Grade 9 Pre-IB Science - Unit 1 Chemistry
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Lesson #1
Lowkey Random
Hands may get more dry in winter because less water vapour in the air
Conversely, not that dry in summer because more water vapour in air
When spinning the bunsen burner, the flame turns from orange to blue
Means there’s more energy, because more oxygen added to the flame
States of Matter
5 States of Matter:
Solid
Ezpz
Liquid
Ezpz
Gas
Ezpz
Plasma
Aurora Borealis + some things in space (quasars, supernovas, etc.) are examples of plasma
Plasma molecules are super duper charged at the top and bottom, and they try to reach for each other (because they’re oppositely charged, and opposites attract)
The more they reach, the faster they move, so they are like very moving with a crazy amount of energy
Highest amount of energy out of the five forms, supercharged when normal particles are hit by solar flares and are EXPLODE
TLDR plasma molecules move really, really fast due to high amount of energy, and when hit by sun it explodes
Bose-Einstein Condensation
Named after two MASSIVE scientists
Taken to an extremely extreme LOW temperature, where the movement of the molecules TAPERS down and FADES
Very rare since particles should always be in motion
Basically opposite of plasma
TLDR so cold that the molecules don’t move at all 👍
Changes: Physical & Chemical
Physical Changes:
Eg. ice freezing or melting is a physical change since the molecular structure of the substance does not change; it does not become something chemically new
Some of these physical changes can be reversed (dissolving sugar in water); some cannot be reversed (cutting logs into lumber, ripping a piece of paper apart, cutting the grass)
The object remains the same chemical that it once was, but the structure of the substance has changed and cannot return to its original state/form
Changes of state (melting, evaporation, condensation, sublimation, dissolving)
Chemical Changes:
Chemical changes DO NOT include changes of the state of a substance
SIGMA SIGMA BOY SIGMA BOY SIGMA BOY Каждая девчонка хочет танцевать с тобой Sigma sigma boy sigma boy sigma boy
Chemical changes change the object with chemical reactions
Such as baking; can’t un-bake a cake, and baking is a series of chemical reactions
Eg. Something (like grass or a bone) growing back, because chemical changes happening to make those grow back
SIGNS OF CHEMICAL CHANGES:
New smell
New colour
Heat / Light is produced
Bubbles of a gas are formed
Precipitate forms (new solid is formed by two liquids)
Change is difficult to reverse
Properties: Physical & Chemical
Physical Properties:
Physical properties are characteristics or descriptions of a substance
H V A TT SS DD MMM CCC
Hardness Viscosity Adhesion Texture Taste Smell Solubility Ductility Density Malleability Melting/boiling point Magnetism Crystal form Cohesion Colour & lustre
Hardness - A substance’s ability to resist being scratched
Texture - A substance’s texture 😋
Eg. Rough, smooth
Smell
Taste
Melting point and boiling point of liquids
Malleability - Ability to flatten a solid
Eg. Aluminum foil
Ductility - A substance’s ability to be stretched into a long wire
Crystal form - solid structure with consistent pattern
Eg. Drug
Solubility - Ability of a substance to dissolve in a solvent (solute dissolves in solvent)
Eg. Salt dissolves in water
Magnetism - the ability for an element or compound to exhibit magnetic properties
Eg. Different metals
Viscosity - How easily a substance flows
The thicker the liquid, the more viscous it is
Eg. Maple syrup VS rubbing alcohol
Cohesion - how well a substance sticks to itself
Adhesion - how well a substance sticks to other substances
All liquids have some form of adhesion
Color and Lustre - the light a substance reflects gives it its color and lustre (shine)
Eg. PRETTY SHINY METALS vs Dull boring plastic…
Eg. Boring grey metals vs COLORFUL BRIGHT PLASTIC
Density - D = m / V
Overall, a physical property is a description of a substance based on your 5 senses
Chemical Properties:
A chemical property is a characteristic behaviour that occurs when the substance changes into something new
Reaction of an acid with a base
Flammability - Fireeee 🔥
Bleaching ability
Corrosion - Eroding of something
Combustion - Gasoline in car
Complete combustion
Equation: CH4 + 2O2 → CO2 + 2H2O + energy
Left part of arrow is the Reactant, Right part is Product
All reactants are used up to produce products
Eg. Flour immediately going up in flames
Incomplete combustion
Equation: CH4 + O2 → CO2 + H2O + energy + CO + other pollutants
Not all reactants mix and it produces other products harmful to the environment
Eg. Exhaust coming out of car
Names of Changes of Matter
Changes of Matter:
ENTHALPY (order by amount of energy) OF SYSTEM is solid, liquid, gas, plasma
Solid + Liquid
Solid → Liquid = Melting
Liquid → Solid = Freezing
Liquid + Gas
Liquid → Gas = Evaporation (unnatural; manual energy since environment will never naturally reach boiling point) / Vaporization (natural state change)
Gas → Liquid = Condensation
Solid + Gas
Solid → Gas = Sublimation
Gas → Solid = Deposition
Gas + Plasma
Gas → Plasma = Ionization
Plasma → Gas = Deionization
Lesson #2
Significant Digits
SIGNIFICANT DIGITS
All #s between 1-9 ARE significant
Eg. 1213.96 → 6 Sig Figs
Any zeros before a # between 1-9 are NOT significant
Eg. 0.00353 → 3 Sig Figs
Any zeros after of between 1-9 ARE significant
Eg. 120.34 → 5 Sig Figs
Eg. 0.0306 → 3 Sig Figs
100 is one Sig Fig, but 100 is 3 Sig Figs
When rounding number 5, all even numbers before stay the same, and all odd numbers before get rounded up
Eg. 4.35, only allowed 2 Sig Figs
Becomes 4.4
Eg. 100.85, only allowed 4 Sig Figs
Becomes 100.8
HOWEVVVVEEEERRRRRR if there’s ANYTHING that follows the five, the number goes UP
Eg. 100.853, only allowed 4 Sig Figs → 100.9
BUT 100.85, only allowed 4 Sig Figs → 100.8 !!!
When multiplying and dividing…
Use lowest number of sig figs in the question for final answer
Eg. 15.431 (5 sig figs) x 6.2 (2 sig figs) = 95.6722
Round to 2 sig figs, because lowest # of sig figs came from 6.2 which has 2 sig figs, therefore 96
Eg. 1.83 (3 sig figs) / 0.03 (1 sig fig) = 61
Round to 1 sig fig, which would be 60 OR 6 x 101 (scientific notation in this case has 1 sig fig)
^ That is so silly 🙁
Adding and subtracting
Use the lowest number of DECIMALS in question for final answer
Eg. 5.632 (3 decimal places) + 7.81 (2 decimal places) + 14.0 (1 decimal place) = 27.442
Round to 27.4, because lowest # is 1 decimal place
^ This is also so silly 🙁
SCIENTIFIC NOTATION
For large numbers we move the decimal to the left just behind the first significant digit
Exponent will be positive
Eg. 120000 = 1.2 x 105
For small decimal numbers we move the decimal to the right just behind the 1st significant digit
Exponent is always negative
Eg. 0.000031 = 3.1 x 10-5
Metric Conversions (Henry Died By Drinking Chocolate)
From most to least:
Giga (G) (chad)
Mega (M)
Kilo (K)
Hecto (h)
Deka (da)
Base units (g, L, etc.)
Deci (d)
Centi (c)
Milli (m)
Micro (µ)
Nano (n)
To go up, /10 per step (excluding giga → mega → kilo, excluding milli → micro → nano)
To go down, x10 per step (excluding giga → mega → kilo, excluding milli → micro → nano)
All the exclusions are either /1000 or x1000 to go up or down, respectively
Eg. 1.2 x 10-5 dag = 120 µg
Lesson #3
Calculating Density
Density = mass / Volume
Mass should be in grams (g)
Volume should be in dm3
Density should be in g/mL OR g/cm3
Alternates: m = D x V , V = m / D
Pure water has a density of 1 g/mL, and we use the value as a reference as a general density when we drop stuff in it 😋🤤🐶🍽🍔
If an object dropped in water has a density greater than 1 it sinks in the water, less than one it floats in the water
When doing calculations, make sure to watch out for significant digits!
Eg. 1. If the mass of a lead pencil is 2.3 g with a volume of 30 cm3, calculate the density.
D = 2.3 g / 30 cm3
Answer should have 1 significant figure, because 30 only has 1 sig fig
D = 0.07666… g/cm3 = 0.08 g/cm3
Would float in water, because it is less dense than water 👍
Eg. 2. The volume of a coke can is 375 mL. It has a density of 1.6 kg/L. Calculate the mass in grams.
Change 375 mL to 0.375 L (divided by 1000) to match the density
1.6 kg/L = M (kg) / 0.375 L
M (kg) = 1.6 kg/L x 0.375 L
M = 0.6 kg = 600g = 6.0 x 102 g 😀
Have to change to scientific notation, because you need 2 significant digits to match 1.6
Eg. 3. The density of a cube is 0.3 g/cm3 and measured to have a mass of 2.2 x 10-2 kg. Calculate the volume in dm3. Is the cube going to sink or float in water?
2.2 x 10-2 has 2 sig figs, 0.3 g/cm3 has 1 sig fig
Divide by 103 to get cm3 to dm3 👍
Mass is 22 g when converted from 2.2 x 10-2 kg
V = m / D
= (22 g) / (0.3 g/cm3)
= 73.333… cm3
= 0.07333… dm3
V = (round to 1 sig fig) 0.07 dm3
The cube would float in water, because the density, 0.3, is less than 1 (density of water).
Eg. 4. A block of lead has dimensions of 4.50 cm by 5.20 cm by 6.00 cm. The block weighs 1587 g. From this information, calculate the density of lead.
Since the dimensions of the block of lead have 3 sig figs each, the final answer should have 3 sig figs. You should look through the whole question for the numbers that are given to you, and then use those numbers to determine how many sig figs the final answer should have.
V = 4.5 x 5.2 x 6 = 140.4 cm3
D = m/V = 1587 g / 140.4 cm3 = 11.3 g/cm3
(As a bare minimum when your calculator gives you a big fat number you should reduce it to one significant digit above the smallest amount of significant digits found within the question)
Lesson #4
Developing the Atomic Theory
* Not required to know names and dates
— Timeline —
Approx. 450 BC
Empedocles proposed matter was composed of 4 elements
Earth, air, fire, and water
Experimentally determined that air exists because it takes up space; therefore must be a form of matter
Approx. 400 BC
Democritus suggests matter was made up of tiny particles that cannot be broken down further
Referred to the articles as atoms
Elements on the Periodic Table are the most broken down form
Approx 500-1600 AD
Alchemists attempted to turn cheap metals such as iron and lead into gold
They were unsuccessful
Through their experiments, scientists discovered many elements and compounds, as well as lab techniques and equipment
Really wanted to be rich 🤑💶
Learned how to reduce mixtures into pure substances for drug use
The creators and teachers of this method never intended to discover it in the first place! How crazy 🫨 (eg. Discovered Viagra on accident)
Approx 1650 AD
Boyle defined an element as a pure substance that cannot be broken down further into simpler substances
Also disagreed with the 4 elements model because he thought air to be more of a mixture
Late 1700s
Priestly experimentally isolated oxygen but it was Lavioster (scientist) who suggested it was an element and used it to conclude that air must be a mixture of at least 2 gases, 1 being oxygen
Priestly is the first person to actually attempt to isolate elements (Using Boyle’s idea)
Cavendish experimented by mixing a metal with acid and produced a gas lighter than air (he did not know he made H, gas)
Also found this gas would burn in oxygen to produce water
1808
Dalton’s atomic model for matter:
All matter is made of atoms, which are particles too small to see
Each element has its own atom with its own mass
Compounds are created when atoms of different elements link to form molecules
Atoms can not be created or destroyed
⭐ Everything is made of energy transforming from one form to the next
The Earth is in constant motion: Energy!
Energy always forever and ever and everrrrrr
Late 1800s
Faraday found electric currents could cause chemical changes in some compounds in solution
The atoms could gain electric charges and form charged atoms known as ions! 🤯
This led to a modification in Dalton’s theory:
Matter must contain positive and negative charges
Opposite charges attract and like charges repel
Atoms form molecules because of electrical attraction between atoms
1869
The Periodic Table
As many different elements began to be discovered, we needed a way to organize it
Mendeleev was the 1st to recognize there were similar characteristics between elements
He suggested if elements are arranged according to their atomic mass a pattern can be seen in which similar properties occur regularly
Such as solubility, density, flammability, etc.
Also properties like lustre, conductivity, malleability help group metals and non metals
Rows on the periodic table are referred to as periods
Each period represents a higher energy level
Rows represent energy → low energy on top and high energy on bottom l
Columns on the periodic table are referred to as a group
Elements in groups share physical and chemical properties
Columns represent properties → similar physical and chemical properties are listed on same column
Properties within groups:
1. Alkali metals
Li, Na, K, Rb, Cs
All these metals are:
Silvery grey in colour
Malleable, ductile, and can conduct electricity
Have a low melting point
Are soft
All react easily with air and water
Are normally found in nature as compounds
The outer orbit has 1 electron and is therefore an unstable arrangement which tends to lose the electron
2. Halogens – group 17
F, Cl, Br, I
All are non-metals and have very noticeable distinct colors
Eg. Chlorine is yellow, Bromine is orange-ish, Iodine is brown
Although Br is a liquid and iodine is a solid at room temperature
With some heat applied they are all gases
All of these are very reactive which means they are classified as compounds
The outer orbit has 7 electrons and they tend to gain electrons to obtain a more stable form/arrangement
3. Noble gases – group 18 – HAPPIEST GASES (stable as pure elements)
He, Ne, Ar, Kr, Xe, Rn
All exist as colourless glass unless an electric current is passed through
Referred to as inert gases due to unreactive state
Have a stable arrangement of electrons (full orbital’s)
Density increases as they go down
Ex. If a balloon is filled with He it floats, but a balloon filled with Xe sinks.
All the elements want to be noble gases because of how cool they are (They rarely react when interacting with other elements due to their full outer valence shell of electrons)
Very very happy to be by themselves🧍, while the other elements depend on other elements to be stable 👬
4. Metalloids
Elements that have metal and non-metal properties
Found on both sides of the zig-zag Periodic Table line
Ex. B, Si, Ge, As, Se, Sb, Te, Po, At
Can conduct electricity but not very well
5. Hydrogen 🧍(Alone gas)
It is colourless, odourless, tasteless, and a highly flammable gas
Like alkali metals it only has 1 electron in its valence shell (last orbital)
Can act like a nonmetal (i.e. gaining 1 electron to complete its valence)
Extremely reactive
6. Transition elements
Groups 3-12 (many can act as catalysts)
Less predictable properties
Multiple charges are possible
Can form colourful compounds
Can act as catalysts
7. Alkaline Earth Metals
Group 2 on the periodic table is called Alkaline Earth Metals
The middle portion of the periodic table is called the transitional metals
–timeline cont.--
1904
Thomson discovered electrons which changes Dalton’s theory again
Atoms contain negative particles called electrons
Electrons have a small mass and a negative charge
The rest of the atom is a sphere of positive charge
Electrons are embedded in the sphere which makes the atom neutral or uncharged
1911
Rutherford tested Thomson’s model in what is called “the Gold Foil Experiment”
He shot alpha particles (type of radiation) at a thin piece of gold foil
The alpha particles should have all passed through the gold foil (according to Thonson), but some bounced back
This led to changes in Dalton’s theory
An atom has a tiny, dense, positive core called the nucleus (which contains protons; positively charged)
The nucleus is surrounded mostly by empty pace containing rapidly moving negative electrons
Dalton began to wonder where the particles were specifically located around the nucleus
Keywords - ⭐ Nucleus, atom, electrons
Bohr’s Suggestion
Electrons move around the nucleus in nearly circular paths called orbits
Each electron in an orbit has a certain amount of energy
The farther the electron is from the nucleus the greater its potential energy
Electrons cannot exist between orbits but can move up or down from 1 orbit to another with enough energy
Electrons are more stable at lower energy and when they’re closer to the nucleus
The order of filling of electrons in the 1st four orbitals is 2, 8, 8, 18 (maximum values)
Basically, Bohr further developed Ruthorford’s
Electrons are more stable at more energy (weaker elements are attracted to the nucleus’ protons, which stronger elements rely on their own energy)
Electron Movement
The behaviour of atoms can be explained in terms of energy
When light passes through a prism we get a spectrum of colours that make white light (i.e. a rainbow)
Different colours have different energies
Eg. Red light has less energy than blue light
Red has lowest energy, violet has highest energy
White moves too fast for us to see the colours, so when we bend light in a prism it slows the electrons down, showing us all the colours of the rainbow
When electrons are energized by heat or electricity they use this energy to jump to higher orbits
This is known as an excited state
This jump of an electron allows us to see a colour which determines the energy level the atom is at
I.e. Aurora Borealis
However, electronics are very unstable in their excited state and tend to fall back to a more stable position in the orbit
This lower energy state is known as the ground state (not been affected by any external states)
Inside the Atom
Subatomic particles:
Protons → positively charged particles with a relative mass of 1
Located in the nucleus
Electrons → negatively charged particles outside the nucleus, orbiting around it
Found travelling in regions of space around the nucleus
Neutrons → neutrally charged particle with a relative mass of 1
Located in the nucleus
Equal numbers of positive and negative charges, making it neutral
Reduce the repelling of the protons
Photons
Electromagnetic radiation carrier
Don’t weigh anything
Energy is proportional to frequency of light
Although more than just the visible spectrum
All forms of electromagnetic radiation are possible
Quarks
Form protons and neutrons
All matter is made of this
Neutrino
Lightweight
Barely interacts with matter
Higgs-Boson “God Particle”
Potential mass provider
Graviton
Force carrier
Massless
Travels at the speed of light
Dark Matter
Fills the unknown space; makes up for unseen/unaccountable mass/observed movement
Lesson #5
Electrons around an atom are placed into seven rows depending on their energy
When energy (electrical, heat, etc) is shot at an atom, electrons that absorb the energy can jump to an excited state
Nothing can exist permanently in an excited high energy state
Electrons will enter the excited state and then shoot back to their ground state
This release of energy is coloured in our visible spectrum → we can see it (chemical sign that something has changed)
Colour can often indicate energy types and levels
I.e. bonfire v.s. Aurora borealis
Changes in the number and type of electrons around an atom differentiates elements.
The positions of electrons are different, which differs electrons from each other
Standard atomic notation
The number of protons help determine what the atom is
Ex. An atom with 13 protons is Al - aluminum
The atomic number is equal to the number of protons
The number of protons = the number of electrons for neutral atoms
Ex. Oxygen has 9 protons, therefore 9 electronics
The mass number is the sum of protons and neutrons in an atom
Number of neutrons = mass # - atomic #
The PURPOSE of a neutron is to control the force of protons and electrons → Hydrogen DOESN’T NEED neutrons, because it only has one proton only, so there is no repulsive force (between protons and electrons)
Tool:
P = 3
E = 3
N = 7 - 3 = 4
Element manipulation always happens with electronics (adding or removing electronics)
It's much more difficult to reach protons and neutrons inside the nucleus than the orbiting electrons
Ions
The number of protons does not = number of electrons
Ions are formed when negatively charged electronics move from 1 atom to another
They can conduct electricity
If an atom loses electronics its ion charge is positive (more protons)
If an atom gains electrons its ion charge is negative (more electronics)
Ionization energy
Amount of energy required to remove an electron from the gaseous states of the atom
Basically process of removing electrons
The electron that is furthest away from nucleus is always removed first (most on the outside)
The most electrons lost, the more energy required to remove them
Each electron is removed 1 at a time → when the electron is gone there are more protons than electrons
All remaining electrons have a stronger pll to the nucleus
General trends
Increases left to right across P.T.
Due to increase in nuclear charge
Increase in the amount of protons
Electron affinity
Energy change when an electron is added to an atom in a gaseous state
When the electron is added it usually causes a release of energy (exothermic) → release of energy the atom doesn’t need
As we try to add more than 1 electron is become more difficult
Additional energy is usually required, making these processes endothermic (absorption of energy)
Often thought of as the negative of the first ionization energy for an ion
F is the most electron affinitive atom on the P.T.
Smallest A.R. and strong nuclear charge
Electron affinity becomes more difficult when going right to left or top to bottom
METALS WANT TO LOSE ELECTRONS
NON-METALS WANT TO GAIN ELECTRONS
Ex. Salt water had sodium and chlorine ions init
Na has 11 protons and 11 electronics
The ion forms of Na want to give up an electron → results in 10 electrons
Cl has 17 protons and 17 electronics
The ion form of Cl wants to gain an electron → results in 18 electronics
Bohr-Rutherford Diagrams
Electricity always naturally produces a magnetic field → attracts things
If one electron travels clockwise, it produces a magnetic field
It another is going counterclockwise, it produces an opposite magnetic field
To Draw:
First, do a summary of the element
# of protons, electrons, and neutrons
Mass # (top left of element) and Atomic # (bottom left of element)
# OF ELECTRONS IS EQUAL TO PROTONS (in a natural state)
# OF NEUTRONS IS EQUAL TO MASS - ATOMIC #
Then, draw nucleus (put how many protons and neutrons there are in the nucleus)
Draw all the orbital you need to put how many electrons there are in the element
First orbital holds TWO electrons
Second and Third orbital and hold EIGHT
Fourth orbital and so on hold EIGHTEEN
Last step, add (in a different colour) / get rid of (by crossing them out) the electrons you need to make the outermost shell full
In other words, stabilize the atom
IF adding electrons, write at top right of element, #-
IF losing electrons, write at top right of element, #+
Eg. Losing 3 electrons 3+
Eg. Adding 1 electron 1-
Notes on how to draw
The shells should be dotted, and the electrons are represented by dots
The electrons are drawn in pairs (max 2 each at the North, East, South, West positions)
For ions we follow a specific pattern based on the groups/columns on the periodic table
Valence shell
The valence shell is the outermost shell of the atom
IF THE VALENCE SHELL IS FULL (8 electrons), IT IS STABLE
The point of moving electrons around is for the atom to become stable
Loses / Gains a certain amount of electrons to make the valence electron full
Loses / Gains depending on which one would move around LESS electrons
Atoms always go for the EASIEST route to become STABLE → makes them want to add or lose electrons
Isotopes
Isotopes are any 2 or more forms of an element each having the same number of protons but a different mass number because of DIFFERENT NUMBER OF NEUTRONS
Isotopes get different number of neutrons through nuclear reactions, radioactive decay, or through artificial means in laboratories
Neutrons don’t affect structure of an atom like protons do
Bohr-Rutherford diagram
Again only thing that changes is # of electrons
Too many neutrons can create a RADIOISOTOPE
Neutrons mess with the atom’s understanding of its properties
A radioisotope opens the atom and frees its energy
NUCLEAR ENERGY
Radioisotopes are atoms that have unstable nuclei due to their radioactivity; they completely break apart and the energy turns into other forms of atoms; law of energy conservation - energy cannot be destroyed
Lesson #6
Electron Configuration
The current understanding of the atom takes the Bohr Rutherford concept and shows other possible sublevels of energy that an exist
This leads to a change of shape and orientation of the electrons around the atom
The order of orbitals then becomes 2 (and the sub level of energy is called s and can hold 2 electrics), 8 (where the sub level is s and p; s can hold 2 and p can hold 6 to equal a total of 8), 8 (where the sub level is s and p; s can hold 2 and p can hold 6 to equal a total of 8), and finally 18 (where the sub levels ares, p and d; d can hold 10 electrons)
MAXIMUM ELECTRONS:
S - 2
P - 6
D - 10
F - 14
Hi :) Note: Fill in one complete ring before assuming we can move on to the next
Eg. 4s^2, 3d^8 → 3d^10
Zn 2+
Orbital Level Diagram
What the letters mean:
S
S only holds 2 electrons (↑↓)
P
Can put 3 electrons by itself (↑↓ ↑↓ ↑)
Then pair two of them up? And start with them by itself just because helps see??? I dont know
D
Can put all 5 of them by itself (↑↓ ↑ ↑ ↑) then can pair them up once
F
8 electrons in final rows? For stability?
6 C
19 K
7 N (3-)
3 Li (1+)
Br +5 1s2 2s2 2p6 3s2 3p6 4s2 3d10