Chapter 1 Chemistry: The Science of Matter Section 1.1: The Puzzle of Matter Section 1.2: Properties...

Chapter 1 Chemistry: The Science of MatterSection 1.1: The Puzzle of Matter

Section 1.2: Properties and Changes of Matter

Section 1.1 Objectives

Classify matter according to its composition.

Distinguish among elements, compounds, homogeneous mixtures, and heterogeneous mixtures.

Relate the properties of matter to its structure.

Composition, Structure and Behavior Chemistry- the science that investigates

and explains the structure and properties of matter.

Matter- anything that takes up space and has mass

Mass- the measure of the amount of matter that an object contains

Matter

Matter is all around you. Phone Your neighbor The desk The metal of your chair The air you are breathing

What isn’t matter Heat Light Thoughts Ideas Radio waves Magnetic fields

Mass

On earth we equate mass with weight.A bowling ball has a larger mass than a tennis

ball. I have more mass than the text book.

Matter

The structure of matter refers to its composition-what is it made of and how is it organized

The properties of matter describe the characteristics and behavior of matter.Changes matter undergoes

Comparing Composition and Behavior (Figure 1.2 page 5) Salt and Water

Salt is Na and Cl Water is H and O You can wash you hair in water, but not in salt. And

you sprinkle water over popcorn. Aspirin and Sucrose

Both are composed of C, H, and O You wouldn’t use aspirin to sweeten cereal or use

sucrose for a headache

Properties

You can determine some of the properties of a particular chunk of matter by examination and manipulation.What is its color? Is it a solid, liquid or gas? Is it soft or hard?Does it dissolve in water?

Properties of Iron

Strong, but can be flattened and stretched Does not dissolve in water Turns to a liquid at high temperatures Is a gray, shiny solid Is attracted to a magnet Conduct electricity

Properties and Composition

You may be able to determine many properties of a piece of matter by examining it and doing some simple tests.

However, you can not determine what it is composed of just by looking at it.

Examining Matter: The Macroscopic View of Matter The macroscopic view of matter is one in

which you touch, smell, taste and see.

The Submicroscopic View of Matter

Gives you a glimpse into the world of atoms You cannot see this world even with the most powerful

microscopic. Matter is made up of atoms Atoms are so small that a period at the end of a

sentence is made up of 100,000,000,000,000,000,000 (100 quintillion) carbon atoms.

If you could count all 100 quintillion atoms at a rate of three per second it would take you a trillion years to finish counting.

Macro, micro, submicro Macroscopic – I can see with my “naked” eye

Microscopic – I need a microscope to see

Submicroscopic – I can’t see even with the most powerful microscope

Scanning Tunneling Microscope (STM) Although you cannot see atoms the STM

can produce images on a computer screen that show the location of individual atoms.

Platinum

Using Models in Chemistry

In chemistry you will use macroscopic and sub-microscopic models to understand certain concepts.

Scientific model- a thinking device, built on experimentation, that helps us to understand and explain macroscopic observations.

Models

A model for the atom was discussed in Greece about 2,500 years ago. However, this was not a scientific model.

The scientific model of the atom was not proposed until the 1800’s and it has with stood much experimentation with little changes.

Classifying Matter

Matter can be classified by its composition There are two main types of classifications

Qualitative- an observation made without measurement.

Quantitative- an observation made with measurement

Qualitative vs. Quantitative

QualitativeThere are students in this roomSucrose contains carbon, oxygen and

hydrogen Quantitative

There are 24 students in this roomSucrose contains 42.1 g of carbon, 51.4 g of

oxygen and 6.5 g of hydrogen.

Pure vs. Mixture

Matter can be classified by its purity. Is the matter pure or is it a mixture? Pure in chemistry means it contains only the

same substance. Substance- matter with the same fixed

composition and properties. Can be an element or a compound Any sample of pure matter is a substance

Substances

The bag of sugar you buy at the store is pure sucrose. It all has the same properties and a fixed composition. Therefore, it is a substance.

Mixed Matter

Mixed matter is referred to as a mixture. Mixture- combination of two or more substances

in which the basic identity of the substances are not changed.

Mixtures do not have a specific composition. Mixtures can be separated into its components

by physical means.

Separating Mixtures

One way is by physical changes. Physical change- a change in matter that does

not involve a change in the identity of individual substances. Boiling Freezing Melting Evaporation Dissolving Crystallization

Physical Properties

Separation by physical changes takes advantage of the physical properties of the mixture.

Physical properties- characteristics that a sample of matter exhibits without any changes in its identity Solubility Melting and boiling point Color Density Electrical conductivity Physical state (solid, liquid or gas)

Types of Mixture

There are two types of mixtures:Heterogeneous

Hetero means “different”

Homogeneous Homo means “the same”

Heterogeneous Mixture

Heterogeneous Mixture- a mixture that does not have a uniform composition.You can see the different composition.Examples:

Granite Chef Salad Lucky Charms Cereal Orange Juice with pulp

Homogeneous Mixture

Homogeneous Mixture- a mixture with a uniform composition. You cannot tell that it is composed of more than one

substance Another name is a solution Examples:

Salt water Tea Sugar water

Solutions

Homogeneous mixture Examples:

Salt waterGasolineAirSteel

Alloys

Alloys- solid solutions that contain different metals and sometimes nonmetallic substance

Table 1.1 page 23

Table 1.1 Some Common AlloysName of Alloy % Composition

Stainless Steel 73-79% iron (Fe)

14-18% chromium (Cr)

7-9% nickel (Ni)

Bronze 70-95% copper (Cu)

1-25% zinc (Zn)

1-18% tin (Sn)

Brass 50-80% copper (Cu)

20-50% zinc (Zn)

Sterling Silver 92.5% silver (Ag)

7.5% copper (Cu)

14-karat gold 58% gold (Au)

14-28% silver (Ag)

14-28% copper (Cu)

18-karat white gold 75% gold (Au)

12.5% silver (Ag)

12.5% copper (Cu)

Solder (electronic) 63% tin (Sn)

37% lead (Pb)

Solutions

When you are dissolving a substance into another substance there are two important terms:Solute – the substance being dissolvedSolvent – the dissolving agent

Salt WaterSolute = NaClSolvent = H2O

Aqueous Solution

Aqueous Solution- a solution in which the solvent is water.

Examples: Soda Tea Contact-lens cleaner Clear cleaning liquids

Most processes of life take place in aqueous solutions.

Substance: Pure Matter

You and everything around you is made up of chemicals.

Elements: The Building Blocks

If you classify an unknown piece of matter as pure; it means that it is made up of one substance

There are two types of substancesCompoundsElements

Elements

Elements- a substance that cannot be broken down into simpler substances.

Simplest form of matter Building blocks for other types of matter All substance in the universe are:

Elements Compounds formed from elements Or mixtures of elements and compound

Elements

118 elements Examples:

Gold Carbon Lead

Elements combine to form millions of compounds.

Chemical elements are often referred to as the building blocks of matter

Elements

118 elements 90 occur naturally

Less than half of these are abundant The remainder are synthesized

Organizing the Elements

Elements are organized in the Periodic Table

The periodic table tells you:NameSymbolAtomic mass

Symbols

The symbols of the elements are extremely important to know.

You will only have to know the most common ones.

The symbols are a one to two letter representation of the elements.

Not all the symbols are the first or second letter of the elements name

Symbols

Oxygen O

Hydrogen H

Bromine Br

Chlorine Cl

Table 1.2 Some Historic Chemical Symbols

Element Symbol Origin LanguageAntimony Sb Stibium Latin

Copper Cu Cuprum Latin

Gold Au Aurum Latin

Iron Fe Ferrum Latin

Lead Pb Plumbum Latin

Potassium K Kalium Latin

Silver Ag Argentum Latin

Sodium Na Natrium Latin

Tin Sn Stannum Latin

Tungsten W Wolfram german

Compounds Are More Than One Element Compound – a chemical combination of two or

more different elements joined together in a fixed proportion.

Every compound has its own fixed composition Therefore, every compound has unique

chemical and physical properties. The properties of a compound are different from

the properties of the elements that make them up.

Compounds

More than 10 million are known (still growing) New natural compounds are being isolated from

plants and colonies of bacteria. New compounds are also being synthesized in

labs. Examples

Sucrose Salt Water

Formulas of Compounds

Formula – a combination of the chemical symbols that show what elements make up a compound and the number of atoms of each element.

Sucrose: Aspartame:

Table 1.3 Some Common Compounds

Compound Name FormulaAcetaminophen C8H9NO2

Acetic Acid C2H4O2

Ammonia NH3

Aspartame C14H18N2O5

Propane C3H8

Salt NaCl

Sodium Hydroxide NaOH

Sucrose C12H22O11

Water H2O

Review

What is the difference between an element and a compound?

What is the difference between a homogeneous mixture and a heterogeneous mixture?

What is the difference between a mixture and a compound?