Name: pressure units and tools for gas measurement
Uploaded: 2020-09-03T13:38:26.000Z
Duration: 2 min 57 s
Channel: JoVE

K12 Standards

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

NC K-12 Science Standard Course of Study

9-12

Chemistry

Energy

PS.Chm.7.3

definition-measurement-pressure-atmospheric-pressure-barometer

Definition and Measurement of Pressure: Atmospheric Pressure, Barometer, and Manometer

기체는 항상 기체가 들어있는 용기의 모양과 부피를 가진다는 것을 상기해 봅시다. 현미경으로 보면, 기체는 서로 충돌하는 움직이는 입자와 용기의 벽으로 구성되어 있습니다. 벽에 충돌하는 매 입자는 충돌 부위에 작은 힘을 가합니다.

그러한 충돌이 많이 발생하여 생기는 힘이 압력이 됩니다. 기체 입자가 적을수록 충돌 횟수가 줄어들고 단위 면적당 힘이 작아지며, 따라서 압력이 작아집니다. 즉 압력은 주어진 부피 안의 입자 수, 또는 기체의 밀도에 정비례합니다.

여러 가지 다른 기체 원자와 분자의 혼합물인 공기는 지구 표면의 모든 곳에 압력을 가합니다. 이것이 대기압이며 기압계를 이용하여 측정합니다. 전통적인 기압계는 수은이 들어있는 접시에 수은을 채운 유리관을 거꾸로 세운 것입니다.

대기에 의해 가해지는 압력에 반응하여 수은주의 높이는 상승하거나 하강합니다. 높이를 측정하면 대기압을 측정할 수 있습니다. 해수면에서 대기압은 1 기압이며 이때 수은주의 높이는 760 밀리미터입니다.

높은 고도에서는 공기 밀도가 낮아져 수은주의 높이가 낮아지고 이것은 대기압이 낮음을 나타냅니다. 용기에 있는 기체의 압력은 압력계를 사용하여 측정합니다. 페쇄형 압력계는 수은이 채워진 U자관으로 구성됩니다.

한쪽 끝은 진공상태로 밀봉되고, 다른 쪽 끝은 기체 샘플로 채워진 용기에 연결됩니다. 기체 입자는 튜브의 한쪽 끝에서 수은주를 밀어내려 기체가 가하는 압력에 해당한 높이 차이를 만듭니다. 개방형 압력계에서는 한쪽 끝이 대기에 열려 있습니다.

이것은 대기압에 상대적인 기체 샘플의 압력을 측정합니다. 기체가 대기압보다 높은 압력을 가하면, 대기압에 높이 차이가 더해집니다. 이것은 기체 샘플의 압력이 됩니다.

반대로 대기가 기체 샘플보다 큰 압력을 가하면 대기압에서 높이 차이를 덜어 기체 압력을 얻습니다.

압력의 정의와 측정: 대기압, 기압계, 압력계

가스 압력은 물체 표면과 충돌하는 가스 분자에 의해 가해지는 힘으로 인해 발생합니다. 각 충돌의 힘은 매우 작지만 감지 가능한 영역의 모든 표면은 짧은 시간에 많은 수의 충돌을 경험하므로 높은 압력이 발생할 수 있습니다.

일반적으로 압력은 주어진 영역에 가해지는 힘으로 정의됩니다.

<img alt="Eq1" src="https://www.jove.com/files/core/CDNSource/lessons/1035/1035_Equations-01.png" style="height: 40px;" />

압력은 힘에 정비례하고 면적에 반비례합니다. 따라서 힘의 양을 늘리거나 힘이 가해지는 면적을 줄임으로써 압력을 높일 수 있습니다. 힘을 줄이거나 면적을 늘려 압력을 줄일 수 있습니다.

SI 압력 단위는 파스칼(Pa)이며 1 Pa = 1 N/m^2입니다. 여기서 N은 1 kg·m/s^2로 정의되는 힘의 단위인 뉴턴입니다. 1파스칼은 작은 압력입니다. 많은 경우 킬로파스칼(1kPa = 1000Pa) 또는 바(1bar = 100,000Pa) 단위를 사용하는 것이 더 편리합니다. 압력은 단위 대기(atm)를 사용하여 측정할 수도 있습니다.

압력 측정

대기압, 즉 대기가 지구 표면에 가하는 힘은 기압계로 측정됩니다. 기압계는 한쪽 끝이 닫혀 있고 수은과 같은 비휘발성 액체로 채워진 다음 뒤집어서 해당 액체가 담긴 용기에 담그는 유리관입니다. 대기는 튜브 외부의 액체에 압력을 가하고, 액체 기둥은 튜브 내부에 압력을 가하며, 액체 표면의 압력은 튜브 내부와 외부에서 동일합니다. 따라서 튜브 내 액체의 높이는 대기에 의해 가해지는 압력에 비례합니다.

기압계에서 수은은 물보다 밀도가 13.5배 더 높기 때문에 물보다 선호됩니다. 대기압은 높이가 약 0.760m에 불과한 수은 기둥을 지탱할 수 있는 반면, 물 기둥의 높이는 10.3m여야 합니다. 이는 수은 기둥을 압력을 측정하는 편리한 방법으로 만듭니다.

해수면 기준 1atm(101,325Pa)의 표준 대기압은 약 760mm(29.92인치) 높이의 수은 기둥에 해당합니다. 중력으로 인해 유체가 가하는 압력을 정수압(p)이라고 합니다.

<img alt="Eq2" src="https://www.jove.com/files/core/CDNSource/lessons/1035/1035_Equations-02.png" style="height: 40px;" />

여기서 h는 유체의 높이, ρ는 유체의 밀도, g는 중력 가속도입니다.

압력계는 용기에 담긴 가스의 압력을 측정하는 데 사용되는 장치입니다. 폐쇄형 압력계는 하나의 닫힌 팔과 측정할 가스에 연결되는 하나의 팔, 그리고 그 사이에 수은이 있는 U자형 튜브입니다. 튜브의 두 팔에 있는 액체 높이 사이의 거리 h는 용기 내 가스의 압력에 비례합니다. 개방형 압력계에서는 튜브의 한쪽 팔이 대기에 열려 있습니다. 이 경우, 액체 높이 사이의 거리는 용기 내 가스와 대기 사이의 압력 차이에 해당합니다.

이 문서는 에서 발췌되었습니다 <a href="https://openstax.org/books/chemistry-2e/pages/9-1-gas-pressure">Openstax, Chemistry 2e, Section 9.1: Gas Pressure</a>.

가스 압력은 기체 분자가 물체의 표면과 충돌할 때 가해지는 힘에 의해 발생합니다. 각 충돌의 힘은 매우 작지만 모든 ...

Education

교육

JoVE Core

화학

하나

Gases

기체

KEY TERMS AND CONCEPTS

주요 용어 및 개념

pressure units and tools for gas measurement

Pressure is the force applied to a given area, and gas pressure comes from gas molecules colliding with surfaces. Each collision is tiny, but many collisions over a small area can create high pressure. Pressure increases when force increases or when the area gets smaller. It decreases when force drops or when the area gets larger.

Pressure is measured in pascals, or Pa, in the SI system. One pascal equals 1 newton per square meter, and a newton is a unit of force equal to 1 kg·m/s2. A pascal is a small unit, so kilopascal (kPa) and bar are often more useful. Pressure can also be reported in atmospheres, or atm.

Atmospheric pressure is the force the atmosphere exerts on Earth’s surface. It is measured with a barometer. A barometer uses a glass tube that is closed at one end, filled with a nonvolatile liquid such as mercury, and then turned upside down in a container of the same liquid. The atmosphere presses on the liquid outside the tube, and the liquid column inside the tube rises to a height that matches that pressure.

Mercury is preferred in a barometer because it is 13.5 times denser than water. That means atmospheric pressure supports only about 0.760 m of mercury, while a water column would need to be 10.3 m tall. Standard atmospheric pressure at sea level is 1 atm, or 101,325 Pa, and it corresponds to a mercury column about 760 mm, or 29.92 in., high.

Fluid pressure from gravity is called hydrostatic pressure. It depends on the height of the fluid, its density, and the acceleration due to gravity. A manometer uses this idea to measure gas pressure in a container. A closed-end manometer has one sealed arm, one arm connected to the gas, and mercury between them. The height difference between the liquid levels gives the gas pressure.

An open-end manometer has one arm open to the atmosphere. In that setup, the height difference shows the pressure difference between the trapped gas and the air around it. Together, barometers and manometers show how fluid height can be used to measure atmospheric pressure and gas pressure.

Pressure Units and Tools for Gas Measurement

pressure-units-and-tools-for-gas-measurement

definition and measurement of pressure: atmospheric pressure, barometer, and manometer

Pressure is the force applied to a given area, and gas pressure comes from gas molecules colliding with surfaces. Each collision is tiny, but many collisions over a small area can create high pressure. Pressure increases when force increases or when the area gets smaller. It decreases when force drops or when the area gets larger. Pressure is measured in pascals, or Pa, in the SI system. One pascal equals 1 newton per square meter, and a newton is a unit of force equal to 1 kg·m/s2. A pascal...

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How Gas Pressure, Volume, and Temperature Change

Gas pressure, volume, temperature, and amount are linked by several gas laws. Scientists found these relationships by studying how a confined gas changes when one variable is held constant and another changes. These patterns apply to an ideal gas, which is a useful model for gases under low pressure and high temperature. Gay-Lussac’s law, also called Amontons’s law, connects pressure and temperature. If gas is trapped in a rigid container, the volume and number of moles stay constant. When the...

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Ideal Gas Law at STP and Gas Density

The ideal gas law links pressure, volume, number of moles, and temperature. It helps explain how gas volume changes when pressure or temperature changes. At standard temperature and pressure, or STP, the values are 273.15 K and 1 atm. At STP, one mole of an ideal gas occupies about 22.4 L. This is called the standard molar volume. The gas can be hydrogen, oxygen, argon, or carbon dioxide, and the volume is still about 22.4 liters. Half a mole occupies 11.2 L, and 2 moles occupy 44.8 L. The...

mixtures of gases: dalton's law of partial pressures and mole fractions

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Gas Pressure in Mixtures: Partial Pressures

Gas pressure in mixtures is described by partial pressure and mole fraction. When gases do not chemically react, each gas in the mixture acts as if it were alone in the container. The pressure from one gas is called its partial pressure. For a mixture of three gases, A, B, and C, the total pressure equals the sum of their partial pressures: PA, PB, and PC. This is Dalton's law of partial pressures. It states that the total pressure of a mixture of ideal gases is the sum of the pressures from...

chemical stoichiometry and gases: using ideal gas law to determine moles

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Stoichiometry of Gases with the Ideal Gas Law

Chemical stoichiometry links the amounts of reactants and products in a chemical reaction. For gases, those amounts can also be measured by volume. If a gas’s volume, pressure, and temperature are known, the ideal gas equation can be used to find the number of moles present. The same idea works in reverse. If the moles of a gas are known, its volume can be found at any temperature and pressure. The transcript gives an example using 8.88 g of gallium reacting with excess hydrochloric acid.

basic postulates of kinetic molecular theory: particle size, energy, and collision

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Kinetic Molecular Theory and Gas Behavior

Kinetic molecular theory explains gas behavior at the particle level. It gives a microscopic model for what happens when pressure or temperature changes. Gas laws describe how macroscopic properties change, but they do not explain why those changes happen. The theory was put into a complete form by Rudolf Clausius in 1857. It was built from hundreds of experimental observations about gases. Those observations helped explain the different gas laws through a few basic postulates. One key idea...

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Gas Pressure Patterns in Kinetic Molecular Theory

Kinetic molecular theory explains gas pressure by linking it to the motion of gas molecules. Gas pressure comes from rapidly moving molecules hitting the walls of a container. It depends on how many molecules strike a unit area in a given time. The theory also helps explain the main gas laws. In Gay-Lussac’s law, also called Amontons’s law, raising temperature increases the average speed and kinetic energy of gas molecules. If volume stays constant, the molecules collide with the walls more...

kinetic molecular theory: molecular velocities, temperature, and kinetic energy

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Gas Particle Speed Distributions and Temperature

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Gas Particle Motion, Diffusion, and Effusion

Gas particle motion, diffusion, and effusion explain how gases spread and escape in everyday settings. Gas molecules move at very high speeds, but they collide with other gas molecules and change direction many times before reaching a target. At room temperature, a gas molecule can experience billions of collisions each second. The mean free path is the average distance a molecule travels between collisions. This distance becomes larger when pressure decreases. In general, the mean free path...

real gases: effects of intermolecular forces and molecular volume deriving van der waals equation

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Real Gases: When the Ideal Gas Law Breaks Down

Real gases are gases that do not always follow the ideal gas law, PV = nRT, especially when pressure is high or temperature is low. The ideal gas model assumes gas particles have no attractive or repulsive forces and take up negligible space compared with the container. At room temperature and 1 atm or less, many gases behave close to ideally. When conditions change, the measured relationships between pressure, volume, and temperature can drift away from the ideal prediction. One way to see...

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Learn how pressure is measured with pascals, atmospheres, barometers, and manometers, plus why mercury columns show atmospheric and gas pressure.

Pressure Units and Tools for Gas Measurement | JoVE K12

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Ohio’s Learning Standards and Model Curriculum

Interactions Of Matter

Gas laws

Virginia  Standards of Learning

HIgh School

CH.6

CH.6.b

Earth Science

ES.11

ES.11.a

Arizona Science Standards

High School

Physical Science

HS+C.P1

HS+C.P1U1.3

Texas Essential Knowledge and Skills

CHEM.10

CHEM.10.B

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Matter and Its Interactions

9-12.C.1.4.e

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9-12.ESS.2.7.c

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Structure and Properties of Matter

HS-PS1-9.

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 ...

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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 ...

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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 ...

Intermolecular vs Intramolecular Forces

Intermolecular forces (IMF) are electrostatic attractions arising from charge-charge interactions between molecules. The strength of the intermolecular ...

Intermolecular Forces

Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions ...

comparing-intermolecular-forces-melting-point-boiling-point

Comparing Intermolecular Forces: Melting Point, Boiling Point, and Miscibility

Intermolecular forces are attractive forces that exist between molecules. They dictate several bulk properties, such as melting points, boiling points, ...

surface-tension-capillary-action-and-viscosity

Surface Tension, Capillary Action, and Viscosity

Surface Tension
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded ...

States of Matter and Phase Changes

The internal energy of a substance&#8212;the total kinetic energy of all its molecules and the potential energy of their associated forces&#8212;depends ...

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 ...

Vapor Pressure

When a liquid vaporizes in a closed container, gas molecules cannot escape. As these gas phase molecules move randomly about, they will occasionally ...

Clausius-Clapeyron Equation

The equilibrium between a liquid and its vapor depends on the temperature of the system; a rise in temperature causes a corresponding rise in the vapor ...

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 ...

phase-transitions-sublimation-and-deposition

Phase Transitions: Sublimation and Deposition

Some solids can transition directly into the gaseous state, bypassing the liquid state, via a process known as sublimation. At room temperature and ...

Heating and Cooling Curves

When a substance&#8212;isolated from its environment&#8212;is subjected to heat changes, corresponding changes in temperature and phase of the substance ...

Phase Diagrams

A phase diagram combines plots of pressure versus temperature for the liquid-gas, solid-liquid, and solid-gas phase-transition equilibria of a substance. ...

Use models to explain how changes in energy affect the arrangement and movement of the particles in solids, liquids, and gases, as well as the relative strengths of their intermolecular forces.

PS.Chm.7.1

Energy Basics

Chemical reactions, such as those that occur when you light a match, involve changes in energy as well as matter.

Chemical changes and their accompanying ...

First Law of Thermodynamics

Energy Conservation

Energy can be converted from one form into another, but all of the energy present before a change occurs always exists in some form ...

Internal Energy

The total of all possible kinds of energy present in a substance is called the internal energy (U), sometimes symbolized as E. Suppose a system with ...

Quantifying Heat

Thermal Energy&#160;

Microscopically, thermal energy is the kinetic energy associated with the random motion of atoms and molecules. Temperature is a ...

Quantifying Work

As a system undergoes a change, its internal energy can change, and energy can be transferred from the system to the surroundings, or from the ...

Enthalpy

Chemists ordinarily use a property known as enthalpy (H) to describe the thermodynamics of chemical and physical processes. Enthalpy is defined as the sum ...

Thermochemical Equations

For a chemical reaction (the system) carried out at constant pressure &ndash; with the only work done caused by expansion or contraction &ndash; the ...

Constant Pressure Calorimetry

Calorimetry is a technique used to measure the amount of heat involved in a chemical or physical process or to measure the heat transferred to or from a ...

Constant Volume Calorimetry

Calorimeters are useful to determine the heat released or absorbed by a chemical reaction. Coffee cup calorimeters are designed to operate at constant ...

using-differential-scanning-calorimetry-to-measure-changes-in-enthalpy

Using Differential Scanning Calorimetry to Measure Changes in Enthalpy

Source: Laboratory of Dr. Terry Tritt &#8212; Clemson University
Differential Scanning Calorimetry (DSC) is a method of thermodynamic analysis based on ...

Hess's Law

There are two ways to determine the amount of heat involved in a chemical change: measure it experimentally, or calculate it from other experimentally ...

Standard Enthalpy of Formation

Enthalpy changes are typically tabulated for reactions in which both the reactants and products are at the same conditions. A standard state is a commonly ...

Enthalpies of Reaction

Hess&rsquo;s law can be used to determine the enthalpy change of any reaction if the corresponding enthalpies of formation of the reactants and products ...

Use mathematics and computational thinking to execute simple calorimetric calculations based on the Law of Conservation of Energy.

PS.Chm.7.2

Gas pressure is caused by force exerted by gas molecules colliding with the surfaces of objects. Although the force of each collision is very small, any ...

Gas Laws: Boyle's, Gay-Lussac, Charles', Avogadro's, and Ideal Gas Law

Through experiments, scientists established the mathematical relationships between pairs of variables, such as pressure and temperature, pressure and ...

Applications of the Ideal Gas Law: Molar Mass, Density, and Volume

The volume occupied by one mole of a substance is its molar volume. The ideal gas law, PV = nRT, &nbsp;suggests that the volume of a given quantity of gas ...

Mixtures of Gases: Dalton's Law of Partial Pressures and Mole Fractions

Unless individual gases chemically react with each other, the individual gases in a mixture of gases do not affect each other&rsquo;s pressure. Each gas ...

Chemical Stoichiometry and Gases: Using Ideal Gas Law to Determine Moles

Chemical stoichiometry describes the quantitative relationships between reactants and products in chemical reactions.

In addition to measuring quantities ...

Basic Postulates of Kinetic Molecular Theory: Particle Size, Energy, and Collision

The ideal-gas equation, which is empirical, describes the behavior of gases by establishing relationships between their macroscopic properties. For ...

Kinetic Molecular Theory and Gas Laws Explain Properties of Gas Molecules

The test of the kinetic molecular theory (KMT) and its postulates is its ability to explain and describe the behavior of a gas. The various gas laws ...

Kinetic Molecular Theory: Molecular Velocities, Temperature, and Kinetic Energy

The kinetic molecular theory qualitatively explains the behaviors described by the various gas laws. The postulates of this theory may be applied in a ...

Behavior of Gas Molecules: Molecular Diffusion, Mean Free Path, and Effusion

Although gaseous molecules travel at tremendous speeds (hundreds of meters per second), they collide with other gaseous molecules and travel in many ...

Real Gases: Effects of Intermolecular Forces and Molecular Volume Deriving Van der Waals Equation

Thus far, the ideal gas law, PV = nRT, has been applied to a variety of different types of problems, ranging from reaction stoichiometry and empirical and ...

Ideal Gas Law

Source: Laboratory of Dr. Andreas Z&#252;ttel - Swiss Federal Laboratories for Materials Science and Technology
The ideal gas law describes the behavior ...

Derivation of the Ideal Gas Law
Gases are a fundamental state of matter. A gas is a collection of molecules that have a significant distance between their ...

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

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

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

	Determining the Mass of the Unknown LiquidExpand
	According to the ideal gas law for a given ...

Use mathematics and computational thinking to explain the relationships among pressure, temperature, volume, and quantity of gas, both qualitatively and quantitatively.

Understand the relationship among pressure, temperature, volume, and phase.

Pressure Units and Tools for Gas Measurement

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