8th Grade Mid-Year Science Review

Vocabulary practice flashcards covering atomic structure, the periodic table, scientific variables, measurements, classification of matter, properties, changes, bonding, and conservation of mass for the 8th grade mid-year review.

Proton

A subatomic particle located in the nucleus with a positive charge and a mass of $1\,\text{amu}$.

Neutron

A subatomic particle located in the nucleus with a neutral charge and a mass of $1\,\text{amu}$.

Electron

A subatomic particle located in the electron cloud with a negative charge and a mass of less than $1\,\text{amu}$.

Metalloids

Elements situated in Groups $13$ through $16$ of the periodic table that share properties of both metals and nonmetals.

Isotope

An atom that contains the same number of protons and electrons as another atom of the same element, but a different number of neutrons (such as a lithium atom with $3$ protons, $3$ electrons, and $6$ neutrons).

Halogens

A group of elements on the periodic table that are very reactive gases.

Independent Variable

The variable in an experiment that is deliberately changed or manipulated by the experimenter (such as amount of zinc or study time), plotted on the x-axis.

Dependent Variable

The variable in an experiment that changes in response to the independent variable and is measured (such as amount of gas created or grade percentage), plotted on the y-axis.

Balance

A laboratory instrument used to measure mass.

Graduated Cylinder

A laboratory instrument used to measure liquid volume.

Mixture

Consisting of several distinct minerals, rather than a chemically bonded compound, same properties as original substances.

Density ($D$)

The ratio of an object's mass to its volume, calculated using the formula $D = \frac{M}{V}$.

Compound

A pure substance formed when two or more different elements chemically combine in a set ratio (such as table salt, $\text{NaCl}$, or sugar), resulting in properties distinct from the individual component elements.

Physical Property

A characteristic of matter that can be observed or measured without changing the chemical identity of the substance, including solubility, malleability, and freezing point.

Chemical Property

A characteristic that describes a substance's ability to participate in chemical reactions or form new substances, such as flammability or non-reactivity with oxygen.

Characteristic Property

A physical or chemical property that remains unchanged regardless of the size or amount of the sample being examined.

Chemical Change

A transformation that produces one or more new substances with different properties, which cannot be undone through physical methods.

Solubility

The physical ability of a solute to dissolve in a solvent, exemplified by table salt dissolving in water.

Covalent Bond

A chemical bond formed between nonmetal atoms (such as oxygen and sulfur) through the sharing of electrons.

Ionic Bond

A chemical bond formed when electrons are transferred from one atom to another, creating oppositely charged ions that attract (such as magnesium and fluorine).

Law of Conservation of Mass

A fundamental principle stating that matter is neither created nor destroyed in a chemical reaction; the total mass of the reactants equals the total mass of the products.