use as much fuel, or as altogether dispensable.








(b) Many people in South Africa do not have access to electricity and have to use fuel wood, paraffin or gas as fuels to cook their food and warm their houses. Fuels, especially wood, are becoming scarcer and people often have to walk great distances to collect what they need. These fuels also need to be used effectively to help with conservation.

Many of the people who depend on fuel wood use open fireplaces and much heat energy is transferred into the surrounding air. Often people also use gas stoves incorrectly and waste energy.


Each group is to select a means that is used for cooking by a majority of South Africans in rural areas, e.g. an open fire, a gas stove, etc. This must be represented practically by means of a model and a report must be written on its use. The report should cover the following questions:

Which fuel is used?

  • Is it easily obtainable?
  • Is a particular colour recommended for the pot? If so, what is the reason for it?
  • Which measures can be taken to limit heat energy being lost into the air around the pot?
  • What is the cost of the fuel?

Educator’s Assessment:

Criteria 1 2 3 4
Assignment: Correctly executed; complete; relevant; handed in on time
Model: Effective; fuel indicated; creative representation
Report: All questions addressed; reporting neat; good language use
Co-operation within group: Effective; differences resolved; all learners involved


Learning Outcome 3: The learner will be able to demonstrate an understanding of the interrelationships between science and technology, society and the environment.

Assessment Standard 3.2: We know this when the learner understands sustainable use of the earth’s resources: analyses information related to renewable and non-renewable sources.

Questions & Answers

what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
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.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!

Source:  OpenStax, Natural sciences grade 7. OpenStax CNX. Sep 16, 2009 Download for free at http://cnx.org/content/col11077/1.1
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Natural sciences grade 7' conversation and receive update notifications?