Definitions

TOPIC 1: CHEMICAL BONDING



Chemical bonds:

  • A chemical bond is an electrostatic force of attraction that holds two or more atoms, ions, or molecules or any combination of these together.

Electrostatic force:

  • The electrostatic force of attraction involves oppositely charged particles.

Ionic bond:

  • Ionic bonds are the strong forces of attraction between oppositely charged ions.

Polyatomic ions:

  • Ammonium → NH4+ 

  • Phosphate → PO43-

  • Carbonate → CO32-

  • Hydroxide → OH-

  • Sulfate → SO42-

  • Nitrate → NO3-

Covalent bond:

  • Covalent bonds are the strong electrostatic forces of attraction between the shared pair of electrons and the positively charged nuclei of both atoms.


TOPIC 2: ACIDS AND ALKALIS



Acid:

  • Acids are substance that form hydrogen ions, H+, when dissolved in water

Alkali:

  • An alkaline is a substance that forms hydroxide ions, OH-, when dissolved in water.



TOPIC 3: CHEMICAL CHANGES AND REACTIONS



Thermal decomposition:

  • Thermal decomposition is the process in which compounds break down into two or more substances with the effect of heat.

Electrolysis:

  • Electrolysis is the process in which compounds break down into two or more simpler substances with the effect of electricity

Oxidisation:

  • Oxidation is the process in which a substance gains oxygen

Reduction:

  • Reduction is the process in which a substance loses oxygen



Law of conservation of mass

  • The law of conservation of mass states that mass is not gained or lost in a chemical reaction. Hence, the total mass of products must be equal to the total mass of reactants.



TOPIC 4: FORCES, MASS, WEIGHT AND PRESSURE



Contact force:

  • Contact forces act when two interacting objects have physical contact with each other

Non-contact force:

  • Non-contact forces act over a distance without physical contact between two interacting objects

Frictional force

  • Frictional force is the contact force that acts between two surfaces/ objects in contact with one another that tends to oppose or resist motion

Inertia: 

  • Inertia refers to the resistance of a body to resist a change in state of rest or motion of the body

Pressure:

  • Pressure refers to the amount of force acting perpendicularly on a unit area



TOPIC 5: TURNING EFFECTS OF FORCES



Principle of moments

  • The Principle of moments states that for an object to be in rotational equilibrium, the sum of clockwise moments about any pivot is equal to the sum of anticlockwise moments about the same pivot

Stability:

  • Stability refers to the ability of an object to return to its original position after its had been tilted slightly

Stable equilibrium:

  • For an object to be in stable equilibrium, the centre of gravity rises then falls back again

Unstable equilibrium:

  • For an object to be in unstable equilibrium, the centre of gravity falls and continues falling.

Neutral equilibrium:

  • For an object to be in neutral equilibrium, the centre of gravity neither rises nor falls; it remains at the same level about the surface supporting it