2. At your age most likely you have already experienced playing under the
sun for several hours.
After even just a couple of hours, you probably already felt your sweat
running down you back or rolling off your face.
You may have felt thirsty and started thinking of cold drinks or even ice
cream.
And you may have felt that your skin was not only reddish but also sticky.
Worse, you may have started to smell a little too musky.
You must have felt all these because of the heat energy that you received
from the sun.
3. SOURCES OF HEAT ENERGY
– form of energy that
is produced from the movement of
the molecules in a solid, liquid, or
gas.
The sun is the main source of heat
energy on Earth. This form is called
solar energy.
Heat also be obtained from sources
such as Earth itself, burning fuel,
and electricity.
4. - Earth as the source of heat energy.
near the surface of the Earth are hot water
and rocks that are trapped to generate
heat energy for homes and other
buildings.
Greater amount of heat energy are
sourced from the Earth’s mantle, which is
composed of molten lava – or extremely
hot rocks. These rocks are thrown off onto
the surface of Earth during volcanic
eruptions.
In countries with many volcanoes such as
Iceland, Italy, New Zealand, and the United
States, heat energy from geothermal
sources are used to produce electricity.
5. - any flammable substance that produces
heat when it is burned.
Among of those: charcoal, gasoline,
kerosene, oil, and wood.
Burning charcoal – needed to grill some of
the food during picnics.
Gasoline – converted into heat energy that
causes vehicle to move.
Kerosene, oil, and wood – also a source of
heat energy they are utilized in the right
manner.
6. - kind of energy that can build up in one
place or flow from one object to another
as it is carried by moving electrons
through a wire.
- considered an artificial source of heat
energy unlike the sun, geothermal
sources, and fuels which are deemed
natural sources.
Flow of electricity can be a source of heat
energy for some appliances such as light
bulbs, electric lamps, stoves, flatirons,
toasters, and heaters.
7. EFFECTS OF HEAT ENERGY ON
MATTER
• Heat energy – measured in terms of temperature.
• Temperature – hotness or coldness of matter.
• Matter with very active molecules has high temperature and is
said to be hot while matter with molecules that move around less
has low temperature and is referred to as cold.
8. A. CHANGES IN PHASE OF MATTER
change from one phase to another.
Ex:
Bar of butter will melt when it is
placed in a pan heated over a fire
Ice cubes will turn into liquid
when taken out of cold
Those changes are called melting.
It is a change from solid to liquid
phase.
9. A. CHANGES IN PHASE OF MATTER
Heat can cause changes from liquid to
gas phase, and it is called evaporation.
Ex:
Boling water in a kettle, amount of
water decreases after some time
because part of it has turned into
water vapor.
When water vapor cools, it releases
heat and turns back into liquid. The
change in phase from water vapor to
liquid is called condensation.
10. B. CHANGES IN VOLUME OF MATTER
Objects get bigger when they get
hotter and get smaller when they cool
down.
Through expansion, solid increase in size
or volume when heat is applied to them.
Ex:
siopao will expand when exposed to
heat and will contract when cooled.
Balloon inflated when heated
11. B. CHANGES IN VOLUME OF MATTER
Liquid also expand when heated. We
often found spilling out of a kettle
when the water boils. Heat increases
the energy of the water molecules
and makes them move faster. In
turns, the movement of the
molecules causes them to occupy
wider space. When heat is released,
the water in the kettle settles.
13. - form of heat energy transfer. Heat
causes molecules to moves faster and
collide with molecules near it,
transferring the heat from molecule
to molecule.
- Materials that conduct heat are called
conductors.
- Ex:
- Metals like aluminum, iron, steel,
and copper
14. - Insulators – materials that does not
transmit, conduct, or allow heat to
pass through.
- Ex:
- Plastic (handles of most frying
pans
- Rubber
- Wood
15. - the movement caused within a fluid by
the tendency of hotter and therefore less
dense material to rise, and colder, denser
material to sink under the influence of
gravity, which consequently results in
transfer of heat.
- Ex:
- When boiling water in a pan, the
heated water molecules near the
bottom of the pan expand and
become less dense.
16. - energy travels in space through waves,
heat is transferred from the source to the
receiver in a form of heat transfer.
- Ex:
- Bringing a hand near a lighted candle
or bulb without touching it, you will
find out, although it is inches away
from the flame, the hand will fell the
heat from the candle or bulb. This is
because the heat from the lighted
source has radiated to the hand.
17. - Ex:
- Sun’s rays radiate to plants provide
them with the sunlight they need for
photosynthesis. The sun is millions of
kilometers away but its intense heat
radiates to Earth and is utilized by
the different living things on the
planet.
18. PROTECTION FROM EXCESSIVE HEAT
Extreme heat can be dangerous for all people, especially for children like you. It
may lead to different conditions such as fainting, heat stroke, muscle cramps, and
prickly heat.
1. Avoid too much exposure to the sun’s heat, especially from ten o’clock in the
morning to two o’clock in the afternoon when the sun’s rays are at their harshest. If
you have to stay outdoors under the sun, wear sunblock or sunscreen on you skin.
You may also put on a wide-brimmed hat or use an umbrella to protect yourself
from the sun’s rays.
2. Drink eight to ten glasses of water and other liquids daily to keep from being
dehydrated. Dehydration is the condition when the body loses much of its fluids
and salts. This is dangerous to the human body; when the body loses a significant
amount of fluids and salts, these are not quickly replaced. Too much loss of water
and salts in the body can cause death.
19. PROTECTION FROM EXCESSIVE HEAT
3. Choose the right kind of clothing. In the Philippines, it is best to wear loose-fitting
clothes that are made of cotton fabric. This kind of textile easily absorbs heat and
allows air to pass through its fibers, thus cooling the body.
4. Stay alert for signs and symptoms of illnesses due to extreme heat such as dizziness
or fainting, nausea, headache, rapid breathing, and extreme thirst. If you feel any of
these signs, move to a cooler place and drink lots of water and other liquids to
replenish the lost salts and prevent dehydration.
5. Never play with any source of light or heat energy. Use heated appliances such as
stoves and flatirons with much caution and under adult supervision. Follow correct
procedures when handling them. For instance, when working with kitchen appliances,
never stay too close to sources of fire and heat. Handle hot spots and pans with pot
holders and never with your bare hands, as the heat from these items will transfer to
your hands and burn them.
