Year 7 Chemistry: Matter, Atomic Structure, Periodic Table, and Reactions

Vocabulary practice flashcards covering foundational chemistry concepts including acids and bases, the periodic table, atomic structure, states of matter, mixtures, solutions, and physical and chemical changes.

Acid

A substance that produces or releases hydrogen ions ($H^+$) in water, resulting in a higher concentration of $H^+$ ions and a pH below 7.

Base

A substance that has a lower concentration of $H^+$ ions, can remove $H^+$ ions, or produces hydroxide ions ($OH^-$) in water, resulting in a pH above 7.

Alkaline Solution

A basic solution that has fewer hydrogen ions ($H^+$) than an acidic solution and more hydroxide ions ($OH^-$).

pH Scale

A scale usually ranging from 0 to 14 used to describe how acidic or basic a solution is, where low values indicate an acid, 7 is neutral, and high values indicate a base.

Indicator

A substance, such as litmus paper, red cabbage anthocyanin, or turmeric curcumin, that changes colour depending on whether a solution is acidic or basic.

Neutralization Reaction

A reaction in which an acid reacts with a base so that hydrogen ions ($H^+$) and hydroxide ions ($OH^-$) form water ($H_2O$) and a salt (such as $HCl + NaOH \rightarrow NaCl + H_2O$), moving the pH toward neutral.

Periodic Table

A table that organizes all known chemical elements in order of increasing atomic number, arranged into periods and groups.

Period (Periodic Table)

A horizontal row of elements in the periodic table.

Group (Periodic Table)

A vertical column of elements in the periodic table that share similar chemical properties.

Metal

An element that is usually shiny, bendable, and a good conductor of heat and electricity.

Non-metal

An element that is generally a poorer conductor of electricity and possesses diverse physical properties, existing as a gas, liquid, or brittle solid at room temperature.

Metalloid

An element that possesses physical and chemical properties intermediate between those of metals and non-metals.

Alkali Metals

The soft, shiny elements in Group 1 of the periodic table that are stored under oil or paraffin because they have one valence electron and react rapidly with water and oxygen.

Halogens

The reactive non-metals in Group 17 that exist as diatomic molecules ($F_2$, $Cl_2$, $Br_2$, $I_2$) and readily gain one electron to complete their outer electron shell.

Noble Gases

The stable, unreactive elements in Group 18 that exist as single atoms because their outermost electron shell is completely full.

Atom

The basic particle of all matter, composed of sub-atomic particles known as protons, neutrons, and electrons.

Nucleus (Atomic)

The dense central core of an atom that contains positively charged protons and neutral neutrons.

Atomic Number

The unique number of protons in an atom's nucleus, which also equals the number of electrons in a neutral atom.

Mass Number

The total number of protons and neutrons contained within the nucleus of an atom.

Niels Bohr

The Danish physicist (1885–1962) who won the Nobel Prize in 1922 and developed a model showing electrons arranged in specific shells around an atomic nucleus.

Bohr Model

An atomic model where electrons orbit the central nucleus in layered shells (energy levels) holding a maximum of 2 electrons in the first shell and 8 in the second.

Valence Electrons

The electrons situated in the outermost shell of an atom.

Element

Matter composed of only one type of atom that cannot be broken down into simpler parts physically or by chemical reaction.

Compound

A pure substance composed of two or more different elements chemically bonded together that can only be separated via a chemical reaction.

Mixture

An impure substance formed by two or more elements or compounds combined without a chemical reaction, which can be physically separated.

Heterogeneous Mixture

A mixture that contains visibly different and distinguishable parts.

Homogeneous Mixture

A uniform mixture, also called a solution, that has no visibly distinguishable different parts.

Solution

A specific type of homogeneous mixture formed when one substance completely dissolves into another.

Solute

The substance that dissolves in a liquid to form a solution.

Solvent

The liquid substance that dissolves the solute when forming a solution.

Matter

Anything that has mass and takes up space.

Mass

The measured amount of matter in an object, typically measured in grams ($g$) or kilograms ($kg$).

Solid

A state of matter characterized by organized, closely packed particles with little energy that remain in fixed positions, giving it a fixed volume and shape.

Liquid

A state of matter in which particles have medium energy and can move around each other, possessing a fixed volume but no fixed shape.

Gas

A state of matter with highly energetic, unorganized particles that are spread far apart, possessing no fixed volume.

Plasma

An extremely energized state of matter consisting of ions and free electrons, observed in the sun, lightning, and neon signs.

Sublimation

The phase change in which a substance changes directly from a solid into a gas upon heating.

Deposition

The phase change in which a substance changes directly from a gas into a solid upon cooling.

Physical Change

A change in an object's state, shape, or size without transforming the substance into a chemically different kind of matter.

Chemical Change

A change in which an object or substance transforms into a completely new kind of matter with different properties.

Physical Property

A measurable or observable characteristic of a substance, such as color, hardness, or temperature, that does not alter its chemical composition.

Chemical Property

A property describing a substance's capability to undergo a chemical reaction and form new matter, such as flammability, toxicity, or reactivity.

Density

A measure of how closely packed particles are in a substance, defined by the formula $\text{Density} = \frac{\text{mass}}{\text{volume}}$.