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Chapter 1Introduction:

Matter and Measurement

John D. Bookstaver

St. Charles Community College

St. Peters, MO

2006, Prentice Hall

Chemistry, The Central Science, 10th editionTheodore L. Brown; H. Eugene LeMay, Jr.;

and Bruce E. Bursten

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Chemistry:

The study of matterand the changes it undergoes.

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Scientific Method:

A systematic approach to solving problems.

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Matter:

Anything that has mass and takes up space.

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Matter

• Atoms are the building blocks of matter.

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Matter

• Atoms are the building blocks of matter.

• Each element is made of the same kind of atom.

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Matter

• Atoms are the building blocks of matter.

• Each element is made of the same kind of atom.

• A molecule is a group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction

• A compound is made of two or more different kinds of elements.

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Kinetic (Molecular) Theory

• All matter is composed of small particles

• Particles are in constant random motion

• Particles collide with each other and the walls of their containers constantly

• When particles collide- small amounts of energy are lost

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States of Matter

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SOLIDS• Has definite shape

• Has definite volume

• Can not be compressed

• Particles close together

• Particles vibrate but don’t move

• No particle motion‐ absolute zero‐ 0K

• Geometric arrangement of particles in a solid‐ determines chemical & physical properties of a solid

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LIQUIDS

• Has definite volume

• Has no definite shape

• Can not be compressed

• Particles farther apart

• Particles move around slowly

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GASES• Has no definite shape

• Has no definite volume

• Can be compressed

• Particles furthest apart

• Particles move around quickly

• Particles of a gas‐have enough KE to overcome the attractions between them completely

– Spread and fill the containers

– Diffusion‐spreading of particles throughout a container until they are uniformly distributed

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PLASMA

• A plasma is a gas that is composed of free‐floating ions (atoms stripped of some electrons ‐ positively charged) and free electrons (negatively charged). 

• A plasma conducts electrical currents. Plasma was discovered by William Crookes in 1879. 

• There are many different types of plasmas. 

• There is plasma in stars (including our Sun); the solar wind in our Solar System is made of plasma.

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Plasma Atoms

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OTHER STATESSupercritical Fluid:

• A supercritical (or critical) fluid is a liquid/gas under extreme pressure.

• These supercritical fluids have unique characteristics, the density of a liquid and the mobility of a gas.

• Supercritical fluids exist deep inside some planets; for example, there is supercritical water deep inside the Earth.

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Degenerate Gas:

• A degenerate gas is one that is super-compressed and very dense.

• The molecules of this degenerate gas are virtually touching one another and the gas acts much like a solid.

• Unlike gases under normal conditions, the temperature in a degenerate gas does not depend on the pressure.

• These gases follow quantum mechanical laws.

OTHER STATES

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In Between States

Super-cooled Liquid – Cooled below freezing but maintains liquid state. Used to form glass.

Recent News – Closer to absolute zero you get motion stops but it appears that matter starts to heat up – wild!

Activity at home: Take a bottle of water, place it in the freezer. Take it out carefully just before it freezes. Tap it gently with your finger and watch what happens.

Super-heated steam– steam heated beyond boiling point but maintains gas state. Used in engineering systems like on battleships.

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Classification of Matter

• The four classes of matter are elements, compounds, mixtures, and solutions

• Pure Substance – Matter that has only 1 set of chemical and physical properties.

• Mixture – Two or more pure substances mixed together.  Each substance in the mixture retains its own set of chemical and physical properties

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Elements

• pure substance that cannot be separated into simpler substance by physical or chemical means. 

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Compounds

Pure substance composed of two or more different elements joined by chemical bonds.

– Made of elements in a specific ratio 

that is always the same

– Has a chemical formula

– Can only be separated by 

chemical means, not physically 

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Mixtures• A combination of two or more pure substances that are not chemically combined.

• substances held together by physical forces, not chemical 

• No chemical change takes place 

• Each item retains its properties 

in the mixture 

• They can be separated physically 

Chem4kids.com

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Mixtures and Solutions

• A mixture is a combination

of two or more components that

are NOT chemically combined,

and retain their identities. 

Mixtures can be physically separated. The identities of the substances DO NOT change.

A homogeneous mixture is also called a

solution.

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Mixtures• When a mixture’s components are easily recognizable, such as pizza, it is called a heterogeneous mixture.

• In a homogeneous mixture such

as chocolate milk, the component particles cannot be distinguished,

even though they still retain their

original properties.

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Solutions

• A mixture that appears to be a single substance but is composed of particles of two or more substances that are distributed evenly amongst each other.

A solution may be liquid, gaseous, or solid.Examples of solutions

Liquid - seawaterGas - airSolid - alloys

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Suspension

• A mixture in which particles of

a material are dispersed through‐

out a liquid or gas but are large

enough that they settle out.

– Particles are insoluble, so they DO NOT dissolve in the liquid or gas.

– Particles can be separated using a filter.• Examples:

• Salad dressing

• Medicines that say

“shake well before use”  

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Colloids

• A mixture in which the particles are dispersed throughout but are not heavy enough to settle out.

• Made up of solids, liquids and gases.– Examples :

• Mayonnaise

• Stick deodorant

• milk

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Classification of Matter

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Properties and Changes of Matter

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Properties of Matter

• Physical Properties:

□ Can be observed without changing a substance into another substance.

• Boiling point, density, mass, volume, etc.

• Chemical Properties:

□ Can only be observed when a substance is changed into another substance.

• Flammability, corrosiveness, reactivity with acid, etc.

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Properties of Matter

• Intensive Properties:

□ Independent of the amount of the substance that is present.

• Density, boiling point, color, etc.

• Extensive Properties:

□ Dependent upon the amount of the substance present.

• Mass, volume, energy, etc.

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Changes of Matter

• Physical Changes:

□ Changes in matter that do not change the composition of a substance.

• Changes of state, temperature, volume, etc.

• Chemical Changes:

□ Changes that result in new substances.

• Combustion, oxidation, decomposition, etc.

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Chemical Reactions

In the course of a chemical reaction, the reacting substances are converted to new substances.

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Chemical Reactions

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Compounds

Compounds can be broken down into more elemental particles.

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Electrolysis of Water

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Separation of Mixtures

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Mixtures

• Common Techniques for Separating Mixtures

Distillation – separates a mixture based on boiling points of the component.

Examples :saltwatercrude oil into gasoline and kerosene

Magnet – separates iron from other objects.

Centrifuge – spins and separates according to densities.

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Distillation:

Separates homogeneous mixture on the basis of differences in boiling point.

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Distillation

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Filtration:

Separates solid substances from liquids and solutions.

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Chromatography:

Separates substances on the basis of differences in solubility in a solvent.

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Units of Measurement

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SI Units

• Système International d’Unités

• Uses a different base unit for each quantity

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Metric System

Prefixes convert the base units into units that are appropriate for the item being measured.

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Volume

• The most commonly used metric units for volume are the liter (L) and the milliliter (mL).

□ A liter is a cube 1 dm long on each side.

□ A milliliter is a cube 1 cm long on each side.

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Uncertainty in Measurements

Different measuring devices have different uses and different degrees of accuracy.

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Temperature:

A measure of the average kinetic energy of the particles in a sample.

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Temperature

• In scientific measurements, the Celsius and Kelvin scales are most often used.

• The Celsius scale is based on the properties of water.□ 0C is the freezing point of water.

□ 100C is the boiling point of water.

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Temperature

• The Kelvin is the SI unit of temperature.

• It is based on the properties of gases.

• There are no negative Kelvin temperatures.

• K = C + 273.15

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Temperature

• The Fahrenheit scale is not used in scientific measurements.

• F = 9/5(C) + 32• C = 5/9(F − 32)

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Density:

Physical property of a substance

d=mV

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Uncertainty in Measurement

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Significant Figures

• The term significant figures refers to digits that were measured.

• When rounding calculated numbers, we pay attention to significant figures so we do not overstate the accuracy of our answers.

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Significant Figures

1. All nonzero digits are significant.

2. Zeroes between two significant figures are themselves significant.

3. Zeroes at the beginning of a number are never significant.

4. Zeroes at the end of a number are significant if a decimal point is written in the number.

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Significant Figures

• When addition or subtraction is performed, answers are rounded to the least significant decimal place.

• When multiplication or division is performed, answers are rounded to the number of digits that corresponds to the least number of significant figures in any of the numbers used in the calculation.

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Significant Digit Calculations

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Accuracy versus Precision

• Accuracy refers to the proximity of a measurement to the true value of a quantity.

• Precision refers to the proximity of several measurements to each other.