Unit 2 Review: Chemistry - PowerPoint Presentation

Unit 2 Review: Chemistry

Matter that has Chemical and Physical Properties

Key Concepts • Particle theory of matter • States of matter • Classifying matter • Observing physical properties • Observing chemical properties • Usefulness and impact of substances’ properties

Matter has many forms Matter – anything that has mass and volume. Mass is a measure of the quantity of an object. (g, kg,) Volume is a measure of space taken up (mL, L) Matter can be found as a solid, liquid or gas. (or even a combination of these)

Changes of State There are 3 states of matter Solid Liquid gas

Terms for changes of state

The Particle Theory of Matter (4 points) Way of describing matter. All matter is composed of very tiny objects called particles. Each Pure substance has its own kind of particles, different from the particles of other pure substances .

The Particle Theory of Matter (4 points) 3. Particles present in matter are always in motion. They may be vibrating back and forth, as in a solid, or moving in all directions, as in a gas. In a liquid, particles stay close together but can slide past one another. 4. The particles in a substance attract each other. The amount of attraction is different for different kinds of particles. All particles have spaces between them.

The Particle Theory of Matter (4 points) The distances between the particles change for different states of matter.

Classification Of Matter

Pure Substances (2) A pure substance is made up of only one kind of matter unique set of properties colour, hardness, boiling point, and melting point. A pure substance is either an element (gold) or a compound (sugar).

Element A pure substance that cannot be broken down into any simpler substance by chemical means. Each element has its own name and symbol. Example: Gold (Au)

Compound A pure substance that is made from two or more elements that are combined together chemically. Example, water (H 2 O) is a compound containing the elements hydrogen and oxygen.

Mixtures (3) A mixture is a combination of pure substances. Each substance remains in its original, pure form, although each is not always easy to see distinctly once the mixture is made.

Mechanical Mixture (heterogeneous mixture) Different substances that make up the mixture are visible Hetero = different

Suspension A cloudy mixture in which tiny particles of one substance are held within another. Can be separated out when the mixture is poured through filter paper. A suspension is also a heterogeneous mixture.

Solution (homogeneous mixture) Different substances that make it up are not individually visible One substance is dissolved in another The prefix “homo-” means same, and all parts of a homogeneous mixture look the same.

Physical Properties - A physical property describes a characteristic of a substance that can be observed or measured without changing the composition of matter. Example: Melting Point, Boiling Point

Observing Physical Properties Property Description Examples What it looks like Colour and lustre The light the substance reflects gives it colour and lustre (shine) The names for some substances, such as gold, are also the names of colours. Gold has lustre; concrete is dull Conductivity Conductivity is the ability of a substance to conduct electricity or heat. A substance that conducts electricity or heat is called a conductor. A substance with little or no conductivity is an insulator. Most metals are good conductors. Copper is a very good conductor of electricity and so is used to make electric wires. Styrofoam® and glass are insulators.

Observing Physical Properties Property Description Examples What it looks like Density Density is the amount of mass in a given volume of a substance. D = m/v The density of pure water is 1 g/mL. The density of gold is 19 g/mL. Water is denser than oil, but gold is denser than water. Ductility Any solid that can be stretched into a long wire is said to be ductile. Copper is a common example of a ductile material.

Observing Physical Properties Property Description Examples What it looks like Hardness Hardness is a substance’s ability to resist being scratched. Hardness is usually measured on the Mohs hardness scale from 1 to 10. The mineral talc is the softest substance on the Mohs hardness scale (1). Emerald is quite hard (7.5). Diamond is the hardest (10). Malleability A substance that can be pounded or rolled into sheets is said to be malleable. Aluminum foil is an example of a malleable substance. Metals such as gold and tin are also malleable.

Physical Change In a physical change, the substance involved remains the same (chemically). The substance may change form or state, however. All changes of state are physical changes. Examples: Dissolving a substance in a liquid, breaking something. NOTE: Most physical changes can be reversed.

Observing Chemical Properties A chemical property describes the ability of a substance to change into a new substance or substances. In order to view a chemical property a chemical change must occur. Chemical change - the formation of a new substance or substances with new properties . A chemical reaction is a process in which a chemical change occurs.

Chemical Properties 1. Combustibility is the ability of a substance to burn. In order to burn a substance requires Oxygen

Chemical Properties Light sensitivity is a chemical property of that can cause new substances to form when light hits it.

Chemical Properties 3. Reacting with an acid is a chemical property where when acid is poured on a substance it produces a gas and bubbles.

Clues that a chemical change has occurred Clue Evidence Change in colour Final product(s) may have a different colour than the colours of the starting material(s). Formation of a solid (precipitate) Final materials may include a substance in a state that differs from the staring material(s): Precipitate

Clues that a chemical change has occurred Clue Evidence Formation of a gas Final materials may include a substance in a state that differs from the staring material(s); commonly, a gas Release / absorption of heat or light Energy (light, electricity, sound or most commonly heat) is given off or absorbed. The change is difficult to reverse The change cannot be reversed or it is difficult to.

Summary • All matter is composed of moving particles that attract one another but have spaces between them. • Matter can be solid, liquid, or gas, or a combination of states and can change from one state to another. • Elements and compounds are pure substances. Mechanical mixtures, suspensions, and solutions are combinations of pure substances.

Summary • Physical properties are characteristics of a substance that can be observed or measured without changing what the substance is. Physical properties include boiling point, colour, conductivity, viscosity, and adhesion, cohesion, and other special properties of water that are important in living systems. • Chemical properties describe how substances react with other substances or to light or heat and can be observed when chemical changes occur.

Key Terms Read each one and then try to define it, if you do not know the meaning of it look it up in your notes and write it down.

The Periodic Table Organizes Elements by Patterns in Properties and Atomic Structure

Key Concepts • Atomic theory • Atomic models • Subatomic particles • Element names and symbols • Properties of common elements • Periodic table • Properties of chemical groups

Evolving Models of the Atom Atomic theory is the study of the nature of atoms and how they combine to form all types of matter. Atomic theory helps us to understand why there are different kinds of atoms. It explains how atoms combine to form over 100 known elements and all other forms of matter, including compounds and mixtures.

John Dalton (1766–1844), a scientist and teacher in England, reconsidered the ancient idea that each different kind of element is composed of a different kind of atom . Dalton thought that the atom would be like a featureless sphere .

John Dalton (1766–1844), He used the following theory to explain the nature of matter: All matter is made of small, indivisible particles called atoms. All the atoms of an element are identical in properties such as size and mass.

John Dalton (1766–1844), Atoms of different elements have different properties. Atoms of different elements can combine in specific ways to form new substances. Atoms cannot be created, destroyed, or subdivided in a chemical change.

J. J. Thomson (1856–1940), He found that the atom is not the smallest particle. There were particles within the atom. He theorized that an atom was a positively charged sphere with negative charges embedded in it.

J. J. Thomson (1856–1940), In 1897 he proposed a revolutionary new model for atoms. It is known as the raisin bun model . The dough would be the positively charged sphere and the raisins would be the negative charges. It is also known as the plum pudding model

Ernest Rutherford (1891–1937) Rutherford had discovered the nucleus, the centre of the atom . This tiny positively charged part of the atom also contains most of the atom’s mass.

Atoms are composed of three subatomic particles Protons- Heavy positively charged found in the nucleus Neutrons - are neutral particles that have the same mass as protons and are located in the nucleus Electrons- Negatively charged particles with almost no mass. They circle the nucleus at different energy levels.

Atoms are composed of three subatomic particles Atoms are electronically neutral so the number of electrons = the number of protons

Niels Bohr (1885–1962),

Name Symbol Relative Mass Electric Charge Location Proton p 1836 1+ Nucleus Neutron n 1836 0 Nucleus Electron e 1 1- In energy levels surround nucleus

The Elements Elements are pure substances that consist of atoms. The periodic table consists of over 100 elements all of which have a certain spot on the table.

Non-Metals Found on the Right side of the periodic table Most of the remaining elements in the periodic table are non-metals (17 of them).

Non-Metals Non-metals generally have these properties: Non-conductor of electricity in its solid form At room temperature most are gasses (11) or solids (5) and only one is liquid. Solids are brittle and lack the lustre of metals

Metalloids Found in the middle-right of the periodic table Some elements do not fit as metals or non-metals. These fit on either side of the staircase that divides the metals and the non-metals. They have some properties of metals and some properties of non-metals. They are called semiconductors because they do not conduct electricity well.

Metalloids It is easier to control the flow of electricity through semiconductors than it is conductors, which explains their wide use in electronics.

Metalloids Silicon is the most common metalloid, in its pure form it is shiny, grey and very brittle. Around 40% of all rock is silicon.

The Modern Periodic Table

Atomic Number (Z) Atomic number - the number of protons in an atom of an element. Each element has a set number of protons and every atom from that element will have that many protons. The pattern for increasing protons moves from left to right and then down to the next row just like reading a book.

Atomic Mass (A) Atomic mass - the average mass of an element’s atoms. Atomic mass is given in atomic mass units ( amu ) . H has a mass of 1.01 amu . This means that iron atoms are about 55.85 times heavier than hydrogen atoms. Atomic masses are always expressed as decimal fractions. One reason that they do not have whole number values is that, except for fluorine, atoms of the same element have different numbers of neutrons.

Atomic Mass (A) Example: A hydrogen atom has one proton and one electron but no neutron. A small percentage of hydrogen atoms have 1 p, 1e, and 1n. 1 p, 1e, and 2n. Atomic mass generally increases in order of atomic number. Exception: iodine (I) has a lower atomic mass than tellurium (Te).

Ion Charge Elements with atoms that can form similar ions are grouped together in the periodic table. Metals generally lose electrons and become positive ions. Many non-metals can gain electrons and so become negative ions.

Calculations Determining the number of protons Look at the atomic number given on the periodic table ( atomic number) Example: H = 1, He = 2, Li = 3

Calculations Determining the number of neutrons Subtract the atomic number (# of protons) from the Atomic mass (# of protons and neutrons) Atomic mass – atomic number (A – Z = N) Example: Iron 55.85 – 26 = 30 neutrons

Calculations Determining the charge of Ions Subtract the number of electrons from the number of protons Protons (P) – Electrons(E) = Ion Charge Example: Iron 26 – 24 = 2+ charge = Fe 2+ 26 – 23 = 3+ charge = Fe 3+ Example: Fluorine 9 – 10 = 1 – Charge = F -

Bohr Diagrams To represent electron arrangements at various orbits we use Bohr diagrams. Each orbit has a set number of electrons. Orbit # # of Electrons 1 2 2 8 3 8 4 18

Every row in the period contains a shell. The farther you move down the table the more shells you added to the diagram. H = 1 shell, Li = 2 shells, K = 3 shells.

Moving left to right on the periodic table adds valence electrons to the shells of that row. Na has 1 valence e- , Mg has 2 valence e - , Al has 3 valence e - , etc.

Metals Tend to have 1, 2, or 3 electrons in the outer orbits (shells) They lose electrons when they combine with other elements to form positive ions ( cations ) : note the t in the word think + They lose electrons, thus they have the same electron arrangement as the Noble gas a row above them

Metal Ion Example Sodium: Na  Na + N 12 P 11 N 12 P 11

Non-Metals Non-metals – Tend to have 4, 5, 6, or 7 electrons in their outer orbits (shells). They gain electrons to form negative ions ( anions ) They gain electrons, thus they have the same electron arrangement as the Noble gas in the same row .

Example Fluorine : F  F - N 10 P 10 N 10 P 10

Summary • Every element is composed of a distinct type of atom. • The atomic model continues to be revised based on new experimental evidence. Bohr diagrams are one way to represent atomic structure. • An atom has a dense nucleus of neutrons and protons, which is surrounded by shells of electrons.

Summary • Each element has a standard name and symbol. • The periodic table organizes the metals, non-metals, and metalloids based on properties such as number of protons in an atom. • The alkali metals share similar properties, such as conductivity, which are different from the properties of the halogens and noble gases.

Key Terms Read each one and then try to define it, if you do not know the meaning of it look it up in your notes and write it down.

Elements Combine to Form Ionic Compounds and Molecular Compounds

Key Concepts • Compounds • Chemical bonds • Chemical names and formulas • Using elements and compounds

Ionic Compounds Ionic compounds are formed by combining metals with non-metals in fixed proportions. An ionic compound is formed when one or more valence electrons are transferred from a metal atom to a non-metal atom.

Ionic Compounds This leaves the metal ion as a cation and the non-metal ion as a anion . The two oppositely charged ions are attracted to each other by a force called a ionic bond . The smallest amount of substance that has the composition given by its chemical formula is the formula

Ionic Compounds Sodium chloride NaCl is a 1:1 ratio

Ionic Compounds Magnesium chloride MgCl 2 is a 1:2 ratio.

Ionic properties Ionic compounds are solids at SATP. In their solid form they form solid ionic crystals . These are more commonly known as salts

The Cross over rule Step 1. Write the symbols, with the metal first (the element with the positive charge) Mg I

The Cross over rule Step 2 Write the Ionic charge above each symbol to indicate the stable ion that each element 2+ - Mg I

The Cross over rule Step 3 Draw an arrow from the metals charge to the non-metal and an arrow from the non-metal charge to the metal. (Cross over the arrows) 2+ - Mg I

The Cross over rule Step 4 Fill in the number of atoms from each element will have by following the arrows. If need be reduce to lowest terms (in other words, if they are the same number, you don’t write those numbers down because you could divide the whole molecule by that number which would = 1) MgI 2 (if the number crossed is a 1, the 1 is not shown)

Molecular Compounds When non-metals combine, a pure substance called a molecular compound is formed. In molecular compounds, the atoms share electrons to form covalent bonds. The atoms bonded together are called molecules .

Nomenclature - a branch of taxonomy concerned with the application of scientific names to taxa, based on a particular classification scheme and in accordance with agreed international rules and conventions

Ionic Compounds: IUPAC Naming Metal non-metal - ide Consists of two types of monoatomic ions ( elements with only one possible ion charge) The metal ion is always written first and retains its whole name The non-metal is written second and has a slight change, the ending (suffix) is changed to – ide

Ionic Compounds: IUPAC Naming Do not write ones (Ex Na 1 Cl 1 ) and if both elements have the same number reduce to lowest terms (Ca 2 O 2­ = CaO)

Example: Na + Cl - use the cross over method NaCl IUPAC name: sodium chloride The metal name is written in full and the non-metal has the –ide­ suffix added to it. Sodium chloride

Binary compounds can be made up of more than two ions, provided that there are only two types of elements. Example: Al 2 O 3 STUDY TIP: All metals in group 1 and 2 follow periodic law. Check all the others metals when naming.

Example:MgS = Magnesium sulphide Magnesium Phosphide = Mg 2+ P 3- Mg 3 P 2

Molecular Compounds Ionic compounds can only bond to non metals in so many ways. Ex for every Ca we can only bond 2 F to it. Molecular compounds do not work that way. Molecular compounds can have various numbers of atoms bonded together to create various molecules. Ex. NO, NO 2 , N 2 O 2 , etc.

Molecular Compounds Due to this method of bonding there are thousands more molecular compounds than there are ionic compounds.

Molecular Compounds Most molecular compounds share the following properties: can be solids, liquids, or gases at room temperature usually good insulators but poor conductors of electricity have relatively low boiling points

Ways of Representing molecular compounds Bohr diagram ball and- stick model Volume Filled model

Summary • Compounds are pure substances composed of atoms of two or more elements that are joined by chemical bonds. • Ions with opposite charges attract each other in ionic compounds, while atoms in molecules share valence electrons.

Summary • The formulas for many common compounds can be determined from their names, and vice versa. • How we make use of electrons and compounds affects society, the economy, and the environment.

Key Terms Read each one and then try to define it, if you do not know the meaning of it look it up in your notes and write it down.

Questions Please do as many of the questions as possible.