Matter

Notes

Matter :

Anything that has mass and occupies space exists as a solid, liquid, or gas.

How do you change from one state to another?  The state of matter depends on temperature (heat energy)

Different terms to describe changes of state:

• Melting

• Evaporation

• Condensation

• Freezing

• Sublimation

• Deposition

To understand how substances differ, you need to observe their properties

All matter has two types of properties:

Physical properties:

• color

• shine (luster)

• melting temp, freezing temp, boiling temp

• density

• hardness

• solubility

• conductivity

• malleability

• ductility

Chemical properties

• Determines the way a material behaves in a chemical reactions

• Ex. reaction to oxygen, acids, heat, water, ability to burn.

Checkpoint 1

• When a substance undergoes a physical change, its state may be altered, but its chemical composition is the same ex. Ice cream melting!

• A chemical change is when 2 or more substances react and form 1 or more new substances ex. H₂ + O₂ forms H₂O

Categorizing Matter

Pure Substance:

Is made of only 1 kind of matter and has a unique set of properties

• A pure substance is further classified into an element or a compound

Element:

Matter that cannot be broken down into any simpler substance.

• The most purest matter because it contains only one kind of atom

• Represented by a symbol of a capital letter, or a capital letter with lower case letters.

Compounds:

A substance formed by 2 or more different elements chemically fixed in proportion.

Molecule:

Similar to a compound but elements are held together via a molecular bond

A mixture is 2 or more substances physically (not chemically) combined

4 main types of mixtures:

Mechanical Mixture (Heterogeneous mixture):

Some or all particles can be seen and be separated (Ex. Salad) 

Solutions (Homogeneous mixture):

Can not visibly separate the particles , as one is dissolved in another (Ex. coffee) 

A substance dissolved in water is called an aqueous solution

Suspension:

Mixture where tiny particles of one substance are held within another. Substances can be separated by centrifuging or filtration. (Ex. Salad dressing)

Colloid:

Cloudy mixture, where the particles are suspended and difficult to separate (Ex. milk) 

Observing Changes in Matter

Physical Change:

When a substance undergoes a physical change, its state may be altered, but its chemical composition is the same

To identify a physical change:

• You can separate the end products (reactants) to form the products again. Ex. Salt water, sand & rocks

• You are able to re-freeze or melt the product again. Ex. Ice cream, plastic mould

Chemical Change:

When 2 or more substances react and form 1 or more new substances (The new substances formed are completely different from the original reactants)

Four actions that identify a chemical change:

1. Change in color

2. Change of odour (if present)…safety!!

3. Change of composition (ex. precipitate formed, gas released)

4. Release or absorption of energy in the form of light or heat

Checkpoint 2

Evolving Theories of Matter

Humans begin manipulating matter in the stone age

8,000 B.C. Humans begin to settle in the Middle East. Metals have yet to be discovered, tools were mostly made of stone. Fire is used to cook, kilns are used to bake glass (silica) , ceramics (clay), and bricks (clay).

 6,000 BC to 1,000 BC - Chemists (more like metallurgist) begin melting metals (smelting) of high value to humans.  Gold was popular due to its properties. Tin and copper are melted together to create bronze. Early human civilizations commonly used seven metals:

1. Gold (Au) 6000 B.C.

2. Copper (Cu) 4200 B.C.

3. Silver (Ag) 4000 B.C.

4. Lead (Pb) 3500 B.C.

5. Tin (Sn) 2750 B.C.

6. Iron (Fe) 1500 B.C.

7. Mercury (Hg) 750 B.C.

2500 BC - Greek philosophers realize that rock can be broken down into small pieces and into powder. The first theory arises that matter is made up of tiny particles.

1200 BC - Hittites (An empire in the Middle East) learns how to extract iron from rocks (ores). Mixing iron with carbon creates steel - a very hard material for armour, weapons, tools. Hittites also create coinage (Iron age begins)

Metals are not the only important chemicals, chemist mix liquids too! Many cultures used juices and oils in everyday life and rituals.

400 BC - Greek philosopher Democritus stated that each type of material was made up of a different type of ‘atomos’ which means indivisible. These different particles gave each material its own unique set of properties. By mixing different atomos, you could make new materials with their own unique properties.

350 BC - A popular greek philosopher Aristotle (among others) stated that everything was made of elements such as earth, air, fire, and water. Because Aristotle was well known and well respected, his description of matter was preferred over Democritus’s description until 1600 AD, even though he was dead wrong.  

The age of Alchemy

350 BC - 1200 AD - The largest empire of the time rises and falls (Roman empire) plunging Europe into the dark ages (a lot of knowledge is lost). Meanwhile chemists of the Middle East practiced pseudo-science of mixing metals and naturally occurring chemicals ( ‘Alkimiya’- Arabic for ‘chemist’ )

1200 AD - Alchemy migrates to Europe. Alchemists try to change common metals into gold (using magic & simple experiments). Alchemists are not wholly interested in understanding the nature of matter. Overall, alchemist do not engage experiments using the scientific method (they rather find the philosopher’s stone), however they have contributed to useful lab tools from their practice. Ex. Beakers, filters, flasks, crucibles, retort.

1597 AD - the German alchemist Andreas Libau published ‘Alchemia’, a book describing the achievements of alchemists and how to prepare chemicals.

From alchemy to atoms

1400 - 1500s - Renaissance begins, scientists begin to rediscover and understand the nature of matter and change. Based their theories on observations and experimentation rather than guesses and assumptions (sounds like scientific method to me).

1600’s - Irish chemist Robert Boyle modernizes chemistry (hypothesizes and observes the nature of chemicals), this is separate from the ‘alchemy’ (mixing chemicals to find gold, magic oriented)

Boyle also experimented with gases, and came up with proof supporting 400 BC Democritus’ tiny particle theory. Boyle believed matter was composed of tiny particles with various shapes and sizes that grouped together to form other individual substances. He wanted to determine what each type of particle was.

1770’s - French scientist Antoine Lavoisier studied chemical interactions between hydrogen, oxygen, and carbon. He developed a system for naming chemicals so all scientists could use the same words and be on the same page. He was given the title of ‘Father of Modern Chemistry’. Neat fact: he had a an awesome, intelligent, and very young wife that helped him. However he had his head chopped off during the french revolution.  

1808 - John Dalton (English scientist and teacher)- suggested matter was made up of elements that are pure substances that contain no other substances. He put forward the first modern theory of atomic structure:

1. Each element is composed of a particle called an atom

2. All atoms of a specific element have identical masses

3. Different elements have different atoms of different masses

He developed the ‘Billiard Ball Model’ where atoms are solid spheres. Theory held true until the discovery of electrons in 1897.

1897 - J.J. Thompson (British physicist), discovered negatively charged sub-atomic particles electrons. He proposed the plum pudding model.

The model ascertains that atoms are like positively charged ‘goop/pudding’ and negatively charged electrons are embedded in it like little plums (yes very weird analogy)

This plum pudding theory held true until electrons were found to be outside the nucleus.

Despite his analogy J.J. Thompson was correct about electron charges balancing out proton charges, therefore atoms have zero electrical charge.

Atoms in the Modern Age

1904 - Hantara Nagaoka (Japanese physicist)- proposed an atomic model that resembled a mini solar system - planetary model. Center had a large positive charge and negative electrons circled the positive center like planets orbiting the sun.

Many did not agree with this model as they couldn’t explain it. The model existed until scientists realized a) nucleus is not massive b) electrons are not closely connected to the nucleus

1907 - Ernest Rutherford (British scientist) working in Montreal won the Nobel Prize for work in radioactivity. Supported Nagaoka’s model but modified it saying electrons float around randomly.

His model suggest that atoms were empty spaces which positive particles could pass through with a positive central core (he called it a nucleus).

Calculated the nucleus to be 1/10000 size of an atom. Like comparing a small green pea in a football field!

Rutherford’s Discovery Was a huge contribution to atomic theory

1913 - Niels Bohr (Danish Physicist) theorized that electrons move in a specific circular orbits (electron shells) and they jumped between shells by gaining or losing energy

Late 1920’s - James Chadwick (British Physicist) discovered the nucleus contains protons (+ charge) and neutrons (no charge). Protons and neutrons have same masses. Electrons are about 2000 times smaller than protons or neutrons. They weigh next to nothing!

Early 1930’s - Quantum Theory explains that electrons do not orbit, but exist in a ‘charged cloud’ surrounding the nucleus. These clouds encircle the nucleus in various shapes. Scientists realize it is close to impossible to know the exact location of each electron in an atom, therefore scientist use ‘clouds’ to roughly estimate where an electron might be.

The grade 9 version of an atom!

Atomic structure

All elements within the periodic table follow the same basic shape of an atom, they all contain protons, electrons, and neutrons. Different elements have a different number of protons, electrons, and neutrons.

Atom structure can be split into two different parts:

Nucleus - The center of the atom, it contains:

Protons:

Sub atomic particle that has a POSITIVE charge (+)

Neutrons:

Sub atomic particle that has NO charge (Ø)

Pro-tip: the mass of an atom is the number of protons added to the number of neutrons.

Orbitals/Shells - Electrons exist in orbits that circle around the nucleus. Orbitals can hold multiple electrons . How many orbitals does an electron have? Depends on the atom, this will make more sense later!

Electrons:

Sub atomic particle that has a NEGATIVE charge (-)

Valence Orbital/Shell - The furthest orbital from the nucleus (electrons in this orbit are referred to as valence electrons)

Atoms! What’s their deal?

Atoms are all about stability, they really dislike instability and will do anything to become stable.

Atoms can achieve stability by completely filling or completely emptying their valence shells. This can be achieve in two ways:

1. The atom gains electrons in its furthest orbital

2. The atom loses electrons in its furthest orbital

Back to chemistry and the Elements

Before scientist knew about atoms they unknowingly referred to different atoms as elements (Aristotle started this ‘elements’ trend). Elements were considered naturally occurring basic components of all matter.

Chemical Element:

A pure substance made up of single atoms (these atoms are identical in structure)

• Ex. A nugget of gold is essentially a collection of individual atoms hanging out together that all have the same proton number (79).

• Ex. A lump of coal (carbon) is essentially a collection of individual atoms hanging out together that have the same proton number (6).

Early chemists looked for patterns and properties of different elements

1808 - John Dalton abbreviates names of the known elements, this is the beginning of using symbols rather than names for elements.

1814 - Jöns Berzelius (Swedish chemist) uses the first letter (capitalized) of the element name as the symbol (Ex. Hydrogen = H). If there were more than two elements starting with the same alphabetical letter- use a small second letter behind the capital (Ex. Helium = He) 

1864 - John Newlands (English chemist) noticed a pattern when elements were listed by increasing atomic mass.

1869 - Dmitri Mendeleev (Russian chemist & card player) organized the known elements according to patterns in the properties of the elements.  He showed that properties of elements repeat periodically with increasing atomic masses.

He charted these known elements into a table (63 elements were known at the time). This table would be the beginning of the periodic table of elements. His table had ‘gaps’ for future elements to be discovered that had properties and atomic masses to fit those gaps.  He did this without even knowing what an atom was made of!

Dmitri Mendeleev noticed that elements in the same column acted similarly...strange?!

2020 - Since Dmitri Mendeleev introduced the periodic table of elements scientist have found all 118 elements.

The Periodic Table…Past and Present

Mendeleev’s periodic table had 63 elements.  Since then, many more elements have been discovered.  Mendeleev’s table also had holes in it…to help place a spot when new elements were discovered.  These holes were placed based upon the patterns noticed.

Today, a Periodic Table has 118 elements.  Some of these elements are very unstable and discovered using specific laboratory conditions.

Checkpoint 3

The Periodic table

All the elements of the periodic table are arranged in a logical sequence.  This sequence is the addition of one proton to each successive element. This arranges all the elements in order of increasing atomic weight.  This method also arranges the elements according to similar properties (groups).

How Today’s Periodic Table Is Organized

Periods:

• 7 horizontal rows

• Left side is more chemically reactive than the right side, which is less chemically reactive

Groups: 

• 18 vertical columns

• All elements in group columns have similar appearance & properties

Atomic Number:

Number above the symbol.  Indicates # of protons or electrons in an electrically neutral atom.  Atomic Numbers increase by one from left to right within the ‘periods’

Atomic mass:

Number below the name.  Total mass of all protons and neutrons in the nucleus. Average mass of element’s atoms

Atomic mass measured in amu’s - atomic mass units where one amu = 1/12 mass of a carbon-12 atom.  Each has a mass of 1 amu.

General Groupings within periodic Table of Elements

The general Groupings are:

Metals:  

Shiny, malleable, ductile, conduct electricity

Found on the left side over to the right past middle (Lithium 3 to Polonium 84)

Metalloids: 

Have both metallic and non-metallic properties

Found between metals and non-metals

Non-metals: 

Solid (dull & brittle) or gases, don’t conduct electricity (insulators)

Specific groupings within the periodic table of elements

Alkali metals:

Group 1 column has the most chemically reactive with air or water.  Reactivity increases as you go down the group (NOT INCLUDING H)

Alkaline-Earth metals:

Group 2 elements also react with air or water, but not as vigorously as group one

Transition Metals:

Group 3 to group 12 metals that are found in the middle of the periodic table. They all have similar properties.

Metalloids:

Group 13 to Group 17 elements that are found under the staircase! Elements found here have properties that can be like typical metals and nonmetals

Halogens:

Group 17 elements are the most reactive non-metals.  F, Cl, Br all react readily with Group 1 elements to produce useful compounds…like salt!

Noble gases:

Group 18 elements are very stable and non-reactive. These gases combine with other elements under specialized lab techniques

Calculating the Number of Protons, Electrons, & Neutrons

• Proton number is the exact same as the atomic number, and it never changes numbers!

• Electron number is the exact same as proton number (in a ‘neutral’ atom, electron number can and will change, we’ll figure that out later)

• Neutron number depends on the atomic mass!

Calculating the amount of neutrons

1. Find the atomic mass and atomic number of the element

2. Round off the atomic mass to the nearest whole number

3. Subtract the atomic number from the rounded atomic mass

Ex. Find the amount of neutrons for Beryllium (Be)

1. Atomic mass = 9.012 , Atomic number = 4

2. Atomic mass rounded (9.012 rounds to 9)

3. Atomic mass rounded (9) - atomic number (4) = 5

There are 5 neutrons per atom of Be

• P.E.N for Be is P = 4, E = 4, N = 5

Drawing  a Sodium Atom the Niels Bohr way

Recall how Niels Bohr envision his atoms:

• Electrons orbit the nucleus in different orbital ‘shells’. These electron shells along with the nucleus create the whole structure that we call an atom.

• Atoms love being stable! Atoms are striving to either empty or fill their valence shell!

How to draw a ‘neutral’ atom:

1. Determine PEN. 

2. Place P & N in nucleus. 

3. Place electrons outside nucleus (2 e-, 8 e-, 8 e-, 18 e- )

NOTE* we are drawing atoms that have a zero net charge, aka it is neutral and has no charge! (We will discuss charges in the next unit)

Isotopes

All atoms are not created equally! Some atoms can have a slightly different nucleus. The only difference is the neutron amount.

Isotopes:

These are atoms of the same element but have different numbers of neutrons in the nucleus. Their mass numbers will be different but atomic number is the same. 

For instance the carbon atom has three different isotopes.

• ¹²C also known as Carbon-12 (most popular type of carbon on Earth, 99% of the time we find carbon it is Carbon-12 )

• ¹³C also known as Carbon-13

• ¹⁴C also known as Carbon-14 (a rare type of carbon) used for carbon dating

Checkpoint 4

Periodic Table Printout here