Elements, Compounds, Mixtures

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What is an element?

Back

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

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What is a compound?

Back

A compound is a substance formed when two or more elements chemically bond together. For example, water (H2O) is a compound made of hydrogen and oxygen.

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What is a mixture?

Back

A mixture is a combination of two or more substances that are not chemically bonded. Examples include air, salad, and sand and salt.

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What is the difference between a compound and a mixture?

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A compound is a chemical combination of elements, while a mixture is a physical combination of substances that retain their individual properties.

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What is a homogeneous mixture?

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A homogeneous mixture is a mixture that has a uniform composition throughout. An example is saltwater.

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What is a heterogeneous mixture?

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A heterogeneous mixture is a mixture where the components can be seen and are not uniform. An example is a salad.

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What is the law of conservation of mass?

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The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction. The total mass of reactants equals the total mass of products.

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What is a chemical change?

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A chemical change is a change that results in the formation of new chemical substances. Examples include rusting iron and burning wood.

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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 ice and dissolving sugar in water.

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What are the three states of matter?

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The three states of matter are solid, liquid, and gas. Each state has distinct properties.