GR 12 Physics and Chemistry Definitions

Flashcards covering essential Grade 12 Physics (Paper 1) and Chemistry (Paper 2) definitions, laws, and concepts.

What is Newton's first law of motion?

A body will remain in its state of rest or motion at constant velocity unless a non-zero resultant/net force acts on it.

What is Newton's second law of motion?

When a resultant/net force acts on an object, the object will accelerate in the direction of the force at an acceleration directly proportional to the force and inversely proportional to the mass of the object.

What is Newton's third law of motion?

When one body exerts a force on a second body, the second body exerts a force of equal magnitude in the opposite direction on the first body.

What is Newton's Law of Universal Gravitation?

Each body in the universe attracts every other body with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres.

How is momentum defined in physics?

Momentum is the product of an object's mass and its velocity.

What is Newton's second law of motion in terms of momentum?

The resultant/net force acting on an object is equal to the rate of change of momentum of the object in the direction of the resultant/net force.

What is impulse?

Impulse is the product of the resultant/net force acting on an object and the time the resultant/net force acts on the object.

What is the symbolic equation for the impulse-momentum theorem?

$$F_{\text{net}}\Delta t = m\Delta v$$

What is a closed or isolated system in Physics?

A system on which the resultant/net external force is zero (it excludes external forces that originate outside the colliding bodies, e.g. friction; only internal forces are considered).

What is the principle of conservation of linear momentum?

The total linear momentum of a closed system remains constant (is conserved).

What is normal force ($N$)?

Normal force is the force or the component of a force which a surface exerts on an object with which it is in contact, and which is perpendicular to the surface.

What is frictional force ($f$)?

Frictional force is the force that opposes the motion of an object and which acts parallel to the surface.

What is static frictional force ($f_s$)?

Static frictional force is the force that opposes the tendency of motion of a stationary object relative to a surface.

What is kinetic frictional force ($f_k$)?

Kinetic frictional force is the force that opposes the motion of a moving object relative to a surface.

How is weight defined in physics?

Weight is the gravitational force the Earth exerts on any object on or near its surface.

What is a projectile in 1D motion?

A projectile is an object upon which the only force acting is the force of gravity.

How is the work done on an object by a constant force $F$ calculated?

The work done is $F\Delta x \cos(\theta)$, where $F$ is the magnitude of the force, $\Delta x$ the magnitude of the displacement, and $\theta$ the angle between the force and the displacement.

What is the work-energy theorem?

The net/total work done on an object is equal to the change in the object's kinetic energy OR the work done on an object by a resultant/net force is equal to the change in the object's kinetic energy ($W_{\text{net}} = \Delta K = K_f - K_i$).

What is a conservative force?

A force for which the work done in moving an object between two points is independent of the path taken (e.g., gravitational force, elastic force in a spring, and electrostatic forces).

What is a non-conservative force?

A force for which the work done in moving an object between two points depends on the path taken (e.g., frictional force, air resistance, tension in a chord).

What is the principle of conservation of mechanical energy?

The total mechanical energy (sum of gravitational potential energy and kinetic energy) in an isolated system remains constant.

What is power?

Power is the rate at which work is done or energy is expended.

What is the Doppler effect?

The Doppler effect is the change in frequency (or pitch) of the sound detected by a listener because the sound source and the listener have different velocities relative to the medium of sound propagation.

What is Coulomb's law?

The magnitude of the electrostatic force exerted by one point charge ($Q_1$) on another point charge ($Q_2$) is directly proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance ($r$) between them.

What is an electric field?

An electric field is a region of space in which an electric charge experiences a force. The direction of the field at a point is the direction that a positive test charge would move if placed at that point.

What is the electric field at a point?

The electric field at a point is the electrostatic force experienced per unit positive charge placed at that point.

What is Ohm's law?

The potential difference across a conductor is directly proportional to the current in the conductor at constant temperature.

What is the rms value of an alternating voltage or alternating current?

The rms value of AC is the DC potential difference/current which dissipates the same amount of energy as AC.

What is the photoelectric effect?

The photoelectric effect is the process whereby electrons are ejected from a metal surface when light of suitable frequency is incident on that surface.

What is threshold frequency ($f_o$)?

Threshold frequency is the minimum frequency of light needed to emit electrons from a certain metal surface.

What is work function ($W_o$)?

Work function is the minimum energy that an electron in the metal needs to be emitted from the metal surface.

How is an atomic absorption spectrum formed?

An atomic absorption spectrum is formed when certain frequencies of electromagnetic radiation that passes through a medium, e.g. a cold gas, is absorbed.

How is an atomic emission spectrum formed?

An atomic emission spectrum is formed when certain frequencies of electromagnetic radiation are emitted due to an atom's electrons making a transition from a high-energy state to a lower energy state.

What volume does $1\,\text{mole}$ of any gas occupy at standard conditions of $0\,^\circ\text{C}$ ($273\,K$) and $1\,\text{atmosphere}$ ($101,3\,kPa$)?

$1\,\text{mole}$ of any gas occupies $22,4\,dm^3$.

What are dipole-dipole forces?

Forces between two polar molecules.

What are induced dipole forces or London forces?

Forces between non-polar molecules.

What is hydrogen bonding?

Forces between molecules in which hydrogen is covalently bonded to nitrogen, oxygen or fluorine - a special case of dipole-dipole forces.

What is boiling point?

The temperature at which the vapour pressure of a substance equals atmospheric pressure.

What is melting point?

The temperature at which the solid and liquid phases of a substance are at equilibrium.

What is vapour pressure?

The pressure exerted by a vapour at equilibrium with its liquid in a closed system.

What is a molecular formula?

A chemical formula that indicates the type of atoms and the correct number of each in a molecule.

What is a structural formula?

A structural formula of a compound shows which atoms are attached to which within the molecule, using chemical symbols for atoms and lines to represent ALL the bonds that hold the atoms together.

What is a condensed structural formula?

This notation shows the way in which atoms are bonded together in the molecule, but DOES NOT SHOW ALL bond lines.

What is a hydrocarbon?

Organic compounds that consist of hydrogen and carbon only.

What is a homologous series?

A series of organic compounds that can be described by the same general formula OR in which one member differs from the next with a $\text{CH}_2$ group.

What are saturated compounds?

Compounds in which there are no multiple bonds between C atoms in their hydrocarbon chains.

What are unsaturated compounds?

Compounds with one or more multiple bonds between C atoms in their hydrocarbon chains.

What is a functional group?

A bond or an atom or a group of atoms that determine(s) the physical and chemical properties of a group of organic compounds.

What are structural isomers?

Organic molecules with the same molecular formula, but different structural formulae.

What are chain isomers?

Organic molecules with the same molecular formula, but different types of chains.

What are positional isomers?

Organic molecules with the same molecular formula, but different positions of the side chain, substituents or functional groups on the parent chain.

What are functional isomers?

Organic molecules with the same molecular formula, but different functional groups.

What is hydrohalogenation?

The addition of a hydrogen halide to an alkene.

What is halogenation?

The reaction of a halogen ($\text{Br}_2$, $\text{C}\ell_2$) with a compound.

What is hydration in organic chemistry?

The addition of water to a compound.

What is hydrogenation?

The addition of hydrogen to an alkene.

What is heat of reaction ($\Delta H$)?

The energy absorbed or released in a chemical reaction.

What is an exothermic reaction?

Reactions that release energy (where $\Delta H < 0$).

What is an endothermic reaction?

Reactions that absorb energy (where $\Delta H > 0$).

What is activation energy?

The minimum energy needed for a reaction to take place.

What is an activated complex?

The unstable transition state from reactants to products.

What is reaction rate?

The change in concentration of reactants or products per unit time.

How does a catalyst increase the rate of a chemical reaction?

A catalyst increases the rate of a reaction by providing an alternative path of lower activation energy. It therefore decreases the net/total activation energy.

What is the difference between an open system and a closed system in chemistry?

An open system continuously interacts with its environment, while a closed system is isolated from its surroundings.

What is a reversible reaction?

A reaction is reversible when products can be converted back to reactants.

What is chemical equilibrium?

A dynamic equilibrium when the rate of the forward reaction equals the rate of the reverse reaction.

What is dehydrohalogenation of haloalkanes?

The elimination of hydrogen and a halogen from a haloalkane.

What is dehydration of alcohols?

Elimination of water from an alcohol.

What is cracking of alkanes?

The chemical process in which longer chain hydrocarbon molecules are broken down to shorter more useful molecules.

What is hydrolysis in the context of salts?

The reaction of a salt with water.

What is a polymer?

A large molecule composed of smaller monomer units covalently bonded to each other in a repeating pattern.

What is addition polymerisation?

A reaction in which small molecules join to form very large molecules by adding on double bonds.

What is condensation polymerisation?

Molecules of two monomers with different functional groups undergo condensation reactions with the loss of small molecules, usually water.

What is Le Chatelier's principle?

When the equilibrium in a closed system is disturbed, the system will re-instate a new equilibrium by favouring the reaction that will oppose the disturbance.

How does the Arrhenius theory define an acid and a base?

An acid is a substance that produces hydrogen ions ($\text{H}^+$)/hydronium ions ($\text{H}_3\text{O}^+$) when it dissolves in water. A base is a substance that produces hydroxide ions ($\text{OH}^-$) when it dissolves in water.

How does the Lowry-Brønsted theory define an acid and a base?

An acid is a proton ($\text{H}^+$ ion) donor. A base is a proton ($\text{H}^+$ ion) acceptor.

What is an ampholyte or amphiprotic substance?

A substance that can act as either an acid or as a base.

What is the equivalence point of a titration?

The point at which the acid/base has completely reacted with the base/acid.

What is the endpoint of a titration?

The point where the indicator changes colour.

What is auto-ionisation of water?

The reaction of water with itself to form $\text{H}_3\text{O}^+$ ions and $\text{OH}^-$ ions ($2\text{H}_2\text{O} \rightleftharpoons \text{H}_3\text{O}^+ + \text{OH}^-$).

What is a Galvanic cell?

A cell in which chemical energy is converted into electrical energy. A galvanic (voltaic) cell has self-sustaining electrode reactions.

What is an electrolytic cell?

A cell in which electrical energy is converted into chemical energy.

How are oxidation and reduction defined in terms of electron transfer?

Oxidation is a loss of electrons; reduction is a gain of electrons.

How are oxidation and reduction defined in terms of oxidation numbers?

Oxidation is an increase in oxidation number; reduction is a decrease in oxidation number.

What is an oxidising agent?

A substance that is reduced/gains electrons.

What is a reducing agent?

A substance that is oxidised/loses electrons.

What occurs at the anode and cathode of an electrochemical cell?

Anode: The electrode where oxidation takes place. Cathode: The electrode where reduction takes place.

What is an electrolyte?

A solution/liquid/dissolved substance that conducts electricity through the movement of ions.

What is eutrophication?

The process by which an ecosystem, e.g. a river or dam, becomes enriched with inorganic plant nutrients, especially phosphorus and nitrogen, resulting in excessive plant growth. As plant growth becomes excessive, the amount of dead and decaying plant material increases rapidly.