Plants are the living things that grow from tiny seeds or spores to mighty trees. They start their life as a weak creature that thrives on ground and water to grow. The starting point of their life is due to a process called germination. Germination allows the seeds – and also spores – to sprout and become a seedling (very young plant). Parts of a Seed Before discussing the process of germination, it is important to know about the parts of seeds. There are 3 main parts of the seed, which are: 1. Seed Coat – The first things you can see on a seed is its coat – also called seed coat. It is usually a hard outer layer that protects the seed from damage. Also, many kinds of seeds have a soft seed coat that can easily be damaged by pressing them with hands. 2. Embryo – The embryo is the actual part of a seed that grows from the cells that it contains to become a plant. It has 4 main parts, which are epicotyl, hypocotyl, radicle, and cotyledons. 3. Endosperm – The endosperm is like a food storage for the seed. It usually surrounds the embryo of the seed, and it provides all the necessary food (starch and protein) until the seed germinates to a seedling. Conditions for Germination Seeds depend on the environmental conditions for germination. Some seeds successfully germinate, while others don’t. Germination needs a right condition to sprout the seeds. The most important environmental conditions that need to be at the right level are water, temperature, oxygen, and light or darkness. Let’s discuss each of these environmental conditions. • Water – The germination process highly depends on the amount of water present in the soil. Because seed coat is usually dry, it needs to be moistened by water to break its coating. Furthermore, when the water is absorbed in the seed, it activates the certain enzymes. These enzymes break down the stored food and convert it into useful chemicals that supply energy to the embryo. • Temperature – Each kind of seed needs a different range of temperatures to germinate. Some seeds germinate in cold temperatures, while others require hot temperatures for germination. The seeds usually don’t germinate if the temperature is not favorable. • Oxygen – seeds use oxygen during metabolism when germinating. Majority of the seeds are buried in the soil. Seed usually take oxygen from the spaces in the soil until they grow their leaves for photosynthesis. If a seed is buried at a great depth, then it is difficult for the seed to get oxygen. • Light or darkness – It is not an important factor to consider. Because the majority of the seeds have no any effect of light or darkness. But, some seeds have the impact of light. The light or darkness usually trigger the germination process for these seeds. Process of Germination Germination of seed follows four main changes that are occurred in steps. These steps are imbibition, respiration, Mobilization of food reserves, and development of the embryo into a seedling. Let’s discuss each of these steps in detail. 1. Imbibition – This is the first step that starts with the absorption of water – also called imbibition. As the seed absorbs the water through small pores in its seed coat, it rehydrates and swells. The swelling of the seeds forces the seed coat to break, which allows the radicle (first root) to come out and absorb nutrients from the soil. 2. Respiration – When water enters into seed, it starts the metabolic activities in the embryo. The oxygen is absorbed by the seed from the soil for generating energy. Oxygen provides the necessary energy to the seed until it grows leaves and starts photosynthesis. 3. Mobilization of Food Reserves – During germination, metabolism takes place. The seed needs food for digestion. The food of the seed is usually stored in the endosperm. The food is mobilized from the endosperm to the embryo. The outer layer of the endosperm secretes the special enzymes that are used for digestion. 4. Development of Embryo into Seedling – The transportation and digestion of food cause the cells of the embryo to develop and divide. The embryo grows until it forms into a seedling. The seedling has every necessary part to start photosynthesis and further grow into the mature plant. Rate of Germination When the seeds are planted in an agricultural area or garden – not every seed in germinated. To measure how many seeds have been germinated from total seeds, it is called germination rate. Germination rate is usually in percentage, which describes how many seeds have been germinated in a given amount of time. For example, 100 seeds are planted in a garden and 65 seeds have been able to germinate. Then, the rate of germination will be 65%. Facts • The seeds of proteas have the unusual ability. They start to germinate after they are exposed to smoke. This ability is definitely evolved in them for surviving in fire-catching forests. • Coco-de-Mer is a seed that has a weight of around 30 kg. It is considered as largest seed on the earth. • Not every plant grows from the seeds. Many plants grow from the spores of their parent plant. Spores are the remaining of a plant after it dies, or they may be the parts of a plant.

Plants are the living things that grow from tiny seeds or spores to mighty trees. They start their life as a weak creature that thrives on ground and water to grow. The starting point of their life is due to a process called germination. Germination allows the seeds – and also spores – to sprout and become a seedling (very young plant). Parts of a Seed Before discussing the process of germination, it is important to know about the parts of seeds. There are 3 main parts of the seed, which are: 1. Seed Coat – The first things you can see on a seed is its coat – also called seed coat. It is usually a hard outer layer that protects the seed from damage. Also, many kinds of seeds have a soft seed coat that can easily be damaged by pressing them with hands. 2. Embryo – The embryo is the actual part of a seed that grows from the cells that it contains to become a plant. It has 4 main parts, which are epicotyl, hypocotyl, radicle, and cotyledons. 3. Endosperm – The endosperm is like a food storage for the seed. It usually surrounds the embryo of the seed, and it provides all the necessary food (starch and protein) until the seed germinates to a seedling. Conditions for Germination Seeds depend on the environmental conditions for germination. Some seeds successfully germinate, while others don’t. Germination needs a right condition to sprout the seeds. The most important environmental conditions that need to be at the right level are water, temperature, oxygen, and light or darkness. Let’s discuss each of these environmental conditions. • Water – The germination process highly depends on the amount of water present in the soil. Because seed coat is usually dry, it needs to be moistened by water to break its coating. Furthermore, when the water is absorbed in the seed, it activates the certain enzymes. These enzymes break down the stored food and convert it into useful chemicals that supply energy to the embryo. • Temperature – Each kind of seed needs a different range of temperatures to germinate. Some seeds germinate in cold temperatures, while others require hot temperatures for germination. The seeds usually don’t germinate if the temperature is not favorable. • Oxygen – seeds use oxygen during metabolism when germinating. Majority of the seeds are buried in the soil. Seed usually take oxygen from the spaces in the soil until they grow their leaves for photosynthesis. If a seed is buried at a great depth, then it is difficult for the seed to get oxygen. • Light or darkness – It is not an important factor to consider. Because the majority of the seeds have no any effect of light or darkness. But, some seeds have the impact of light. The light or darkness usually trigger the germination process for these seeds. Process of Germination Germination of seed follows four main changes that are occurred in steps. These steps are imbibition, respiration, Mobilization of food reserves, and development of the embryo into a seedling. Let’s discuss each of these steps in detail. 1. Imbibition – This is the first step that starts with the absorption of water – also called imbibition. As the seed absorbs the water through small pores in its seed coat, it rehydrates and swells. The swelling of the seeds forces the seed coat to break, which allows the radicle (first root) to come out and absorb nutrients from the soil. 2. Respiration – When water enters into seed, it starts the metabolic activities in the embryo. The oxygen is absorbed by the seed from the soil for generating energy. Oxygen provides the necessary energy to the seed until it grows leaves and starts photosynthesis. 3. Mobilization of Food Reserves – During germination, metabolism takes place. The seed needs food for digestion. The food of the seed is usually stored in the endosperm. The food is mobilized from the endosperm to the embryo. The outer layer of the endosperm secretes the special enzymes that are used for digestion. 4. Development of Embryo into Seedling – The transportation and digestion of food cause the cells of the embryo to develop and divide. The embryo grows until it forms into a seedling. The seedling has every necessary part to start photosynthesis and further grow into the mature plant. Rate of Germination When the seeds are planted in an agricultural area or garden – not every seed in germinated. To measure how many seeds have been germinated from total seeds, it is called germination rate. Germination rate is usually in percentage, which describes how many seeds have been germinated in a given amount of time. For example, 100 seeds are planted in a garden and 65 seeds have been able to germinate. Then, the rate of germination will be 65%. Facts • The seeds of proteas have the unusual ability. They start to germinate after they are exposed to smoke. This ability is definitely evolved in them for surviving in fire-catching forests. • Coco-de-Mer is a seed that has a weight of around 30 kg. It is considered as largest seed on the earth. • Not every plant grows from the seeds. Many plants grow from the spores of their parent plant. Spores are the remaining of a plant after it dies, or they may be the parts of a plant.Plants are the living things that grow from tiny seeds or spores to mighty trees. They start their life as a weak creature that thrives on ground and water to grow. The starting point of their life is due to a process called germination. Germination allows the seeds – and also spores – to sprout and become a seedling (very young plant).

Parts of a Seed

sunflower-seed
sunflower-seed

Before discussing the process of germination, it is important to know about the parts of seeds. There are 3 main parts of the seed, which are:

  1. Seed Coat – The first things you can see on a seed is its coat – also called seed coat. It is usually a hard outer layer that protects the seed from damage. Also, many kinds of seeds have a soft seed coat that can easily be damaged by pressing them with hands.
  2. Embryo – The embryo is the actual part of a seed that grows from the cells that it contains to become a plant. It has 4 main parts, which are epicotyl, hypocotyl, radicle, and cotyledons.
  3. Endosperm – The endosperm is like a food storage for the seed. It usually surrounds the embryo of the seed, and it provides all the necessary food (starch and protein) until the seed germinates to a seedling.

Conditions for Germination

seedlingsSeeds depend on the environmental conditions for germination. Some seeds successfully germinate, while others don’t. Germination needs a right condition to sprout the seeds. The most important environmental conditions that need to be at the right level are water, temperature, oxygen, and light or darkness. Let’s discuss each of these environmental conditions.

  • Water – The germination process highly depends on the amount of water present in the soil. Because seed coat is usually dry, it needs to be moistened by water to break its coating. Furthermore, when the water is absorbed in the seed, it activates the certain enzymes. These enzymes break down the stored food and convert it into useful chemicals that supply energy to the embryo.
  • Temperature – Each kind of seed needs a different range of temperatures to germinate. Some seeds germinate in cold temperatures, while others require hot temperatures for germination. The seeds usually don’t germinate if the temperature is not favorable.
  • Oxygen – seeds use oxygen during metabolism when germinating. Majority of the seeds are buried in the soil. Seed usually take oxygen from the spaces in the soil until they grow their leaves for photosynthesis. If a seed is buried at a great depth, then it is difficult for the seed to get oxygen.
  • Light or darkness – It is not an important factor to consider. Because the majority of the seeds have no any effect of light or darkness. But, some seeds have the impact of light. The light or darkness usually trigger the germination process for these seeds.

Process of Germination

germination-processGermination of seed follows four main changes that are occurred in steps. These steps are imbibition, respiration, Mobilization of food reserves, and development of the embryo into a seedling. Let’s discuss each of these steps in detail.

  1. Imbibition

    This is the first step that starts with the absorption of water – also called imbibition. As the seed absorbs the water through small pores in its seed coat, it rehydrates and swells. The swelling of the seeds forces the seed coat to break, which allows the radicle (first root) to come out and absorb nutrients from the soil.

  2. Respiration

    When water enters into seed, it starts the metabolic activities in the embryo. The oxygen is absorbed by the seed from the soil for generating energy. Oxygen provides the necessary energy to the seed until it grows leaves and starts

  3. Mobilization of Food Reserves

    During germination, metabolism takes place. The seed needs food for digestion. The food of the seed is usually stored in the endosperm. The food is mobilized from the endosperm to the embryo. The outer layer of the endosperm secretes the special enzymes that are used for digestion.

  4. Development of Embryo into Seedling

    seed-to-seedlingThe transportation and digestion of food cause the cells of the embryo to develop and divide. The embryo grows until it forms into a seedling. The seedling has every necessary part to start photosynthesis and further grow into the mature plant.

Rate of Germination

When the seeds are planted in an agricultural area or garden – not every seed in germinated. To measure how many seeds have been germinated from total seeds, it is called germination rate. Germination rate is usually in percentage, which describes how many seeds have been germinated in a given amount of time. For example, 100 seeds are planted in a garden and 65 seeds have been able to germinate. Then, the rate of germination will be 65%.

Facts

  • The seeds of proteas have the unusual They start to germinate after they are exposed to smoke. This ability is definitely evolved in them for surviving in fire-catching forests.
  • Coco-de-Mer is a seed that has a weight of around 30 kg. It is considered as largest seed on the earth.
  • Not every plant grows from the seeds. Many plants grow from the spores of their parent plant. Spores are the remaining of a plant after it dies, or they may be the parts of a plant.
water-cycle

water-cycleOur earth has abundant water on its surface. This water is in form of oceans, rivers, lakes, and glaciers. But, the only small percentage of water is freshwater that we drink and use. The rest of the water lies in oceans which is very salty. Have you ever thought, how this freshwater reaches us? We get this freshwater in a cyclic process called water cycle.

What is Water Cycle?

The water cycle is a continuous process that happens all the time around the earth. This process is very crucial in delivering the water from oceans to lands, and back again. For example, the water you see in the rivers, lakes, and glaciers is available to us due to the water cycle.

There are various methods through which the water circulates around the earth. Some methods bring the water from land to the atmosphere and form clouds. While other methods bring water back to ground on various places. This way the water is distributed across the whole planet.

How Water Moves to Atmosphere

Water moves to the atmosphere in form of vapors (gaseous state) from all around the earth – leaving behind all the salts and other impurities. There are 3 main methods that can transport water from land to atmosphere.

  1. Evaporation

    evaporationThis is the most important method than other two. This method is responsible for 90% of the water vapors that are produced around the earth. Evaporation happens at the surface of the water – where atmosphere touches it. As the air moves above the surface of the water, it takes away the some of the water with them as vapors. The hot water evaporates quicker than the cold water. Our sun provides heat energy all the time to earth. When sunlight reaches oceans, lakes, and rivers, it raises their temperature and speed-up the evaporation. The major portion of the water in the atmosphere comes from oceans. These oceans cover 71% of the earth’s surface. All the freshwater – that we get – is indirectly taken from oceans.

  2. Sublimation

    This method only works with ice or snow. Sublimation is a process in which the ice is directly converted into vapors (gaseous state) – without moving through the liquid The sublimation process is favored by cold temperature and high wind speed with sunlight.

  3. Transpiration

    It is similar to evaporation. But instead of groundwater, evaporation happens on the leaves of plants. Plants release a lot of water on their leaves – due to some cellular processes. This water is then evaporated into the atmosphere.

How Water Moves Across Land

Now the water has been transported into the atmosphere by various methods. But, how this water come back to the land and moves across it? Let’s discuss them.

  • Precipitation

    raining-cloudsThis is the process in which water vapors that escaped from the land, come back. It happens due to condensation of the water vapors. When vapors rise above the land, they form clouds. Vapors start to condense in the clouds and form the tiny droplets. These tiny droplets attach to each other and form big These big droplets are heavy enough to fall back on the land – which is also called raining. Precipitation is not always in form of rain, but it is also in form of snow, sleet, and hail – depending on the weather of the region.

  • Rivers

    riverRivers play the main role in distributing the water across the land. The precipitation on mountains and melt-down of glaciers gather very large amount of freshwater. This freshwater flows down the high altitude regions towards low altitude region through a path. People usually carry and store the needed water, and rest of the water flows down towards oceans.

  • Water Storage

    glaciersThis is also an important part of the water cycle in which water is stored naturally. The stored fresh water is in form of glaciers, snow caps. This water is stored on top of mountains – where the temperature is low. Precipitation also occurs on these high mountains, but due to low temperature, the water is in solid form (ice). When the temperature of these regions increases – due to weather – we get the liquid water flowing in the rivers.

Importance of Water Cycle

ecosystemSo far, we have discussed the water cycle technically. But it is necessary to discuss its importance in everyday life. All the humans, animals, and plants around the earth have access to fresh water – that’s why we are alive. For example, we humans get the water from rivers, ground, or direct precipitation. All the plants in the jungle need periodic precipitation to stay alive. Animals need ponds or lakes for drinking water. These all the things are possible only due to the natural water cycle.

Effects of Pollution on Water Cycle

pollution-caused-by-power-plant
Power plants are polluting the atmosphere

Today, human-caused activities have caused very adverse effects on the natural water cycle. The most harmful activity that humans are causing is carbon emission – that is a greenhouse gas. Carbon emission cause global warming. As a result, the average temperature of the earth is rising, and glaciers are melting at a higher rate than they are forming. It will cause water shortages in near future. The disturbance in water cycle is so severe that many regions have no precipitation at all – that used to have regular precipitation. While some regions have more than normal precipitation, causing floods.

The second disastrous effect is caused by pollution. Pollution of land, water, and atmosphere increase the toxicity of fresh water. As a result, the health and life of animals, marine, plants, and even humans have damaged severely.

For more information on global warming and pollution go to:

  1. http://science4fun.info/global-warming/
  2. http://science4fun.info/land-pollution/
  3. http://science4fun.info/water-pollution/
  4. http://science4fun.info/air-pollution/

Facts

  • It is estimated that transpiration accounts for 10% of the vapors in the atmosphere.
  • Underground water resources are called aquifers. These aquifers are replenished by water cycle. The water in aquifers can remain there for thousands of years – sometimes millions of years.
  • Clouds may contain water in all three states (solid, liquid, and gas) at the same time.
  • The water that earth got at the time of its formation is the same water that you drink today – even dinosaurs drank that water too.
  • Our earth has only 3% freshwater, from which only 30% is in the liquid state – the rest of the fresh water is in glaciers and ice caps.
photosynthesis

photosynthesis

Every living thing on Earth needs food to survive and live a healthy life. Plants are also living things, so they need food regularly. But instead of waiting for someone to feed them, they produce their own food. They produce their food in a process called ‘Photosynthesis’ and generate oxygen for us.

Plants need three things to make their food which are sunlight, water, and carbon dioxide. These materials are crucial for plants, they get them from nature. Sunlight from the sun and carbon dioxide from the atmosphere are available for free. But, water is available in the ground due to rain, rivers, or human irrigation system. So, getting water is a little bit difficult when rivers are dry and precipitations are very low.

How Plants Absorb the Necessary Ingredients

  • Carbon dioxide is absorbed by leaves of the plants. The leaves of the plants contain small pores called “stomata”. The carbon dioxide is absorbed through these small pores.leaves-of-a-plant
  • Water along with necessary minerals is absorbed by the roots of the plants. These absorb the water from the ground. Water is then sent to different parts of the plants through vessels in its stem.
  • Sunlight is absorbed by chloroplasts in the leaves of plants. Chloroplasts have a green color and those are responsible for the green color of leaves.

Process of Photosynthesis

The photosynthesis process happens in two phases in a plant.

  • 1st Phase: In this phase, the sunlight is absorbed by chloroplasts in the cells of plant’s leaves. The chloroplasts contain a substance called chlorophyll, which stores the energy from sunlight into a chemical called ATP.
  • 2nd Phase: The ATP produced in the first phase is used to produce glucose and oxygen from the water and carbon dioxide. The 2nd phase can happen in the night time because it is not dependent on direct sunlight. This phase is also called Calvin Cycle.calvin-cycle

Photosynthesis in terms of chemistry is a chemical reaction that is activated by light. In this reaction, light and chlorophyll break-up the water into its two constituents; oxygen and hydrogen. The oxygen and hydrogen combine with carbon dioxide to produce glucose, and oxygen is released as a gas in the atmosphere.

photosynthesis-process

The glucose is like a fuel for the plants, it is used to provide energy for the growth of plants. Plants also store some glucose in their leaves, fruits, and roots to use them later.

Importance of Photosynthesis

Photosynthesis process is very necessary for all living things on Earth. It produces oxygen as a byproduct in food preparation. The oxygen is very necessary for all living things in breathing. All the oxygen on Earth has been produced by these plants and some other creatures (some algae and bacteria) since few billion years ago.

growing-plantIt is very difficult to predict the fate of earth without photosynthesis. But it is clear that, if photosynthesis stops suddenly, no more oxygen will be produced. Gradually, the available oxygen will be consumed and every oxygen breathing creature would die. Besides the oxygen, plants are considered as producers of food. All the animals highly depend on the plants for their food, because animals just eat food without producing it. Some animals directly eat plants are called herbivores (e.g. sheep, and cow), and others eat the herbivores are called carnivores (e.g. lion, tiger, and dog). Carnivores are indirectly dependent on the photosynthesis.

Increasing the number of plants, taking a good care of them not only provide oxygen to us, but also provide us with food.

Fun Facts

  • Scientists think that first organism to use photosynthesis were cyanobacteria. They used photosynthesis about 3.5 billion years ago.
  • It is estimated that an adult person consumes about 740 kg of oxygen in a year. This amount of oxygen is produced by about eight trees in a year.

Our planet started to turn green after the evolution of photosynthesis in bacteria and plants.

carbon-atom

carbon-atom

Atom is the smallest building block of an element – it can’t be further broken by any chemical process. Everything you see around yourself is made of trillions-of-trillions atoms. They are so small that, it is not possible to see them with a powerful microscope. Only specialized microscopes (electron microscope) are able to zoom the atoms.

Composition of an Atom

hydrogen-atomAn atom is composed of electrons, protons, and neutrons. Neutrons and protons are held together in the center of an atom called nucleus. But, electrons orbit around atoms at fixed distances called orbits or shells. A neutral atom (without charge) contains an equal number of electrons and protons.

The total mass of the atom is concentrated in its nucleus, which is measured in a.m.u (atomic mass unit). One a.m.u is about  kilogram. Mass of the atom is equal to the number of nucleons (sum of the number of protons and neutrons). One nucleon – either a proton or a neutron – has a mass equal to 1 a.m.u.

Elements are distinguished from each other by the number of protons. If somehow number of protons is changed in an element – as it happens during radioactivity – then the original element will be converted into another element. However, changing the number of neutrons doesn’t change the element itself. Instead, it will give a different isotope of the same element. An isotope of an element has the same number of protons but a different number of neutrons.

different-elements

There 118 different kinds of atoms based on the number of protons, that builds 118 different elements. These elements are classified into “Periodic Table” on the basis of similarities between them.

periodic-tablee

Electron

Electrons are negatively charged particles, they orbit around the nucleus in certain energy levels. The orbiting speed of electrons is very fast – almost impossible to predict 100% accurately where they located. The number of electrons in a neutral atom is equal to protons. Electrons are 1800 times smaller than neutrons and protons.

Proton

Protons are positively charged particles. They are held together with neutrons in the nucleus of an atom. They have a mass of 1 a.m.u. Elements are distinguished from each other by the number of protons. Hydrogen is a unique element that contains only one proton in its nucleus, and one electron orbiting around it. If an electron is somehow removed from the hydrogen atom, then only one proton will remain there; you can say a proton is a positively charged hydrogen.

hydrogen-atom

Neutron

Neutrons are charge-less particles. They are also located in the nucleus of an atom – together with protons. The number of neutrons predicts the isotope of an element. An isotope of the element is the same element but with a different mass. Changing the number of neutrons will change the isotope of an element. For example, Hydrogen has three isotopes (Protium, Deuterium, and Tritium) – each one contains one proton but a different number of neutrons.

hydrogen-isotopes

History of Atom

  • Democritus developed the idea of an atom in 460 B.C. He thought that, if you break a piece of matter in half, and again break that in half, and continue this process. At some point, you will get the smallest piece of matter which will not divide further. He called that piece of matter “Atom”.
  • In 1800’s, John Dalton – an English chemist – performed some experiments on many chemicals. He showed that atoms are made up of elementary particles. He didn’t know about their structure. But, he found some evidence which showed that there are more fundamental particles than an atom.
  • In 1897, J.J Thomson presented a model of the atom. He knew that electrons have a negative charge, so there must be an equal positive charge to make the atom neutral. He thought that electrons are stuck on the protons like raisins in the pudding.

raisin-pudding-model

  • In 1911, Earnest Rutherford performed an experiment by bombarding alpha particles on gold foil. He came up with the result that, most of the volume of the atom is empty. The nucleus containing positive charge lies in the center of the atom. The electrons are orbiting around the nucleus in the empty space like planets around the sun. But, there was a problem with his model. According to the theory of electricity and magnetism – opposite charges attract each other so protons will attract electrons. As a result, electrons – gradually losing its energy – must fall in the nucleus spirally, and give a continuous spectrum of light. But in reality, it was not happening.
  • In 1912, a physicist Neil Bohr came up with an idea. He rectified the error from atomic model of Rutherford. He said that electrons don’t spiral into the nucleus. Instead, he gave two rules about the motion of electrons which are:
    • Rule 1 – Electrons orbit around the nucleus at certain allowed distances called “orbits”.
    • Rule 2 – Atoms radiate energy only when electrons jump from higher energy orbit to lower energy orbit. They absorb radiation when electrons jump from lower energy orbit to higher energy orbit.

Many people came with different ideas and the atomic model was developing until it reached the present day model of the atom.

heat-transfer

heat-transfer

Heat transfer is the transfer of thermal energy from one object to another. It occurs between two objects when they are at different temperatures – the heat will transfer from hot object to cold object. In our environment heat transfer occurs all the time. The sun is transferring some of its heat energy towards earth, and we get days hotter than nights. We cook our food on stoves – it is possible due to heat transfer.

Methods of Heat Transfer

There are 3 methods of heat transfer, which are conduction, convection, and radiation. Let’s discuss each of them individually.

Conduction

conduction-heat-transferWhen two objects with different temperatures come in contact with each other, the heat is transferred from the hot object towards the cold object. This happens due to the collision of the molecules at the contact area of two objects.

In solids, molecules of hot objects vibrate more frequently than cold objects. When hot and cold objects come in contact with each other, their molecules collide. As a result, the collisions of molecules transfer the energy from the hot object to cold object. This transfer of thermal energy continues until hot and cold objects reach the same temperature. For example, when you boil water on a gas stove, the heat is conducted to the pot from fire.

Convection

convection-heat-transferConvection is the heat transfer method that only occurs in fluids (liquid and gases).  It is caused by the flow and diffusion of fluids. This flow happens in the closed path – from hot regions of fluids towards cold regions and back again.

For example, when water is boiled on the gas stove, the heat is conducted by metal pot. The temperature of metal pot increase, which increases the temperature of the water that is in contact with it. Hot water rises to the surface and is replaced by cold water. This process continues and causes circular motion. As a result, the heat is distributed towards all the regions of water.

Radiation

radiation-heat-transferIn this process, heat is transferred by electromagnetic waves – also known as light. This process doesn’t depend on any medium or material to transfer the heat. Instead, the radiations travel through space or air to transfer the heat.

The heat is transferred to objects that absorb the radiation. As a result, their temperature increases. For example, the Sun transfer the heat energy as radiations that heats-up our Earth. Furthermore, the reflecting objects like mirrors can’t completely absorb the radiations. So, their temperature doesn’t increase.

Facts

  • Insulators don’t conduct the heat very well. So, they are used to cover the objects whose heat we want to preserve. For example, when ice-creams are taken on a ride, they are stored in a styrofoam box to prevent the heat by conduction.
  • Materials that are good conductors of electricity are also good conductors of heat. For example, copper is the best conductor of electricity, so it is also the best conductors of heat. Copper heat sinks are used on computer processors to remove the excess heat quickly by conduction.
  • Sometimes it is necessary to transfer the heat from cold object to hot object – opposite to the natural heat transfer. This kind of heat transfer is called forced heat transfer. Today, we use forced heat transfer in air-conditioners and refrigerators to cool-down things.