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Matter & Change. Chemistry -- a Physical Science. The natural sciences were once divided into 2 broad categories Biological sciences – study of anything in the living realm Physical sciences – study of anything in the nonliving realm
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Chemistry -- a Physical Science The natural sciences were once divided into 2 broad categories Biological sciences– study of anything in the living realm Physical sciences– study of anything in the nonliving realm However, both living and nonliving matter have a chemical structure Chemistry is central to all the sciences No longer distinct divisions between biological and physical sciences
Chemistry -- a Physical Science Chemistry is the study of matter Matter’scomposition Matter’sproperties And the changesmatter undergoes The use of instruments is vital in Chemistry It extends our ability to make observations and measurements With them it is possible to look at microstructures (things too tiny to be seen with the naked eye)
Chemistry -- Branches Chemistry includes different branches of study and research. Organic Chemistry: study of most carbon-containing compounds Inorganic Chemistry: study of all substances not classified as organic, mainly those compounds that do not contain carbon. Physical Chemistry: study of the properties & changes of matter & their relationships to energy
Chemistry -- Branches Analytical Chemistry: The identification of the composition of new materials Biochemistry: The study of substances and processes occurring in living things Theoretical Chemistry: The use of math & computers to understand the principles behind observed chemical behavior & to design & predict the properties of new compounds In each branch, scientists work with chemicals
Chemistry -- Branches A chemical is any substance that has a definite composition For instance sucrose, or sugar…all sugar is composed of the same atoms in the same ratios, which is what makes it taste sweet Knowing what makes up chemicals, like sugar, helps scientists create other useful chemicals For instance, aspartame, which is another chemical that tastes sweet…even sweeter than sugar
The Known Universe Everything in the known universe can be classified as either matter or energy. Matter describes the physical things around us: the earth, the air, your pencil, etc. Energy is the ability to cause change or do work: including light, heat, electrical energy and mechanical energy, such as movement. Energy is conserved, which means there is a constant amount of energy in the universe Energy is transformed from one type to another
Matter & Its Properties The definition of matter has two parts All matter has volume, which is the 3-D spacean object occupies All matter has mass, which is a measure of the amount of matter in an object. To explain what matter is, involves finding properties that all matter has in common. All forms of matter (no matter what it looks like) can be classified into one of two categories
Classification of Matter Pure substances Are uniform in composition Are composed of only one component Like pure water (every piece is uniform) No impurities Mixtures Are composed of more than one component blended together Are not composed of only one component Like Koolaid (composed of water & flavor)
Classification of Matter: Pure Substances A pure substance has a fixed composition Every sample has exactly the same characteristics and composition If they can be separated they can only be separated by chemical means (elements can not be broken down further) Pure substances are either pure elements or pure compounds An element is a pure substance made up of only one type of atom
Classification of Matter: Pure Substances A compound is a chemically combined collection of elements To be a pure substance each molecule of the compound must be alike At it’s most basic unit, all matter is com-posed of tiny building blocks called atoms Atoms combine to make up molecules, atoms and/or molecules can combine to make up mixtures
Carbon atoms Hydrogen atoms Oxygen atoms Classification of Matter: Pure Substances element element element element element element element element compound compound compound compound compound compound compound compound Both elements & compounds are made of atoms in these models of diamond & Vit-C.
Pure Substances: Elements Elements are the tiny pieces that knit together to make up everything in the known universe There are 100+ different kinds of elements 92 of the elements are naturally occurring Every element has a unique name the origin of which might be greek, latin, in honor of a scientist, for the place where it was discovered, or gods of mythology Each element has unique properties that cause them to behave predictably
Polyatomic Elements P4 Sulfur S6 Phosphorus
Pure Substances: Elements They are collectively organized in a huge chart called the periodic table (PT)
Pure Substances: Elements Each square on most Periodic Tables gives information about the element that the square represents. 7 • Atomic Number N • Atomic Symbol • Atomic Name • Atomic Weight NITROGEN 14.007
Pure Substances: Elements Atomic Number This number is the order that the atom is on the Periodic Table Atomic Symbol This is the abbreviation of the element Composed of a capital letter, or a capital letter and 1 or 2 lower case letter(s) This symbol is used when writing chemical formulas
Pure Substances: Elements Atomic Name This is the name of the element, which may be named from mythology, latin, scientist of discovery, country of discovery, etc. It is extremely important to memorize the most common elements and symbols Atomic Weight This is a measure of the mass of the average atom of that element
Your Turn… Use the clue provided to identify the element Boron • Atomic number: 5 Gallium • Symbol: Ga Carbon • Atomic weight: 12.011 Lead • Symbol: Pb Astatine • Atomic weight: 210 Polonium • Atomic number: 84
Pure Substances: Elements The PT is organized into vertical columns called groups or families. There are 18 columns Each family contains elements with similar chemical characteristics for instance elements in group 2 are reac-tive metals with similar abilities to bond to other kinds of atoms Or group 18 which are all gases that are extremely resistant to chemical change
Pure Substances: Elements The horizontal rows of elements in the PT are called periods. Physical and chem characteristics change predictably across the period Elements close to each other tend to have similar characteristics, while elements farther apart become increasingly different For example the elements on the far left of the PT tend to be soft, shiny solids that are good conductors The far right are gases
Pure Substances: Elements The two sets of elements below the PT make up what are called the lanthanide and actinide series. They are metallic and radioactive and should be placed after elements 57 & 89
Pure Substances: Elements There is another major division of the elements, metals, nonmetals & metalloids.
Metals • Nonmetals • Metalloids
Pure Substances: Elements A metal is a shiny element that is a good conductor of heat and electricity At room temp, most metals are solids. Mercury is an exception, it’s standard state is liquid (standard state is the state of matter at 25 C and 1 atm) Most metals are also malleable That is they can be hammered or rolled into thin sheets
Pure Substances: Elements Metals tend to be ductile. Which means they can be drawn into a fine wire Metals behave this way because of their high tensile strength Tensile strength deals with its resistance to breaking. The metal atoms just realign themselves as the metal is being stretched or hammered.
Pure Substances: Elements Nonmetals are elements that are poor conductors of heat and electricity Many nonmetals are gases at room temperature (H, O, N, F, Cl) One nonmetal is a liquid (Br) The rest tend to be brittle solids (C, S, P, Se, I).
Pure Substances: Elements Metalloids are elements that have some of the characteristics of metals and some of nonmetals on the stair step pattern that separates the metals from the nonmetals All metalloids are solids at room temp Tend to be less malleable than metals, but not as brittle as nonmetals Metalloids tend to be semiconductive
Pure Substances: Elements The elements in the far right column are the noble gases They are unique in that they are generally unreactive All are gases at room temp Ne, Ar, Kr, and Xe are all used in lighting Helium is used in party balloons and weather balloons
Pure substances: Compounds A compound is a substance that contains 2 or more elements The composition of a pure compound does not vary, regardless of the method of preparation The term molecule is often used for the smallest unit of a compound that retains all of the properties of the compound Examples: Table salt (sodium chloride, NaCl), sugar (sucrose, C12H22O11), and water (H2O)
Pure substances: Compounds Compounds have characteristics very different than the elements that form them Produced as the result of chemical reactions Compounds can be separated into 2 cate-gories according to how they were formed Ionic compounds – brittle crystalline solids that have very high melting point (table salt, epsom salts, chalk, etc) Covalent compounds – solids, liquids, and gases that exist because of molecular interaction (water, sugar, etc.)
Metals • Nonmetals • Metalloids • Ionic • Covalent
Classification of Matter: Mixtures Matter that isn’t pure must be a mixture of pure substances The components in a mixture are simply blended together physically, which means they can be separated physically When pure substances are blended together the collection of components have different properties when they are together than when they are separate Melting point, boiling point, strength, resistance to chemical change, etc.
Classification of Matter: Mixtures The components in a mixture are chemically different & continue to retain their individuality For example, a mixture like Total cereal, contains iron filings (nutritional supplement) yet they are still magnetic A mixture of salt water contains dissolved salt particles that are still salty There are 2 types of mixtures Heterogeneous Homogeneous
Your Turn… Classify each of the following as a mixture or a pure substance Pure substance • Water Mixture • Blood Pure substance • Table salt Pure substance • Iron Mixture • Brass Pure substance • Uranium Mixture • Wine Mixture • Leather
Mixtures: Homogeneous Mixtures Homogeneous mixtures are uniform in composition They have the same proportion of components throughout This type of mixture is only composed of a single phase Liquid, solid, gaseous, etc. AKA solutions For example salt water, KoolAid, air, ink, etc.
Mixtures: Heterogeneous Mixtures Heterogeneous mixtures are not uniform Often have more than one phase e.g. banana pudding, granite, blood A heterogeneous mixture of large (visible) solid particles in a liquid is called a suspension e.g. jar of muddy water A mixture of smaller particles that don’t settle out, but are still visible is called a colloid e.g. Milk, paint, smoke, cheese
