Chapters 17/23 Classification of Matter

Pure Substance One substance and only one substance is in the material. A pure substance can be an element or a compound.

Element A substance found on the periodic table. An element cannot be broken into a smaller substance and remain a substance.

Compound A pure substance that is a chemical combination of two or more elements.

Compound A compound has these characteristics: 1. They are hard to separate into their components. 2. They are chemically combined to form a new substance. 3. The components must be in proportion to each other.

Compound Sodium metal + chlorine gas yields sodium chloride (table salt)

Mixtures A physical combination of two or more pure substances. The substances remain what they were, but may change size, shape or state of matter

Mixtures A mixture has 3 characteristics: 1. It can be easily separated. 2. It is physically combined so all substances retain their original properties. 3. Combined substances are not in certain proportions: a little or a lot can be combined to form the same type of mixture.

A mixture can be easily separated in three ways Sifting: particles are “picked” apart Evaporation: A liquid is heated to the gaseous state and move from container; solid(s) remain in container Distillation: A liquid as it evaporates is collected another container and cooled to a liquid again, leaving impurities in original container

Types of Mixtures There are 2 types of mixtures : Heterogeneous Homogeneous

Heterogeneous Mixture A mixture where individual substances can easily be identified just by looking at the mixture. The particles of a heterogeneous mixtures are called a precipitate.

Heterogeneous Mixtures 2 types Colloid: Particles in the mixture stay suspended Suspension: Particles in the mixture settle out to the bottom

Homogeneous mixtures A mixture that looks the same throughout.

Homogeneous Mixtures These mixtures can also be called solutions. A solution consists of two parts: –Solute: the substance that is dissolved –Solvent: the substance that causes the dissolving

Special Solutions Air: a gaseous solution Alloy: a solid solution of metals

Solubility Solubility is the rate at which a given amount of solute is dissolved in a given amount of solvent at a given temperature. Solubility depends on 1. The temperature of the solvent and/or solute 2. The size of the solute particles 3. Whether or not the mixture is agitated.

Classification of Solutions Solutions can be –Diluted: much solvent; little solute –Concentrated: much solute; little solvent Solutions can also be classified as –Saturated: No more solute can be dissolved into solution –Unsaturated: more solute can be dissolved into solution –Supersaturated: more solute than normal has been dissolved into solution.

Physical Changes A physical change changes the appearance of the substance only. The substance remains what it was originally. A physical change can be 1. a change in size 2. a change in shape 3. a change in state of matter

Chemical Change A chemical change in a substance results in a new substance being formed. The new substance will have completely difference properties from the material that was combined

Chemical Change A chemical change can be detected with the following signs: 1. There is a complete color change. 2. Gas is released upon the combination 3. A precipitate is formed when two clear liquids are combined 4. Energy is transformed: Exothermic: heat is given off Endothermic: heat is taken in