Grade 11 Physics and Chemistry Definitions

Comprehensive vocabulary flashcards covering key definitions and laws across Grade 11 Physics and Chemistry.

Scalar

A physical quantity that has magnitude only.

Vector

A physical quantity that has magnitude and direction.

Resultant

A vector sum of two or more vectors, or a single vector having the same effect as two or more vectors together.

Equilibrium

When the forces are balanced and the resultant is zero.

Contact force

A force that must touch or be in contact with an object to cause a change.

Non-contact force

A force that acts at a distance and does not have to touch an object to cause a change.

Normal force

The force or the component of a force exerted by the surface on an object in contact with and is always perpendicular to the surface.

Frictional force

The force that opposes the motion of an object and which acts parallel to the surface or motion.

Static friction

The frictional force on a stationary object that opposes the tendency of motion of the object.

Kinetic friction

The frictional force on a moving object that opposes the motion of the object.

Inertia

The tendency of an object to resist changes in its velocity.

Newton’s first law of motion

An object continues in a state of rest or uniform (moving with constant) velocity unless it is acted upon by an unbalanced (net or resultant) force.

Newton’s second law of motion

When a net force is applied to an object of a mass, the object accelerates in the direction of the net force. The acceleration is directly proportional to the net force and inversely proportional to the mass.

Newton's third law of motion

When Object A exerts a force on Object B, Object B SIMULTANEOUSLY exerts an oppositely directed force of equal magnitude on Object A.

Newton’s law of universal gravitation

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

Angle of incidence ($\theta_i$)

The angle between the normal to a surface and the incident light ray.

Angle of reflection ($\theta_r$)

The angle between the normal to a surface and the reflected light ray.

Refraction

The change in direction of a light ray due to a change in speed when light travels from one medium to another one with a different optical density.

Angle of refraction ($\theta_r$)

The angle defined between the normal to a surface and the refracted light ray.

Snell’s law

The ratio of the sine of the angle of incidence in one medium to the sine of the angle of refraction in the other medium is a constant.

Critical angle

The angle of incidence in the optically denser medium for which the angle of refraction in the optically less dense medium is $90^\circ$.

Diffraction

The ability of a wave to spread out in wavefronts as the wave passes through a small aperture or around a sharp edge.

Huygens's principle

Every point of a wavefront serves as a point source of spherical secondary waves that move forward with the same speed as the wave.

Coulomb’s law

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

Electric field

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

Electric field strength

The electrostatic force experienced per unit positive charge placed at that point.

Faraday's law of electromagnetic induction

The magnitude of the induced electromotive force (emf) across the ends of a conductor is directly proportional to the rate of change in the magnetic flux linkage with the conductor.

Ohm's law

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

Ohmic conductors

Conductors that follow Ohm’s law, which means that their resistance remains the same when the current and voltage change.

Non-ohmic conductors

Conductors that do not follow Ohm’s law, which means that their resistance changes when the current and voltage change.

Power

The rate at which work is done or energy is transferred.

Covalent bond

The bonding between non-metal atoms through a process of electron sharing.

Ionic bond

The bonding between a metal atom and a non-metal atom through the process of electron transfer.

Metallic bond

The force that holds atoms together in a metallic substance.

Dative covalent bond

A description of covalent bonding that occurs between two atoms in which both electrons shared in the bond come from the same atom.

Bond length

The distance between the nuclei of two atoms when they bond.

Bond energy

The amount of energy that must be added to a system to break the bond that has formed or the energy that is released when a bond is formed.

Electronegativity

A measure of how strongly an atom pulls a shared electron pair towards it.

Non-polar covalent bond

A covalent bond where the pair of electrons is shared equally between the two atoms.

Polar bond

A type of covalent bond in which the electrons forming the bond are unequally distributed.

Intramolecular forces

Forces that hold atoms together within a molecule OR forces that exist between molecules.

Induced dipole

A momentary dipole in a nonpolar molecule when it attains a polarity.

Vapour pressure

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

Boiling point

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

Melting point

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

Viscosity

The resistance to the flow of a liquid.

Density

A measure of the mass in a unit volume.

Surface tension

The property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of its molecules.

Cohesion

The action or property of like-molecules sticking together, being mutually attractive.

Specific heat capacity

The amount of heat needed to raise the temperature of $1\,\text{gram}$ of a substance $1\,\text{degree Celsius}$ ($^\circ\text{C}$).

Ideal gas

A hypothetical gas that has identical particles of zero volume, with no intermolecular forces between them, where the atoms or molecules move at the same speed.

Temperature

A measure of the average kinetic energy of the particles of a substance.

Pressure

The force exerted by a gas in terms of the collision of the molecules with the walls of the container.

Boyle's law

The pressure of an enclosed gas is inversely proportional to the volume it occupies at a constant temperature.

Charles’ law

The volume of an enclosed gas is directly proportional to its kelvin temperature provided the pressure is kept constant.

Gay-Lussac's law

The pressure of a gas is directly proportional to its temperature in kelvin at constant volume.

Avogadro's law

States that equal volumes of gases, at the same temperature and pressure, contain the same number of molecules.

The mole

A quantity of matter that has the same number of elementary units as there are atoms in $12\,\text{grams}$ of carbon-12.

Carbon-12

An isotope of carbon with $12$ nucleons (or a mass number of $12$).

Standard solution

A solution of accurately known concentration, which remains constant for a period of time.

Limiting reactant (or limiting reagent)

The reactant that gets consumed first in a chemical reaction and therefore limits how much product can be formed.

Molecular formula

A concise way of expressing information about the atoms that make up a particular covalent molecular compound, giving the exact number of each type of atom in the molecule.

Empirical formula

A way of expressing the relative number of each type of atom in a chemical compound that shows the simplest ratio of the atoms in the compound rather than the exact number.

Exothermic reactions

Reactions that release energy.

Endothermic reactions

Reactions that absorb energy.

Activation energy

The minimum energy needed for a reaction to take place.

Activated complex

The unstable transition state from reactants to products.

(Positive) Catalyst

A substance that increases the rate of a chemical reaction without itself undergoing a permanent change.

Negative catalyst

Decreases the rate of reaction by increasing the activation energy and activated complex.

Arrhenius acid

A substance that produces hydrogen ions ($H^+$)/hydronium ions ($H_3O^+$) when it dissolves in water.

Arrhenius base

A substance that produces hydroxide ions ($OH^-$) when it dissolves in water.

Lowry-Brønsted acid

A proton/$H^+$ ion donor.

Lowry-Brønsted base

A proton/$H^+$ ion acceptor.

Ampholyte

A substance that can act as either acid or base is amphiprotic.

Monoprotic acid

When an acid is only able to donate one hydrogen ion.

Diprotic acid

An acid that has two hydrogen ions or protons to donate.

Triprotic acid

An acid that has three hydrogen ions or protons to donate.

Strong acids

Acids that ionise completely in water to form a high concentration of $H_3O^+$ ions.

Weak acids

Acids that ionise incompletely in water to form a low concentration of $H_3O^+$ ions.

Strong bases

Bases that dissociate completely in water to form a high concentration of $OH^-$ ions.

Weak bases

Bases that dissociate/ionise incompletely in water to form a low concentration of $OH^-$ ions.

Dissociation

The process in which solid ionic crystals are broken up into ions when dissolved in water.

Neutralisation reaction

When acids and bases react with each other to form salt and water.

Equivalence point

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

End point

The point of a titration where the indicator changes colour.

Concentration

The number of moles of solute per unit volume of solution.