Year 8 Chemistry

Cards · 55

Atom

The tiny building block that makes up all matter. Example: A pure gold ring is made entirely of gold atoms.

Element

A pure substance made of only one type of atom that cannot be broken down chemically. Example: Oxygen gas (O2) contains only oxygen atoms.

Compound

A substance formed when two or more different elements are chemically bonded together. Example: Pure water (H2O) contains hydrogen and oxygen.

Mixture

Two or more substances combined physically without forming chemical bonds. Example: Saltwater or a bowl of mixed nuts.

Molecule

A group of two or more atoms held tightly together by chemical bonds. Example: Carbon dioxide (CO2) is a molecule of one carbon and two oxygen atoms.

Proton

A positively charged particle found in the nucleus of an atom. Example: Every carbon atom contains exactly 6 protons.

Neutron

A neutral particle with no electric charge found inside an atom's nucleus. Example: Most helium atoms have 2 neutrons in their core.

Electron

A tiny, negatively charged particle that orbits the nucleus of an atom. Example: Electrons flowing through a wire create electric current.

Atomic Number

The total number of protons in an atom's nucleus, identifying the element. Example: Hydrogen has an atomic number of 1.

Mass Number

The total number of protons plus neutrons in the nucleus of an atom. Example: Carbon-12 has 6 protons and 6 neutrons, giving a mass number of 12.

Periodic Table

A chart organizing all known elements by their atomic number and properties. Example: Scientists use it to see that neon and argon behave similarly.

Period

A horizontal row in the periodic table showing elements with the same number of electron shells. Example: Period 2 contains lithium across to neon.

Group

A vertical column in the periodic table of elements sharing similar chemical properties. Example: Group 1 contains highly reactive alkali metals.

Metal

An element that is typically shiny, hard, and a good conductor of heat and electricity. Example: Copper used in household electrical wires.

Non-metal

An element that is usually a poor conductor and brittle or gaseous at room temperature. Example: Sulfur powder or oxygen gas.

Metalloid

An element with properties between metals and non-metals. Example: Silicon, widely used in computer chips as a semiconductor.

Solid

A state of matter with a fixed shape and fixed volume whose particles vibrate in place. Example: An ice cube.

Liquid

A state of matter with a fixed volume that takes the shape of its container. Example: Liquid water poured into a glass.

Gas

A state of matter with no fixed shape or volume whose particles move freely and spread out. Example: Helium filling a birthday balloon.

Melting

The change of state from a solid into a liquid when heated. Example: An ice cube melting into liquid water on a warm countertop.

Freezing

The change of state from a liquid into a solid when cooled. Example: Water turning into ice inside a kitchen freezer.

Evaporation

The process of a liquid slowly changing into a gas at its surface below boiling point. Example: A puddle drying up on a sunny day.

Boiling

Rapid vaporization of a liquid throughout its entire volume at a specific temperature. Example: Water bubbling vigorously in a kettle at 100 degrees Celsius.

Condensation

The change of state from a gas into a liquid when cooled. Example: Water droplets forming on the outside of a cold glass of soda.

Sublimation

The direct change of state from a solid to a gas without turning into a liquid first. Example: Dry ice (solid CO2) producing visible vapor.

Deposition

The direct change of state from a gas to a solid without becoming a liquid. Example: Frost forming on a cold car windshield overnight.

Physical Change

A reversible change in form or state where no new substances are created. Example: Tearing a sheet of paper or melting chocolate.

Chemical Change

A change where chemical bonds break and form to create one or more new substances. Example: Baking a cake or a campfire burning wood to ash.

Reactant

A starting substance in a chemical reaction that gets changed. Example: Wood and oxygen are reactants when a campfire burns.

Product

A new substance formed as a result of a chemical reaction. Example: Ash and carbon dioxide are products of burning wood.

Exothermic Reaction

A chemical reaction that releases energy, usually as heat or light. Example: A burning match or a disposable hand warmer.

Endothermic Reaction

A chemical reaction that absorbs heat energy from its surroundings, feeling cold. Example: An instant cold pack used to treat sports injuries.

Law of Conservation of Mass

The scientific rule that matter cannot be created or destroyed in a chemical reaction. Example: The total weight of reactants equals the total weight of products.

Solute

The substance that dissolves into a liquid to make a solution. Example: Table salt or sugar stirred into water.

Solvent

The liquid substance capable of dissolving other substances. Example: Water, which is often called the universal solvent.

Solution

A homogeneous mixture formed when a solute completely dissolves in a solvent. Example: Clear saltwater where the salt is evenly spread out.

Soluble

Able to dissolve into a particular solvent. Example: Sugar is soluble in hot tea.

Insoluble

Unable to dissolve into a particular solvent. Example: Sand is insoluble in water and settles at the bottom.

Saturated Solution

A solution that contains the maximum amount of dissolved solute at a given temperature. Example: Sweet tea that cannot dissolve any more sugar crystals.

Filtration

A technique using a barrier with tiny holes to separate an insoluble solid from a liquid. Example: Using a coffee filter to separate coffee grounds from brewed coffee.

Distillation

A separation method that boils a liquid mixture and condenses the vapor to collect pure liquid. Example: Purifying seawater into fresh drinking water.

Chromatography

A method used to separate different colored pigments based on how fast they travel through paper. Example: Separating black marker ink into blue and yellow dyes.

Decanting

Carefully pouring off a liquid to separate it from a heavier settled solid. Example: Pouring off liquid water after muddy sediment sinks to the bottom.

Acid

A substance with a sour taste that turns blue litmus paper red and has a pH below 7. Example: Citric acid in lemon juice or acetic acid in vinegar.

Base (Alkali)

A substance that feels slippery, tastes bitter, and has a pH above 7; alkalis dissolve in water. Example: Soapy water or bleach.

pH Scale

A measurement scale from 0 to 14 showing how acidic or basic a substance is. Example: Battery acid is around pH 1, pure water is 7, and bleach is around 13.

Neutral Substance

A substance with a pH of exactly 7 that is neither an acid nor a base. Example: Pure distilled water.

Indicator

A chemical dye that changes color depending on the acidity or alkalinity of a liquid. Example: Red cabbage juice changing color when mixed with vinegar.

Universal Indicator

A liquid mixture of dyes that shows the full spectrum of pH by changing into specific colors. Example: It turns red in strong acids and purple in strong bases.

Neutralisation

A chemical reaction where an acid and a base cancel each other out to make salt and water. Example: Taking an antacid tablet to soothe an acidic stomach ache.

Combustion

A rapid chemical reaction between a fuel and oxygen that produces heat and light. Example: Natural gas burning on a kitchen stove.

Rusting

The slow corrosion of iron or steel when exposed to both oxygen and water. Example: An old bicycle chain turning orange-brown after being left in the rain.

Corrosion

The gradual destruction of a metal caused by chemical reactions with substances in the air or water. Example: Tarnishing of silver jewelry over time.

Chemical Formula

A shorthand way of showing the elements and number of atoms in a compound. Example: NaCl is the chemical formula for ordinary table salt.

Word Equation

A simple way of writing a chemical reaction using the names of substances and an arrow. Example: Iron + Oxygen -> Iron Oxide.