Module 1 (Properties of Matter) Flashcards
Solution
Separation Methods
Utilises property of solubility.
A mixture of two solids which have significantly different solubilities can be entirely mixed into a solvent and some constituents will dissolve more readily.
The procedure must be performed with filtration, evaporation or crystallisation in order to remove the solvent afterwards.
Magnetic Separation
Separation Methods
Utilises property of magnetism.
By inserting the magnet into the mixture of different sized solids and moving it around, the particles with magnetism will attach to the magnet.
This may need to be done multiple times and/or other particles may come up with the magnetic ones, such as powder.
Crystallisation
Separation Methods
Utilises property of solubility in cold water.
A substance’s solubility in cold water can also be utilised where the entire mixture is dissolved in hot water.
The solution will then begin to cool, one substance crystallising sooner, while the other is left dissolved.
The solid components can then be separated through a method of filtration.
Filtration
Separation Methods
Utilises property of particle size.
When the mixture is passed through a screen, often filter paper, undissolved solid particles of a larger particle size are unable to pass through, collecting above the screen while the liquid filtrate passes through.
Evaporation
Separation Methods
Utilises property of boiling point.
A mixture consisting of two materials, one of which has a higher boiling point, can be put over a heat source, where one substance will evaporate more readily, leaving the other behind.
Used to collect the solid solute of a solution.
Distillation
Separation Methods
Utilises property of boiling point.
While this utilises boiling point similarly to evaporation, distillation separates the liquids with the use of a condenser to capture and cool the vapour to condense it back into a liquid distillate in another container.
Used to collect the liquid solvent of a solution.
Separation Methods
Fractional Distillation
Separation Methods
The method and setup are similar to distillation but this involves the separation of more than two liquids by utilizing their specific boiling points.
The setup includes evaporation and the use of a condenser, but the temperature of the original mixture must be monitored in order to ensure that the final distillate is composed of one substance only.
Gas Chromotography
Separation Methods
Chromatography is effective in disclosing the individual components of a gas mixture by passing the entirety of the mixture through a glass or metal column.
The components can be detected and recorded due to the particle frequency at which they travel.
Sieving
Separation Methods
Utilises the property of particle size.
A sieve, whose size of netting must be chosen in accordance with the mixture, utilises particle size to allow the smaller particles to fall through the holes while the larger particles are unable to pass through the gaps and can then be transferred into another container.
Sedimentation
Separation Methods
Utilises the property of particle density.
Solid particles will eventually settle at the bottom of the liquid it is combined with due to gravity in that the solid particles have a higher density than the liquid, allowing them to settle towards the bottom of the container as sediment.
Decantation
Separation Methods
Utilises the property of particle density.
This can be performed after sedimentation caused by particle density and is simply pouring off the liquid that is now sitting above the sediment.
Centrifugation
Separation Methods
Utilises the property of particle density.
While this utilises particle density similarly to sedimentation, it occurs more rapidly through the use of a centrifuge, which is a spinning mechanism that will cause higher density substances to gravitate towards the edges while lower density substances gravitate towards the axis due to centrifugal force.
Linear (2)
Molecular Shapes
Two atoms
Linear (3)
Molecular Shapes
Three atoms.
No lone pairs on the central atom.
Bent/Angular (with Single Bonds)
Molecular Shapes
Three atoms.
Two sets of lone pairs on the central atom.
Bent/Angular (with Single and Double Bond)
Molecular Shapes
Three atoms.
One set of lone pairs on the central atom.
Trigonal Pyramidal
Molecular Shapes
Four atoms.
One set of lone pairs on the central atom.
Trigonal Planar
Molecular Shapes
Four atoms.
No lone pairs on the central atom.
Tetrahedral
Molecular Shapes
Five atoms.
Four bonds on the central atom and no lone pairs.
Homogenous Mixture
A mixture with equal concentration of all components throughout.
Heterogenous Mixture
A mixture with a composition that is not uniform.
Mineral
Gravimetric Analysis
A naturally-occurring solid element or compound with a definite composition/range of compositions e.g. quartz (silicone + oxygen)
Rock
Gravimetric Analysis
Made up of two or more minerals.
Ore
Gravimetric Analysis
Concentrations of minerals in rocks that are economically viable for extraction.
Yield
Gravimetric Analysis
The quantity (often in %) of material recovered from an ore after it has been processed.
Uses of Gravimetric Analysis
Three main uses
- To measure the amount of mineral in an ore deposit to determine it if is worth extracting
- To measure pollutant chemical quantities in water/air
- To determine soil composition to see if it is suitable for growing crops
Physical Properties of Metals
6
Lustrous
Malleable
Ductile/Tensile
Dense
High melting/boiling point
High conductivity of heat/electricity
Physical Properties of Non-Metals
6
Dull
Not malleable
Not ductile
Not dense
Low melting/boiling point
Poor conductivity of heat/electricity
Reactivity with Water
Chemical Properties
Group 1 alkali metals react vigorously with water to form hydroxides and hydrogen gas.
Reactivity with Oxygen
Chemical Properties
Group 2 alkaline earth metals react with oxygen to form metal oxides.
Electronegativity (EN)
Chemical Properties
A numerical measure of the electron-attracting power of the atom within a covalent bond. An atom’s ability to attract electrons. Increases diagonally from bottom left to top right.
0-1.7 → covalent bond
>1.7 → ionic bond
Ionisation Energy
Chemical Properties
An atom’s ability to remove an electron from the electrostatic force of the positive nucleus.
Elements with low ionisation energy tend to lose electrons readily and form cations.
Isotopes
Same protons, different neutrons.
Stable isotopes have a balanced number of protons and neutrons.
Unstable isotopes have an imbalance in the number of protons and neutron, leading to nuclear instability and radioactive decay.
The Schrodinger Atomic Model
Electrons occupy orbitals instead of shells.
Each shell is spearated into subshells and each subshell into orbitals.
s subshell = 1 orbital
p subshell = 3 orbitals
d subshell = 5 orbitals
f subshell = 7 orbitals
Pauli Exclusion Principle
Subshell Notations
Each orbital can contain a maximum of 2 electrons. Each electron has a different spin.
Aufbau Principle
Subshell Notations
The lowest energy orbitals are always filled with electrons first.
Hund’s Rule
Subshell Notations
Every orbital in a subshell must be filled with one electron with the same spin before an orbital is filled with a second electron.
Relative Atomic Mass
The average mass of an element’s isotopes, weighted by their natural abundance.
Ar = ∑(Isotopic Mass × Abundance) / 100
Emission Spectrum
Bohr Model
An emission spectrum is produced when heated atoms give off electromagnetic radiation (light), producing a number of coloured lines on a black background. Each line corresponds to a light of different energy (red = lowest, violet = highest).
After an element has absorbed energy, it rapidly reurns to its original energy level and drops down to its original electron shell, releasingthe energy as light.
Proves that subshells have different energy levels.
Absorption Spectrum
Bohr Model
An absorption spectrum is produced when atoms absorb electromagnetic radiation, producing a number of black lines on a coloured background. Each line corresponds to a light of different energy (red = lowest, violet = highest).
When an element is heated, the electrons absorb the energy and briefly jump to the next shell.
Proves that subshells have different energy levels.
Alpha Decay
Types of Radiation
Process:
- The nucleus of an atom splits into 2 parts.
- One part (the α particle, consisting of 2 protons and 2 neutrons or a helium nucleus) goes zooming off into space.
- The nucleus left behind has its atomic number reduced by 2, and mass number reduced by 4 (by the 2 protons and 2 neutrons).
Properties:
- Very low penetration power, can be stopped by a sheet of paper, human skin, or a few centimetres of air.
- Very high ionising ability, meaning that they can remove electrons from atoms or molecules to create ions.
Beta Minus
Types of Radiation
Occurs when the nucleus has too many neutrons compared to protons.
Process:
- The nucleus breaks down, converting a neutron → proton
- During this conversion, an electron (the β particle) is ejected from the nucleus and goes zooming off into space
- The nucleus left behind has its atomic number increased by 1 (because it gained a proton) but the mass number remains the same (since the total number of protons and neutrons hasn’t changed; it lost a neutron but gained a proton)
Properties:
- Much lighter than alpha particles
- Moderate penetration power. Beta particles are stopped by a few mm of aluminium or plastic
- Moderate ionising ability
Neutron → Proton + Electron (β-) + Antineutrino.
Beta Plus/Positron Emission
Types of Radiation
Occurs when the nucleus has too many protons compared to neutrons
Process:
- Inside the nucleus, a proton → neutron
- During this conversion, a positron (the positive counterpart of an electron) and neutrino are created
- The positron (β+particle) is ejected from the nucleus and goes zooming off into space
- The nucleus left behind has its atomic number reduced by 1 (because it lost a proton), but the mass number remains the same (since the total number of protons and neutrons hasn’t changed; it lost a proton but gained a neutron)
Properties:
- Much lighter than alpha particles
- Moderate penetration power. Beta particles are stopped by a few mm of aluminium or plastic
- Moderate ionising ability
Proton → Neutron + Positron (β+) + Neutrino.
Gamma Radiation
Types of Radiation
Process:
- After a nucleus undergoes alpha or beta decay, it might be in an excited energy state
- To return to a stable state, the nucleus releases excess energy in the form of a high-energy photon, a gamma ray
- The gamma ray goes zooming off into space
- The nucleus left behind has the same atomic and mass number as before, but is now in a lower energy state
Properties:
- Very high penetration power, can pass through several cm of lead or metres of concrete
- Low ionising power per interaction
States of Matter at Room Temperature
Periodicity
Elements in the same group often share the same state of matter at room temperature (25°C).
Across periods, elements typically start as gases on the right and become solids moving left.
Electron Configuration and Atomic Radii
Periodicity
Down a group, elements have the same number of valence electrons but in higher energy levels, further from the nucleus (more shells). Atomic radium increases down a group.
Across a period, the number of electrons increases in the same energy level, leading to more protons in the nucleus and pulling the electrons closer. Atomic radium decreases across a period.
First Ionisation Energy and Electronegativity
Periodicity
First ionisation energy decreases down a group because the outer electrons are further from the nucleus and more shielded by inner electrons. Electronegativity also decreases down a group due to increasing atomic size and shielding.
Increases across periods for both ionisation energy and electronegativity as nuclear charge increases, holding electrons more tightly.
Reactivity with Water
Periodicity
Alkali metal reactivity increases down a group as the atomic radium increases, making it easier to lose the outer electron. Alkaline earth metals show the same trend but are less reactive than Group 1.
Metals are generally less reactive with water across periods as metals become less metallic and more nonmetallic.
Lewis Dot Diagrams
- Determine the central atom
- The atom further to the right on the Periodic Table is generally an outer atom.
- Hydrogens and halogens are almost always OUTER atoms.
- Arrange outer atoms around central atom
- Count up valence electrons
- Draw a bond between each outer atom and the central atom. Count the atoms you’ve used and minus them from your total valence electrons
- Use the remaining electrons to fill octets around the outer atoms
- Now that all outer atoms have octets, fix up the central atom for an octet. Outer atoms may have electron pairs etc.
Electronegativity Difference in Polar and Non-Polar Bonds
0.5-1.7 difference: covalent polar. More electronegative atom is slightly negatively charged and vice versa, as electrons are attracted to the atom with greater electronegativity.
Less than 0.5 difference: covalent non-polar.
Allotropy
The existence of two or more different physical forms of the same element within the same physical state. These different forms, called allotropes, have distinct structures and properties, even though they are composed of the same element.
Allotropes differ in their arrangements of atoms or molecules, meaning their properties vary.
Diamond
Carbon Allotropes
Structure: Each carbon atom is tetrahedrally bonded to four other carbon atoms in a 3D lattice.
Properties: Extremely hard, high melting point, transparent, and a good insulator.
Uses: Cutting tools, jewelry.
Graphite
Carbon Allotropes
Structure: Each carbon atom is bonded to three others in flat layers or sheets, with weak forces between layers.
Properties: Soft, slippery, conductive of electricity, opaque.
Uses: Lubricants, pencils, electrodes.
Graphene
Carbon Allotropes
Structure: A single layer of carbon atoms arranged in a hexagonal lattice.
Properties: Extremely strong, lightweight, excellent conductor of electricity and heat.
Uses: Electronics, nanotechnology.
Fullerenes
Carbon Allotropes
Structure: Carbon atoms arranged in a hollow sphere (buckyballs), ellipsoid, or tube (carbon nanotubes).
Properties: Varies, but can be very strong, conductive, and have unique chemical properties.
Uses: Nanotechnology, medicine, materials science.
Dioxygen (O2)
Oxygen Allotropes
Structure: Two oxygen atoms bonded together (double bond).
Properties: Colorless, odorless gas at room temperature, essential for respiration.
Uses: Breathing, combustion, industrial processes.
Ozone (O3)
Oxygen Allotropes
Structure: Three oxygen atoms bonded together in a bent structure.
Properties: Pale blue gas with a strong odor, much less stable than O₂, powerful oxidizing agent.
Uses: Disinfection, ozone layer protection, industrial applications.
Ionic Bonding Model
Large numbers of cations and anions combine to form a 3D lattice, held together strongly by the electrostatic attractive forces between the oppositely charged ions, called ionic bonding.
Electrical Conductivity
Ionic Network
In the solid form, ionic compounds do not conduct electricity because the ions in the crystal lattice are not free to move. This makes ionic compounds useful for insulators.
When solid ionic compounds melt, the ions become free to move, enabling the cations and anions to conduct electricity. When an electric current is applied to either a molten ionic compound or a solution of the compound in water, positive ions move towards the negatively charged electrode, and negative ions move towards the positively charged electron, resulting in an electric current.
Electrolyte: solution or molten substance that conducts electricity by the movement of ions
Melting/Boiling Point
Ionic Network
Ionic compounds have high melting points that indicate that the forces between the particles are strong, so a large amount of energy is needed to overcome the electrostatic attraction between the oppositely-charged ions to allow them to move freely.
Hardness/Brittleness
Ionic Network
The strong electrostatic forces of attraction between ions in an ionic compound mean that a strong force is needed to disrupt the crystal lattice.
Although crystals are hard, they will shatter under a strong force, because it causes layers of ions to move relative to one another. Ions of like charge are shifted so that they are next to each other, resulting in repulsion that causes the crystals to shatter, which is why they are brittle.
Solubility
Ionic Network
Some ionic compounds are very soluble in water but some are very insoluble.
Whether an ionic compound is soluble or insoluble depends on the relative strength of the forces of attraction between the positive and negative ions in the lattice, and the water molecules and the ions.
Covalent Network
Contains neutral non-metal or semi-metal atoms bonded by convalent bonds in 3 dimensions.
Electrical Conductivity
Covalent Network
No delocalised electrons makes majority of covalent networks insulators.
The exception is graphite, which has covalent bonds confined to 2D parallel planes, so delocalised electrons allow graphite electrical conductivity.
Melting Point
Covalent Network
Strong covalent bonds hold the atoms together in the network.
Hardness
Covalent Network
Strong covalent bonds hold the atoms together in the network.
Graphite
Covalent Network
There are weak dispersion forces between the layers. Graphite is thus hard in one direction but slippery and soft in another direction. The weak intermolecular forces between graphite’s 2D parallel planes hold the structure together, and hence graphite powder is used as a dry lubricant.
Diamond
Covalent Network
Brittle and does not conduct electricity because it has no freely moving charged particles.
Thermal conductivity is very high because atoms are held together very strongly.
No small molecules in diamond, so no weak forces between atoms = high sublimation point.
Only strong covalent bonds, no weak intermolecular forces present = hardest naturally occurring mineral known.
Silicon Dioxide (Silica)
Covalent Network
Silica also exists as a continuous 3D covalent network structure. Each silicone atom is at the centre of a tetrahedron and is covalently bonded to four oxygen atoms. Each oxygen atom is bonded to 2 silicone atoms.
Silica is hard, has a high melting point and does not dissolve in water or organic solvents due to the strong covalent bonding between the silicone and oxygen atoms.
Covalent Molecular
Contain individual molecules arranged in a pattern within the crystal lattice.
The atoms within each molecule are bonded covalently but the forces between each molecule involve weak intermolecular attractions.
Brittle and Soft
Covalent Molecular
Weak intermolecular forces between each molecule
Melting Point
Covalent Molecular
Weak intermolecular forces between each molecule break easily.
Electrical Conductivity
Covalent Molecular
Absence of mobile charge carriers means that they do not conduct in the solid or liquid state.
Metallic Bonding Model
Positive ions/cations are arranged in a closely packed 3D lattice, occupying fixed positions.
Sea of delocalised electrons from the outer shells of atoms belong to the lattice as a whole but can move freely throughout the lattice.
Cations are held in the lattice by the electrostatic attractive force between the cations and the delocalised electrons.
Does not explain the range in melting points, hardness and densities of different metals; the differences in electrical conductivities; and the magnetic nature of metals such as cobalt, iron, and nickel.
Melting/Boiling Point
Metallic Structure
Delocalised electrons make the forces between the particles in the element are very strong.
Electrical Conductivity
Metallic Structure
Metals are good conductors of electricity in both the solid and molten liquid states, because metals have freely-moving charged particles.
Malleability/Ductility
Metallic Structure
Attractive forces between particles are stronger than the repulsive forces between the particles, when layers of particles are shifted.
Heat Conductivity
Metallic Structure
Metals are good conductors of heat because energy is quickly transferred throughout the metal object.
When delocalised electrons bump into one another and into the metal ions, they transfer energy to each other. Heating a metal gives the ions and electrons more energy and causing them to vibrate faster, transmitting this energy rapidly throughout the lattice by the freely moving electrons.
Lustrous
Metallic Structure
Refers to how light interacts with the surface of a crystal, mineral, or rock.
Metals, for example, are lustrous or reflective, meaning that free electrons are present, allowing for metals to reflect light of all wavelengths and appear shiny.
Ion-Ion Interactions
Intermolecular Forces
Large ionic solids are held together by these strong intermolecular forces.
They have formal charges, and the interactions are between formally charged ions.
Ion-Dipole
Intermolecular Forces
A side of the molecule with some electron excess and deficiency.
Dipole-Dipole Forces
Intermolecular Forces
Ppolar molecules attract one another or other polar molecules.
The slightly positive end of one molecule will attract the slightly negative end of another. The presence of dipole-dipole attraction creates some ordering of molecules in the liquid and solid states.
The melting and boilign points of such molecules is higher than similar weight non-polar molecules, because of the increased attraction.
Dispersion Forces
Intermolecular Forces
Non-polar molecules must attract one another, otherwise they couldn’t be condensed to form liquids/solids.
All covalent molecular sustances attract one another by weak intermolecular forces called dispersion forces, which arise due to the the formation of temporary dipoles between atoms and molecules.
Temporary Dipoles
Intermolecular Forces
Caused by fluctuating electron distributions in atoms.
The heavier an atom/molecule, the larger the dispersion forces between neighbouring atoms.
Hydrogen Bonds
Intermolecular Forces
A strong intermolecular force that arises from a type of polar attraction, the strongest intermolecular force. [FINISH]
