Properties of Matter 1 Flashcards
Learn about elements, compounds, atoms, molecules and mixtures and to explore homogenous and heterogenous mixtures
What is an atom?
An atom can be described as the basis of the creation of everything. In other words, everything is made up of atoms. Atoms are tiny particles that are too small to see, even with a microscope.
What is an element?
An element is made up of the exact same atoms.
In other words, the atoms in a particular element are the same as each other, however they are different from the atoms of all other elements
For example, Helium is an element because it is only made up of helium atoms.
Note: In some elements, the atoms do not join together but stay as separate atoms. The noble gases are like this and they are called monoatomic molecules
What is a compound?
A compound is a substance that contains two or more different elements and these are chemically joined together.
Note: compounds always have the elements present in the same ratio by mass
What is a molecule?
Molecules are usually small groups or clusters of atoms chemically bonded together. They can have as few as two atoms(e.g. hydrogen and oxygen) or can have millions of atoms (e.g. a molecule of DNA)
Note: Molecules containing only one type of atom are elements
What is a mixture
A mixture is a physical combination of two or more different compounds. There can be homogenous or heterogenous mixtures.
What is a heterogenous mixture?
A heterogenous mixture has compounds in which proportions vary throughout the sample
In other words a heterogenous mixture is not consistent throughout the whole mixture.
What is a homogeneous mixture?
A homogenous mixture is a solid or liquid or gaseous mixture that has the same proportions of its components throughout.
In other words the components of a homogenous mixture is consistent throughout the whole mixture.
A mixture can be separated by physical means, e.g. sieving, filtration, distillation etc.
What is an impure substance?
An impure substance is something which is contaminated with other small amounts of one or more other substances.
A mixture is considered an impure substance.
What is a pure substance?
Pure substances cannot be decomposed by physical means. They also have a constant chemical composition
Thus, an element is a pure substance because it can’t be decomposed into anything simpler. For example Ca, Al, Zn, Fe.
Compounds are pure substances because they can be broken down by chemical means
What is a gravimetric analysis?
A gravimetric analysis is a quantitative technique used to calculate the mass of components in a mixture or compound
What are ionic compounds?
Ionic compounds are formed between metals and nonmetals
When naming ionic compounds, does the metal or non metal go first?
The metal is named first and then the non-metal ion has -ide at the end
How is the valency of transition metals shown?
Roman numerals in brackets afteer the metal
What are covalent compounds?
Covalent compounds are formed between two nonmetals
When naming ionic compounds, does the metal or non metal go first?
Use the normal elemental name for the first element and -ide for the second
What is an isotope?
An isotope is an element with the same number of protons but a different nucleon/ mass number
What is a nucleon number?
A nucleon number includes the number of neutrons and protons in the nucleus of an atom (equal to mass number)
What is an allotrope?
It is the different physical forms of the same element but still being in the same state (e.g. diamond and graphene)
What are radioisotopes?
These are isotopes which are radioactive
What atomic numbers are guaranteed to be radioactive?
Any atomic number which is over 83
What are transuranic elements?
These refer to elements which are man made
What does radioactivity mean?
The spontaneous emission of an unstable nucleus through the emission of particles, electromagnetic radiation or both
What does the atomic number tell us?
Tells us the number of protons and electrons
What does the mass number tell us?
Tells us the number of protons + neutrons
What is the difference between mass number and atomic mass?
They are basically the same except that atomic mass is expressed in amu
What is Atomic weight
The weighted average of all the isotopes
What is relative molecular mass?
The sum of all the relative atomic masses that make up the molecule
What did Niels Bohr suggest about the atom?
He proposed that the electrons orbit around the nucleus in fixed circular ‘energy shells’
Electrons can ‘jump’ to higher energy shells by absorbing wavelengths of light, thus when they fall back they emit a quantized packet of light
What did Schrodinger suggest about the atom?
Schrodinger based his model on Bohr model, but modelled electrons as waves instead. From there, Schrodinger was able to predict where an electron would be, and he named this area an orbital (which had a 90% chance of being right)
What is an orbital?
An orbital is a region of space where a maximum of two electrons can occupy at the same time
What is a subshell?
The combination of one or more orbitals that make up an electron shell of an atom
What is a shell
The shells are discrete energy levels of an atom, the larger the shell, the larger the subshells of it
What is part of the SPDF notation (groups and how many electrons it holds)?
S subshell - Holds 2 electrons (groups 1-2)
P subshell - Holds 6 electrons (groups 3-8)
D subshell - Holds 10 electrons (transition metals)
F subshell - Holds 14 electrons (Lanthanides and Actinides)
What are the exceptions to the SPDF notation, and why?
Copper and Chromium. This is because the 4s and 3d subshells have basically the same energy levels, and by Hund’s rule, it would be better to not have repulsive forces between electrons and instead just have each electron occupy one orbital
What are the copper and Chromium SPDF notations?
Copper: [Ar] 3d10 4s1
Chromium: [Ar] 3d5 4s1
What does the Aufbau Principle state?
It states that electrons with lower energies always fill first
What does the Pauli Exclusion Principle state?
It states that there is a maximum of 2 electrons per orbital
What does Hund’s Rule state?
It states that each electron in an orbital in a subshell must be filled with one electron before they double up. This is because there is a repulsive force between them so they don’t like being together
How do you calculate the relative atomic mass of each isotope?
Multiply the atomic mass by its abundance and then add it with other common isotopes
Atomic mass = (atomic mass * % abundance) + (atomic mass * % abundance)
What is the spectral evidence for the Bohr Model?
As the electrons become ‘excited’ through heating the electrons, they move to higher energy levels, and after they lose energy and they fall to lower energy levels, their excess energy is released as light which comes in the form of visible, ultraviolet or infrared
Because of this, it can be assumed that different metal atoms release different amounts of energy and thus different colours
What is the atomic spectra?
It refers to the spectrum of light absorbed or emitted by specific chemical elements
What is line spectra?
Refers to the spectrum which contains a number of ‘bands’ that are caused by light being emitted or absorbed
What is alpha decay?
Alpha decay is caused when there are too many protons relative to neutrons (so the nucleus is unstable)
This results in the emission of a helium nucleus, also known as an alpha particle (2 neutrons, 2 protons). Thus, the atomic mass goes down by 4, and the atomic number goes down by 2
What is beta decay?
Beta decay is caused when there are too many neutrons relative to protons, so the neutron turns into a proton and an electron. This electron is expelled from the nucleus
This results in the emission of an electron, also known as a beta particle. Thus the atomic mass stays the same, and the atomic number goes up by 1
What is gamma decay?
A gamma wave does not have any protons or any mass. It is basically just added at the end of a nuclear equation as the result of too much excess energy. Gamma rays are emitted in the form of electromagnetic radiation
What is positron emission?
This occurs when there are too many protons, and this means the protons turn into a neutron and a positron (positron is an electron but with the opposite charge). This positron is emitted from the nucleus
What is electron capture?
Electron capture turns one of the inner orbital electrons and protons into a neutron. This occurs if there are too many protons in the nucleus
Which magnetic plate do alpha particles go towards?
Towards negative electric field
Which magnetic plate do beta particles go towards?
Towards the positive electric field
What is the penetrating power of an alpha particle?
Very weak, it can only go through a piece of paper
What is the penetrating power of a beta particle
Moderate, it can go through paper but stops after aluminium
What is the penetrating power of a gamma particle?
Very high, it can go through lead and the ionising power will decrease by about 50% but won’t completely stop
What are the properties of a solid?
Is rigid and has a fixed shape and volume. Their particles can’t move freely
What are the properties of a liquid?
Takes the shape of the container and has a fixed volume. Their particles can move relatively freely
What are the properties of a gas?
Takes the shape and volume of the container. Their particles are spaced out and have weak attractive forces
Sublimation
Deposition
Vaporisation
Condensation
Freezing
Melting
Solid to gas
Gas to solid
liquid to gas
gas to liquid
liquid to solid
solid to liquid
What is a physical property?
It is a characteristic of matter that can be observed or measured without changing the chemical composition
What are some examples of physical properties?
Includes density, solubility, particle size, appearance
What is a chemical property?
It is a characteristic of matter that will determine how it will react with other substances
What are some examples of chemical properties? (4)
Includes flammability, reactivity, solubility, heat of combustion
What is a chemical change?
When a substance changes it’s chemical composition
What are some features of chemical change? (5)
The original matter cannot be easily recovered
Change of colour
Change of smell
Formation of precipitate
Formation of a gas
Breaking and forming of bonds
What is the ratio required for a stable light element (what elements are considered light)
1:1 (neutron to proton)
everything up to 20 is considered light
What is the ratio for a stable heavy element
1.5 : 1 (neutron to proton)
What is the standard nuclear notation of an element?
Mass number on top left, Atomic number on bottom left and then the element to the right of them and big.
