ALL SCIENCE TOPICS

Atom

The building block of matter made of protons, neutrons, and electrons

Proton

A positively charged particle found in the nucleus of an atom

Electron

A negatively charged particle found in shells around the nucleus

Valence electron

Electrons in the outermost shell

Ion

An atom or molecule with an electrical charge

Neutral

No charge

Ionic Compound

A neutral compound consisting of positive and negative ions held together by ionic bonds

Ionic Bond

Electrostatic attraction between positive and negative ions

Group

A vertical column of elements

What do elements in the same group have in common?

They have the same number of outer electrons, called valence electrons

Period

Horizontal row on the periodic table

What do elements in the same period have in common?

As you move across a period from left to right, each element adds one proton and one electron, changing properties from metal to non-metal

Reaction Rate

The speed at which a chemical reaction takes place

Successful Collision

A particle collision in the correct orientation and with enough energy for a reaction to occur

Frequency of Collisions

The number of particle collisions per second

Surface Area

The total outer area of a solid reactant exposed to a liquid or gas

What happens when an acid reacts with a solid?

When an acid reacts with a solid, a larger surface area means more particles are exposed. This allows more collisions to happen at the same time, which makes the reaction go faster

Kinetic Energy (Ek)

Energy due to motion; higher temperature increases kinetic energy and particle speed

What increases kinetic energy?

- More Ek = faster moving particles - Temperature increases kinetic energy of particles

Particle Collision Theory

Chemical reactions happen when reactant particles bump into each other

What are the requirements for the particle collision theory to occur?

- Must have enough speed (activation energy) - The right angle to break and make bonds

Acid

A substance that releases H+ ions in solution

Base

A substance that releases OH- ions in solution

H+

Hydrogen ion/proton

OH-

Hydroxide ion

pH

A measure of the acidity of a solution based on concentration of H+ ions relative to OH- ions

Neutral

Solution with equal concentrations of OH- and H+ ions

Concentration

The number of particles in a given volume, represented by square brackets

Neutralisation

A chemical reaction where an acid reacts with a base to form a neutral salt and water

Allele

A different version of the same gene

What is asexual reproduction?

Reproduction that only involves one parent

What is a characteristic of offspring produced by asexual reproduction?

Offspring are all genetically identical to each other and the parent

Chromosome

Long strands of DNA tightly wound together

Crossing Over

Homologous chromosomes exchange genetic material, producing new unique combinations of alleles

What is the structure of DNA?

Large molecule that is coiled up into a double-helix structure

What are the components that make up DNA?

Ribose/sugar, phosphate, and a base

Which bases pair up in DNA?

A with T and G with C

DNA Sequencing

A laboratory process that determines the exact order of bases in DNA

Dominant

A dominant allele shows its trait even if only one copy is present

Fertilisation

The fusion of two gametes (e.g., sperm and egg).

Founder Effect

When a small group starts a new population, carrying only a small sample of the original genetic variation

Gene

A section of DNA that codes for a trait

Genetic Screening

Testing DNA to identify genes or mutations, often for health or inherited conditions

Genetic Variation

The difference between the genes/alleles in a population

Genotype

The allele combination (for a specific trait) on a chromosome.

Inheritable Variation

Variation in traits/alleles/genes that can be passed on to the offspring by gametic cells

Heterozygous

An organism has two different alleles for a gene

Homozygous

An organism has two identical alleles for a gene

Independent Assortment

Homologous chromosomes line up in the middle of a cell in a random order before separating into gametes

Meiosis

Process of cell division that produces gametes

Migration

Movement of individuals in or out of a population, changing allele frequencies

Mutation

A permanent change an organism's DNA sequence, leading to new alleles

Natural Selection

The process where individuals with advantageous traits survive and reproduce, becoming more common

Non-Inheritable Variation

Variation caused by environmental effects on somatic cells that cannot be passed on to offspring

Pedigree Chart

A family tree diagram showing how traits are inherited across generations

Phenotype

The traits that are physically expressed

Population

A group of individuals of the same species living in the same area, capable of interbreeding

Sexual Reproduction

The fusion of gametes to create a new individual, with variation from the combination of alleles

Force

A push or pull causing a change in speed, direction, or shape

Balanced Force

Equal in size and opposite in direction, giving a net force of zero

Unbalanced Force

Causes a change in motion (acceleration, deceleration, or change in direction)

Net Force

The overall force acting on an object after all forces are combined

SI Unit (Force)

Newtons (N)

Mass

The amount of matter contained within an object, measured in kilograms (kg)

Weight

The force of gravity acting on an object's mass, measured in newtons (N)

Gravity

A force that attracts objects with mass toward each other

Normal Force

The support force exerted by a surface on an object, acting perpendicular (90°) to the surface

Friction

A force that opposes motion between two surfaces in contact

Air Resistance (Drag)

A frictional force that opposes motion when an object moves through air

Applied Force

A force exerted on an object by a person or another object

Thrust

A force that pushes an object forward, often produced by engines or explosions

Newton's First Law

An object remains at rest or moves at constant speed unless acted on by an unbalanced force

Inertia

The tendency of an object to resist changes in its motion; more mass means more inertia

Newton's Second Law

An object accelerates in the direction of an unbalanced force (Fnet = ma)

Newton's Third Law

For every action force, there is an equal and opposite reaction force

Delta (Δ)

Physics symbol representing final minus initial values

Distance

How far an object travels, measured in metres (m)

Time

How long motion takes, measured in seconds (s)

Speed

Distance divided by time, measured in metres per second (m s⁻¹)

Acceleration

Rate of change of speed in one direction (m s⁻²)

Deceleration

Acceleration that decreases speed, or negative acceleration

Distance-Time Graph

Graph where gradient represents speed and a flat line means rest

Speed-Time Graph

Graph where gradient is acceleration and area under it is distance

Energy

The ability to do work

SI Unit (Work & Energy)

Joule (J)

Gravitational Potential Energy (ΔEp)

Energy stored due to height above Earth

Gravitational Potential Energy (ΔEp) Formula

ΔEp = mgΔh

Kinetic Energy (Ek)

The energy of an object due to its motion

Kinetic Energy (Ek) Formula

Ek = ½mv²

Energy Transformation

When energy changes from one form to another

Law of Conservation of Energy

Energy cannot be created or destroyed, only transferred or transformed

Work

Energy transferred when a force moves an object in the direction of the force

Work Formula

W = Fd

Work Done

Equal to the change in energy

Power

The rate at which work is done

Power Formula

P = W/t

SI Unit (Power)

Watts (W)