Name: how scientists test a hypothesis
Uploaded: 2020-09-03T13:38:25.000Z
Duration: 3 min 50 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Chemistry

Matter and its Interactions

PS.Chm.1.1

The Scientific Method

O método científico é uma abordagem sistemática seguida por todas as disciplinas científicas. Segue seis passos principais fazer uma observação, fazer uma pergunta, desenvolver uma hipótese, realizar experiências, interpretar dados, e finalmente, chegar a uma conclusão. O método científico começa com uma observação e uma pergunta para ajudar a compreender essa observação.Por exemplo, o químico francês Antoine Lavoisier observou os fenómenos da combustão. Ele formulou uma pergunta para compreender o que acontece quando algo é queimado. Para onde vai a matéria?O terceiro passo do método científico é desenvolver uma hipótese uma explicação provisória para a observação em questão, que pode ser testada. Em resposta à sua pergunta de para onde vai a matéria? Lavoisier formulou a hipótese de que numa reação química, a matéria não foi criada, nem destruída.Uma boa hipótese também é testável e falsificável. Uma hipótese testável é uma hipótese que faz previsões que podem ser confirmadas por experiências ou observações. É falsificável quando pode ser refutada pela experimentação.O quarto passo do método científico é a experimentação e o recolhimento de dados. As experiências são observações ou medições realizadas sob ambientes controlados tais como temperatura, pressão ou volume. Este passo investiga até que ponto o mundo real se encaixa no previsto pela hipótese.Algumas experiências e observações são qualitativas descrevem como um processo acontece. Outras são quantitativas medem ou quantificam algo sobre o processo. Lavoisier testou a sua hipótese através do aquecimento do mercúrio num ambiente fechado.Isto levou à formação de uma substância avermelhada. As suas experiências foram quantitativas, por isso, registou cuidadosamente a massa de reagentes e os produtos no sistema fechado bem como separadamente. O quinto passo é a interpretação e análise de dados avaliar se os resultados apoiam ou refutam a hipótese e caso seja necessária mais experimentação.Lavoisier observou que a massa total do frasco e do seu conteúdo antes e depois da reação permaneceu igual, embora a massa do produto vermelho fosse maior do que o mercúrio original. O passo final é chegar a uma conclusão lógica e decidir se se aceita ou se rejeita a hipótese. Se os resultados apoiarem fortemente a hipótese, então é aceite.Também pode ser submetida a mais testes ou refinada, fazendo novas perguntas, e realizando novas experiências. A partir das suas experiências, Lavoisier concluiu que uma vez que a massa total do frasco permaneceu inalterado durante a reação, o oxigénio no frasco aliado com o mercúrio para formar o novo produto, agora conhecido como óxido de mercúrio Esta conclusão apoiou fortemente a sua hipótese sobre a conservação da massa que a massa total dos objetos permanece inalterada durante o processo de combustão. No entanto, se uma hipótese for refutada, então os cientistas podem formular uma nova hipótese aproveitando as pistas das experiências falhadas, e começarem de novo.Ainda que vejamos o método científico como uma série de passos, as novas informações ou ideias podem fazer um cientista ter de recuar e repetir passos em qualquer momento durante o processo. Desta forma, o método científico é um processo iterativo.

o método científico

A química é uma ciência empírica. Os cientistas muitas vezes fazem perguntas para entender a química na vida cotidiana e procuram respostas para essas perguntas. Para alcançar este objectivo, os cientistas seguem uma série definida de passos que, em conjunto, constituem o método científico. Esta abordagem envolve fazer observações, fazer perguntas, criar uma hipótese, realizar experiências, analisar resultados, e formar uma conclusão. 

<h4>Observação e Pergunta</h4>

O primeiro passo no método científico é observar um fenómeno no mundo físico. Em seguida, coloca-se uma questão para compreender melhor esse fenómeno. Por exemplo, a pergunta poderia ser: “O que congela mais rapidamente, água pura ou água com adição de sal?”

<h4>Hipótese </h4>

O próximo passo é formular uma explicação para a observação específica. Esta interpretação provisória de um conjunto de observações que atua como guia para a compreensão do fenómeno observado é chamada de hipótese. Por exemplo, para a questão acima, uma hipótese poderia sugerir que a adição de sal altera o ponto de fusão da água pura. 

Os cientistas muitas vezes usam estudos e literatura anteriores para iniciarem a sua investigação e formularem uma hipótese que poderia ser testada através de experiências. Uma hipótese forte é tanto testável como falsificável. É considerada testável se puder ser provada correcta, e falsificável se puder ser provada incorrecta—nesse caso, o cientista deve modificar ou descartar a hipótese. 

<h4>Experimentação </h4>

O terceiro passo é projectar e realizar experiências para testar a validade da hipótese. As experiências são medições e observações efectuadas em condições controladas. Algumas observações e experiências são qualitativas (descrição de como um processo acontece), enquanto que muitas são quantitativas (medição ou quantificação de algo sobre o processo). Para testar a hipótese da água salgada, o cientista pode ter dois copos com quantidades iguais de água, à temperatura ambiente. Pode ser adicionada uma colher de sal a um dos copos, e ambos os copos colocados no congelador. O estado da água em cada copo pode ser observado a cada 15 minutos e o tempo necessário para cada copo de água ficar completamente congelado pode ser registado.  

O desenho experimental é um passo crítico no método científico. Deve-se ter cuidado para controlar o número de factores variáveis para que o efeito de um factor específico em questão possa ser monitorizado. 

<h4>Análise de Resultados e Conclusão</h4>

O próximo passo é analisar os resultados das experiências e concluir se esses resultados validam ou não a hipótese. Se a conclusão é que validam, então a hipótese é aceite e pode ser sujeita a novas experiências para responder a novas perguntas. Quando se prova que uma hipótese está errada, pode-se propor uma nova hipótese, e o processo continua. 

No exemplo da água salgada, os resultados indicam que a água salgada demora mais tempo a congelar do que a água pura. Isto fornece a conclusão de que a água com sal congela a uma velocidade mais lenta do que a água pura. Assim, os resultados validam a hipótese. 

Este texto é adaptado de <a href="https://openstax.org/books/chemistry-2e/pages/1-1-chemistry-in-context">Openstax, Chemistry 2e, Section 1.1: The Scientific Method.</a>

O Método Científico

A química é uma ciência empírica. Os cientistas costumam fazer perguntas para entender a química na vida cotidiana e buscar respostas para essas perguntas. Para...

Education

JoVE Core

Química

Introduction: Matter and Measurement

Introdução: Matéria e Medida

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

how scientists test a hypothesis

Chemistry uses the scientific method to turn observations into testable answers. Scientists begin by observing a phenomenon in the physical world and then asking a question about it. This process helps explain everyday chemistry through evidence.

A question leads to a hypothesis, which is a tentative explanation for what is being observed. Scientists often use earlier research and published literature to shape that idea. A strong hypothesis must be testable, meaning it can be supported by evidence, and falsifiable, meaning it can also be proven wrong.

The next step is experimentation. Scientists design and carry out experiments under controlled conditions to test the hypothesis. These tests can include qualitative observations, which describe how a process happens, and quantitative measurements, which record how much or how long something changes.

A clear example is the freezing of plain water and salt water. A scientist can place equal amounts of room-temperature water into two glasses, add salt to one glass, and put both in a freezer. By checking the glasses every 15 minutes and recording the time until each one freezes, the scientist can compare the results while keeping other variables controlled.

After the experiment, the results are analyzed and used to form a conclusion. If the data support the hypothesis, it may be accepted and tested further with new questions. If the hypothesis is not supported, a new one can be proposed and the process begins again. In the salt-water example, the results show that salt water freezes more slowly than plain water, so the hypothesis is validated.

How Scientists Test a Hypothesis

scientific laws and theories

How Science Explains Laws and Theories

Scientific laws and scientific theories describe science in two different ways. A law is a concise verbal or mathematical statement that summarizes many experimental observations. It describes or predicts aspects of the natural world that stay the same under the same conditions. A scientific theory is different because it explains why natural events happen. It is a unifying principle that gives a well-supported and testable explanation for a broad set of observations. Strong theories are the...

the scientific method

Chemistry uses the scientific method to turn observations into testable answers. Scientists begin by observing a phenomenon in the physical world and then asking a question about it. This process helps explain everyday chemistry through evidence. A question leads to a hypothesis, which is a tentative explanation for what is being observed. Scientists often use earlier research and published literature to shape that idea. A strong hypothesis must be testable, meaning it can be supported by...

physical and chemical properties of matter

physical-and-chemical-properties-of-matter

Distinguishing Physical and Chemical Changes

Matter can be identified by its properties, which are the features that help us tell one substance from another. These properties fall into two main groups: physical properties and chemical properties. Understanding the difference helps explain how matter changes. A physical property is a feature of matter that is not linked to a change in chemical composition. Examples include density, color, hardness, melting point, boiling point, and electrical conductivity. Some physical properties can be...

what is energy?

Energy Forms and Conservation

Energy is a property of matter that appears in many forms. On Earth, most energy starts with the Sun. Plants capture light energy from the Sun and use photosynthesis to turn it into chemical energy. That stored energy can then move through living things and materials in several ways. People get energy from plant foods, and wood or coal, which come from fossilized plants, can be burned to produce heat and electricity. Energy is defined as the ability to do work. Work happens when a force moves...

classifying matter by state

States of Matter and Their Properties

States of matter help describe how matter behaves in chemistry. Matter is anything that has mass and takes up space. It is found everywhere, including air, water, soil, mountains, and even our bodies. The three common states on Earth are solid, liquid, and gas. A solid has a definite shape and a definite volume. Its particles, such as atoms or molecules, are packed very closely together and held in place by strong forces, so they only vibrate slightly. This tight arrangement makes solids...

measurement: standard units

Measurement: SI Units and Conversions

Measurement gives three kinds of information: a number, a unit, and an estimate of uncertainty. The number shows size or magnitude. The unit gives a standard for comparison. The uncertainty reflects possible error in the measurement. Numbers can be written in more than one way. A value may appear in decimal form or in scientific notation, which is also called exponential notation. For example, the maximum take-off weight of a Boeing 777-200ER airliner is 298,000 kilograms, or 2.98 × 10^5 kg. <br...

classifying matter by composition

Matter: Elements, Compounds, and Mixtures

Matter can be grouped by composition into pure substances and mixtures. A pure substance has a constant composition throughout and uniform properties. For example, any sample of sucrose has the same composition and the same physical properties, such as melting point, color, and sweetness, no matter where it is isolated from. A mixture contains two or more kinds of matter in varying amounts. Its parts can be separated by physical changes, such as evaporation. The components keep their own...

measurement: derived units

SI Units, Density, and Property Types

SI units and derived units help describe physical properties in chemistry. The International System of Units, or SI system, uses agreed-upon base units for seven fundamental properties: length, mass, time, temperature, electric current, amount of substance, and luminosity. Units made by combining these base units are called SI-derived units. Speed is one example. If distance is measured in meters and time in seconds, the derived unit for speed is meters per second, or m/s. Miles per hour is...

dimensional analysis

Using Conversion Factors to Cancel Units

Dimensional analysis is a method for using conversion factors to cancel units and solve measurement problems. It is also called the factor label method. The main rule is that units must be treated the same way as the numbers attached to them. A conversion factor is a ratio of two equal quantities written in different units. For example, 1 meter is equal to 1.0936 yards. That relationship can be used to build a factor that converts one unit into the other. When a value is multiplied or divided...

uncertainty in measurement: accuracy and precision

uncertainty-in-measurement-accuracy-and-precision

Measurement Error: Reading Results Correctly

Measurement error affects how scientists judge the quality of their results. Repeated measurements help show whether results are precise and accurate. A measurement is precise when repeated values are very similar. A measurement is accurate when it is very close to the true or accepted value. Precise values agree with each other, while accurate values agree with the true value. A pharmaceutical quality control chemist can use this idea to check machines that dispense 500 mL of cough syrup. The...

uncertainty in measurement: reading instruments

uncertainty-in-measurement-reading-instruments

Measurement Uncertainty and Significant Figures

Measurement uncertainty and significant figures show how carefully a value can be read from an instrument. Counting is different. If the number of objects does not change during counting, the result is exact. Defined quantities are exact too. For example, 1 foot is exactly 12 inches, 1 inch is exactly 2.54 centimeters, and 1 gram is exactly 0.001 kilograms. Most other measurements are not exact because the measuring process has limits. The result depends on the device used and on the person...

uncertainty in measurement: significant figures

uncertainty-in-measurement-significant-figures

Significant Figures and Rounding Rules

Significant figures and rounding rules help students report measurements with the right level of certainty. A measurement includes every digit that was actually measured, including the last uncertain digit. That is why a value can look simple but still carry useful information about the tool used to measure it. Zero can also be significant when it is part of a measured value. For example, if a scale reads 140 pounds to the nearest pound, the 1, 4, and 0 are all significant. Reporting...

key terms and concepts

Explore how scientists use observations, hypotheses, controlled experiments, and data analysis to test ideas, using a salt water freezing example.

How Scientists Test a Hypothesis | JoVE K12

chemistry

JoVE Core - Química dá vida a conceitos gerais de química usando vídeos de animação fáceis de entender. Além disso, nos vídeos Cientistas em ação, demonstramos experimentos de pesquisa clássicos e originais realizados atualmente por cientistas em laboratórios em todo o mundo.

Virginia  Standards of Learning

HIgh School

Earth Science

ES.1

ES.1.a

ES.1.f

Life Science

LS.1

LS.1.a

LS.1.f

Physical Science

PS.1

PS.1.f

Physics

PH.1

PH.1.f

Texas Essential Knowledge and Skills

High School

CHEM.1

CHEM.1.A

CHEM.1.H

Florida Department of Education

Nature of Science

SC.912.N.1

SC.912.N.1.1

SC.912.N.1.2

SC.912.N.2

SC.912.N.2.1

PHYS.4

PHYS.4.A

PHYS.4.B

Chemistry and Physics

IPC.4

IPC.4.A

Scientific Laws and Theories

Scientific Laws

In science, a law is defined as a concise, verbal or mathematical, statement that summarizes a vast number of experimental observations. ...

Chemistry is an empirical science. Scientists often pose questions to understand the chemistry in everyday life and seek answers to these questions. To ...

Classifying Matter by State

Chemistry is the study of matter and the changes it undergoes. Matter is anything that has mass and occupies space. Matter is all around us; the air, ...

Classifying Matter by Composition

Matter: Pure Substances and Mixtures
According to its composition, the matter can be classified into two broad categories &mdash; pure substances and ...

The Atomic Theory of Matter

The earliest recorded discussion of the basic structure of matter comes from ancient Greek philosophers. Leucippus and Democritus argued that all matter ...

Subatomic Particles

Dalton was only partially correct about the particles that make up matter. All matter is composed of atoms, and atoms are composed of three smaller ...

Elements: Chemical Symbols and Isotopes

A chemical symbol is an abbreviation used to indicate an element or an atom of an element. For example, the symbol for mercury is Hg. The same symbol is ...

Use models to explain how the scientific understanding of atomic structure has evolved.

Radioactivity and Nuclear Equations

Nuclear chemistry is the study of reactions that involve changes in nuclear structure. The nucleus of an atom is composed of protons and, except for ...

Types of Radioactivity

The most common types of radioactivity are &#945; decay, &#946; decay, &#947; decay, neutron emission, and electron capture.
Alpha (&#945;) decay is the ...

Nuclear Stability

Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10&#8722;15 meters, a nucleus is ...

Nuclear Binding Energy

The difference between the calculated and experimentally measured masses is known as the mass defect of the atom. In the case of helium-4, the mass defect ...

Radioactive Decay and Radiometric Dating

Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. ...

Nuclear Fission

Many heavier elements with smaller binding energies per nucleon can decompose into more stable elements that have intermediate mass numbers and larger ...

Nuclear Power

Controlled nuclear fission reactions are used to generate electricity. Any nuclear reactor that produces power via the fission of uranium or plutonium by ...

Nuclear Fusion

The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process ...

Nuclear Transmutation

Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with ...

Use models to compare nuclear reactions including alpha decay, beta decay and gamma decay; nuclear fusion and nuclear fission.

PS.Chm.1.2

Atomic Orbitals

An atomic orbital represents the three-dimensional regions in an atom where an electron has the highest probability to reside. The radial distribution ...

The Pauli Exclusion Principle

The arrangement of electrons in the orbitals of an atom is called its electron configuration. We describe an electron configuration with a symbol that ...

The Energies of Atomic Orbitals

In an atom, the negatively charged electrons are attracted to the positively charged nucleus. In a multielectron atom, electron-electron repulsions are ...

The Aufbau Principle and Hund's Rule

To determine the electron configuration for any particular atom, we can build the structures in the order of atomic numbers. Beginning with hydrogen, and ...

electron-configuration-of-multielectron-atoms

Electron Configuration of Multielectron Atoms

The alkali metal sodium (atomic number 11) has one more electron than the neon atom. This electron must go into the lowest-energy subshell available, the ...

Use models to explain how electrons are distributed in atoms.

PS.Chm.1.3

Periodic Classification of the Elements

The periodic table arranges atoms based on increasing atomic number so that elements with the same chemical properties recur periodically. When their ...

The Periodic Table

As early chemists discovered more elements, they realized that various elements could be grouped by their similar chemical behaviors. One such grouping ...

Atomic Mass

Atoms &mdash; and the protons, neutrons, and electrons that compose them &mdash; are extremely small. For example, a carbon atom weighs less than 2 ...

Molar Mass

The identity of a substance is defined not only by the types of atoms or ions it contains but by the quantity of each type of atom or ion. For example, ...

Use the Periodic Table as a model to predict the relative properties of elements based on the pattern of valence electrons in the outermost energy levels of atoms.

PS.Chm.2.1

atomic-radii-and-effective-nuclear-charge

Atomic Radii and Effective Nuclear Charge

The elements in groups of the periodic table exhibit similar chemical behavior. This similarity occurs because the members of a group have the same number ...

Ionic Radii

Ionic radius is the measure used to describe the size of an ion. A cation always has fewer electrons and the same number of protons as the parent atom; it ...

Ionization Energy

The amount of energy required to remove the most loosely bound electron from a gaseous atom in its ground state is called its first ionization energy ...

Electron Affinity

The electron affinity (EA) is the energy change for adding an electron to a gaseous atom to form an anion (negative ion).



This process can be either ...

Construct an explanation to infer the atomic size, reactivity, electronegativity, and ionization energy of an element based on its position in the Periodic Table.

PS.Chm.2.2

Types of Chemical Bonds

Chemical bonding theories were pioneered by American chemist Gilbert&#xA0;N. Lewis. He developed a model called the Lewis model to explain the type and ...

Lewis Symbols and the Octet Rule

Chemical bonds are complex interactions between two or more atoms or ions, which reduce the potential energy of the molecule. Gilbert N. Lewis developed a ...

Ionic Bonding and Electron Transfer

Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence ...

The Born-Haber Cycle

Lattice Energy&#xA0;

An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a ...

trends-in-lattice-energy-ion-size-and-charge

Trends in Lattice Energy: Ion Size and Charge

An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a compound is a measure ...

Covalent Bonding and Lewis Structures

Compared to ionic bonds, which results from the transfer of electrons between metallic and nonmetallic atoms, covalent bonds result from the mutual ...

Electronegativity

Whether a bond is nonpolar or polar covalent is determined by a property of the bonding atoms called electronegativity.&#xA0;

Electronegativity values of ...

bond-polarity-dipole-moment-and-percent-ionic-character

Bond Polarity, Dipole Moment, and Percent Ionic Character

Bond Polarity

The absolute value of the difference in electronegativity (&Delta;EN) of two bonded atoms provides a rough measure of the polarity to be ...

lewis-structures-of-molecular-compounds-and-polyatomic-ions

Lewis Structures of Molecular Compounds and Polyatomic Ions

To draw Lewis structures for complicated molecules and molecular ions, it is helpful to follow a step-by-step procedure as outlined:


	Determine the ...

Resonance

The Lewis structure of a nitrite anion (NO2&minus;) may actually be drawn in two different ways, distinguished by the locations of the N-O and N=O ...

Formal Charges

In some cases, there are seemingly more than one valid Lewis structures for molecules and polyatomic ions. The concept of formal charges can be used to ...

Exceptions to the Octet Rule

Many covalent molecules have central atoms that do not have eight electrons in their Lewis structures. These molecules fall into three categories:


	...

Bond Energies and Bond Lengths

Stable molecules exist because covalent bonds hold the atoms together. The strength of a covalent bond is measured by the energy required to break it, ...

Analyze and interpret data to explain the mechanisms and properties of the two main types of intramolecular (ionic and covalent) bonds.

PS.Chm.3.1

molecular-comparison-of-gases-liquids-and-solids

Molecular Comparison of Gases, Liquids, and Solids

Particles in a solid are tightly packed together (fixed shape) and often arranged in a regular pattern; in a liquid, they are close together with no ...

Construct an explanation to summarize the influences intermolecular forces have on the properties of chemical compounds.

PS.Chm.3.2

Analyze the structure of atoms and isotopes.

How Scientists Test a Hypothesis

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