Chemical Changes

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Chemical Change Noun

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[kem-i-kuhl cheynj]

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Chemical Change

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A process where matter transforms into a new substance with different chemical properties, occurring at a molecular level.

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Example: This diagram shows a chemical change by illustrating how atoms in the starting molecules (reactants) rearrange to form completely new molecules (products).

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Chemical Reaction Noun

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[kem-i-kuhl ree-ak-shun]

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Chemical Reaction

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A process where molecules interact to form new substances by breaking and creating new chemical bonds between atoms.

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Example: Mixing iron powder and hydrochloric acid causes a chemical reaction, creating a new substance and releasing gas bubbles as evidence of a chemical change.

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Reactant Noun

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[ree-ak-tuhnt]

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Reactant

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A substance that is present at the start of a chemical reaction and is consumed to form a product.

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Example: This diagram shows that reactants (like methane and oxygen on the left) are the starting materials that combine and change during a chemical reaction.

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Product Noun

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[prod-uhkt]

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Product

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A new substance that is formed as the result of a chemical reaction between two or more reactants.

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Example: This diagram shows that in a chemical reaction, the new substances formed at the end, like carbon dioxide and water, are called the products.

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Chemical Properties Noun

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[kem-i-kuhl prop-er-teez]

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Chemical Properties

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Characteristics of a substance that describe its ability to undergo changes that transform it into a different substance.

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Example: This diagram shows that iron has the chemical property of reacting with oxygen and water to form a new substance, rust, which is a chemical change.

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Precipitate Noun

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[pri-sip-i-teyt]

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Precipitate

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An insoluble solid that emerges from a liquid solution as a result of a chemical reaction.

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Example: This image shows a chemical reaction where a solid, called a precipitate, forms and settles at the bottom of a liquid solution.

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Combustion Noun

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[kuhm-buhs-chuhn]

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Combustion

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A rapid chemical reaction between a substance and an oxidant, usually oxygen, to produce heat and light.

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Example: This diagram shows that a hydrocarbon (fuel) chemically reacts with oxygen to produce new substances: carbon dioxide, water, and energy as heat and light.

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Molecule Noun

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[mol-i-kyool]

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Molecule

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A group of two or more atoms held together by chemical bonds, representing the smallest unit of a compound.

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Example: This diagram shows a water molecule, which is made of two hydrogen (H) atoms chemically bonded to one oxygen (O) atom.

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Atom Noun

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[at-uhm]

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Atom

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The basic and smallest unit of a chemical element, whose bonds are rearranged during a chemical reaction.

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Example: This diagram shows a Sodium atom, with a central nucleus (Na) and electrons in shells. Its single outer electron makes it reactive in chemical changes.

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Methane Noun

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[meth-eyn]

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Methane

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A simple hydrocarbon and the main component of natural gas, which combines with oxygen during combustion.

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Example: This image shows a model of a methane molecule (CH₄), which has one central carbon atom bonded to four hydrogen atoms.