Physical Science Cycle Test 16/04/24 Flashcards
To prepare for my cycle test
Chemical Bonds
These are attractive forces between the nucleus of an and its own electrons.
Covalent Bonds
The sharing of at least one pair of electrons by two non-metal atoms.
TRUE or FALSE: The sharing of the electrons with same spin then occurs when two half-filled orbitals overlap to form a new filled orbital.
FALSE. The sharing of the electrons with (opposite) spin then occurs when two half-filled orbitals overlap to form a new filled orbital.
TRUE or FALSE: Covalent bonds have the lowest melting and boiling points, as the forces of attraction between atoms are weaker if the bonds between are covalent.
TRUE. Covalent bonds DO have the lowest melting and boiling points, as the forces of attraction between atoms are weaker if the bonds between are covalent.
TRUE or FALSE: Noble gases do not bond with other elements, except with each other.
FALSE. Noble gases do not bond with other elements (and maybe not each other).
Lewis notation and structures ( or electron-dot structures)
We can use Lewis notation to represent atoms and core electrons (chemical symbol) and their valence electrons (dots and crosses).
Chemical bonds types
- Covalent bonds
- Ionic bonds
- Metallic bonds
Dipole
If one positive charges and one negative charges are separated, a small distance is formed.
Polar covalent bond
When two atoms bond together but share the electron pair unequally and a small dipole is formed.
Non-polar covalent bond
When two atoms bond together and share the electron pair equally, then no dipole will be formed. One atom will not be more negative and the other more positive.
Electronegativity
Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. Atoms with a strong attraction to the shared electrons in a bond have high electronegativity, and atoms with a weak attraction have low electronegativity.
TRUE or FALSE: Polar covalent bonds have one atom with high electronegativity and one with low electronegativity, thus the shared electron pair will be unequal. One atom will be more negative and the other more positive.
TRUE. Polar covalent bonds have one atom with high electronegativity and one with low electronegativity, thus the shared electron pair will be unequal. One atom will be more negative and the other more positive.
TRUE or FALSE: For non-polar covalent bonds, each will have the same electronegativity and therefore the difference between the each ones electronegativity is zero. The attraction to the shared paired of electrons is the same for one of the atoms.
FALSE. The attraction to the shared paired of electrons is NOT the same for one of the atoms but both of the atoms.
Ionic Bonds
This occurs between atoms where the difference in electronegativity is so large that no sharing, or very little sharing, of electrons between the atoms occurs. Instead, electrons are transferred from one atom to the other atom.
An ionic bond generally forms between a metal (or ammonium) ion and a non-metal (or polyatomic) ion.
It is a transfer of electrons and subsequent electrostatic attraction.
Properties of Ionic substances
- high melting and boiling points, which is a result of the strong attractive forces between the ions
- cannot conduct electricity in the solid phase because they do not have ions that can move, to act as carriers of electricity
Metallic bonds
A bond between a positive kernel and a sea of delocalised electrons.
TRUE or FALSE: To form a metallic bond, the atoms must have low ionisation energy. The valence electrons must be able to be loosened easily. The atoms must also have empty valence orbitals for more movement space.
TRUE.
Properties of Metallic Substances
Metals are good conductors of electricity. Metals are also malleable because the atoms can glide across each other when the piece of metal is deformed.
Atoms
Atoms are the very small particles of which all substances are made.
Elements
Elements are substances that contain only one kind of atom.
Diatomic molecules
Certain gases are made of molecules that consist of two of the same atom, because they do not exist as single atoms in their natural state.
Monoatomic elements
The noble gases of Group 18 on the periodic table exist in nature as single atoms.
Compounds
A COMPOUND is formed when two or more atoms of different elements join together through relatively strong forces or bonds. The elements that a compound consists of appear in a fixed ratio.
Types of Compounds
- Covalently-bonded compounds
- Ionic compounds
- Metallic compounds
Chemical formulae
It use symbols representing the different atoms, as well as the ratio in which the atoms are present in an element or a compound.
Empirical and Molecular Formulae
An empirical formula is a chemical formula that shows the simplest ratio between atoms in a compound.
The molecular formula is the chemical formula showing the actual number and type of atoms in a molecule.
Models of elements and compounds
- Circle Diagrams – Each circle represents an atom or ion and it shows the arrangement of the atoms or ions in the compounds.
- Space-filling Model – Spheres with different colours.
- Ball-and-Stick Model – Each ball represents an atom or an ion and the sticks represent the bonds between the atoms or ions.
Covalent Molecular Structures
The molecules represented as a molecular formula can together form a covalent molecular structure. They are held together by intermolecular forces.
Crystal Lattice
The particles are arranged in a regular pattern, in a crystalline state.
Covalent network structures
Structures where the covalent bonds extend throughout the structure of the substance.
Allotropes
substances with the same atoms but with different physical and chemical properties.
Vector quantities
A physical quantity that has both magnitude and direction.
Scalar quantities
A physical quantity that has magnitude only.
Resultant vector
The single vector which has the same effect as the original vectors acting together.
TRUE or FALSE: Speed and velocity measure how fast something is moving.
TRUE.
TRUE or FALSE: An object moving at a constant speed will cover unequal distances at any time interval.
FALSE. An object moving at a constant speed will cover EQUAL distances in equal time intervals.
Average Speed
Average speed is the total distance travelled divided by the total time taken to travel the distance.
Distance
Distance is the length of path travelled.
Displacement
Displacement is a change in position.
Velocity, speed, and acceleration
Velocity is the rate of change of position.
Speed is the rate of change of distance.
Acceleration is the rate of change of velocity.
Uniform or constant velocity
The magnitude and direction of a velocity remain the same throughout a period of time.
Average velocity
Average velocity is the total displacement (or change in position) divided by the time taken.
mm to m
x 10-3
cm to m
x 10-2
dm to m
x 10-1
km to m
x 103
g to kg
x 10-3
min to sec
x 60
hours to sec
x 3600 (60 x 60)
Instantaneous velocity and instantaneous speed
Instantaneous velocity is the displacement divided by an infinitesimal time interval. Instantaneous speed is the speed of an object at a specific moment of time.
