pure substances and mixtures

Question 1

what is a pure substance

Answer 1

A pure substance is a material that consists of only one type of particle (atoms, molecules, or ions). Pure substances have consistent properties and cannot be separated into other substances by physical methods.

Question 2

types of pure substanes

Answer 2

Elements:
Made of only one kind of atom.
Cannot be broken down into simpler substances by chemical means.
Examples: Oxygen (O), Carbon (C), Gold (Au), Sodium (Na).

Compounds:
Made up of two or more types of atoms chemically bonded together.
Have a fixed ratio of elements.
Can be broken down into simpler substances by chemical reactions.
Examples: Water (H₂O), Sodium chloride (NaCl), Carbon dioxide (CO₂).

Question 3

Characteristics of Pure Substances

Answer 3

Fixed Composition: Every sample of a pure substance has the same properties and composition.

Constant Melting/Boiling Point: Pure substances have a specific temperature at which they melt or boil.

Homogeneous: A pure substance looks uniform throughout, no visible difference in composition.

Question 4

mixture

Answer 4

A mixture is a combination of two or more pure substances in which each substance retains its individual chemical properties. Mixtures can be separated into their components by physical means.

Question 4

types of mixtures

Answer 4

Heterogeneous Mixtures:

In a heterogeneous mixture, the components are not evenly distributed. You can usually see the different parts of the mixture. Examples:
Salad
Sand and water
Oil and water
Homogeneous Mixtures (Solutions):

In a homogeneous mixture, the components are evenly distributed, and you cannot see the individual substances. The mixture appears as a single phase. Examples:
Salt dissolved in water
Air (a mixture of gases)
Steel (a mixture of iron and carbon)

Question 5

Separation Methods for Mixtures

Answer 5

Filtration: Used to separate solid particles from a liquid or gas (e.g., separating sand from water).

Distillation: Separates substances based on their boiling points (e.g., separating salt from water).

Evaporation: Used to remove a liquid from a solid (e.g., evaporating water from saltwater).

Chromatography: Separates different substances based on their solubility and interaction with a stationary phase (e.g., separating pigments in ink).