Properties Of MatterUnit

Unit TEKS

(6.5) Matter and energy. The student knows the differences between elements and compounds. The student is expected to:

(A) Know that an element is a pure substance represented by chemical symbols;

(C) Differentiate between elements and compounds on the most basic level

(D) Identify the formation of a new substance by using the evidence of a possible chemical change such as production of a gas, change in temperature, production of a precipitate, or color change.

(6.6) Matter and energy. The student knows matter has physical properties that can be used for classification. The student is expected:

(A) Compare metals, nonmetals, and metalloids using physical properties such as luster, conductivity, or malleability

Unit Guided Questions & Objectives

• Understand that matter is made up elements and compounds

• Name elements and symbols

• Classify compounds as being made up of two or more elements

• Recognize that the formula of a compound represents its composition

• Why is it important to know physical properties of element?

• Periodic Table

– How is the periodic table arranged (alphabetically, atomic number, atomic mass, color)?

– What separates the metals from the nonmetals?

– How do you determine the characteristics of an element (atomic number, etc.)

– Identify the groups, periods, families on the table

– Know common elements and symbols

– Memorize the chemical symbols for the first 25 elements

Unit Vocabulary

MatterMoleculesElementsCompoundsChemical SymbolAtomsProtonsNeutrons

MetalsNonmetalsMetalloidsAtomic numberAtomic massElectronsNucleus

Lesson 1: What Matter Is Made Of

All substances are made of tiny building blocks of matter. The

identity, quantity, and arrangement of the elements in

a substance account for the uniqueness of that material.

What Matter Is Made Of

• Matter– Anything that has mass & takes up

space–Matter can be solid, liquid, or gas– Some matter are too small to be

seen, called molecules–Molecules are the smallest pieces of

matter that can be broken into w/out changing the kind of matter

How Do We Know What’s “Inside” Matter?

• In studying matter, scientist must perform tests from the outside to infer what basic particles make up matter.

• Remember, the basic particles that make up matter are too small to be seen directly.

• In the past, the test scientists performed on matter gave only hints about how matter is put together. That’s because particles of matter cannot be observed.

How Do We Know What’s “Inside” Matter?

• People have experimented with matter for thousands of years. In ancient times the goal was often a practical product like a colorful dye, a metal sword, or a plow.

• In recent centuries matter has also been studied with carefully planned scientific experiments.

• The ancient Greek philosopher Aristotle believed that all matter was composed of four elements—earth, air, fire, and water.

• However, during the last three centuries, scientists have identified the true chemical elements.

Elements

• Elements are the basic building blocks of all matter

• Elements are the pure substances that cannot be broken down into anything simpler

Elements• One of the most

interesting elements is shown in the photograph.

• This element is also known as liquid silver. It is beautiful but highly poisonous. It is often used in thermometers because is expands very evenly when warmed.

• What is it?

What Are the Elements?

• Elements are pure substances that cannot be broken down into any simpler substances.

• You are probably familiar with many of them. Several are shown in the photographs. How many do you recognize?

Au

Al

Cu

C O

S

What Are the Elements? Cont’d

• Each element is given a special symbol of one or two letters.

• The first letter is always a capital.

• The second letter, if there is one, is never a capital.

• Sometimes the letters match the English name, such as Ni for nickel or Zn for zinc.

• In other cases the symbol comes from an ancient name. Gold, for instance, is given the symbol Au from its Latin name, aurum.

What Are Compounds?• Imagine looking at pure water

through a microscope. It would look the same everywhere. Water has this appearance because it is a single substance. Yet the photograph shows how passing electricity through water breaks it apart into two elements, hydrogen and oxygen. If water is a single substance, how could it contain the elements hydrogen and oxygen?

• Actually, the hydrogen and oxygen in water are chemically combined. This makes them act like single substance. Any substance that is formed by the chemical combination of two or more elements is called a compound.

• Compounds have different properties than the elements that make them up. How does the photograph illustrate that this statement is true?

• The water is liquid & the hydrogen & oxygen are both gases. Therefore, water is made of hydrogen and oxygen, as this experiment shows.

Compounds

• All compounds are single substances that can only be broken apart into simpler substances by chemical reactions.

• Compounds have different properties than the elements that make them up, as the water experiment illustrated.

How Do You Write a Compound’s Name?

Table of Compounds

Compound Chemical Formula

Water H2O

Carbon dioxide CO2

Baking soda(bicarbonate of soda)

NaHCO3

Table salt NaCI

Table sugar C12H22O11

Glucose (a sugar) C6H12O6

• As you know, each element has a one-or-two-letter symbol. Scientist also write symbols for compounds called chemical formulas.

• A compound’s chemical formula contains the symbols for the elements that make it up.

• The formula also contains numbers below the element symbols called subscripts. The table shows chemical formulas for some familiar compounds.

• The subscripts in a chemical formula tell us the number of particles that combine together in a compound. For example, water is made up of two elements—hydrogen & oxygen. For every oxygen particle, there are two hydrogen particles. The formula for water is written H2O.

What Happens When Sulfuric Acid Is Added To Sugar?

• Table sugar is made up the elements carbon, hydrogen, and oxygen. For every 12 carbon particles, there are 22 hydrogen particles and 11 oxygen particles. We write C12H22O11 for table sugar’s chemical formula.

• The photo shows what happens to table sugar when it is treated with strong sulfuric acid. (Warning: Sulfuric acid is a dangerous substance.)

• The acid takes out all the hydrogen and oxygen, leaving a black mass. The black mass is the element

carbon. Elements do not retain their properties when they combine to form compounds.

Lesson 2: What Are Elements Made Of?

Tiny particles called electrons, protons, and neutrons make up an

atom. Two or more atoms can combine to form a molecule.

What Are Elements Made Of?• In 1803 an English

scientist named John Dalton stated an important theory: Matter is made up of tiny particles that cannot be cut apart into smaller pieces. Today we call Dalton’s tiny particles atoms.

• An atom is the smallest unit of an element that still has the properties of the element

Atom’s Image• Many experiments since

Dalton’s day have shown us what atoms are like. Yet atoms are so small that we cannot see them directly, even through a microscope. Scientists have had to observe atoms indirectly, in much the same way as you would observe matter inside “mystery” canned goods.

• A special microscope called a scanning tunneling microscope uses a very sharp needle that can trace the bumps in a surface made by individual atoms. The photograph shows some of what such special microscopes can “see.”

Individual carbon atoms

Images made by these microscopes show that atoms are discrete & often occur in well-ordered arrays.Atoms are 3D (three-dimensional in shape).

What’s Inside Atoms?

• John Dalton imagined that atoms were like tiny steel marbles—solid & unbreakable. Yet we know that atoms are made of still smaller particles.

• Atoms are far from being solid—they are mostly empty space!

• Atoms contain three kinds of particles called protons, neutrons, and electrons.

What’s Inside Atoms?• The protons & neutrons are located in a tiny, very dense

body in the atom’s center, called the atomic nucleus. The electrons are in the space outside the nucleus.

• Protons & neutrons have nearly the same mass, but electrons are about 2,000 times less massive than protons & neutrons. Protons carry one unit of positive electric charge, while electrons carry one unit of negative electric charge.

• Neutrons have no electric charge. All atoms have equal numbers of electrons & protons, so they have no overall electric charge.

• The number of protons in an atom determines what element it is. For example, any atom with six protons is a carbon atom. Any atom with eight protons is an oxygen atom.

Atoms Consists of: Protons, Neutrons, Electrons, & Nucleus

• Atom – the smallest unit of an element that still has the properties of the element

• Proton – a particle with a positive charge in the nucleus of an atom

• Neutron – an uncharged particle in the nucleus of an atom

• Electron – a particle with a negative charge moving around the nucleus of an atom

• Nucleus – the dense center part of an atom

Atoms

Proton

Electron

Nucleus

What Properties Do Elements Have?• We know of 112

elements. These substances have many different properties. Yet there are patterns in the properties of the elements: Chemical Reactivity; Melting & Boiling Temperatures; Metal Versus Nonmetal.

• Study the photographs to learn about properties that can demonstrate these patterns.

Aluminum

Phosphorus

Copper

METALS

Carbon Iodine

NONMETALS

Properties of Elements

Chemical Reactivity•Some elements take part in chemical reactions much more easily than others. The magnesium reacts rapidly with the acid. Yet the copper hardly reacts at all.•Reactive elements, like magnesium, are usually combined with other elements when found in nature.

Magnesium takes part in chemical reactions much more easily than copper. Here the

magnesium reacts rapidly with the acid. Yet the copper hardly

reacts at all.

Copper Magnesium

Properties of ElementsMelting & Boiling Temperatures•The elements shown are all at room temperature, about 22°C. Lead does not melt until it reaches 328°C, so it is a solid at 22°C. Bromine, though, melts at -7.2°C (7.2° below 0°C), and it is a liquid at 22°C. Fluorine is a gas at 22°C because it boils at -188°C (188° below 0°C).

Lead

Bromine

Melted Lead

Liquid Bromine

Bromine swimming pool tablets

Solid Lead

Solid Bromine Crystals

Fluorine

Solid Fluorine

Liquid Fluorine

Properties of ElementsMetal Versus Nonmetal•About three-fourths of the elements are metallic, like copper, gold, silver, aluminum, iron, and nickel. Metals conduct electricity and heat well. Metals are also shiny when freshly polished, and many can be worked into thin sheets or different shapes.•In contrast nonmetals, like iodine, phosphorus, and carbon, are often poor conductors of heat and electricity. They are not reflective like metals and are brittle.

METALS

NONMETALS

Goldleaf Aluminum

Copper

CarbonPhosphorus

Iodine

History & Development of the Periodic TableIn 1869 a Russian scientist name Dmitri Mendeleev found that the properties of the elements went through repeating cycles. Mendeleev created a table of elements based on these cycles. To Mendeleev’s surprise, groups in his table contained elements with similar chemical properties. For example, one group contained lithium (Li), sodium (Na), potassium (k), rubidium (Rb), and cesium (Cs).

All of these elements combine with chlorine in the same way. The formulas for their chlorine compounds are LiCI, NaCI, KCI, RbCI, and CsCI.

We call Mendeleev’s table the Periodic Table after the “periodic” changes he found in the element’s properties. The elements are arranged in the periodic table by their chemical properties.

Russian Scientist, Dmitri Mendeleev (1834 – 1907)

Science BackgroundPeriodic Table: Mendeleev’s early periodic table arranged the elements in columns; today they are in rows. When Mendeleev first developed his table, the noble gases were not known. Argon was discovered in 1894 and neon was discovered in 1898. These and subsequent discoveries necessitated the addition of a column of noble gases. For many years these gases were called inert, meaning “not reactive.” Modern chemistry has succeeded in combining the larger noble gases with fluorine.The element fluorine is a highly reactive, corrosive, poisonous substance. Drinking water that contains large amounts of fluorine compounds can cause teeth and bones to become extremely brittle. However, a small amount of fluorine compounds in water or toothpaste has been effective in preventing tooth decay, especially among children.

How Can the Elements Be Grouped?

1. The metals lie on the left, and the nonmetals lie mainly on the right, with elements called metalloids in between.

2. Most of the elements are solids at room temperature, and all metals are solids except mercury.

3. The most reactive metals are at the lower left, and the most reactive nonmetals are in the second column from the right.

How Can the Elements Be Grouped?• Elements are arranged numerically ( by atomic number.)

• Read & observe the color key to understand the significance of the various colors.

• Do you see that the most reactive metal is francium (symbol Fr) in the lower-left corner of the table.

• Do you see that the most active nonmetal is fluorine 9sumbol F) in the upper-right corner of the table.

Let’s Use the Periodic Table to Answer the READING CHARTS’

Questions?

READING CHARTS’ Answers1. Sodium is a metal; chlorine is a nonmetal.2. Sodium chloride (NaCI) is one example of a

substance that is formed by the combination of a reactive metal and reactive nonmetal.