Name: absorbance spectra and beer-lambert analysis
Uploaded: 2020-03-26T07:22:26.000Z
Duration: 2 min 53 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Chemistry and Physics

IPC.7

IPC.7.E

Beer's Law

Wiele reakcji chemicznych przebiega w dwóch kierunkach, do przodu i do tyłu. Z biegiem czasu reakcje do przodu i do tyłu będą zachodzić w tym samym tempie, a stężenie reagentów i produktów nie będzie się już zmieniać. Jest to tak zwana równowaga chemiczna.
W równowadze chemicznej stężenia każdego składnika są powiązane ze sobą stałą równowagi K, która jest stosunkiem stężeń produktu do stężeń reagentów, z których każdy jest podniesiony do potęgi ich współczynników stechiometrycznych.
Ale jak określić stężenia równowagi? Jedna z metod mierzy intensywność długości fali światła, którą produkt pochłania przed i po przejściu przez próbkę. Różnica intensywności nazywana jest absorbancją i odpowiada ilości związku absorbującego w próbce.
Być może pamiętasz, że elektrony w większości zajmują stan podstawowy. Kiedy pochłaniają pewną ilość energii, są wzbudzone do wyższego poziomu energii. Energia ta odpowiada określonej długości fali światła. Możesz znaleźć tę długość fali i zmierzyć absorbancję za pomocą spektrofotometru, który kieruje wiązkę światła przez próbkę i mierzy zmianę intensywności na jednej lub więcej długościach fali.
Absorpcja jest równa ujemnemu logarytmowi natężenia światła tłumionego w stosunku do natężenia światła padającego. Wykreślając wartości absorbancji wielu roztworów o różnych znanych stężeniach produktu, obserwujemy liniową zależność między absorbancją a stężeniem. Jest to przykład prawa Piwa.
Prawo Beera jest wyrażone matematycznie za pomocą tego równania, gdzie A to absorbancja, epsilon to molowy współczynnik tłumienia, stała zmienna dla każdego związku, l to długość drogi światła przez próbkę, a c to stężenie związku.
Identyfikując funkcję liniową dla danego związku przy określonej długości fali i długości ścieżki, można wykorzystać dane absorbancji roztworu w stanie równowagi do określenia stężenia równowagowego produktu. Stamtąd możesz obliczyć stężenia równowagowe reagentów i rozwiązać stałą równowagi. W tym laboratorium przygotujesz roztwory izotiocyjanianu żelaza(III) i użyjesz spektrofotometru do określenia jego absorbancji przy różnych stężeniach.

prawo piwa

Absorbancja i fluorescencja
Kiedy światło pada na substancję, jest albo pochłaniane, przepuszczane, albo odbijane. Zazwyczaj substancja oddziałuje z zakresem długości fal światła, z których każda oddziałuje inaczej z cząsteczkami lub atomami. Substancja może absorbować określony zakres długości fal, odbijać inny zakres długości fal i transmitować inne długości fal światła.
Kiedy cząsteczka pochłania światło, energia jest wykorzystywana na cztery różne sposoby: (1) translacja, która powoduje, że cząsteczka zmienia swoją prędkość cząsteczkową; (2) wibracje, które powodują gwałtowną zmianę odległości między cząsteczkami; (3) rotacja, która powoduje, że atomy obracają się wokół wiązań w cząsteczce; oraz (4) wzbudzenie elektronów, które powoduje przejście elektronów na wyższe poziomy energetyczne.
<h4>Poziomy energii</h4>
W 1913 roku Niels Bohr zaproponował model atomu wodoru, w którym elektrony poruszają się wokół jądra po stałych, kołowych orbitach, zwanych stanami stacjonarnymi. Energia związana z każdą orbitą lub stanem stacjonarnym istnieje tylko przy stałych, dyskretnych energiach. Tylko wtedy, gdy elektron przemieszcza się na inną orbitę, energia jest pochłaniana lub emitowana. Elektron nigdy nie znajduje się w stanach pośrednich. Zmiana ta występuje tylko wtedy, gdy pochłonięta lub wyemitowana energia jest równa różnicy między dwoma stanami energetycznymi.
W modelu Bohra liczba kwantowa n reprezentuje energię elektronu. Kiedy elektron znajduje się w najniższym możliwym stanie energetycznym, mówi się, że zajmuje stan podstawowy, który wynosi n = 1. Kiedy elektron absorbuje foton, którego energia jest równa różnicy między stanem pierwszym a drugim, elektron zostaje wzbudzony i przechodzi ze stanu podstawowego do stanu wzbudzonego, gdzie n = 2. Jeśli energia fotonu jest równa różnicy między pierwszym a trzecim stanem, elektron przechodzi do stanu trzeciego, czyli n = 3 i tak dalej.
Elektrony mogą spontanicznie powrócić do stanu podstawowego lub dowolnego innego niższego, wzbudzonego stanu. Kiedy tak się dzieje, nadmiar energii, który został uzyskany w wyniku wzbudzenia, jest uwalniany w postaci wyemitowanego fotonu. Energia fotonu jest równa różnicy między dwoma stanami energetycznymi i odpowiada różnym długościom fal światła.
<h4>Widma absorpcyjne i emisyjne</h4>
Podczas gdy większość substancji pochłania lub emituje maksymalną ilość światła na jednej długości fali, mają one również tendencję do pochłaniania lub emitowania światła o różnych długościach fal. Ten zakres długości fal nazywa się widmem. Energia pochłoniętego światła jest określana ilościowo i wizualizowana za pomocą widma absorpcyjnego, podczas gdy energia emitowanego światła jest określana ilościowo i wizualizowana za pomocą widma emisyjnego.
Widma absorpcyjne i emisyjne są mierzone za pomocą spektrofotometru, który jest urządzeniem, które przepuszcza światło przez próbkę, a następnie mierzy zarówno długość fali, jak i intensywność światła, które przez nią przechodzi. Wewnątrz spektrofotometru znajduje się albo siatka dyfrakcyjna, albo pryzmat, który rozdziela wpadające światło na długości fal składowych. Różne długości fal są następnie przesyłane przez próbkę, a intensywność jest rejestrowana w detektorze liniowego urządzenia sprzężonego z ładunkiem (CCD). CCD to układ scalony wytrawiony na powierzchni krzemu, który tworzy światłoczułe elementy zwane pikselami. Matryca CCD zbiera i sortuje światło dyfrakcyjne i odczytuje je z powrotem na długości fali absorpcyjnej.
Podczas pomiaru absorbancji próbki substancja rozpuszczona jest zwykle rozpuszczana w rozpuszczalniku i umieszczana w pojemniku zwanym kuwetą. Następnie próbkę umieszcza się w spektrofotometrze, a natężenie przepuszczanego światła mierzy się wraz z długościami fal światła w celu uzyskania widm absorbancji. Zgodnie z oczekiwaniami natężenie przepuszczanego światła jest mniejsze niż w przypadku, gdy wewnątrz spektrofotometru nie ma próbki.
Dzieje się tak, ponieważ przepuszczane światło jest pochłaniane przez próbkę, kuwetę i rozpuszczalnik. Przed pomiarem próbek spektrofotometr musi zostać skalibrowany za pomocą "ślepej próby". Ślepa próba to kuweta, która zawiera tylko rozpuszczalnik używany do rozpuszczenia substancji rozpuszczonej. Spektrofotometr jest kalibrowany w taki sposób, że całkowita absorbancja spowodowana przez kuwetę i rozpuszczalnik jest odejmowana od zmierzonej absorbancji próbki. Dzięki temu możemy zarejestrować absorbancję, która jest przypisywana tylko do gatunku będącego przedmiotem zainteresowania.
Absorbancja jest często mierzona przy jednej długości fali, maksymalnej długości fali absorbancji. Jednak absorpcję można również zmierzyć w zakresie długości fal, aby uzyskać widmo absorpcyjne. W tym celu próbka jest wystawiana na działanie zakresu długości fal padającego światła, a absorpcja jest rejestrowana na każdej długości fali. Jeśli próbka emituje światło, widmo emisyjne mierzy się podobnie, z wyjątkiem tego, że długość fali padającej jest ustalona na długości fali o maksymalnej absorbancji. Następnie instrument mierzy intensywność emitowanego światła w zakresie długości fal.
<h4>Prawo Beera-Lamberta</h4>
Absorbancja próbki przy długości fali maksymalnej absorbancji dostarcza informacji o próbce, a mianowicie o jej stężeniu. Prawo Beera-Lamberta to równanie, które wiąże transmitancję ze stężeniem próbki. Przepuszczalność lub intensywność światła przechodzącego to ułamek światła pierwotnego, który przechodzi przez próbkę, I, podzielony przez natężenie padającego światła, I0.
<img src="/CDNSource/lm/labs/49/49_Concepts_1.jpg" alt="Równanie transmitancji \(T = \frac{I}{I_0}\), wykres do analizy gęstości optycznej." data-altupdatedat="1754907201000">
Prawo Beera-Lamberta mówi, że absorbancja optyczna A gatunku w roztworze jest związana z ujemnym logarytmem transmitancji.
<img src="/CDNSource/lm/labs/49/49_Concepts_2.jpg" alt="Wzór absorbancji A=-log(T), równanie do analizy absorpcji optycznej w badaniach spektroskopowych." data-altupdatedat="1754907201000">
Alternatywna wersja prawa Beera-Lamberta mówi, że absorbancja optyczna A gatunku w roztworze jest liniowo proporcjonalna do stężenia c tego gatunku, gdy długość fali λ i długość drogi l są utrzymywane na stałym poziomie.
<img src="/CDNSource/lm/labs/49/49_Concepts_3.jpg" alt="Równanie prawa Beera-Lamberta, A=εcl, koncepcja absorpcji, spektroskopowa analiza danych, diagram fizyczny." data-altupdatedat="1754907201000">
Molowy współczynnik tłumienia ε jest miarą tego, jak silnie gatunek pochłania światło o danej długości fali. Im większy molowy współczynnik tłumienia, tym większa absorbancja. Długość ścieżki, l, to odległość, jaką światło pokonuje przez próbkę, czyli szerokość kuwety. Standardowe kuwety mają długość ścieżki 1 cm.
Ta liniowa zależność między absorbancją a stężeniem jest potężnym narzędziem, które służy do określania stężenia nieznanej próbki na podstawie jej absorbancji. W tym celu generowana jest krzywa standardowa przy użyciu gradientu znanych stężeń substancji rozpuszczonej. Absorbancja przy szczytowej długości fali absorbancji, λmax, jest mierzona dla każdego stężenia.
Wykreślając stężenie w funkcji absorbancji, obserwuje się zależność liniową, która odpowiada równaniu Beera-Lamberta. Nachylenie tej linii jest równe iloczynowi długości drogi i molowego współczynnika tłumienia. Korzystając z tej obliczonej funkcji liniowej, jeśli znana jest absorbancja nieznanej próbki, można łatwo określić stężenie.
Jeśli analizowana próbka jest reakcją w stanie równowagi, prawo Beera można wykorzystać do określenia stężenia równowagowego produktu lub reagenta, jeśli absorbancja jest mierzona przyλ max specyficznym dla tego produktu lub reagenta. Gdy stężenie jest znane, można określić stężenia równowagowe pozostałych reagentów i produktów, a następnie rozwiązać stałą równowagiK eq.
<h4>Odwołania</h4>
<ol>
	<li style="font-size:17px">Kotz, J.C., Treichel Jr, P.M., Townsend, J.R. (2012). Chemia i reaktywność chemiczna. Belmont, Kalifornia: Brooks/Cole, Cengage Learning.</li>
	<li style="font-size:17px">Silderberg, M.S. (2009). Chemia: molekularna natura materii i zmiana. Boston, Massachusetts: McGraw Hill, Boston.</li>
	<li style="font-size:17px">Harris, D.C. (2015). Ilościowa analiza chemiczna. Nowy Jork, NY: W.H. Freeman and Company.</li>
</ol>

Prawo piwa

Absorbancja i fluorescencja
Kiedy światło pada na substancję, jest albo pochłaniane, przepuszczane, albo odbijane. Zazwyczaj substancja wchodzi w interakcje z zakresem ...

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absorbance spectra and beer-lambert analysis

Absorbance spectra and the Beer-Lambert Law show how light can be used to study molecules in solution. When light hits a substance, it may be absorbed, transmitted, or reflected. A substance often interacts with a range of wavelengths, and each wavelength can affect the molecules or atoms in a different way.

When a molecule absorbs light, that energy can be used for translation, vibration, rotation, or electron excitement. Electron excitement is especially important in spectroscopy because it moves an electron to a higher energy level. In Niels Bohr’s model, electrons in the hydrogen atom move in fixed circular orbits called stationary states, and each state has a discrete energy. An electron can move only when it absorbs or emits energy equal to the difference between two states.

The lowest energy state is the ground state, or n = 1. If a photon has the right energy, the electron can move to a higher state such as n = 2 or n = 3. When the electron returns to a lower state, it releases the extra energy as an emitted photon. The photon energy matches the energy gap between the two states and corresponds to specific wavelengths of light.

Most substances absorb or emit most strongly at one wavelength, but they usually interact with a range of wavelengths. That range is called a spectrum. An absorption spectrum shows how much light a sample absorbs at different wavelengths, and an emission spectrum shows the light a sample gives off. These spectra are measured with a spectrophotometer, which sends light through a sample and records the wavelength and intensity of the light that passes through.

Inside the spectrophotometer, a diffraction grating or a prism separates incoming light into its component wavelengths. The light then passes through the sample, and a linear charge-coupled device, or CCD, detector records the intensity. A CCD is an integrated circuit on silicon that contains light-sensitive pixels. It collects and sorts the diffracted light and reads it back at an absorption wavelength.

For absorbance measurements, the solute is usually dissolved in a solvent and placed in a cuvette, which is the container used in the instrument. The sample is then placed in the spectrophotometer, and the intensity of transmitted light is measured along with wavelength to produce an absorbance spectrum. The transmitted light is lower than when no sample is present because light is absorbed by the sample, the cuvette, and the solvent. Before samples are measured, the spectrophotometer is calibrated with a blank, which is a cuvette that contains only the solvent. This step removes the absorbance from the cuvette and solvent so the reading reflects only the species of interest.

Absorbance is often measured at the wavelength of maximum absorbance, but it can also be recorded across a range of wavelengths. For emission spectra, the incident wavelength is fixed at the wavelength of maximum absorbance, and the instrument measures emitted light over a range of wavelengths. The Beer-Lambert Law then connects absorbance to sample concentration. Transmittance is the fraction of light that passes through the sample, I divided by I0, and absorbance is related to the negative log of transmittance.

A second form of the Beer-Lambert Law shows that absorbance is directly proportional to concentration when wavelength and pathlength stay constant. The molar attenuation coefficient, ε, describes how strongly a species absorbs light at a given wavelength. The pathlength, l, is the distance the light travels through the sample, which is the width of the cuvette. Standard cuvettes have a 1 cm pathlength. This linear relationship makes it possible to find the concentration of an unknown sample from its absorbance.

To do that, a standard curve is made with known concentrations of the solute. The absorbance at λ max is measured for each standard, and the results are plotted as concentration versus absorbance. The line that appears matches the Beer-Lambert equation, and its slope equals the product of the pathlength and the molar attenuation coefficient. Once that line is known, the concentration of an unknown sample can be calculated from its absorbance.

Beer’s Law can also be used for reactions at equilibrium. If absorbance is measured at the λ max of a specific product or reactant, the equilibrium concentration of that species can be found. The concentrations of the other reactants and products can then be determined, and the equilibrium constant K eq can be solved.

Absorbance Spectra and Beer-Lambert Analysis

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extraction

Separating Mixtures with Solvent Extraction

Solvent extraction is a common way to separate and isolate a target compound in organic chemistry. In this process, a solute moves from one phase to another so it can be separated from unreacted starting materials or impurities. Extraction is also useful when a product is dissolved in a reaction solvent that is hard to remove by evaporation, such as a solvent with a high boiling point. There are three main types of extraction. In solid-liquid extraction, the solute moves from a solid phase...

simple distillation

Separating Liquids by Boiling Point

Separating liquids by boiling point is the goal of distillation. A miscible mixture contains liquids that mix evenly, and it can be heated so that the more volatile liquid evaporates first. Volatility is a liquid’s tendency to vaporize, and boiling begins when bubbles form in the liquid phase. In a closed container, liquid and vapor can reach equilibrium, which means the rate of vaporization equals the rate of condensation. The pressure from the vapor above the liquid is called vapor pressure.

steam distillation

Steam Distillation and Low-Boiling Separation

Steam distillation is a separation method for temperature-sensitive organic compounds. It works best when the organic compound is immiscible in water, meaning the two liquids do not mix. The method helps remove the organic molecule from a non-volatile contaminant without using the higher temperatures needed for many other separations. In steam distillation, the immiscible mixture is heated until both water and the volatile organic compound distill together. The vapor rises to a condenser,...

thin-layer chromatography

TLC Separation by Polarity

Thin-layer chromatography (TLC) separates compounds in a mixture by polarity. It uses the same basic parts as other chromatography methods: a stationary phase, a mobile phase, and the solute. In TLC, the stationary phase is a thin coating on a plate instead of material packed into a column. The stationary phase in most TLC systems is polar silica gel, a form of silicon dioxide. Its surface has OH groups that can form hydrogen bonds. The sample is first spotted on a pencil start line with a...

column chromatography

Separating Mixtures by Polarity

Column chromatography separates compounds in an organic chemistry lab by using differences in physical properties. It is especially useful for microscale separations when less than 10 grams of material is available for analysis. The method can separate a mixture based on solubility, polarity, hydrophobicity, size, and charge. Any chromatography system has three main parts: the stationary phase, the mobile phase, and the sample mixture. In column chromatography, the stationary phase is usually...

hydrolysis of an ester

Soap Formation from Triglycerides

Triglycerides are lipids made of a glycerol backbone linked to three fatty acids. They are common in vegetable oils and animal fats. Plant lipids are the basis of vegetable oils, while animal lipids are used as lard or general sources of fats. A fatty acid has a long carbon chain, usually between 12 and 20 carbons, with a weak organic acid at one end. Some fatty acids contain double bonds. These are unsaturated fats. The double bond usually gives the chain a bent, cis shape. As a result,...

synthesis of luminol

Luminol Chemiluminescence in Forensics

Luminol chemiluminescence shows how a chemical reaction can produce light and help with blood detection. Chemical reactions may be endothermic or exothermic, depending on whether they absorb or release heat as reactants become products. The enthalpy of a reaction is the energy difference between reactants and products, or ΔH. A positive ΔH means the reaction is endothermic. A negative ΔH means it is exothermic. Many reactions do not happen in a single step. They can pass through intermediates...

esterification

Ester Formation and Everyday Fragrances

Esters are organic compounds with a carbonyl group attached to an oxygen that connects to another alkyl or aryl group. Their general formula is RCOOR'. They are often made by reacting a carboxylic acid with an alcohol in an esterification reaction. In this process, the hydroxyl group of the acid is replaced by an alkyl or aryl group. Many simple esters have familiar fruit and flower smells because their structures are small and less complex. Formic acid and methanol can combine to form methyl...

identification of unknown aldehydes and ketones

identification-of-unknown-aldehydes-and-ketones

Carbonyl Tests for Aldehydes and Ketones

Aldehydes and ketones are carbonyl compounds, which means they contain a C=O functional group. A ketone has two alkyl or aryl groups attached to the carbonyl carbon. Acetone is the simplest ketone, with two methyl groups. An aldehyde is similar, but it has at least one hydrogen attached to the carbonyl carbon. Formaldehyde is the simplest aldehyde, and acetaldehyde has one hydrogen and one methyl group. The carbonyl carbon in both aldehydes and ketones is electrophilic because the oxygen atom...

uv-vis spectroscopy of dyes

How Dyes Absorb Visible Light

Dyes absorb visible light because their molecular structure lets them interact with specific wavelengths. When light hits a substance, some light is absorbed and the rest is reflected or transmitted. The color we see depends on the wavelength that is reflected. A blue substance reflects blue light, around 430 to 480 nm, and absorbs the complementary orange region, around 590 to 630 nm. Compounds that do not absorb in the visible range appear colorless to the human eye. Light also has energy and...

identifying alcohols

Alcohol Tests for Primary, Secondary, and Tertiary

Alcohol tests can help sort alcohols by structure and reactivity. Alcohols are organic molecules with a hydroxyl group attached to an alkyl or aryl group, written as ROH. If the carbon with the hydroxyl group has one R group, the alcohol is primary. If it has two R groups, it is secondary. If it has three R groups, it is tertiary. Alcohols can also be aromatic when they contain a benzene ring. Phenol is the simplest aromatic alcohol. To identify an alcohol, chemists can use its chemical...

chemistry

Comprehensive, curriculum-focused videos for both instructors and students in introductory chemistry lab courses.

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Explore how spectrophotometers measure absorbance spectra, how blank calibration works, and how Beer-Lambert Law is used to find concentration and equilibrium values.

Absorbance Spectra and Beer-Lambert Analysis | JoVE K12

Louisiana Student Standards for Science

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Motion And Stability: Forces And Interactions

HS-PS2-6

Przygotuj się do nauczania Prawo piwa dzięki temu 7-minutowemu przewodnikowi dla instruktorów. Obejmuje kluczowe kroki przygotowawcze dla laboratorium Chemistry na JoVE Lab Manual.

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Postępuj zgodnie z procedurami Prawo piwa krok po kroku w tym 17-minutowym filmie z protokołem studenckim. Część kolekcji Chemistry na JoVE Lab Manual.

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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 ...

Ions and Ionic Charges

In ordinary chemical reactions, the nucleus &mdash; which contains the protons and neutrons of each atom and thus identifies the element &mdash; remains ...

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, ...

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 ...

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 ...

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 ...

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, ...

Bonding in Metals

Metallic bonds are formed between two metal atoms. A simplified model to describe metallic bonding has been developed by Paul Dr&#xFC;de called the ...

Model basic atomic structure and relate an element's atomic structure to its bonding, reactivity, and placement on the Periodic Table.

IPC.7.A

physical-and-chemical-properties-of-matter

Physical and Chemical Properties of Matter

The characteristics that enable us to distinguish one substance from another are called properties.

Physical Properties of Matter

A physical property is ...

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 ...

Alkali Metals

Group 1 elements are soft and shiny metallic solids. They are malleable, ductile, and good conductors of heat and electricity. The melting points of the ...

Halogens

Group 17 elements, known as halogens, are nonmetals. At room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine a solid. ...

Noble Gases


The elements in group 18 are noble gases (helium, neon, argon, krypton, xenon, and radon). They earned the name &ldquo;noble&rdquo; because they were ...

Use patterns within the Periodic Table to predict the relative physical and chemical properties of elements.

IPC.7.B

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 ...

Phase Transitions

Whether solid, liquid, or gas, a substance&#39;s state depends on the order and arrangement of its particles (atoms, molecules, or ions). Particles in the ...

phase-transitions-vaporization-and-condensation

Phase Transitions: Vaporization and Condensation

The physical form of a substance changes on changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize ...

Phase Transitions: Melting and Freezing

Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy ...

Explain how physical and chemical properties of substances are related to their usage in everyday life such as in sunscreen, cookware, industrial applications, and fuels.

IPC.7.C

Science concepts. The student knows that relationships exist between the structure and properties of matter. The student is expected to:

Absorbance Spectra and Beer-Lambert Analysis

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