Definitions for Kids


The United States constitution has separated the powers of the state. The constitution clearly lays out the three different branches of governance: the legislative, the executive and the judiciary. The legislative branch is responsible for making laws. The executive branch of the government is responsible for executing the laws. The judicial branch is responsible for upholding the laws and evaluating them.

Judicial Branch: Explained!

Before democracy and excluding some kingdoms in the past that had a constitution, most regions of the world were ruled by a king, queen or monarch. The method of governance was autocratic, dictatorial or an absolute monarchy. The king, queen, monarch or ruler would make laws, execute them and also evaluate them, thus making changes at the whims and mercies of the sole authoritarian ruler. Modern democracy has no space for absolute power. Hence, the segregation of powers plays the most important role in ensuring freedom and a plethora of other fundamental rights of common people.

It is difficult to study the judicial branch in isolation without first illustrating what the legislative and executive are and what they do. It must be remembered that all the three branches are interrelated, completely connected and are used as a check or balance for one another.

• The legislative comprises of the Senate and the House of Representatives, collectively forming the US Congress. The senate has a hundred members, known as senators. There are four hundred and thirty five representatives forming the lower house or the House of Representatives. The purpose of the legislative or the US Congress is to make laws. Every law that the country has can be changed or done away with by the Congress. New laws have to be made by the legislative alone which should then stand the scrutiny of the judicial branch.

• The executive comprises of the President, the Vice President and the Cabinet. The President or the Vice President don’t have powers to make laws but can take executive decisions based on the laws that bestow certain privileges and responsibilities upon them. The President is the head of government while the Vice President presides over the senate. The Cabinet is picked, nominated or chosen by the President but must have the approval of the Senate.

• The judicial branch is responsible for evaluating laws. It has the power to ensure that laws are exercised as they were meant to be. The judicial branch can strike down laws, recommend amendments to exist laws and can interpret the constitution with all the laws ever made given the context of a legal proceeding. Every law excluding the executive decisions stand scrutiny of the judicial branch.

Judicial Branch: Illustrated!

The judicial branch has a large network of courts. There are federal laws and state laws. The entire judicial branch or the justice system is headed by the Supreme Court. It is the apex court of the country. The Supreme Court has nine judges, also referred to as justices. These judges can also be called chief justices. The nine judges of the Supreme Court are recommended or chosen by the President. These nominations must be approved by the Senate with a minimum of 51 votes.

The Supreme Court is a federal court and doesn’t deal with local cases. It only deals with federal laws and any crime that is beyond the jurisdiction of state laws or lower federal courts and district courts. There are many lower federal courts in the country, known as the United States courts of appeals. These are also known as intermediate federal appellate courts. Then there are the United States district courts. There are 94 federal judicial districts and all have one district court. Additionally, there are three territorial courts. These are general trial courts and the higher courts, including the courts of appeals and the Supreme Court, would only take up cases if the crimes are federal or if either party appeals for a review of the judgment of the lower court.

The judicial branch has many specialized departments and also special courts. There are quasi judicial departments and tribunals as well. For instance, there is the Court of International Trade, the Foreign Intelligence Surveillance Court and the Alien Terrorist Removal Court. There Article I or Article IV tribunals, the Court of Appeals for Veterans Claims and the Court of Appeals for the Armed Forces, bankruptcy courts, the immigration courts, the Court of Federal Claims and the Tax Court.

The judicial branch of government is completely free from executive and legislative influence. However, the judicial branch can seek the standpoint of the legislative and the executive in matters of national interest, international matters and other issues that require a larger legal perspective than the domestic state and federal laws in the country.

Once appointed, judges cannot be removed at whim. They can retire voluntarily or they would serve till their term is up and they can be promoted. Judges can be removed only by impeachment and new judges can be appointed if a seat has been vacated due to the death of the sitting judge or some other reason.


Heterozygous and homozygous are two genetic possibilities in humans. There are of course other exceptional possibilities and even heterozygous or homozygous genes have variations. However, most newborns are either homozygous or heterozygous.

As is the case with the standards of nomenclature in biology, including genetics, homo means one or the same and hetero means two or different. Homozygous is a pair of genes that have the same characteristics. Heterozygous is a pair of genes that have different characteristics.

Heterozygous: Explained

You are perhaps aware that humans get two genes from their parents, one from the father and one from the mother. These two genes are also known as alleles that go on to form the one gene of the newborn. The two genes from the mother and father respectively may be of similar nature, thus having the same characteristics, or they may be different.

For instance, the mother and the father may be both genetically tall or short, they may have light or dark hair and they may both have black eyes, blue eyes or brown eyes. In every case, the genes of the father and mother can be dominant or recessive. For instance, tall parents have a dominant gene while short parents have a recessive gene. But that doesn’t matter as long as both the genes have the same traits, regardless of being dominant or recessed.

Heterozygous genes are a result of two different genes. Hence, if one gene is dominant then another has to be recessive and vice versa. Two dominant or two recessive genes cannot be heterozygous. They have to be homozygous. To make it simpler, if a tall parent and a short parent have a child, then it would be a heterozygous pair of genes. If both parents are tall or short, they it would be a homozygous pair of genes.

In case of heterozygous genes, the newborn may pick the trait of either parent or they may develop a new trait of their own as a result, which is referred to as mutation. For instance, a child born to a tall parent and short parent may not be short or tall. He or she may be somewhat of an average height. However, there is the possibility of the child being too short or too tall. A similar example can be drawn with eyes. If one parent has blue eyes and the other parent has brown eyes, then it is possible that the child may have blue eyes or brown eyes. It is also possible that the newborn will have green eyes. In this case, the green eyes are a result of the mutation of the two alleles of the gene. Neither blue nor brown eyes get inherited by the child.

In most cases, heterozygous genes offer more possibilities than homozygous genes. In homozygous genes, most kids will pick up the dominant trait of their parents. Tall parents will have tall kids. Both parents with black or brown eyes will have kids with black of brown eyes. Both white parents will have white kids. Both black parents will have black kids. If you replace one dominant trait with a recessive trait, one particular characteristic with another, then you have the possibility of either trait dominating or a new trait forming. Heterozygous genes are at the crux of mutation.

Heterozygous Genetic Traits

Let us imagine a scenario where ‘G’ is the dominant gene and ‘g’ is the recessive gene. Hence, homozygous genes or a homozygous pair of genes will be either GG or gg. A heterozygous pair of the same genes would be Gg or gG. Now, let us consider the possibility of one or both genes being affected by some disease or ailment as well as genetic traits that would be passed down to the newborn.

• If both parents are healthy, that is having GG and GG pairs, then the newborn will be absolutely healthy and normal. The baby will be born with GG. There is no possibility of any other trait.
• If one of the parents has a heterozygous pair, Gg or gG, and the other parent has GG or dominant homozygous pair, then the child has a fifty-fifty chance of going either way. The newborn may have a homozygous dominant pair, GG. The newborn may have a heterozygous pair, Gg or gG.
• If both parents have heterozygous pairs, Gg or gG, then the newborn has a three fourth possibility of having the same traits. The newborn could still be healthy with dominant homozygous pair of genes but that is just 25%.
• If both parents have recessive gene pairs (gg and gg), then the newborn would have recessive genes. If one parent has a homozygous recessive pair and the other parent has a homozygous dominant pair (gg and GG), then the result would be a heterozygous pair, one dominant and one recessive gene.


Our planet earth is classified into four spheres, which are just a way of creating subsystems of a similar kind. The planet is made of four major components: air, water, land and living things. The realm of our planet comprising of air is known as atmosphere. The realm comprising of water is known as hydrosphere. All living organisms, right from the algae to the plants, the wildlife to human beings, form the biosphere. All land or rocks and ground form the geosphere.

Geosphere: Explained!

The atmosphere encapsulates the planet. The hydrosphere forms a humongous majority of the surface and also a substantial part of the earth’s crust, including ground water. Biosphere comprising us is typically on the surface and at the most across the ocean floors, sea beds and some underground, which is again just the tip of the crust of the planet.

Geosphere is all the land and rock the planet is made of. The hard rocks on the surface of the earth or crust, the molten magma inside the earth or in the mantle, the mountains that stand tall above the sea level or surface, the hard and cold rocks, minerals and all kinds of hard or molten structures inside the earth including the core form the geosphere.

It must be noted that geosphere is not lithosphere. Many people mistakenly confuse the two. Lithosphere only comprises of the rocks and land that are on the surface of the earth. In other words, lithosphere is restricted to the earth’s crust. The molten magma and all the metal and minerals or solid and liquid components inside the mantle and the core do not form a part of the lithosphere. They do form a part of geosphere.

Everything other than air, water and living organisms is a part of geosphere, from the various types of rocks to the different levels of soil atop the crust, the deposits of oxygen and silicon, iron and magnesium to the gold, diamond and precious gemstones, from the radioactive elements to the fossils, natural gas reserves to coal.

Geosphere may be deemed by many to be the most important of the four spheres or subsections but it cannot be seen in isolation. The formation of the planet’s solid and molten structure is just as much significant as the formation of the other elements, from water to atmosphere because they coexist. Other than living organisms or the biosphere, the three spheres cannot be considered in isolation in an as is condition.


Fulcrum is any pivotal point that supports the movement of a lever. It is also referred to as fulcrum point by many. Usually, there is only one fulcrum or fulcrum point in a lever. Literally, fulcrum had an existence before being endorsed by the scientific community and defined by physicists.

Fulcrum: Explained!

Imagine a lever and how it works. There is a load at one end of the lever or someplace else in specific circumstances, there is the point at the other end or some other part of the lever where the effort is applied and there is one pivotal point that allows the lever to be in place, to be moved, lifted, rotated or just to have the effort applied resulting in the movement of the load.

The easiest to understand example of a fulcrum is the seesaw. There is a plank set on a fixed support. The two halves of the plank on either side of the fixed support are equal in length and weight. The fixed support is the fulcrum. The two kids sitting on the two ends of the plank are the load and effort respectively. In a given swing, one is the load and the other is the effort. In the subsequent swing, there is a role reversal. When one child gently kicks the ground allowing the plank to go up and the other child who is hoisted up swings down, the former is the effort and the latter is the load. This gets reversed. The fixed support in the middle which is firmly installed in the ground works as the fulcrum.

Fulcrum makes a lever functional. It is the secret to facilitating the lifting of heavier loads with little effort. Imagine a crowbar, pry bar and wrecking bar. They all work on the concept of a lever which wouldn’t work without the fulcrum.

Animals or humans also have fulcrum. Any fixed or pivotal point that allows movement can be referred to as a fulcrum. Hence, the shoulder joint that allows you to move your arms, the knee that allows you to bend your legs, the spine that lets you twist your body and the vertebral column in the neck that helps you to turn and look around are all fulcrums.

The word fulcrum is from the Latin verb ‘fulcire’ which literally means ‘to prop’. In Latin, fulcrum was used to refer to ‘bedpost’. Sometime in the 17th century when English got heavily influenced by Latin and numerous Latin words made into the English dictionary, also resulting in the creation of new words, the word ‘fulcrum’ was inducted and it was used to mean any point that supported movement or a certain action.


There are many types of literature or writings. There’s fiction and nonfiction. Both fiction and nonfiction are split into several categories, known as genres. There’s biography and autobiography, self help books and research papers or textbooks in nonfiction. There’s literary fiction, young adult fiction, science fiction, romance, drama and fantasy among others. Blurring the lines and beyond the realms of fiction and nonfiction are folklores, mythologies and legends.

Every form of writing or text has a certain style. There’s narrative text where the author writes from one or multiple perspectives. Narrative text can have beginnings, well formed plots and subplots, many characters and an ending among other literary structures. The narrative can be in first person, second person or third person and multiple perspectives are also facilitated by many authors. These types or styles of writing exist in fiction and nonfiction. One such style of writing is expository text.

Expository Text: Defined!

The term expository text comes from the term exposition. It is a method used in writing, even in plays and filmmaking, to get the audience or readers accustomed with certain facts or the reality. Exposition can also pertain to fiction where some matters of fact within the fictional world are established without playing a role in the narrative.

A narrative is just a narration of events, one leading to another, perhaps more than one event and then culminating in a climax. Expository text is more informational. It helps the readers or the audience to understand a particular process, concept, reality or just lays out the ground rules as a matter of fact.

Expository text can be at the very beginning of a written piece, somewhere in the middle or anywhere in the book or play.

Expository Text: Explained!

Let us consider a crime or mystery novel where the perpetrator has been caught and the trial is on. Now, the author may use expository text to lay out the legal process of trying the accused, how the evidence is being stacked up, under what sections the defendant is being tried and how the prosecution should go ahead and prove the accused or defendant to be guilty. This may or may not happen in the narrative but the process is laid out so the reader can understand.

Expository text can be used in all kinds of writing but is more popular in nonfiction. Expository text in fiction is used more as the foundation for dramatization and getting the audience accustomed with something imagined by the author than stating a fact.


Let us begin with two caveats. Energy pyramid is not exactly similar to the food chain. While there are similarities between an energy pyramid and a food chain, the latter includes many factors. An energy pyramid is strictly confined to the energy produced, consumed and released. It doesn’t really delve into the reasons why a certain food chain or the pyramid itself is designed that way.

Energy Pyramid: Definition

An energy pyramid is a diagram or a graphical representation of how energy is produced and how it flows from one group to another or one organism to another. An energy pyramid can be used to depict a food chain, it may be used to depict the various processes in a chemical equation and it may also be used to illustrate or depict a natural process of energy conversion and transmission in a graphical way.

Let us confine our discussion to food chain or energy producers and consumers. It is well known that only one form of life can produce their own food and is thus the energy producers. These producers can generate energy from nonliving elements in the ecology. These producers are also the ones that introduce the energy in the community of consumers. The producers are the plants and some single celled microorganisms that can make their own food.

The producers form the absolute bottom level of the energy pyramid. The second level from the bottom is of primary consumers who obtain energy from the producers. In other words, the primary consumers are herbivores as they feed on plants, fruits and vegetables. The third level from the bottom is of secondary consumers. These feed on the primary consumers. These are carnivores as they feed on living organisms. The fourth level from the bottom which is usually the topmost level at the tip of the pyramid feed on secondary consumers.

The number of levels can vary depending on the food chain. If humans are factored in along with all animals in the world, then the food chain would have more than ten levels. If only plants, fishes and birds are taken into consideration then four levels would be sufficient for the energy pyramid.

One may wonder why it is called an energy pyramid and why the graphical representation is in the form a triangle or pyramid. The reason is that every level upward, there is a decline in available and useful energy. The producers are the richest sources of energy, then the primary consumers and finally the secondary consumers. Tertiary consumers have very little energy left in them to become food or source of energy for another level.


Electromagnetic spectrum is the entire range of radiation that the sun produces and emits, a part of which is received by our planet earth. In some discussions, electromagnetic spectrum is often referred to as the heat generated by the sun and that heat traveling across the space and reaching different planets and satellites in the solar system. At times electronic magnetic spectrum is used to refer to the light emitted by the sun. It is not the heat or light in isolation. Electromagnetic spectrum pertains to the entire range of electromagnetic radiation of the sun, which includes heat and light.

Electromagnetic Spectrum: Explained

The sun has a substantial range of electromagnetic radiation. It is felt as heat and observed as light when it hits opaque objects in space but there is a large part of the radiation that is neither felt as hot nor observed as light in plain vision; that is unaided human sight. These radiations travel in waves. It is similar to how waves are created in the sea, lakes or even a small pond. Just as you would create waves if you throw a pebble or stone in a pond, lake or river, the sun creates waves of electromagnetic radiation. Some waves are very small, like the ones created in a lake if you throw a small stone. Some waves are large, like the ones created in a lake if you drop a large boulder in the water. You can consider the smaller waves as ripples in the river and the larger electromagnetic waves as the large waves in the sea. Just as the waves in rivers, lakes and seas vary, depending on the tides and other factors, the electromagnetic waves also vary in their sizes and distance traveled. Waves are measured as wavelengths.

Electromagnetic spectrum is the complete range that includes all the wavelengths of electromagnetic radiation. From the tiniest of wavelengths to the largest wavelength, everything forms the complete electromagnetic spectrum.

Types of Waves in the Electromagnetic Spectrum

For convenience and ease of study, the entire range of wavelengths has been broken down into three categories: short waves, medium sized waves and long waves. The short waves are known as ultraviolet waves. The midsized waves are known as visible light or visible light waves. The longer waves are known as infrared waves. The longest waves are further classified as radio waves and micro waves among others.

Let us quickly check the various types of electromagnetic waves and their wavelengths. To keep it simple, we are avoiding the frequency and energy of such waves.

  • The shortest wave is gamma rays with a wavelength of less than 10 pm. Then comes x-rays with wavelengths shorter than 10 nm. Extreme ultraviolet or UV has wavelength shorter than 200 nm and near UV has wavelength shorter than 380 nm.
  • Visible light shares a small range of wavelength with near UV and can be up to 780 nm. Wavelengths greater than that of visible light are infrared (IR).
  • Near IR has wavelength shorter than 2.5 um, mid IR is shorter than 50 um, far IR is shorter than 1 mm, microwaves are shorter than 100 mm and then there are radio waves. Radio waves are classified as ultrahigh frequency radio with wavelength shorter than 1 m, very high frequency radio is shorter than 10 m, shortwave is less than 180 m, medium radio wave is short of 650 m and long wave is short of 10 km. Very low frequency radio wave has a wavelength greater than 10 km.

Ultraviolet, visible light and infrared have been well defined and classified based on their wavelengths but every category does overlap with its preceding and succeeding category for a considerable portion of one another’s wavelengths. It has been observed that low energy gamma rays can have wavelengths greater than high energy x-rays.

These wavelengths are in vacuum or space. The wavelengths vary very little when the radiation enters the earth’s atmosphere. The air of our planet doesn’t interfere much with the wavelengths. However, if there is an opaque body or some kind of obstruction and medium that is not as unaffecting as the air or our atmosphere, then there can be substantial changes to the wavelengths of most waves.

The entire range of waves, right from gamma rays to very low frequency radio waves is the electromagnetic spectrum. This is the reason why it is factually and technically incorrect to simply refer to the visible light or the heat generated by the sun as the basis of the electromagnetic spectrum. It is essentially all the waves and not just what we can see or feel.

The recently discovered gravitational waves, which have been observed not once but twice now and the inferences have been peer reviewed, are not a part of the electronic spectrum.


There was no concept of a dwarf planet till 2006. There were planets, satellites, comets and asteroids, meteors and of course stars including the sun among others. In 2006, the concept of dwarf planet was developed and adopted by the International Astronomical Union. The idea and the objective were to classify a few objects in the solar system that are not as big to be planets but also not satellites, comets or asteroids. It must be noted that the concept of dwarf planet is not universally accepted. There are many who reject the definition and hence the classification of Pluto as a dwarf planet.

Dwarf Planet: Definition

There is a list of criteria that qualifies an object/rock in space as a dwarf planet. The body must orbit the sun, it should have its own gravity and should have a stable form, one that has attained hydrostatic equilibrium. The object while having enough gravity of its own should have failed to clear the neighborhood as it rotates/revolves and along its orbital path. Also, it must not be a satellite that orbits a planet.

The most notable incident that started the naming and subsequent debate pertaining to dwarf planet was the de-recognition of Pluto as a planet. Till 2008, Pluto was a planet but according to the definition of dwarf planet, it became one. There are four other dwarf planets that have been recognized and studied to an extent: Eris, Ceres, Makemake & Haumea.

Pluto did not have a cleared neighborhood, it was not too big in size for a planet and it was observed that there was no defined atmosphere for the object to be called a planet. However, latest evidences from the New Horizon’s mission of NASA may lead to re-recognize Pluto as a planet. There is evidence of cloud formation in the atmosphere of Pluto which will be debated in time to come.

Pluto is considered to be the biggest dwarf planet along with Eris. Ceres is a dwarf planet in the asteroid belt, which is between the orbits of Mars and Jupiter. Ceres was discovered long ago but it was regarded as a planet upon discovery and later was classified as an asteroid. It was classified as a dwarf planet after the concept was defined. Eris is considered by many as the largest dwarf planet. It was discovered in 2005 and was mistaken as the tenth planet. Eris and Makemake may have their orbits farther away from that of Pluto.


Cytoskeleton is the structure that gives living cells their form, shape and help in the movement of the cell. Imagine a cell being observed with the help of a microscope. It is a self contained unit having life of its own. This living cell would lack form or structure if there is nothing that keeps it intact. Just as our skeleton or the skeletal system of bones along with the muscles provide the physical form of our bodies, cytoskeleton defines the physical form and structure as well as movement of living cells.

Cytoskeleton: Explained

Cytoskeleton comprises of intercellular proteins which provide the shape, support the form and facilitate the movement of the living cells. The cytoskeleton also helps with cellular motility. It helps to move the vesicles within a cell. The cytoskeleton has three structural components known as microfilaments, intermediate filaments and microtubules. These form a network of fibrous proteins in a biological cell.

The framework inside the cell composed of actin filaments and microtubules extend throughout the fluid within the cell, which is known as cytosol. The cytoskeleton also helps in the growth of cells, including differentiation and division. All living multi-cellular structures or eukaryotic cells have a cytoskeleton. You could call cytoskeleton the backbone of a living cell.

Without the cytoskeleton, a living cell would not have any form or structure. It would not be a self contained unit with the nucleus or the larger cytoplasm. The cell would fall apart and it would not give birth to larger life, such as a living organism. Humans and all other living species can be reduced to the microscopic cells that also contain genetic information, thus helping in reproduction, growth and evolution. Without the cytoskeleton, none of this would be possible. It is possible that some other kind of living structures would be formed of cells that don’t have a cytoskeleton. Living organisms having a fixed or even a flexible form owe it to these tiny structures ensured by the cytoskeleton.

In a way, the structure and shape as well as the stretch of every bone, muscle, tissue and also the nerves, veins and arteries among others such as blood corpuscles can be broken down to the tiny cytoskeleton in every living cell.

Cytoskeleton is quintessential for the structural integrity, form, function and also the resistance of every living cell. Although the structure doesn’t have any role in evolution of the cell but it provides the foundation of every living cell as it is.


In an experiment, there are elements that are beyond your control. These could be constants or variables. Then there are elements that can be controlled. Such elements are changed or kept constant depending on the demands of the experiment, including the aim or objective. There are some fixed elements which are constants and some elements that change or can be changed which are called variables. The elements whose values can be changed can be classified into three types: dependent variable, independent variable and controlled variable.

Controlled Variable: Explained!

In simple words, a controlled variable is any element, quantum or feature in a given experiment or equation that can be fixed or would not be changed at all during the course of the experiment or equation. The controlled variable is not a constant. The element, its value or quantum can be changed but it would not be changed. Now, let us understand the dependent and independent variables to have a more lucid explanation of a controlled variable.

In any scientific experiment or even an equation, there will be many elements. Some elements are constant and some are variables. You cannot have all variables fluctuating or changing their values through the equation or the course of the experiment. Then, you would not have the desired result or outcome. The aim of the experiment will remain unaccomplished.

Usually, there is a cause of a reaction or process, an element that reacts and another element that facilitates the reaction. This is a simple way of explaining a scientific experiment, physical or mathematical equation and even chemical processes. The experimenter has to fix an element so it facilitates the equation or experiment in a specific way and doesn’t behave randomly or have any effects that are untraceable or unnecessary. This is the controlled variable. The experimenter needs one variable to have fluctuating values which is essentially the causal element. This is the independent variable. The value of this element can be changed at will. The independent variable and the controlled variable would facilitate the outcome which is the dependent variable. It must be noted that the dependent variable is not a constant. The value will change depending on the chosen value of the controlled variable and the specific value of the independent variable in a given equation or an experiment.

The value of a controlled variable will remain the same in one specific experiment regardless of how many times the same experiment is repeated with different values of the independent variable. The outcome which is the dependent variable will change depending on the value of the independent variable while acknowledging the constant value of the controlled variable.

Significance & Illustration of Controlled Variable

A controlled variable is quintessential in an experiment that has more than two elements, where the two elements are one cause and one outcome. If there are two elements in the causal phase, then one has to be controlled. If both elements change their values then the change in the outcome cannot be attributed to either of the elements or both. It would be difficult to truly understand which element changed the outcome and to what extent when their corresponding values underwent a change. Hence, one element must be fixed. The value must be unchanged. Changing the value of the other element, which is the independent variable, will lead to a change in the value of the outcome, the dependent variable.

Controlled variable is more than significant. It is quintessential for any experiment that has more than two elements. In cases where there are multiple elements, say four or more, there can be more than one controlled variable. It is quite desirable to have just one independent variable and all other controlled variables leading to one dependent variable. That is the simplest and fairest of all scientific experimentations or mathematical equations.

A controlled variable has to be an element that can be managed or kept constant. If the value is beyond the control of the experimenter then it cannot be a controlled variable. However, most elements can be controlled, be it the amount of light, temperature, force, humidity or time. It may be argued that time cannot be stopped or sped up so one doesn’t actually get to control time. But you can always fix the time. It is possible that a certain chemical process takes two minutes and another takes three minutes. By opting for a fixed time for both experiments, say two and a half minutes, you can observe the changes of the elements in regards to the allotted time.

Over the years, it has been formulated and also made imperative that only one independent variable be used in an experiment to have one outcome, the dependent variable. All other elements must be controlled variables. You can change that by controlling the independent variable and allowing one controlled variable to become independent in another set of experiments.