Name: measuring with accuracy in the lab
Uploaded: 2020-03-26T07:22:24.000Z
Duration: 4 min 14 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Specialised Topic in Science

112.51.c.1.

112.51.c.1.D.

Lab Techniques

Dans la recherche scientifique, la reproductibilité d’une expérience est extrêmement importante. Ainsi, la tenue d’un cahier de laboratoire contenant des enregistrements détaillés des procédures ainsi que des techniques de laboratoire appropriées permet de reproduire les résultats expérimentaux.
Par exemple, des mesures simples, comme le volume de liquide, doivent être effectuées à l’aide de la verrerie appropriée pour garantir la précision. Mesurez toujours le volume à l’aide d’une verrerie jaugée, comme une fiole jaugée, un cylindre gradué ou une pipette jaugée. Le volume est mesuré au bas du ménisque.
Les marquages de volume sur les béchers et les erlenmeyers ne sont pas précis et ne servent que de lignes directrices. Lors de la sélection de la verrerie volumétrique, sélectionnez le plus petit récipient possible pour le volume nécessaire. La verrerie volumétrique est calibrée soit pour livrer, soit pour contenir.
Les récipients calibrés pour l’administration sont conçus pour fournir le volume indiqué, étant entendu qu’une petite quantité de liquide restera dans la verrerie après qu’elle a été vidée. Dans ce cas, il n’est pas nécessaire de retirer le liquide restant ou de vider plus que le volume souhaité. La verrerie calibrée pour contenir conservera et délivrera le volume indiqué, mais nécessite que le liquide restant soit versé afin que le volume complet soit reçu.
Nous mesurons pour obtenir une valeur juste. Cependant, il y aura toujours un certain niveau d’incertitude et d’erreur. La valeur mesurée est notre meilleure estimation de la valeur réelle, qui nous est souvent inconnue. L’erreur est la différence entre les valeurs mesurées et les valeurs réelles. L’incertitude de mesure décrit la plage dans laquelle nous pensons qu’il est probable que la valeur réelle se situe. Lors de l’enregistrement des mesures, il est important de conserver le nombre approprié de chiffres significatifs.
Les chiffres significatifs sont les chiffres d’une mesure qui ont une signification. Le dernier chiffre enregistré définit le niveau d’incertitude. Tous les nombres autres que les zéros de début et de fin sont significatifs. Et les zéros à droite sont significatifs lorsqu’ils sont précédés d’une virgule.
Par exemple, dans une mesure de longueur à l’aide d’une règle, nous voyons que la longueur est d’au moins un pouce, mais certainement pas de 2 pouces. Ainsi, le premier chiffre significatif est un. La graduation suivante représente 0,1 pouce et est également significative.
Un enregistrement de 1,1 pouce comporte deux chiffres significatifs et implique que l’incertitude se situe à la dixième place. Cependant, l’épaisseur réelle se situe entre deux graduations. Ainsi, l’incertitude réside ici à la place des centièmes car la longueur est de 1,15 pouce.
Lorsque vous effectuez des calculs à l’aide de valeurs mesurées, n’oubliez pas de ne pas effectuer de calculs à une résolution supérieure à celle de la mesure d’origine. Ces chiffres supplémentaires ne sont pas significatifs et ne doivent pas être inclus. Par exemple, lorsque l’on calcule l’aire du carré avec une longueur de côté de 1,15, on voit que la longueur a trois chiffres significatifs. Ainsi, la réponse devrait également avoir trois chiffres significatifs.
La surface calculée de 1,3225 pouces carrés comporte cinq chiffres et introduit dans le calcul une certitude qui n’était pas présente dans la mesure initiale. Ainsi, la zone correcte est de 1,32 pouces carrés.
Dans cet atelier, vous mettrez en pratique les compétences de laboratoire appropriées en mesurant la densité d'un œuf et en utilisant des chiffres significatifs dans vos calculs et enregistrements. De plus, vous vous exercerez à tenir des registres dans votre cahier de laboratoire et à examiner la précision des mesures avec de la verrerie volumétrique.

techniques de laboratoire

<h4>Précision de mesure</h4>
La capacité de répéter une expérience et d’obtenir les mêmes résultats, ou reproductibilité, est essentielle dans la recherche scientifique. Cependant, il est impossible de répéter une expérience si vous ne savez pas comment vous l’avez faite. Ainsi, les scientifiques conservent des enregistrements détaillés de leurs expériences dans des cahiers de laboratoire. Ces registres contiennent des informations importantes telles que la quantité de chaque matériau utilisé et les descriptions de chaque étape de la procédure.
Les équipements, tels que les balances et la verrerie volumétrique ou graduée, sont utilisés pour mesurer les composés solides et liquides pour les expériences. La précision de chaque mesure est limitée par l’équipement utilisé. Les balances et autres équipements dotés d’affichages numériques affichent automatiquement les valeurs avec la précision maximale qu’ils peuvent prendre en charge. La précision de la verrerie graduée et des règles dépend de l’incrément, qui est la quantité représentée par la plus petite distance entre deux marques.
La surface de la plupart des liquides s’incurve vers le haut sur les bords des récipients en verre. Ce type de surface liquide incurvée est appelé ménisque concave. Lorsque les bords du liquide se courbent vers le bas, on parle de ménisque convexe. Lors de la mesure des volumes de liquide, le point de référence pour le haut du liquide est le bas d’un ménisque concave ou le haut d’un ménisque convexe. Pour identifier avec précision la position du ménisque, les volumes de liquide sont lus en regardant la surface du liquide de côté au niveau des yeux. En regardant le liquide d’en haut ou d’en bas, le niveau de surface du liquide apparaîtra plus haut ou plus bas qu’il ne l’est réellement.
Lorsque le point de référence du ménisque touche une marque sur une verrerie graduée ou volumétrique, la verrerie maintient le volume défini pour cette marque. La verrerie volumétrique est conçue pour mesurer un volume spécifique, elle n’a donc qu’une seule marque. La verrerie graduée est conçue pour mesurer une gamme de volumes, elle comporte donc de nombreuses marques, ou graduations, qui sont étiquetées à intervalles réguliers. La verrerie graduée et volumétrique peut avoir des informations supplémentaires fournies par le fabricant sur leur précision.
<h4>Calibrage et incertitude</h4>
Les fabricants étalonnent l’équipement pour s’assurer que les mesures sont précises dans une plage d’incertitude spécifiée. Par exemple, une balance analytique de haute précision peut lire à quatre décimales près (0,0000 g) avec une incertitude de ± 0,0001 g. Une valeur de 0,0345 g indique que la valeur réelle est comprise entre 0,0344 g et 0,0346 g.
L’incertitude de mesure est généralement imprimée sur la verrerie. Pour enregistrer avec précision les mesures de volume, vous devez tenir compte à la fois de l’incrément et de l’incertitude. Par exemple, une mesure précise du volume dans un cylindre gradué de 100 mL avec des incréments de 1 mL et une incertitude de ± 0,5 mL serait enregistrée au dixième près (000,0 mL ± 0,5 mL). Si le point de référence du ménisque se situe entre deux marques, vous devez estimer une valeur pour la dixième place ; Sinon, laissez-le à 0. Étant donné que la température affecte le volume, la température pour laquelle la verrerie est calibrée sera imprimée sur celle-ci.
La verrerie est calibrée soit pour contenir (TC), soit pour livrer (TD). La verrerie TC conserve le volume de liquide spécifié lorsqu’elle est remplie jusqu’à la marque, mais une petite quantité de liquide sera laissée lorsqu’elle est versée dans un autre récipient. Les solutions sont souvent préparées dans la verrerie TC car la précision du volume de la solution affecte la précision de la concentration. Les flacons jaugés sont généralement calibrés pour contenir.
La verrerie TD contient un peu plus que la quantité de liquide spécifiée lorsqu’elle est remplie jusqu’à la marque, mais elle ne distribue que le volume spécifié. Ainsi, la verrerie TD ne doit pas être complètement vidée lors de la distribution de liquides. Ce type de verrerie est utile pour transférer un volume précis de liquide dans un autre récipient. Les pipettes graduées et volumétriques sont généralement calibrées pour être administrées.
Sauf indication contraire, l’incertitude d’un nombre est supposée être à l’échelle du dernier chiffre. Par conséquent, il est particulièrement important de signaler l’incertitude d’une mesure si l’incertitude se situe à une plus grande échelle. Pour les règles et la verrerie graduée sans incertitude connue, l’incertitude est estimée à la moitié du plus petit accroissement. Le chiffre incertain est basé sur l’endroit où le ménisque se situe entre deux graduations.
<h4>Chiffres significatifs</h4>
Les chiffres significatifs sont les nombres d’une valeur qui sont significatifs ou essentiels pour exprimer cette valeur avec la précision appropriée. Tous les nombres autres que les zéros non significatifs (0,001), les zéros finaux (1 000) ou les multiplicateurs de notation scientifique (10x) sont toujours significatifs.
Les zéros non significatifs ne sont jamais significatifs car ils peuvent être supprimés en réécrivant le nombre soit en notation scientifique, soit, s’il s’agit d’une unité SI, en unités plus petites. Par exemple, il n’y a que trois chiffres significatifs dans la valeur 0,00123 m car elle peut être réécrite comme 1,23 × 10-3 m ou 1,23 mm sans perdre d’information. Notez que le facteur d’échelle entre différents multiples d’une même unité SI n’affecte pas le nombre de chiffres significatifs.
Les zéros à droite sont significatifs lorsqu’ils se trouvent avant ou après une virgule. Par exemple, la mesure 100,110 ml comporte six chiffres significatifs et 100,0 ml en a quatre. Les zéros à droite d’un nombre écrit sans virgule décimale sont considérés comme non significatifs, sauf indication contraire. Il existe plusieurs conventions différentes pour marquer des zéros significatifs dans ces cas, mais pour éviter toute ambiguïté, il est conseillé de réécrire ces valeurs en notation scientifique. Si la mesure est en unités SI, utilisez des unités plus grandes.
La précision d’une mesure limite la précision des valeurs calculées à partir de celle-ci. Une valeur calculée a le même nombre de chiffres significatifs que la mesure ou la valeur la moins précise utilisée dans son calcul. Si le résultat comporte trop de chiffres significatifs, il est arrondi à la précision appropriée. Si le résultat comporte trop peu de chiffres significatifs, il est prolongé avec des zéros de fin significatifs pour préserver la précision. Les chiffres significatifs des valeurs dérivées expérimentalement, comme la masse molaire, la masse volumique ou certains facteurs de conversion unitaires, doivent également être pris en compte lorsqu’ils sont utilisés dans les calculs.
Le nombre de chiffres significatifs dans une valeur calculée n’est pas limité par des constantes physiques ou mathématiques dans des formules ou des nombres exacts, comme le nombre de points de données acquis dans une expérience. Par exemple, la formule de calcul du volume d’une sphère est V = 4/3πr3. Le nombre de chiffres significatifs dans le volume calculé n’est affecté que par le nombre de chiffres significatifs dans la mesure du rayon r. 4/3 et π sont des constantes, et 3 est simplement la notation d’une opération mathématique.
Les facteurs de conversion définis sont également traités comme des constantes. Par exemple, le pouce est défini comme exactement 25,4 millimètres ; Par conséquent, le nombre de chiffres significatifs de la valeur convertie ne dépend que de la mesure d’origine. Vérifiez toujours si le facteur de conversion est exactement défini ou s’il s’agit d’une valeur expérimentale lors de la conversion entre unités.
Pour l’addition et la soustraction simples de mesures, nous utilisons l’arithmétique de signification pour déterminer le nombre de chiffres significatifs. Dans ce cas, la réponse comporte autant de décimales que la mesure avec le moins de décimales, quel que soit le nombre de chiffres significatifs. Ainsi, 15 643,7 mL + 0,613 mL = 15 644,3 mL.
Pour les calculs en plusieurs étapes ou les équations complexes que vous divisez en parties plus petites pour les résoudre, vous devez conserver au moins un ou deux chiffres non significatifs sur les valeurs intermédiaires. Par exemple, si vous calculez les valeurs du numérateur et du dénominateur d’une fraction séparément avant de les diviser, vous devez conserver les chiffres non significatifs du numérateur et du dénominateur lorsque vous les divisez. Cela minimise l’erreur d’arrondi, qui est la différence par rapport au nombre que vous obtiendriez si vous entriez la formule entière dans votre calculatrice en une seule fois. Si vous notez ces valeurs intermédiaires, vous devez noter quels chiffres sont non significatifs.
<h4>Références</h4>
Harris, D.C. (2015). Analyse chimique quantitative. New York, NY : W.H. Freeman et compagnie.

Techniques de laboratoire

Précision de mesure
La capacité de répéter une expérience et d’obtenir les mêmes résultats, ou reproductibilité, est essentielle dans la recherche scientifique. Toutefois...

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measuring with accuracy in the lab

Measuring with accuracy in the lab starts with careful records, the right tools, and correct reading of data. Scientists use lab notebooks to record how an experiment was done. These notes include the amounts of materials used and each step of the procedure. Without that record, an experiment cannot be repeated in the same way.

Balances and glassware are used to measure solids and liquids for experiments. The precision of a measurement depends on the equipment used. Digital balances show the maximum precision they can support. For rulers and graduated glassware, precision depends on the increment, which is the smallest distance between two marks.

Liquid levels must also be read correctly. Most liquids curve upward at the edges in glass containers. This curved surface is called a concave meniscus. When the edges curve downward, it is called a convex meniscus. To measure volume, the reference point is the bottom of a concave meniscus or the top of a convex meniscus. The reading should be taken from the side at eye level. Looking from above or below can make the level seem higher or lower than it really is.

Graduated and volumetric glassware are designed for different jobs. Volumetric glassware measures one specific volume and has only one mark. Graduated glassware measures a range of volumes and has many marks, or graduations, at regular intervals. When the meniscus reference point touches the mark, the glassware is holding the volume defined by that mark. Both types may also include manufacturer information about precision.

Manufacturers calibrate equipment so measurements stay within a stated range of uncertainty. A high-precision analytical balance may read to four decimal places, such as 0.0000 g, with an uncertainty of ±0.0001 g. That means a reading of 0.0345 g could represent a true value between 0.0344 g and 0.0346 g. Glassware usually has its uncertainty printed on it. For a 100 mL graduated cylinder with 1 mL increments and an uncertainty of ±0.5 mL, the volume should be recorded to the tenths place.

Temperature also affects volume, so calibrated glassware lists the temperature it is made for. Glassware can be calibrated to contain, or TC, or to deliver, or TD. TC glassware holds the stated volume when filled to the mark, but some liquid remains after pouring. This is why volumetric flasks are usually TC and are often used to prepare solutions, since solution concentration depends on volume accuracy. TD glassware dispenses the stated volume and should not be emptied completely. Graduated and volumetric pipettes are typically TD and are useful for transferring an exact volume to another container.

Recording numbers correctly also requires understanding uncertainty and significant figures. Unless stated otherwise, uncertainty is assumed to be on the scale of the last digit. If a ruler or glassware has no known uncertainty, estimate it as half of the smallest increment. Significant figures are the digits that are meaningful for the precision of a value. Leading zeroes are not significant, while trailing zeroes are significant when they appear before or after a decimal point. A number written without a decimal point may need scientific notation to avoid ambiguity.

Calculated values must match the precision of the measurements used to find them. The result should have the same number of significant figures as the least precise value in the calculation. If the answer has too many significant figures, round it. If it has too few, add significant trailing zeroes to show the correct precision. Constants such as 4/3 and π in the sphere volume formula do not limit the number of significant figures, and exact conversion factors like 1 inch = 25.4 millimeters also do not. For addition and subtraction, the answer keeps the same number of decimal places as the least precise value. For multi-step problems, keep one or two extra digits during intermediate steps to reduce rounding error.

Measuring with Accuracy in the Lab

lab techniques

Measuring with accuracy in the lab starts with careful records, the right tools, and correct reading of data. Scientists use lab notebooks to record how an experiment was done. These notes include the amounts of materials used and each step of the procedure. Without that record, an experiment cannot be repeated in the same way. Balances and glassware are used to measure solids and liquids for experiments. The precision of a measurement depends on the equipment used. Digital balances show the...

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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

Des vidéos complètes, axées sur le programme de cours pour les travaux pratiques de Chimie, adaptées à la fois aux professeurs et aux étudiants.

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Learn how students measure liquids and solids, read meniscus levels, use TC and TD glassware, and apply uncertainty and significant figures.

Measuring with Accuracy in the Lab | JoVE K12

CHEM.1

CHEM.1.D

Biology

BIO.1

BIO.1.E

Préparez l'enseignement de Techniques de laboratoire avec ce guide instructeur de 1 minutes. Couvre les principales étapes de préparation pour le laboratoire Chemistry sur JoVE Lab Manual.

Préparation de l'instructeur pour Techniques de laboratoire dans Chemistry - 9.8K+ vues | JoVE Lab Manual

Suivez les procédures étape par étape de Techniques de laboratoire dans cette vidéo de protocole étudiant de 9 minutes. Fait partie de la collection Chemistry sur JoVE Lab Manual.

Protocole étudiant de Techniques de laboratoire dans Chemistry - 30K+ vues | JoVE Lab Manual

The Scientific Method

The scientific method is a detailed, empirical problem-solving process used by biologists and other scientists. This iterative approach involves ...

Inductive Reasoning

Inductive reasoning is a form of logical thinking that uses related observations to arrive at a general conclusion. It is uncertain and operates in ...

Deductive Reasoning

Deductive reasoning, or deduction, is the type of logic used in hypothesis-based science. In deductive reasoning, the pattern of thinking moves in the ...

Correlation and Causation

Correlation and CausationStatistical tests can calculate whether there is a relationship, or correlation, between independent and dependent variables. A ...

Ask questions and define problems related to specialized topics of study based on observations or information from text, phenomena, models, or investigations;

112.51.c.1.A.

Scientific Method

The scientific method is used to solve problems and explain phenomena. The development of the scientific method coincided with changes in philosophy ...

Demonstrating the Scientific Method with Tree Branches
ExpandObtain branches containing a few dozen typical leaves from five different local tree species. ...

Observation and Background Research
ExpandNOTE: The first two steps in the scientific process involve studying and observing natural phenomena of ...

Problem-Solving

A problem-solving strategy is a plan of action used to find a solution. It involves trial and error, algorithms, heuristics, and insights. Effective ...

Problem Definition

Problem definition is the initial and the most essential step in research.
The researcher identifies and explains the specific issue or gap to be ...

Apply science practices related to specialized topics of study to plan and conduct investigations or use engineering practices to design solutions to problems;

112.51.c.1.B.

Proper Personal Protective Equipment

Robert M. Rioux &#38; William A Elliott, Pennsylvania State University, University Park, PA
Hazards are many and varied in the laboratory, but the right ...

Emergency Eyewash and Shower Stations

Robert M. Rioux, Pennsylvania State University, University Park, PA
The Occupational Safety and Health Administration (OSHA) mandates that an emergency ...

Electrical Safety

Robert M. Rioux &amp; Suprita Jharimune, Pennsylvania State University, University Park, PA
Among the many hazards present in the laboratory, electrical ...

Working with Centrifuges

Source: Robert M. Rioux &amp; Suprita Jharimune, Pennsylvania State University, University Park, PA
Earth's gravitational force is capable of separating ...

Working with Hot and Cold Sources

Source: Robert M. Rioux &amp; Suprita Jharimune, Pennsylvania State University, University Park, PA
Working with extreme temperatures, both high and low, ...

guidelines-in-case-of-a-laboratory-emergency

Guidelines in Case of a Laboratory Emergency

Robert M. Rioux &amp; Zhifeng Chen, Pennsylvania State University, University Park, PA
The most common laboratory emergencies include chemical spills, ...

chemical-storage-categories-hazards-and-compatibilities

Chemical Storage: Categories, Hazards And Compatibilities

Source: Robert M. Rioux &amp; Taslima A. Zaman, Pennsylvania State University, University Park, PA
While the use of various chemicals in experimental ...

Safe Handling of Mineral Acids

Source: Robert M. Rioux &#38; Taslima A. Zaman, Pennsylvania State University, University Park, PA
A mineral acid (or inorganic acid) is defined as a ...

Handling Chemical Spills

Source: Robert M. Rioux &#38; Taslima Zaman, Pennsylvania State University, University Park, PA
Since chemicals are commonly used for laboratory research ...

Proper Use of Autoclaves

Robert M. Rioux &amp; Zhifeng Chen, Pennsylvania State University, University Park, PA
Autoclaving is one of the most commonly used methods in the ...

Fume Hoods and Laminar Flow Cabinets

Robert M. Rioux &amp; William A. Elliott, Pennsylvania State University, University Park, PA
Fume hoods and laminar flow cabinets are engineering controls ...

Decontamination for Laboratory Biosafety

Robert M. Rioux and Zhifeng Chen, Pennsylvania State University, University Park, PA
Decontamination is essential for laboratory biosafety, as the ...

Proper Waste Disposal

Robert M. Rioux and Taslima A. Zaman, Pennsylvania State University, Pennsylvania, PA

Users are responsible for the proper disposal of the waste ...

Use appropriate safety equipment and practices during laboratory, classroom, and field investigations as outlined in Texas Education Agency-approved safety standards;

112.51.c.1.C.

Common Lab Glassware and Uses

Source: Laboratory of Dr. Neal Abrams &#8212; SUNY College of Environmental Science and Forestry
Glassware is a regular appearance in the professional ...

Measurement Accuracy
The ability to repeat an experiment and get the same results, or reproducibility, is essential in scientific research. However, ...

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Preparation of LaboratoryExpand
	Here we show the laboratory preparation for 10 students ...

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Determining the Density of an EggExpand
	Density is a measure of how compact a substance or ...

Proper Lab Notebook Keeping

Organic Lab Notebook Keeping
Record keeping is a vital skill in science and organic chemistry labs. Without proper notes, descriptions, quantities, or ...

Source: Lara Al Hariri at the University of Massachusetts Amherst, MA, USA

	Preparation of the LaboratoryExpand
	Here, we show the laboratory preparation ...

Source: Lara Al Hariri and Ahmed Basabrain at the University of Massachusetts Amherst, MA, USA

	Nitration of Methyl BenzoateExpand
	From this lab onward, ...

Use tools appropriate to the specialized topic of study;

SI Units: 2019 Redefinition

Measurement is integral to analytical chemistry. Each record comprises a number &#8211; denoting the magnitude&#160; &#8211; and the unit &#8211; a ...

International System of Units

The International System of Units, known as the SI system, is a universally accepted measurement system recognized and used worldwide. The SI system is ...

Measurement: Standard Units

Every measurement provides three kinds of information: the size or magnitude of the measurement (a number), a standard of comparison for the measurement ...

Measurement: Derived Units

The International System of Units or SI system, by international agreement, has fixed measurement units for seven fundamental properties: length, mass, ...

Collect quantitative data using the International System of Units (SI) or qualitative data as evidence as appropriate to the specialized topic of study;

112.51.c.1.E.

Scientific and engineering practices. The student, for at least 40% of instructional time, asks questions, identifies problems, and plans and safely conducts classroom, laboratory, and field investigations to explain phenomena or design solutions using appropriate tools and models. The student is expected to:

Measuring with Accuracy in the Lab

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