Chemistry review Flashcards
Chemistry Review
What are organisms composed of?
Matter
What is matter composed of?
Elements, Compounds, and Trace elements
How many elements are there?
92 natural elements, 20 man made elements (112 total)
What contains 2 or more elements in fixed ratios?
Compounds
What is the smallest unit of life?
The atom
What are the components of an atom?
Neutrons (neutral charge, mass = 1 Dalton)
Protons (positive charge, mass = 1 Da)
Electrons (negative charge, mass = 0.0005Da)
What is the sum of the protons and neutrons in the nucleus?
The atomic mass
What indicates the number of protons in the atom?
Atomic number
What are isotopes?
Same number of protons, different number of neutrons
What releases subatomic particles and energy as the nucleus decays?
Radioactive Isotopes
What does a half life measure?
The rate at which the parent isotope decays to the daughter isotope
What are the 3 naturally occurring isotopes?
Carbon 12- stable (most common)
Carbon 13 - 7 neutrons (stable)
Carbon 14 - 8 neutrons (unstable)
What is chemical behaviour of an atom is determined by?
Electron distribution
What surrounds the nucleus?
Electron shells (orbitals)
What are the properties of an electron shell?
Differ in energy amounts
Matter wants to be at its lowest stage of potential energy (lowest orbital)
It takes energy to jump orbitals
1st shell can hold (blank) electrons
2
2nd shell can hold (blank) electrons
8
Why do atoms give/take electrons?
To fill their orbital shell, or to lose a shell to then have a full shell
What are the types of bonds?
Ionic bonds and Covalent bonds
Two or more atoms held together by covalent bonds are called?
Molecules
The number of unpaired electrons required to complete the valence shell is called?
Valence
Electronegativity
The attraction of an atom’s electrons in a covalent bond
Non-polar covalent bond
The electrons are shared equally due to the same electronegativity
Polar covalent bond
The electrons are shared unequally due to one atom being more electronegative than the other
Which element is one of the most electronegative?
Oxygen
What are hydrogen bonds?
A weak chemical interaction where hydrogen is covalently bonded to an electronegative atom due to partial charges
What are Van der Waals interactions?
Weak interactions between molecules that have varying partial charges. Atoms must be very close together
ex. geckos climbing walls
How does a molecule get its shape?
By the position of the atoms’ orbitals
What are the types of orbitals?
s orbitals
Three p orbitals
Four hybrid orbitals
How do chemical reactions change the composition of matter?
By making or breaking chemical bonds
What is chemical equilibrium?
When the forward and reverse reaction rates are the same
What is the shape of water?
a V
Water is life due to these 4 properties
- Water molecules can stay together
- Water moderates temperature
3.Solid water is less dense than liquid water - Water is the solvent of life
How are water molecules held together?
Hydrogen bonds
What is cohesion?
The linking together of water molecules via hydrogen bonding
What is adhesion?
The clinging together of one substance to another
What is suface tension?
A measure of how hard it is to break/stretch the surface of a liquid
cohesion results in surface tension
What is specific heat capacity?
The amount of heat that must be absorbed or lost to change the temperature of 1g of substance 1 degree celsius
What is a solution?
Homogenous mixtures of two or more substances
Hydrophilic vs hydrophobic
Hydrophilic = water loving (dissolves in water)
Hydrophobic = water repelling (non-polar, non-ionic substances)
What is concentration?
The number of moles of solute per litre of solution
What increases the hydrogen concentration of a solution?
An acid
What decreases the hydrogen concentration of a solution?
A base
What does the PH scale tell us?
Measures the concentration of hydrogen atoms
What does a buffer do?
Minimises changes in H+ and OH- concentrations
