Science 9

Unit 1

Atoms, Elements and Compounds

WHMIS

What does WHMIS stand for? Workplace Hazardous Materials

Information SystemWhy do we need WHMIS? WHMIS is a system of symbols that allows

us to see clearly and quickly the potential dangers (hazards) that a chemical can cause.

A chemical container may have one or several symbols on it.

WHMIS Symbols

Dangerous Product

Dangerous Container

Compressed Gas

Contents under high pressure. Cylinder may explode or burst when heated, dropped or damaged.

Flammable and Combustible Material

May catch fire when exposed to head, spark or flame. May burst into flames.

Oxidizing Material

May cause fire or explosion when in contact with wood, fuels or other combustible material.

Immediate and Serious Toxic Effects

Poisonous substance. A single exposure may be fatal or cause serious or permanent damage to health.

Other Toxic Effects

Poisonous substance. May cause irritation. Repeated exposure may cause cancer, birth defects, or other permanent damage

Biohazardous infectious material

May cause disease or serious illness. Drastic exposures may result in death.

Corrosive Materials

Can cause burns to eyes, skin or respiratory system.

Dangerously reactive material

May react violently causing explosion, fire or release of toxic gases, when exposed to light, heath, vibration or extreme temperatures.

Textbook Using your

notes and pages 10 and 11 of your textbook, answer questions

1 to 6 on page 15.

What’s the Matter? All fields of science deal with matter.

Matter is anything that has a mass and takes up space (i.e. anything that has mass and volume).

We know from last year that volume is the amount of space an object occupies (measured in millilitres or cm3), and mass is the amount of matter in a substance or object (measured in grams).

A substance that is made up of only ONE type of matter is called an element (everything on the periodic table).

Properties of Matter

There are two types of properties of matter: physical properties (e.g. What a substance looks like, feels like, if it`s flexible), and chemical properties (e.g. What you can see when a substance reacts with other substances)

Physical Properties of Matter Physical properties fall under two categories, qualitative

(things you can observe) and quantitative (things you can measure).

Qualitative Properties

Colour

Malleability – how well a substance bends or can be beaten into sheetsDuctility – how well a substance can be pulled into wiresTexture - what a substance looks and feels likeMagnetism – whether or not a substance is attracted to a magnetLustre – how well a substance reflects light

Quantitative Properties

Solubility – how well a substance dissolves in waterConductivity – how well a substance conducts electricity or heatViscosity - *remember from last year* resistance to flowDensity - *remember from last year* the ratio of mass to volumeMelting point – the temperature that a substance changes from solid to liquidBoiling point – the temperature that a substance changes from liquid to gas

Chemical Properties of Matter

Chemical properties let us know how a substance can be used. For example, gold and platinum are made to use jewellery because they don’t react easily with water or air. Trinitotoluene (TNT) is a favourite choice as an explosive because it remains relatively stable when exposed to shocks and vibrations, and does not react with water. There are 3 chemical properties:

Chemical Property Description

Reactivity How well a substance combines chemically (reacts) with other substances

Combustibility How well a substance burns – how well it reacts with air or pure oxygen

Toxicity Whether or not a substance reacts with the body to produce a harmful substance(s) – ex: lead, carbon monoxide

Textbook

Using your notes and pages 16-19 in your book, answer questions 1, 4, 5, 6, 8, 9, 10, 13 on page 23

Lab Safety

Refer to pages 10 and 11 in your textbook.

Watch the Lab Safety Video Bring your Lab Safety form home for

your parents to sign. Even if you had it signed last year, you have to get a new one for this year.

Core Lab 1-2C (p. 20) Read through the procedure on page 20 of your

textbook. Take out a piece of loose-leaf. Write the word

“Predictions” on the top of the page. Copy the table on the next slide on the page:

Aluminum Magnesium Iron Copper Zinc Lead

Lustre

Malleability

Magnetism

Conductivity

Reactivity (with acid)

Combustibility

Texture

Predictions

Using the table that you just copied, fill in predictions (what you think will happen) for each of the tests that we will perform in the lab. Write your name on the page and hand it in to Ms. Saville.

Theories versus Laws In science, we have theories and laws. There are very

important differences between the two: A law is a way to describe events, relationships or patterns that

happen over and over again. A theory is a way to explain observations that uses reliable

evidence. Scientific theories must be testable to be valid. Some theories stand up to every test and become accepted. Others are accepted, but with some exceptions. Still others are rejected because they’ve been proven wrong.

Laws do not explain, and never change. Theories can change when new facts become available (this happened this week with Einstein’s theory of Relativity).

Atomic theory has changed a lot over time as we discover more and more about the structure and function of atoms.

Atoms An atom is the smallest particle of an

element that retains the properties of that element. Atoms ARE NOT the smallest or most basic particles.

There are smaller particles called subatomic (below atom) particles called protons, neutrons and electrons. These particles all have mass (i.e. They are made of matter). Protons and electrons have a charge, neutrons do not (i.e. They are neutral).

Protons Protons are found in the nucleus of the

atom and have a positive charge (a charge of +1).

Protons are one of the larger subatomic particles, and account for about half of the mass of an atom.

Protons attract electrons because their positive charge attracts the negative charge of the electron. Atoms have an equal number of protons and electrons.

Protons cannot leave the nucleus of the atom under normal circumstances (everyday chemical reactions)

Neutrons Neutrons are also fairly large subatomic particles,

and account for almost half of the mass of the atom. The mass of a neutron is slightly higher than that of a proton.

Neutrons are also found in the nucleus of the atom, and cannot leave under normal circumstances (anything other than nuclear fission or fusion)

Neutrons have no charge (a charge of zero) Neutrons determine the isotope of an atom. Isotopes

are different forms of the same atom (i.e. They have the same number of protons and electrons, but different numbers of neutrons).

Carbon, for example, has two isotopes: carbon-12 (6 protons, 6 electrons, 6 neutrons) is the type of carbon you are most familiar with, and is found all over the world. Carbon-14 has 6 protons and electrons, but 8 neutrons. Carbon-14 is radioactive and very rare.

Electrons Electrons are the smallest subatomic particle. Their

mass hardly contributes to the overall mass of an atom (they have 1800X less mass than neutrons or protons)

Electrons have a negative charge (-1) Electrons are not found in the nucleus, but in regions

called energy levels around the nucleus (kind of like Saturn’s rings)

The energy levels take up most of the size of the atom (99.99 %). The nucleus itself is tiny (0.01%) in comparison.

Because the electrons are not bound inside the nucleus, this is the part of the atom that reacts with other atoms in chemical reactions.

How do we know all this stuff anyway? Our current understanding of the

structure of an atom was developed based on several different atomic theories. Some of these have been adapted based on new information, and others have been discarded completely. We will look at 5 of these.

The Early Greeks There were two Greeks that we remember for

attempting to explain matter, Empedocles and Democritus.

Democritus thought that any substance when cut, would eventually be cut into a piece that couldn’t be divided any more (the atomos).

Empedocles thought that all matter was made of four elements (earth, air, wind and water).

Oddly enough, Empedocles’ theory was the most respected of the time. Aristotle agreed with him, and as one of the most respected thinkers of the day, most people went along with what he thought.

John Dalton Dalton said that the particles that make up

matter are like small, hard spheres that are different for different elements.

He called the atom the smallest part of the element, and said that all matter is made of atoms. The rest of his theory stated:Atoms cannot be created, destroyed or divided

into smaller particlesAtoms of the same element are identicalCompounds are created when atoms of different

elements link together

JJ Thomson

Thomson thought that atoms were made of much smaller particles. Through his experiments, he determined that these smaller particles had a negative electric charge (electrons).

His atomic model proposed that an atom looked like a raisin bun – a positively charged ball embedded with negatively charged particles.

Ernest Rutherford Rutherford was Thomson’s student, and designed

an experiment to try to discover what was inside atoms. He sent a beam of positively charged alpha particles to a thin sheet of gold. He watched the results from a detector screen around the gold, and saw what happened to the alpha particles.

Most of the alpha particles went through the gold atoms without being affected – this confirmed that there were large spaces within atoms.

What he saw that he was very surprised by was that some of the alpha particles bounced back from the atoms. This was the first discovery of the nucleus.

He later discovered that there were two kinds of particles in the nucleus of an atom, one with a positive charge and one with a neutral charge.

Niels Bohr Bohr was a student of Rutherford and

studied the area surrounding the nucleus of an atom.

By passing an electric current through a gas he saw that he could make them glow. He said that this was because they surround the nucleus in specific energy levels.

He discovered that the electrons in each energy level have a specific amount of energy and can jump from one energy level to another.

`

Review for Quiz

Do all questions under Checking Concepts and Understanding Key Ideas on pages 34 and 35 except for:# 2, 5, 6, 16, 20 and 21.

Elements Remember from the last section, and

element is a pure substance that can’t be broken down or separated into other substances. Each element is made of one type of atom (e.g. a lump of pure gold is made of only gold atoms).

There are 115 elements (92 are found in nature). Each is represented by a chemical symbol. Chemical symbols consist of one or two letters. The first letter is ALWAYS capitalized. The second letter is not.

The Periodic Table

The Periodic Table

Divided into 4 sections – Metals (to the left of the staircase), Nonmetals (to the right of the staircase), Metalloids, and Transition Metals.

There are two liquids and 11 gases on the periodic table, all of the rest are solids.

Activity

Using the periodic table (p. 50), list the first twenty elements (Go by the

atomic number), their state at room temperature, and their chemical symbol.

Put this list in your portfolio when you are finished.

Elements You MUST Know

Atomic Number VS Atomic Mass The atomic number is the

number of protons in the nucleus of an atom.

The atomic mass is the mass of the average atom of an element (mass of protons and neutrons usually)

Questions in Textbook

Answers questions p.59 1, 2,4, 5, 6, 9, 10, 11, 12, 13, 14, 15, 25

Elements are divided into 4 groups on the periodic tableEach family on the periodic table has specific

properties: Metals are shiny, ductile, good conductors of

heat and electricity, and malleable.Transition metals have all of the same properties

as metals, however their electrons are arranged differently in the energy levels around the atom.

Non-metals are dull, poor conductors of heat and electricity, brittle, and not ductile.

Metalloids can by shiny or dull, can conduct electricity, are poor conductors of heat, and are brittle and not ductile.

Period and Family Period: the horizontal (sideways) rows

on the periodic table, numbered from 1 to 7. The higher the period # the higher the reactivity of the element in a given family.

Family: also called group. Elements in the same family have the same chemical properties. Families are in vertical columns on the periodic table

(1-18).

Chemical FamiliesThere are 4 chemical families:1. Alkali metals: column 1 besides hydrogen. All

of the alkali metals are very reactive. Elements at the top of the column are less reactive than elements at the bottom. They react strongly with water and oxygen, and

combine with nonmetals to make chemical compounds. All of the alkali metals melt below 200oC, and all are soft enough to be cut with a knife.

2. Alkaline earth metals: column 2. These are less reactive than alkali metals. They will burn in the air if they are heated (remember magnesium from the lab). They will react with water, but not as explosively as alkali metals.

Chemical Families continued3. Halogens: these are non-metals. They

react very well with metals and other compounds. They are found in column 17.

4. Noble gases: these are found in column 18. Noble gases are not reactive because they have full energy levels. Some glow in bright colours (neon).

p. 67

Answer all questions except for number 12.

When it says to do a Bohr-Rutherford diagram, draw a modified Bohr diagram.

Chemical Compounds

Chemical compounds are pure substances made of two or more kinds of elements that have chemically combined. When they combine, atoms form bonds with one another. There are two types of bonds, ionic bonds and covalent bonds.

Ionic Bonds Ionic Bonds occur when oppositely charged

ions attract together. That is, when a metal and one or more non-metals come together. This is because metal ions are always positively charged (lose electrons), and non-metal ions are always negatively charged (gain electrons).

You will be responsible for knowing the following ionic compounds:sodium chloride (table salt): NaClcalcium carbonate (chalk): CaCO3

sodium hydroxide (a strong base): NaOH

Naming Ionic Compounds When naming simple ionic compounds,

the metal name remains the same, and the non-metal name is changed to end in “ide”.

For example, sodium and chlorine combine to form sodium chloride… you drop the “ine” and replace it with “ide”.

The name of the metal ALWAYS goes first!

Covalent Bonds Covalent bonds are different from ionic bonds.

In ionic bonds, atoms gain or lose electrons. In covalent bonds, atoms share electrons to form a molecule. Molecules are made from nonmetal atoms coming together.

You will be responsible for knowing the formulas and names of the following covalent molecules:sucrose (table sugar): C12H22O11 carbon dioxide (what you breathe out): CO2 methane (what cows fart out): CH4water (what you should drink instead of

Gatorade): H2O

Naming Covalent Compounds Naming covalent compounds is more difficult than naming ionic

compounds First, name the first element in the compound. Second, if there is more than one of the 1st element, add in the

prefix for that number Third, name the second atom and switch the end out for “ide” Fourth, add a prefix to the second atom based on how many of

it there are: 1 - mono 6 - hexa

2 - di 7 - hepta3 - tri 8 - octa4 - tetra 9 - nona5 – penta 10 - deca

Then write the full name of the compound. For example, let’s look at NO3. N is nitrogen. O is oxygen, but will be changed to “oxide”. There are 3 oxygen atoms, so the entire name of the molecule will be nitrogen trioxide.

And now, a song.

p. 85

Questions 1 to 8,

EXCEPT #4

Notebook Activity Read pages 88 and 89 in your book. In your notebook:

Define physical and chemical change. Give two examples of each. Define reactants and products. Draw a table similar to the one below (about half a page in your book):

Define/describe each type of evidence in your table (you can use words or pictures or both)

In a chemical change, are elements or compounds conserved? What does this mean?

Physical Change

Chemical Change

Evidence

Chemical vs Physical Changes

Physical Change Chemical Change

Evidence Condensation Colour change

Evaporation Heat, light, or sound produced

Melting Bubbles forming (gas produced)

Freezing Precipitate forming

Dissolving Process is difficult to reverse

Cutting

Combustion

Read page 89 in your textbook. Define combustion What type of energy is released during

combustion? Give two examples of how this energy can by used directly and two examples of how it can be used indirectly (make sure to include what the energy is changed into).

Corrosion Read page 90 in your textbook. Define corrosion What is rust? What is one way to protect metals from

rust? Why can it be a good thing when aluminum

corrodes? What colour does copper turn when it

corrodes? What is the Statue of Liberty made of?

Fruit Ripening

Look at figure 3.12 on page 89. What evidence of a chemical reaction do

you know occur when food rots? What is the kind of gas released by food

rotting called? Why can one piece of fruit rotting make

all of the other fruit around it rot too?

Question page 95

Answer questions 1-8

Lab 3-3C (pages 92-93) Read through the lab procedure for Part 1 and Part 2 Copy the following prediction table onto a sheet of loose-leaf:

Test Observations Chemical/Physical Change

Li2CO3 + CaCl2

Filtering solution

Ca2+ ion flame test

Li+ ion flame test

White powder flame test

Unknown ion flame test

Lab writeup

Include your prediction table, your observation table, and your questions.

Under the “Analyze section”, add the following question:

3. In the Li2CO3 + CaCl2 test, are these reactants or products? How do you know?

Review for Unit Test

Chapter 2 worksheets & Questions pages 68-69 (end of worksheets)

Chapter 3 textbook review

(p. 96-97) Unit 1 textbook review

(p. 102-103)