Chemical Reactions

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What is an element?

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An element is a pure substance that cannot be broken down into simpler substances by chemical means. Examples include oxygen (O), hydrogen (H), and gold (Au).

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What is a compound?

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A compound is a substance formed when two or more elements chemically bond together. Examples include water (H2O) and carbon dioxide (CO2).

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What is a physical change?

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A physical change is a change that affects one or more physical properties of a substance without altering its chemical composition. Examples include melting, freezing, and dissolving.

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What is a chemical reaction?

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A chemical reaction is a process that leads to the transformation of one set of chemical substances to another, resulting in the formation of new substances.

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What is pH?

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pH is a scale used to measure the acidity or basicity of a solution. A pH of 7 is considered neutral, below 7 is acidic, and above 7 is basic.

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What is an acid?

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An acid is a substance that donates protons (H+) in a chemical reaction and has a pH less than 7. Examples include hydrochloric acid (HCl) and sulfuric acid (H2SO4).

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What is a base?

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A base is a substance that accepts protons (H+) or donates hydroxide ions (OH-) in a chemical reaction and has a pH greater than 7. Examples include sodium hydroxide (NaOH) and ammonia (NH3).

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What is a neutral substance?

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A neutral substance is one that has a pH of 7, meaning it is neither acidic nor basic. Pure water is a common example.

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What happens during a chemical change?

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During a chemical change, the chemical bonds between atoms are broken and new bonds are formed, resulting in the creation of new substances.

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What are some examples of physical changes?

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Examples of physical changes include breaking glass, tearing paper, chopping vegetables, and dissolving sugar in water.