Name: distinguishing physical and chemical changes
Uploaded: 2020-09-03T13:38:25.000Z
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.7.1

physical-and-chemical-properties-of-matter

Physical and Chemical Properties of Matter

תכונות המאפשרות לנו להבחין בין סוג אחד של חומר למשנהו נקראות מאפיינים. לחומר יש שני סוגי מאפיינים:פיזיקליים וכימיים. מאפיינים פיזיים של החומר ניתנים למדידה ולבחינה ללא שינוי בהרכב החומר או בזהותו.ריח, טעם, צבע, מראה, קושי, צפיפות, נקודת רתיחה והמסה ומוליכות חשמלית כל אלה הם דוגמאות של מאפיינים פיזיים. חלק ממאפיינים פיזיים אלה ניתנים לבחינה ללא שינוי של המצב הפיזי של החומר. אז כשאנחנו אמרים שגז הליום קל יותר מהאוויר, אנחנו מתייחסים למאפיין פיזי.בדומה לכך, ריח הבנזין גם הוא מאפיין פיזי. מאפיינים פיזיים אחרים ניתנים לבחינה רק כשהחומר עובר שינויים פיזיים. לדוגמה, זהב טהור במצבו המוצק עשוי מאטומי זהב צפופים.אבל כשהוא מומס בטמפרטורה גבוהה, הוא משנה את מצבו מוצק לנוזל. יחד עם זאת, הנוזל עדיין מורכב מאטומי זהב, לכן זהו שינוי פיזי. בדומה לכך, כשמים נוזליים קופאים לקרח מוצק, ההרכב הכימי של המים והקרח לא משתנה.ולכן, שינוי הפיזי רק משנה את מצב הצבירה של החומר או את תנאיו הפיזיים, מבלי לשנות את ההרכב הכימי. גריסה, טחינה, חיתוך, ערבוב, מגנוט או ביטול המשיכה המגנטית ה דרכים נפוצות נוספות לשנות את המצב הפיזי של החומר. לעומת זאת, מאפיינים כימיים של החומר הם מאפיינים שניתן למדוד ולבחון אותם רק כשהחומר עובר שינוי בהרכבו הכימי.קורוזיה, דליקות, רעילות, חומציות או פעילות כימית הן דוגמאות של מאפיינים כימיים של החומר. על מנת לזהות מאפיין כימי, אנחנו מחפשים שינוי כימי. שינויים כימיים כוללים תגובות כימיות ולרוב נבחנים לפי שינוי בצבע או בריח.לדוגמה, כשמטבע נחושת נחשף לאוויר ולמים נוצר שינוי כימי. הנחושת עוברת סדרה של תגובות כימיות, שאחת מהן, שנראית כאן, יוצרת שכבה של פלטינה כחולה-ירוקה על המטבע, שאחרת היה נותר בצבעו החום הטבעי. לכן, השינוי הכימי יוצר מצבים חדשים לגמרי של החומר, שמשתנה ממצבו הקודם.לדוגמה, הדליקות של בנזין היא מאפיין כימי שניכר מהשינויים הכימיים בהרכבו של הבנזין כאשר הוא נשרף והופכים את הבנזין לחומרים חדשים לגמרי בעיקר פחמן דו חמצני ומים.

תכונות פיזיקליות וכימיות של חומר

<div style="direction:rtl">המאפיינים המאפשרים לנו להבחין בין חומר אחד לחומר אחר נקראים תכונות. <h4>תכונות פיזיים של חומר</h4> תכונה פיזיקלית היא מאפיין של חומר שאינו קשור לשינוי בהרכבו הכימי. דוגמאות מוכרות לתכונות פיזיקליות כוללות צפיפות, צבע, קשיות, נקודות התכה ורתיחה ומוליכות חשמלית. אנו יכולים לראות כמה תכונות פיזיקליות, כגון צפיפות וצבע, מבלי לשנות את המצב הפיזי של החומר הנצפה. תכונות פיזיקליות אחרות, כגון טמפרטורת ההיתוך של הברזל או טמפרטורת ההקפאה של המים, ניתנות להבחין רק כאשר החומר עובר שינוי פיזיקלי. שינוי פיזיקלי הוא שינוי במצבו או בתכונותיו של החומר ללא כל שינוי נלווה בהרכבו הכימי (זהות החומרים הכלולים בחומר). אנו רואים שינוי פיזי כאשר, למשל, שעווה נמסה, סוכר מתמוסס בקפה, ואדים מתעבים למים נוזליים. דוגמאות נוספות לשינויים פיזיים כוללות מגנט ופינוי מתכות (כפי שנעשה עם תגי אבטחה רגילים נגד גניבה) וטחינת מוצקים לאבקות. בכל אחת מהדוגמאות הללו חל שינוי במצב הפיזיקלי, בצורתו או בתכונותיו של החומר, אך אין שינוי בהרכבו הכימי. <h4>תכונות כימיות של החומר</h4> השינוי של סוג אחד של חומר לסוג אחר (או חוסר היכולת לשנות) הוא תכונה כימית. דוגמאות לתכונות כימיות כוללות דליקות, רעילות, חומציות, תגובתיות (סוגים רבים) וחום בעירה. ברזל, למשל, מתחבר עם חמצן בנוכחות מים ויוצר חלודה; כרום אינו מתחמצן. ניטרוגליצרין מסוכן מאוד מכיוון שהוא מתפוצץ בקלות; הניאון אינו מהווה כמעט סכנה מכיוון שהוא כמעט ולא מגיב. כדי לזהות תכונה כימית, אנו מחפשים שינוי כימי. שינוי כימי מייצר תמיד סוג אחד או יותר של חומר השונה מהחומר שהיה לפני השינוי. היווצרות החלודה היא שינוי כימי מכיוון שחלודה היא חומר מסוג שונה מהברזל, החמצן והמים שהיו לפני היווצרות החלודה. הפיצוץ של ניטרוגליצרין הוא שינוי כימי מכיוון שהגזים המיוצרים הם סוגים שונים מאוד של החומר מהחומר המקורי. דוגמאות נוספות לשינויים כימיים כוללות תגובות המבוצעות במעבדה (כגון נחושת המגיבה עם חומצה חנקתית), כל צורות הבעירה (שריפה), הבשלת פירות ומזון שמתבשל, מתעכל או נרקב. טקסט זה מותאם מ <a href="https://openstax.org/books/chemistry-2e/pages/1-3-physical-and-chemical-properties">Openstax, Chemistry 2e, Section 1.3: Physical and Chemical Properties.</a></div>

המאפיינים המאפשרים לנו להבחין בין חומר אחד למשנהו נקראים תכונות.

תכונות פיזיקליות של חומר

תכונה פיזית היא ...

Education

JoVE Core

כימיה

אחד

Introduction: Matter and Measurement

מבוא: חומר ומדידה

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

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 observed without changing the state of the matter, such as density and color. Others appear only during a physical change, like the melting temperature of iron or the freezing temperature of water.

A physical change alters the state or form of matter without changing what the substance is made of. Wax melting, sugar dissolving in coffee, and steam condensing into liquid water are all physical changes. Magnetizing and demagnetizing metals, such as in anti-theft security tags, and grinding solids into powders are also physical changes. In each case, the material looks or behaves differently, but its chemical composition stays the same.

Chemical properties describe whether matter can change into a different type of matter, or resist that change. Common chemical properties include flammability, toxicity, acidity, reactivity, and heat of combustion. Iron reacts with oxygen and water to form rust, while chromium does not oxidize. Nitroglycerin explodes easily, but neon is very unreactive.

To identify a chemical property, we look for a chemical change. A chemical change produces one or more new kinds of matter that are different from the starting material. Rust formation is a chemical change because rust is not the same as iron, oxygen, or water. Nitroglycerin exploding is also a chemical change because the gases produced are different from the original substance. Other chemical changes include copper reacting with nitric acid, burning, fruit ripening, and food being cooked, digested, or rotting.

Distinguishing Physical and Chemical Changes

distinguishing-physical-and-chemical-changes

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

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...

physical and chemical properties of matter

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

Learn how to tell physical properties from chemical properties using clear examples like melting, rusting, burning, and dissolving for grades 9–12.

Distinguishing Physical and Chemical Changes | JoVE K12

chemistry

JoVE Core Chemistry brings general chemistry concepts to life using concise and easy-to-understand animated video lessons. Plus, in the scientist-in-action videos, we demonstrate classical and original research experiments performed in today's laboratories worldwide.

Physical Science

Matter and its Interactions

PS.PSc.1.3

Pennsylvania State Academic Standards

Earth and Space Science

Earth's Systems

3.3.9-12.K

Louisiana Student Standards for Science

High School

Matter And Its Interactions

HS-PS1-2

HS-PS1-7

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Study Of Matter

Classification of matter

Physical Geology

Minerals

properties-minerals-hardness-luster-cleavage-streak-crystal-shape

Properties of minerals (hardness, luster, cleavage, streak, crystal shape, fluorescence, flammability, density/specific gravity, malleability)

Virginia  Standards of Learning

HIgh School

CH.7

CH.7.a

Earth Science

ES.4

ES.4.a

PS.3

PS.3.a

Physics

PH.9

PH.9.e

Arizona Science Standards

HS.E1

HS.E1U1.12

HS.E1U1.13

HS+C.P1

HS+C.P1U1.5

new-jersey-student-learning-standards-for-science

New Jersey Student Learning Standards for Science

Earth's Place in the Universe

HS-ESS1-2

Texas Essential Knowledge and Skills

CHEM.2

CHEM.2.A

Alabama Course of Study Science

Matter and Its Interactions

9-12.PS.3.5

9-12.PS.3.5.a

Next Generation Science Standards

HS-PS1-6

HS-PS1-4

Florida Department of Education

SC.912.P.8

SC.912.P.8.2

Chemistry and Physics

IPC.7

IPC.7.B

IPC.7.C

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

C-PS1-1

C-PS1-2

C-PS1-3.

motion-and-stability-forces-and-interactions

Motion and Stability: Forces and Interactions

C-PS2-6.

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Chemical Reactions

HS-PS1-2.

Georgia Standards of Excellence

SPS5.

States of Matter

SC2.

Intermolecular vs. Intramolecular Forces

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

Physical Properties of Matter

A physical property is ...

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 ...

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.

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 ...

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

PS.Chm.7.2

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

Distinguishing Physical and Chemical Changes

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