introduction to chemistry

Introduction to Chemistry

•Matter: is anything that has mass and takes up space

Properties of Matter •Chemistry is the study of the properties of

matter and how matter changes

•Every form of matter has two kinds of properties physical properties and chemical properties.

Properties of Matter

• Physical Property is a characteristic of a pure substance that can be observed without changing it into another substance

• Examples:▫ Color ▫ Texture▫ States of matter▫ Size ▫ Temperature ▫ Smell ▫ Shape ▫ Boiling point ▫ Melting point ▫ Density

What are some physical properties?

Chemical Properties of Matter• Chemical property is a

characteristic of a pure substance that describes its ability to change into a different substance

• Examples: • Burning • rusting • Film processing

Elements •Elements are the simplest pure substance

•Elements are often called the building blocks of matter because all matter is composed of one or more element or a combination of two or more elements.

Particles of Elements- Atoms •An atom is the basic particle from which

all elements are made.

•DIFFERENT ELEMENTS HAVE DIFFERENT PROPERTIES BECAUSE THEIR ATOMS ARE DIFFERENT!!

When Atoms Combine •The majority of element’s atoms combine

with other atoms.

•When atoms combine, they form a chemical bond—which is the force of attraction between two atoms.

•In many cases, atoms combine to form larger particles called molecules

Compounds •A compound is a pure substance made of

two or more elements that are combined in a specific ratio.

•Example:▫Sodium chloride (table salt)

•When elements are chemically combined, they form compounds having properties that are different from those of the uncombined elements.

Mixtures•A mixture is two or more substances-

elements, compounds, or both—that are in the same place but not chemically combined.

•Examples:▫Gasoline ▫Soil▫Air

• Heterogeneous mixtures – you can see the different parts

• Homogeneous mixtures – substances are mixed evenly

Changes In Matter Chapter One Section Three

Physical Change •A physical change is any change in the

form or appearance of matter but does not change the substance.

•A substance that undergoes a physical change is till the same substance after that change

Types of Physical Changes •Changes of state- moving from between

solids, liquids, and gases.•Changes in Shape or form

Chemical Change •A change in matter that produces one or

more new substance is a chemical change

•A chemical change produces a new substance with properties that are different from those of the original substance.

Conservation of Mass•The fact that matter is not created nor

destroyed in any chemical or physical change is called The law of conservation of mass

•No mass is lost, because during a chemical change, atoms are not lost or gained, only rearranged

Matter and Energy •Energy is the ability to do work or cause

change.

•Every chemical or physical change in matter includes a change in energy.

Temperature and Thermal Energy

•Temperature is the measure of the average energy of random motion of particles of motion.

•Thermal energy is the total energy of all of the particles in an object.▫Thermal energy always flows from warmer

to cooler areas

Thermal Energy and Changes in Matter

•Endothermic energy – a change in which energy is taken in or absorbed ( substance gets cold)

•Exothermic Energy – when energy is given off (substance gets warm)

Introduction to Atoms Chapter three section one

Structure of an Atom •What is an element?

▫A pure substance that cannot be broken down into other substance by chemical of physical means

•What is an atom?▫The basic particle from which all elements

are made up.•http://www.brainpop.com/science/mattera

ndchemistry/atoms/

Structures of an Atom

Particles of Atoms • An atom consists of a nucleus surrounded by one

or more electrons.

• Neutron found in the nucleus of an atom (has no charge)

• Protons found in the nucleus, have a positive electric charge (+)

• Electrons move rapidly around the nucleus and have a negative charge (e-)

Particles of an Atom

A Cloud of Electrons •Electrons move within a sphere shaped

region surrounding the nucleus.

•Electrons with lower energy usually move in the space near the atom’s nucleus.

•Electrons with higher energy move within the space farther from the nucleus.

A Cloud of Electrons

A Cloud of Electrons •Most of the atom’s volume is the space in

which electrons move.

•The space is huge compared to the amount of space taken by the nucleus.

•http://www.brainpop.com/science/matterandchemistry/atomicmodel/

Comparing Particle Masses•Electrons take up the majority of space in

the atom but they account for very little of the mass.

•It takes about 2,000 electrons to equal the mass of just one proton.

•Together the proton and the neutrons make up nearly all the mass of an atom.

Comparing Particle Masses •Atoms are too small to be measured in

everyday units of mass, such as grams or kilograms.

•Scientists use atomic mass units (amu) to measure the mass of an atom.

Comparing Particle MassesParticle Mass (amu)

Proton 1 amuNeutron 1 amu Electron ½,000 amu

Atomic Number •An element can be identified by the

number of protons in the nucleus of its atoms

•Every atom of an element has the same number of protons.

•Each element has a unique atomic number – the number of protons in its nucleus.

Isotopes •Atoms with the same number of protons

but different numbers of neutrons are called isotopes

•An isotope is identified by its mass number which is the sum of the protons and neutrons in the nucleus of an atom

Ion •An atom where the total number of

protons is not equal to the total number of electrons is an Ion ▫Results in a overall positive or negative

charge

Modeling Atoms •One speck of dust may contain about one

million billion atoms!!!!!!!!!!

•Because atoms are so small, scientists create models to describe them.

•Model- may be a diagram, a mental picture, a mathematical statement, or an object that helps explain ideas about the natural world.

Modeling Atoms •In chemistry, models of atoms are used to

explain how matter behaves.

•The modern atomic model explains why most elements react with other elements, while a few elements hardly reacts at all.

Organizing the Elements Chapter three section two

Pattern in the Elements •By 1869 there were 63 known elements.

Each of these elements have different chemical and physical properties.

•A Russian scientist, Dmitri Mendeleev, discovered a set of patterns that applied to all the elements in order to organize the elements.

•http://www.brainpop.com/science/matterandchemistry/periodictableofelements/

Mendeleev’s Work

Mendeleev’s Work •Elements have similar chemical and

physical properties.

•Example:▫Fluorine and Chlorine –gases that irritate

the skin ▫Silver and Copper – shinny metals that

tarnish if exposed to air.

Mendeleev’s Work •Mendeleev started organizing elements

by their color, density, melting point, atomic mass, and the number of chemical bonds the element can form.

•The atomic mass of an element is the average mass of all the isotopes of that element.

Mendeleev’s Work

•He noticed that a pattern of properties appeared when he arranged the elements in order of increasing atomic mass

Mendeleev’s Periodic Table

Predicting New Elements •Mendeleev found that arranging the

known elements strictly by increasing atomic mass did not always group similar elements together.

•He arranged the elements so they did have similar properties.

The Modern Periodic Table

The Modern Periodic Table •In the modern period table, the properties

of the elements repeat in each period or row of the table.

•In 1913 Henry Mosely discovered a way to measure the positive charge on an atoms nucleus- in other words, the atomic number.

Finding Data on Elements

•Each square includes the element’s atomic number, chemical symbol, name, and atomic mass.

Finding Data on Elements

Average atomic Mass •The average atomic mass for chlorine is 34.453 amu

•The atomic mass is an average because most elements consists of a mixture of isotopes

Organization of the Periodic Table

•Remember the periodic table is arranged by atomic number.

•Atomic numbers as they increase from left to right, and read across each row.

•The Properties of an element can be predicated from its location in the periodic table.

Periods

Periods •The table is arranged in horizontal rows

called periods

•A period contains different elements that have different properties

•As you move from left to right in a period the properties change in pattern

Groups

Groups •The modern period periodic table has 7

periods which form 18 vertical columns.

•The elements in a columns are called a group

•The groups are number from 1-18 going from left to right.

Group•Most groups are named for the first

element in the group.

•Elements in each group have similar properties and react in similar ways.

Metals Chapter three section three

Properties of Metals •Metals are a class of elements

characterized by physical properties that include shininess, malleability, ductility, and conductivity.

•http://www.brainpop.com/science/matterandchemistry/metals/

Physical Properties of Metal

•The physical properties of metals include: shininess, malleability, ductility, and conductivity.

Malleable•A substance is malleable when it can be

hammered or rolled in to flat sheets and other shapes.

Ductile •A ductile material is one that can be

pulled or drawn into long wire.

•Copper is one example

Conductivity •Conductivity is the ability of a substance

to transfer heat or electricity to another object

•The majority of all metals are good conductors

•Most metals are solids at room temperature

•One metal- Mercury- is liquid at room temperature

Chemical Properties •The ease and speed with which an

element combines, or reacts with other elements and compounds is called a reactivity

•http://www.youtube.com/watch?v=VVxWucoVn9A

•Metals usually react by losing electrons to other atoms.

•Some elements are very reactive and others are very rarely reactive

•Some metals take a very long time to react.

•Example:▫Iron ▫Iron reacts with oxygen in the air to form

iron oxide or RUST

•Corrosion is the gradual wearing away of a metal element due to a chemical reaction

Corrosion

Metals in the Periodic Table•The metals in a group, or family, have

similar properties, and these family properties change gradually as you move across the table.

•The reactivity of metal tends to decrease as you move from left to the right across the periodic table.

Alkali Metals •The metals in Group 1, from lithium to

francium are called the alkali metals.

•Alkali metals react with other elements by losing one electron.

•So reactive they are hardly ever found as an uncombined element.

Alkaline Earth Metals •Group 2 of the periodic table contains the

Alkaline Earth Metals

•Each group 2 metal is fairly hard, gray-white, and a good conductor of electricity.

•Reacts by losing two electrons

•Not as reactive as group 1, but they are more reactive then most other metals.

Transition Metal •The elements in Groups 3 through 12 are

called the transition metal

•Most of the transition metals are hard and shinny.

• All of the transition metals are good conductors of electricity.

•Less reactive then Groups 1 and 2

Metals in Mixed Groups •Only some of the metals in groups 13

through 15 are metals.

•However these metals are not nearly as reactive as those on the left side of the periodic table.

•The most well known are aluminum, tin, and lead.

Lanthanides •There are two rows placed below the

periodic table. By doing so it makes it more compact.

•The top row are called the lanthanides.

•Lanthanides are soft, malleable shinny metals with high conductivity.

•They are mixed with more common metals to make alloys.

•An alloy is a mixture of a metal with at least on other element, usually another metal.

•They are difficult to separate from one another because they share similar properties.

Actinides •The elements below the lanthanides are

called actinides.

•Only four of these naturally occur on earth including Uranium.

•All elements heavier then uranium were made in a lab.

•The nuclei of these elements are unstable, they will break into smaller nuclei

•Many of the elements last for only a fraction of a second after they are made.

Synthetic Elements •Elements with an atomic number higher

than 92 are sometimes described as synthetic elements because they are not found naturally on Earth.

•Elements that follow uranium are made—or synthesized—when nuclear particles are forced to crash into one another.

Nonmetals and Metalloids Chapter three section four

Properties of Nonmetals •A nonmetal is an element that lacks most

of the properties of a metal.

•Most nonmetals are poor conductors of electricity and heat, and are reactive with other elements.

•Solid nonmetals are dull and brittle

Sulfur

Physical Properties •Ten of the 16 nonmetals are gases at

room temperature ▫The two main ones are oxygen and nitrogen

that make up the air we breath

•There are five that are solid at room temperature

•Only one nonmetal that is a liquid at room temperature

Physical Properties •The physical properties of nonmetals are

the opposite of those that are metals.

•Solid nonmetals are dull (meaning not shinny), and brittle.

•Nonmetals are also poor conductors of heat and electricity.

Chemical Properties •Most nonmetals are reactive.

•Atoms of nonmetals usually gain or share electrons when they react with other atoms.

•When nonmetals and metals react, electrons move from the metal atoms to the nonmetal atoms

Chemical Properties

•Many nonmetals can also form compounds with other nonmetals. The atoms share electrons and become bonded together into molecules.

Families of Nonmetals •All of group 18 are nonmetals

•Group 14 through 17 have a mix of nonmetals and other kinds of elements.

The Carbon Family •Atoms in the carbon family can either

gain, lose, or share electrons.

•In group 14 only carbon is a nonmetal

•Carbon is vital to life. All life contains carbon.

The Nitrogen Family •Group 15 is the nitrogen family.

•There are only two nonmetals in the nitrogen family- nitrogen and phosphorous.

•In order to become stable elements in group 15 must gain or share three electrons.

The Nitrogen Family •Nitrogen doesn’t readily react with other

elements.

•Nitrogen is an example of an element that occurs naturally as a diatomic molecule, as N²

•A diatomic molecule is a molecule consisting of two atoms.

•Prosperous is the other nonmetal in the nitrogen family.

•Much more reactive than nitrogen, it is always found in nature in compounds.

The Oxygen Family •Group 16, the oxygen family, contains

three nonmetals – oxygen, sulfur, and selenium.

•Gain or share two electrons when reacting with other elements.

•Like nitrogen, oxygen also occurs as a diatomic molecule. o²

•You may also breath in ozone. Which is a triatomic molecule 0³

•Oxygen is highly reactive and it can combine with almost any other element.▫2nd most abundant element

•Sulfur is the other common nonmetal in the oxygen family

The Halogen Family •Group 17

•Contains:▫Fluorine ▫Chlorine ▫Bromine ▫Iodine ▫Astatine

•These elements are also known as the halogens which means “salt forming”

•All but astatine share the same properties

•A halogen atom gains or shares one electron when it reacts with other elements.

•Halogen atoms are VERY REACTIVE

•Fluorine is so reactive that it reacts with almost every other known substance.

•Some of the elements in the halogen group are very reactive and dangerous but many of the halogens are quite useful.

•Carbon and fluorine make up the nonstick coating on cookware.

•Fluorine is added to water to prevent tooth decay.

The Noble Gases • The elements in group 18 are known as

the noble gases.

•They don’t normally form compounds because they are already stable.

•All noble gases exist in Earth’s atmosphere, but only in small amounts.

Hydrogen •Hydrogen is found in the uppermost left

corner of the periodic table – the element with the simplest and smallest

•Because the chemical properties of hydrogen are so different from those of the other families it can’t really be put into a family.

•Hydrogen makes up about 90% of the atoms in the universe

•Rarely found as a pure element

•Most hydrogen is combined with oxygen as water.

The Metalloids •Along the boarder of the metals and

nonmetals are the metalloids which consist of seven elements.

•The metalloids have characteristics of both metals and nonmetals▫Solid at room temperature ▫Brittle ▫Hard▫Somewhat reactive

•The most useful property of the metalloids is their varying ability to conduct electricity.

•Semiconductors are substances that can conduct electricity under some conditions but not under other conditions