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Natural sciences

Energy transfers and forces

Educator section

Memorandum

Observations:

(i) The smoke rises.

(ii) The smoke rises.

(iii) The smoke rises.

Conclusion:

Hot air rises.

During the day the land heats up more rapidly than the sea. The warm air above the land rises. Cooler air above the sea flows to the land to fill the place of the warm air. This is how sea winds originate.

At night the land cools down more rapidly than the sea. Therefore the air above the sea is warmer and rises. Cooler air from above the land flows to the sea to take the place of the warmer air. This is how a land-wind (offshore wind) originates.

Leaner section

Content

Ativity: to explain convection as a natural phenomenon [lo 1.2, lo 1.3]

(b) Convection

Convection is the main way in which heat moves through liquids. Water is a poor conductor of heat, but a kettle does manage to let water boil quickly. The reason is that liquids are able to move. Water rises when it becomes warm. The colder water then sinks down to take the place of the warmer liquid that is rising. The accompanying illustration shows how the circular movement, the convection current, distributes the warmth through the liquid until all the water is hot enough to come to a boil (100°C – boiling point for water at sea level).

Although air is a poor conductor of heat, it is possible to heat a room with the help of a heater. Take a burning candle. Note the direction of the smoke while you

(i) hold the candle in an upright position ___________________________________

(ii) hold the candle at an angle ___________________________________________

(iii) Hold the candle upside-down _________________________________________

Have you noted your observations? What do you deduce from this?

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As warm air rises, convection also occurs in nature. Have you ever thought about the origins of wind? Warm air rises and cold air moves to take its place.

Consider the principle of convection currents in air to help you distinguish between land and sea winds. You could make a sketch to help explain your observations.

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(c) Radiation

The transfer of heat by means of conduction or convection requires a solid substance, a liquid or a gas. There must be some substance to transfer heat energy. Such a transfer of energy through empty space is possible through radiation. Heat energy from the sun moves through space and the earth’s atmosphere and heats any object that it reaches.

If you drive along any road where you can see ahead into the distance on a hot day, it often seems as if there is water on the road. The hot tar of the road radiates heat. Using an electric heater to heat a room in winter is an example of the use of radiation in an everyday situation.

6. Conversion of energy

Which kind of energy is used when a boy hits a tennis ball?

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What kind of energy does the moving tennis ball have?

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This has probably made you suspect that energy can be changed. When there is a change in energy from one kind to another kind, we speak of the conversion of energy.

Assessment

Learning Outcome 1: 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.

Assessment Standard 1.2: We know this when the learner conducts investigations and collects data: organises and uses apparatus/equipment or sources to gain and record information:

Assessment Standard 1.4: We know this when the learner evaluates data and communicates findings: generalises in terms of relevant aspects and describes how the data support the generalisation:

Questions & Answers

what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
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.
Bharti
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
Daniel
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
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
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
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
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.
Tarell
what is the actual application of fullerenes nowadays?
Damian
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.
Tarell
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.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
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.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
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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