8th Grade Science Study Guide Flashcards

Vocabulary flashcards based on the provided science study guide, covering topics from atoms to genetics.

Atom

The smallest unit of matter.

Electron

Negatively charged particle that orbits the nucleus.

Nucleus

Center of an atom; contains protons and neutrons.

Proton

Positively charged particle in the nucleus.

Neutron

Neutral particle in the nucleus.

Atomic number

Number of protons in an atom.

Isotope

Atoms of the same element with different numbers of neutrons.

Mass number

Sum of protons and neutrons.

Atomic mass

Average mass of all isotopes of an element.

Periodic table

Chart that organizes elements by atomic number.

Chemical symbol

One- or two-letter abbreviation for an element.

Period

Horizontal row on the periodic table.

Group

Vertical column on the periodic table; elements share properties.

Compound

Substance made of two or more elements chemically bonded.

Valence electron

Electrons in the outer shell; involved in bonding.

Reactivity

How easily an element reacts with others.

Ion

Atom that has lost or gained electrons.

Polyatomic ion

A group of atoms that act as a single ion.

Ionic bond

Transfer of electrons between atoms (usually metal + nonmetal).

Covalent bond

Sharing of electrons between atoms (usually nonmetals).

Molecule

Group of atoms bonded covalently.

Nonpolar bond

Electrons shared equally.

Polar bond

Electrons shared unequally.

Malleable

Can be hammered into shapes.

Ductile

Can be drawn into wires.

Luster

How shiny a material is.

Semiconductor

Material that conducts electricity under certain conditions.

Acid

Substance that produces hydrogen ions (H+); pH < 7.

Corrosive

Ability to wear away other materials (like metals).

Indicator

Substance that changes color in acids or bases.

Base

Produces hydroxide ions (OH-); pH > 7.

Synthetic

Made by humans in a lab.

Natural resource

Found in nature, not man-made.

Polymer

Large molecule made of repeating units (natural or synthetic).

Motion

Change in position over time.

Reference point

Place used to determine motion.

Force

A push or pull.

Newton

SI unit for force.

Friction

Resistance between surfaces.

Gravity

Force that pulls objects toward each other.

Net force

Total force acting on an object.

Speed

Distance traveled over time.

Slope

Steepness of a line (used in speed graphs).

Velocity

Speed with direction.

Acceleration

Change in velocity over time.

Inertia

Resistance to change in motion.

Weight

Force of gravity on an object.

Neutralization

Reaction between an acid and a base.

Salt

Product of neutralization (besides water).

Mixture

Two or more substances not chemically bonded.

Colloid

Mixture with small undissolved particles.

Suspension

Mixture with large particles that settle out.

Solution

Homogeneous mixture where one substance dissolves in another.

Solvent

Substance that does the dissolving (usually water).

Solute

Substance being dissolved.

Solubility

How much solute can dissolve in a solvent at a given temp.

Physical change

Change in appearance, not chemical makeup.

Chemical change

New substances are formed with different properties.

Reactant

Starting substances in a reaction.

Product

New substances formed.

Exothermic reaction

Releases heat.

Endothermic reaction

Absorbs heat.

Law of conservation of mass

Matter is not created or destroyed.

Open system

Matter can enter/exit the system.

Closed system

No matter enters or leaves.

Heredity

Passing of traits from parents to offspring.

Dominant allele

Trait that shows up when present.

Recessive allele

Trait that only shows up when two copies are present.

Probability

Likelihood of a genetic outcome.

Genotype

Genetic makeup (e.g., Bb, BB).

Phenotype

Physical appearance (e.g., brown eyes).

Chromosome

Structure in cells that contains DNA.

Cell cycle

Process of cell growth and division.

Pedigree

Chart showing genetic relationships in a family.

Meiosis

Cell division that produces sex cells (gametes).

Chromatids

Identical halves of a duplicated chromosome.

Mitosis

Cell division that produces body cells.

DNA

Genetic material that holds instructions for life.

Protein synthesis

Process of making proteins from DNA instructions.

Messenger RNA (mRNA)

Carries DNA code to ribosome.

Transfer RNA (tRNA)

Brings amino acids to ribosome.

Variation

Differences between individuals.

Sex chromosomes

Determine gender (X and Y).

Autosomal chromosomes

All other chromosomes not related to gender.

mutation

change in dna sequence

sex linked genes

genes on sex chromosomes often X linked

artificial selection

Humans choosing traits to breed

genetic engineering

Directly modifying DNA

Gene therapy

Replacing faulty genes

clone

Genetically identical copy

Genome

All the DNA in an organism