Classification of Matter

Mixtures, elements, compounds Scientists like to classify things. One way that scientists classify matter is by its composition. Ultimately, all matter can be classified as mixtures, elements and compounds.

Why isn’t it a good idea to classify matter by its phases? Because one kind of substance can exist in more than one phase – such as H20. And matter changes phases rather easily.

Why isn’t matter classified according to its physical characteristics, such as color? Scientists wouldn’t find it very useful to group gold, sunflowers, and the sun together.

Composition of Matter Flowchart yes no Can it be physically separated? MIXTURE PURE SUBSTANCE Is the composition uniform? no yes Can it be chemically decomposed? no yes Homogeneous Mixture (solution) Heterogeneous Mixture Compound Element

Classifying Matter by Composition Mixtures- are a blend of two or more kinds of matter, each of which retains its own identity and properties. A mixture is mixed together physically. Variable composition, often expressed by a percent composition by mass or volume (Ex. 5% salt and 95% water

Classifying Matter by Composition Homogeneous – matter with a uniform composition. They are also called solutions. Ex. Salt water and Kool –aid Heterogeneous - matter without a uniform composition

Homogeneous Mixtures A mixture that appears to be the same throughout. It is “well mixed.” The particles that make up the mixture are very small and not easily recognizable.

Examples of homogeneous mixtures Milk, toothpaste, and mayonnaise are homogeneous mixtures. They are also colloids.

Colloids In a colloid the particles are mixed together but not dissolved. The particles are relatively large and are kept permanently suspended.

Colloids A colloid will not separate upon standing. The particles are constantly colliding, and this allows a colloid to scatter light – thus colloids often seem cloudy.

Solutions A solution is a type of homogeneous mixture formed when one substance dissolves in another. It is the best mixed of all mixtures. A solution always has a substance that is dissolved and a substance that does the dissolving. The substance that is dissolved is the solute and the substance that does the dissolving is the solvent.

Ocean water is a solution

Water as a solvent Many liquid solutions contain water as the solvent. Ocean water is basically a water solution that contains many salts. Body fluids are also water solutions.

Metals dissolved in metals are called alloys. Types of solutions Solute Solvent Example Gas Air (oxygen in nitrogen) Liquid Soda water (carbon dioxide in water) Solid Ocean water (salt in water) Solid Gold jewelry (copper in gold) Metals dissolved in metals are called alloys.

Air is a solution of oxygen and other gases dissolved in nitrogen

Alloys Stainless steel is a mixture of iron and chromium. Brass is an alloy of copper and zinc.

Classifying Matter by Composition A heterogeneous mixture is not the same throughout (not uniform). Considered the “least mixed.” Does not appear to be the same throughout. Particles are large enough to be seen and to be separated from the mixture.

Examples of heterogeneous mixtures Sand and pebbles, gravel, soil, rocks Oil and water, salad, M & M’s, Chocolate cookies.

Granite is a heterogeneous mixture.

Mixtures are separated by their physical properties. Separating Mixtures Mixtures are separated by their physical properties. Primary methods of separating mixtures are: filtration distillation centrifuge chromatography

Separating Mixtures Filtration is a method used to separate the components of mixtures that contain an insoluble solid and a liquid. Example: sand and water

Separating Mixtures Distillation is a method of separating substances in a mixture by evaporation of a liquid and subsequent condensation of its vapor. Example: desalination of salt water

Distillation Apparatus

Separating Mixtures Centrifuge Used to separate solid-liquid mixtures such as those in blood. The centrifuge spins rapidly and causes the solid to settle to the bottom. Ex. Separating blood

Separating Mixtures Chromatography is a method of separating mixtures that uses a stationary phase and a mobile phase. Paper chromatography can be used to separate pigments because they move at different rates on the paper.

Composition of Matter Flowchart yes no Can it be physically separated? MIXTURE PURE SUBSTANCE Is the composition uniform? no yes Can it be chemically decomposed? no yes Homogeneous Mixture (solution) Heterogeneous Mixture Compound Element

Classifying Matter by Composition Pure Substances- A pure type of matter that does not vary from sample to sample. Includes elements and compounds

Classifying Matter by Composition 1-Elements- simplest kind of matter, made of one type of atom An atom is the smallest unit of an element that maintains the properties of that element. Cannot be broken down into simpler substances by ordinary chemical means Ex. gold, copper, oxygen (on the periodic table)

Classifying Matter by Composition 2-Compounds – matter composed of the atoms of two or more elements chemically bonded Compounds can be broken down by chemical methods When they are broken down, the components have completely different properties than the compound. Ex. Sugar, salt, water, carbon dioxide

Compounds Compounds are also pure substances. But compounds are made from more than one element. Water is a compound. Water can be broken down into simpler substances – hydrogen and oxygen.

Classify It copper wire, aluminum foil

Classify It element Magnesium- hetero. mixture Pizza - compound Homo. (solution) Examples: Magnesium- Pizza - Calcium chloride Orange juice Club soda

States of matter Solid- matter that can not flow and has definite volume and shape Liquid- definite volume but no definite shape and can flow Gas- a substance without definite volume or shape and can flow. Plasma- a substance that is similar to a gas, but loses electrons due to its high temperature

States of Matter Definite Volume? Definite Shape? Particle position and movement Packed tightly, vibrate about fixed pt Solid YES YES Close together, can move past each other - flow Liquid NO YES Far apart, move rapidly - flow Gas NO NO