LISTENING AND SPEAKING
WHERE DOES OUR
WHAT IS ENERGY?
Energy is essentially the ability
or the capacity to do work.
We use energy to do work and
make all movements.
Energy takes many forms:
•Kinetic energy, etc.
WHAT FOR DO WE USE ENERGY?
In our daily lives, there are many things in which we
• Cooks our food,
•Lights our cities,
•Powers our vehicles,
•Gives us pictures on TV,
•Plays our music
and so on.
E.g. When we eat, our bodies transform
the food into energy.
HAVE YOU EVER WONDERED WHERE OUR ENERGY
All of our energy comes from:
• The Sun by solar power cells
•Plants got their energy by a process called photosynthesis.
WHAT IS THE DIFFERENCE BETWEEN HEAT AND
Heat is molecules moving.
Temperature is a measure of how fast the molecules are moving.
HOW IS TEMPERATURE MEASURED?
Temperature is usually
measured with a thermometer.
WHAT IS ABSOLUTE ZERO?
Absolute zero is the coldest
possible temperature. When
atoms stop moving altogether.
By international agreement,
absolute zero is defined as
•0 K on the Kelvin scale.
•–273.15 degrees Celsius on the
•–459.67 degrees F on the
“Energy can be neither created nor destroyed, but can
E.g. Chemical energy can be converted to kinetic energy in the
explosion of a stick of dynamite.
HOW IS ENERGY CONSERVED?
WHY DO WE NEED TO SAVE ENERGY?
It is easy to forget how important energy is or how much energy costs
because energy is there whenever we need.
•Energy is not free. All of us pay for the all electricity we use in our
houses. Wasting energy is the same as wasting money.
•Wasting energy is not good for our environment either. Most
of the sources we depend on, like coal and natural gas, cannot
be replaced. Once we use them they are gone forever.
•Coal: a hard, black substance that is found in the ground and
burned as fuel.
•Temperature: is the measurement of how hot or cold
•Heat: the quality of being hot or warm.
•Cell: the smallest living part of an animal or a plant.
•Photosynthesis: is a process used by plants and other
organisms to convert light energy from the sun into chemical
•Fossil fuels: have been formed from organic remains of
prehistoric plants and animals.
•Remains: the parts of something that exist when other
parts of it have gone.