Elements Compounds and Molecules

Front

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, oxygen, and gold.

Front

What is a compound?

Back

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

Front

What is a molecule?

Back

A molecule is the smallest unit of a chemical compound that retains its chemical properties. It consists of two or more atoms bonded together.

Front

What is a mixture?

Back

A mixture is a combination of two or more substances that are not chemically bonded. Each substance retains its own properties. Examples include air and salad.

Front

How can mixtures be separated?

Back

Mixtures can be separated by physical changes, such as filtration, evaporation, or distillation.

Front

What is the chemical formula for water?

Back

The chemical formula for water is H2O, which indicates it is made of two hydrogen atoms and one oxygen atom.

Front

What is the difference between a molecular element and a molecular compound?

Back

A molecular element consists of two or more atoms of the same element bonded together (e.g., O2), while a molecular compound consists of atoms of different elements bonded together (e.g., CO2).

Front

What is krypton?

Back

Krypton is an element, represented by the symbol Kr, and is a noble gas.

Front

What are the main components of air?

Back

The main components of air are nitrogen (about 78%) and oxygen (about 21%), along with small amounts of other gases.

Front

What is the difference between physical and chemical properties?

Back

Physical properties can be observed without changing the substance (e.g., color, boiling point), while chemical properties describe how a substance reacts with other substances.