Science 10UNIT 1: ENERGY AND MATTER IN CHEMICAL CHANGE

Chapter 1: Atoms, Elements, and Compounds1.1 INVESTIGATING AND WORKING WITH CHEMICALS

Modern Chemistry has a recent history dating back to the late 1700s. However, chemical properties and uses have been known to different civilizations for thousands of years:

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North American Aboriginal Peoples

Tanning leathers Herbal medicines

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Ancient Egypt

Embalming and mummification

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Ancient Rome, Greece, PersiaMetal working for armourDyes for art and paint

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Material Data Safety Sheets (MSDS)

Even natural chemicals must be handled properly to ensure safety. Each chemical today has a Material Safety Data Sheet (MSDS) to inform you of its physical properties (melting point, boiling point, odour) and hazards and instructions for handling and storing it safely.

Workplace Hazardous Materials Information System (WHMIS)WHMIS identifies eight classes of hazards:

Hazardous Materials are covered by the Workplace Hazardous Materials Information System (WHMIS) which informs workers about the chemicals they work with in three ways:

1. Controlled products must have informative labels in both English and French on their containers

2. Each controlled product must have an MSDS

3. Workers must complete an education program that the employer provides

Classifying Matter

Matter- Anything with mass and volume- May be solid, liquid or gas

Mixture- Combinations of

matter that can be separated by physical means

- Do not have definite composition

Pure Substance- Matter that has a definite composition

Heterogeneous Mixture (Mechanical Mixture)- Different components of the mixture

are visible- Composition is variable throughout

the mixture

Homogeneous Mixture (Solution)- Different

components are not visible

- Composition is constant throughout the mixture

Element- Cannot be chemically broken down into simpler substances

Compound- Two or more

elements that are chemically combined

- Can be separated chemically into simpler substances

Practice Problems pg. 10 #1-4

Chapter 1: Atoms, Elements, and Compounds1.2 DEVELOPING ATOMIC THEORIES

From Ancient Greece to today…

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Assignment Create a chart that follows the development of the Atomic Model

throughout history. You can use the chart below to get started:Model of the Atom

Why Model was Proposed

Key Points of the Model

Why Model was rejected or modified

DemocritusJohn Dalton’s Billiard BallJ.J. Thomson’s Raisin Bun or Plum-PuddingErnest Rutherford’s ModelNiels Bohr’s Model

John Dalton’s AtomThe Billiard Ball Model1. All matter is made up of small

particles called atoms2. Atoms cannot be created, destroyed,

or divided into smaller particles3. All atoms of the same element are

identical in mass and size but different in mass and size to atoms of other elements

4. Compounds are formed when atoms of different elements combine in fixed or definite proportions

5. Chemical reactions change the way atoms are grouped but the atoms do not change

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The Cathode Ray Tube (CRT)

A gas discharge tube contains gas at a low pressure.

When electricity is run through it, a ray is formed and light is produced across the tube.

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J.J. Thomson (1856-1950)

J.J. Thomson determined that the ‘ray’ in the Cathode Ray Tube was made up of a stream of negatively charged particles

He added charged plates to bend the cathode rays.

Based on the radius of the path, he determined that the mass of the particle was much less than that of an atom and that the negatively charged particle was a unique particle – the electron.

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The Raisin-Bun or Plum-Pudding Model

Since these negatively charged electrons appeared to be present in all samples of matter, Thomson proposed that every atom contained electrons.

Since most matter was neutrally charged, there must also be a positively charged part of the atom.

Thomson thus proposed a positively charged sphere with many negatively charged electrons present on the surface of the sphere.

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Ernest Rutherford (1871-1937)

Rutherford conducted his gold foil experiment to further examine the structure of atoms

He directed strongly positive alpha particles towards a thin layer of gold foil.

Most of the particles passed straight through, however some were deflected and even bounced back.

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Protons and a Nucleus

Since most of the particles passed straight through, Rutherford concluded most of the atom is empty space

Since some of the particles reflected and deflected there must be a dense, massive nucleus to each atom. He determined that this was positively charged, made up of protons

The negatively charged electrons must orbit around the positively charged nucleus much like planets orbit the sun.

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The Discovery of the Neutron The Hydrogen atom is made up

of 1 proton and 1 electron Rutherford hypothesized that the

next biggest atom, helium, would be 2 protons and 2 electrons. Therefore it should have a mass that is twice that of hydrogen.

Helium is 4 times more massive than hydrogen.

The neutron was discovered as a neutrally charged particle in the nucleus that has the same mass as a proton

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Niels Bohr (1885-1962) According to physical theory, the

electrons orbiting the nucleus, should be losing energy in the form of light or radio waves. Losing energy would mean that the electron would come out of orbit and crash into the nucleus. This does not happen.

When electrical energy is applied to gases, they do emit light – a specific colour of light for each gas. Each colour corresponds to a specific wavelength of light or a specific energy. Rutherford’s model did not explain this, but Bohr’s did.

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Energy Levels

Electrons in an atom have certain allowed energies that enable the atom to remain stable – energy levels.

Electrons can only move from one of these allowed energy levels to another – they cannot exist between them.

In order to jump from one level to the next they will absorb a specific amount of energy (jumping up a level), or emit a specific amount of energy (falling back down a level)library.thinkquest.org 

Our Working Model of the Atom…

Nucleons (protons and neutrons) make up the nucleus of an atom and electrons fill the space around the nucleus.

Subatomic Particle

Relative Charge

Symbol Mass (in g) Radius (in m)

proton 1 + p+ 1.67 x 10-24 10-15

neutron 0 n0 1.67 x 10-24 10-15

electron 1 - e- 9.02 x 10-28 Smaller than 10-18

Nuclear Notation

Isotopes – atoms made up of the same number of protons, but different number of neutrons

The atomic number is the number of protons and identifies the atom

The mass number is the total number of protons and neutrons

An atom has a neutral charge so there are equal numbers of protons and electrons in every atom

Ex.

11H - mass number is top, atomic

number is bottom

There is one proton, zero neutrons, and one electron.The name is hydrogen - 1

Homework: pg. 23 #5-8, pg.24 #2, 4

Chapter 2: Names, Formulas, and Properties2.1 CHEMICAL NAMES AND FORMULAS

International Union of Pure and Applied Chemistry (IUPAC)

Founded in 1919, IUPAC developed a systematic method to name chemicals according to their composition.

The systematic name allows us to determine the chemical formula and predict some of its properties.

Binary Compounds

Compounds that are made up of two elements are called binary compounds.

The names of binary compounds almost always end with the suffix “-ide”.

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Binary Molecular Compounds

A binary molecular compound forms when two non-metallic elements come together and form a covalent bond (sharing electrons).

Example – dihydrogen monoxide – fatal if inhaled

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Rules for Naming Binary Molecular Compounds

1. The first element in the name and formula is usually the one that is furthest to the left on the periodic table.

2. The suffix “-ide” is attached to the name of the second element.

3. Prefixes are used to indicate how many atoms of each type are present in one molecule of the compound.

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Examples:

NO N2O NO2

N2O3

N2O4

N2O5

Practice Problems pg. 44 #1-4

Names and Formulas for Binary Ionic Compounds

A binary ionic compound is composed of ions of one metal element and ions of one non-metal element joined by ionic bonds.

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Rules for writing names and formulas:

Ex. An ionic compound is made between calcium and fluorine.

The name is calcium fluoride The formula is CaF2

1. The first element in the name and formula is the metal.

2. The second element is the non-metal. The suffix “-ide” is attached to the name.

3. The chemical formula shows the simplest whole number ratio of each type of ion in the compound.

*The names of ionic compounds DO NOT contain prefixes*

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Example: Predict the formula of Lithium Oxide

Solution:1. Identify the type of compound – metal & non-metal therefore

ionic2. Determine the charges on the ions – Li1+ and O2-

3. The compound must be electrically neutral. Therefore it will take two lithium ions to balance with one oxide ion.

4. The formula is Li2O

Practice Problems: pg. 45 #5-8

Cation Charges

Many of the transition metals (elements in groups 3-12) are able to form more than one type of cation.

Ex. Nickel can form Ni2+ or Ni3+

Ex. Copper can form Cu+ and Cu2+

If you are given the formula of an ionic compound you can determine the charge on the cation.

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Example: Which copper cation, Cu+ or Cu2+, is in CuCl2

Solution:1. Begin by writing out the two ions involved. Chloride is always a

Cl1- and the copper could be either Cu+ or Cu2+

2. The compound must be electrically neutral. If there are two Cl1- ions then the single copper must be a 2+ charge.

3. Therefore the cation is Cu2+

Practice Problems: pg. 46 #9, 10

Naming Cations Using the Stock System

When writing the name of an ionic compound that consists of a transition element that could be different charges, the charge on the cation is written in parentheses, as a Roman numeral after the name of the metal.

Example: Cu2+ is copper (II)

Example: Write the chemical formula for copper(II) oxide

Solution:1. The copper cation is named copper(II) and therefore is Cu2+

2. The oxide anion is always O2-

3. The compound must be electrically neutral so the charges must cancel.

4. Therefore, one copper(II) ion will combine with one oxide ion.5. The formula is CuO

Practice Problems: pg. 47 #11-12

Homework: Investigation 2-A

Compounds Containing Polyatomic Ions

Many ionic compounds are not binary because they are made up of one or both ions containing more than one type of atoms – polyatomic ions.

Polyatomic ions are made of covalent bonds that as a group have a collective positive or negative charge.

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Example: What is the formula of ammonium sulfide?

Example: What is the name of CuCO3

Practice Problems: pg. 52 #13-16

Families of Polyatomic Anions

Ex. Nitrate, nitrite or sulfate, sulfite

Patterns exist:1. In each family, the anion ending

with “-ate” serves as a reference point. The other anions are named according to the number of oxygen atoms in their formula, in relation to the reference anion.

2. Compared with an “__-ate” anion, an “___-ite” anion has one less oxygen in its formula

4. Compared with an “____-ate” anion, a “hypo___ite” has two less oxygen atoms in its formulas5. Compared with an “____-ate” anion, a “per_____ate” has one more oxygen atom in its formula.

Practice Problems: pg. 53 #17-19

Hydrogen Compounds

Hydrogen is a non-metal even though it appears on the left side of the periodic table.

Therefore, these hydrogen compounds are molecular but they do not use prefixes

Common examples are on Table 2.5 on pg. 54 in textbook.

Homework: pg. 55 #1-6

Chapter 2: Names, Formulas, and Properties2.2 EXPLAINING PROPERTIES OF SUBSTANCES

Bonding and Properties

One of the ways Chemists determine features about the structure and bonding of different substances is to observe physical and chemical properties such as: Melting point Boiling point Electrical conductivity when

dissolved in water Chemicals have different

properties in different states so we use subscripts to show the state of a substance – (s) , (l) , (g) , (aq)

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Properties of Ionic Compounds1. In solid state, ionic compounds

have regular crystalline shapes with flat sides.

2. Ionic compounds tend to have high melting points suggesting the bonds between cations and anions is very strong.

3. In the solid state, ionic compounds do not conduct electricity suggesting ions are not free to move.

4. When melted or dissolved in water, ionic compounds are electrolytes – they conduct electricity.

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Properties of Molecular Compounds

1. Most molecular compounds have relatively low melting points suggesting that the attractive forces between molecules must be weak.

2. Once melted, molecular compounds can be heated further without decomposing suggesting the covalent bonds within molecules are strong.

3. Molecular substances are non-electrolytes or they do not conduct electricity in any pure state.

4. Some molecular compounds do conduct electricity when dissolved in water

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Toxic Properties of Substances

Every chemical has potential risks that can be harmful.

Deciding to use chemicals always involves balancing risks and benefits based on what you know about their properties.

Table 2.8 on pg. 60

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Check Your Understanding:

Pg. 62 #1-5

Chapter Two Project

Investigation 2-C Reducing the Risk

Pg. 61

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