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Natural sciences grade 8

Energy: electricity, heat and light

Module 1: energy to begin

Energy is derived mainly from the sun and is available to us in various forms.

Some facts concerning energy:

  • Energy is the capacity for doing work . We measure energy in joule (J).
  • There are two main types of energy:
  • The energy of action or motion is known as KINETIC energy
  • The energy of position is known as POTENTIAL energy
  • Energy also occurs in various forms, e.g.:

Chemical energy, which is obtained from chemical substances like petroleum, oil, gas, batteries and foodstuffs;

Electrical energy, which is derived from electricity;

Sound energy, from loudspeakers

Radiant energy, from light and heat. The sun is our largest source of radiant energy.

Nuclear energy , is stored in the nucleus of the atom.

Energy cannot be created or destroyed. It can only be converted from one form to another.


To identify the different types of energy

[lo 2.1, lo 2.2, lo 2.4]


In the following list, indicate the form of energy that is present:

  1. Car battery
  2. Paraffin stove
  3. Wind-up toy car
  4. Hair drier
  5. Rubber band (shooting)
  6. Radio
  7. Food
  8. A growing plant
  9. Burning candle
  10. Nuclear power station

Assessment of forms of Energy

Were you able to indicate the forms of energy correctly?

[LO 2.2]


LO 2: Constructing Science Knowledge:

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

This is evident when the learner:

  • recalls meaningful information;
  • categorises information;

2.4 applies knowledge.



1. Car battery – CHEMICAL to ELECTRICAL

2. Paraffin stove - CHEMICAL TO HEAT

3. Wind-up toy car – POTENTIAL TO KINETIC

4. Hair dryer – ELECTRICAL TO HEAT

5. Elastic band (being shot) - POTENTIAL TO KINETIC



8. A growing plant – RADIANT TO KINETIC

9. Burning candle – CHEMICAL TO LIGHT AND HEAT

10. Nuclear power station – KINETIC TO ELECTRICAL

  • Explain this to grade 8 with the help of a simple example.
  • It is generally known that the common light bulb provides us with light, but also becomes so hot that it can hardly be touched after a few moments. Approximately 100J of electric energy are converted to light energy AND heat energy within one second. The light energy has the value of about 5J, while the heat equals about 95J.
  • The conversion therefore is as follows:
  • A light bulb therefore is altogether uneconomical!
  • If you consider this, you will realise that the food provides the SOURCE OF ENERGY of human beings, but electricity and fuels provide all other aspects of energy. This brings us to the next learning unit.

Questions & Answers

how do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
I'm not sure why it wrote it the other way
I got X =-6
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
Commplementary angles
Idrissa Reply
im all ears I need to learn
right! what he said ⤴⤴⤴
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
is it 3×y ?
Joan Reply
J, combine like terms 7x-4y
Bridget Reply
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris 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?
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
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 8. OpenStax CNX. Sep 12, 2009 Download for free at http://cnx.org/content/col11050/1.1
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