Chemistry: The Study of Matter

Chemistry is the study of matter. Matter is anything that has mass and volume. Matter comes in a variety of forms. - elements - compounds - mixtures Matter comes in a variety of phases. - solids - liquids - gases Chemistry: The Study of Matter

Elements and compounds are examples of pure forms of matter. A pure form of matter is called a substance. An impure form of matter is called a mixture. All Matter Pure Matter Impure Matter Elements CompoundsMixtures substances Chemistry: The Study of Matter

Elements and compounds have a definite composition and a unique set of properties. All copper in the universe … - is shiny - is orange - melts at 1084 o C - has a density of 8.96 g/cm 3 - has a specific heat J/g o C - is a very good electrical conductor Chemistry: The Study of Matter

Elements and compounds are homogeneous which mean their composition is uniform throughout. The copper here …has the same composition as the copper here! Chemistry: The Study of Matter

An element is a pure form of matter that cannot be decomposed by ordinary chemical or physical means. A compound is a pure form of matter that is composed of two or more different elements that are chemically combined (bonded) in a definite ratio. A compound cannot be decomposed by physical means but can be decomposed by chemical means. Chemistry: The Study of Matter

Oxygen (O 2 ) is an element. Silicon (Si) is an element. Aluminum (Al) is an element. Chemistry: The Study of Matter

Table salt (NaCl) is a compound. Water (H 2 O) is a compound. Table sugar (C 12 H 22 O 11 ) is a compound. Chemistry: The Study of Matter

Mixtures are not pure forms of matter. A mixture is not a substance because all not all samples are alike in their composition. A mixture is a form of matter that is composed of two or more elements, two or more compounds, or a mixture of elements and compounds. A mixture is physically combined and its components need not be composed in a definite ratio. Chemistry: The Study of Matter

A mixture can be homogeneous. In a homogeneous mixture all of the different components are uniformly distributed (there is even mixing of the different components). Chemistry: The Study of Matter The salt-water mixture here …has the same composition as the salt-water mixture here!

A mixture can be heterogeneous. In a heterogeneous mixture the different components are not uniformly distributed (there is uneven mixing of the different components). The iron-sulfur mixture here …has the a different composition from the iron-sulfur mixture here! Chemistry: The Study of Matter

Solutions are the only type of homogeneous mixture! Suspensions are a type of heterogeneous mixture! Colloids are a type of heterogeneous mixture! Chemistry: The Study of Matter

A mixture of two or more gases is always homogeneous. Air is a homogeneous mixture. Air is composed of nitrogen gas, oxygen gas, and argon gas. Air is a solution. Chemistry: The Study of Matter

Alloys are homogeneous mixtures of two or more metals! Alloys are solutions. Brass, bronze, sterling silver, and stainless steel are examples of alloys. Chemistry: The Study of Matter

On earth, all forms of matter usually exist in one or more of three phases – solid, liquid, and/or gas. Chemistry: The Study of Matter

A solid is sample of matter that has a definite shape and a definite volume. Crystalline “true” solids will melt at a single specific temperature. Amorphous solids are solids that “melt” over a range of temperatures. Chemistry: The Study of Matter Glass is an amorphous solid. When strongly heated is gets soft and gooey. Glass “melts” over a range of temperatures.

A liquid is a sample of matter that has no definite shape but that does have a definite volume. A liquid will take the shape of its container. A gas is a sample of matter that has neither a definite shape nor a definite volume. A gas will take the shape and volume of its container. Chemistry: The Study of Matter

Plasma is a phase of matter that consists of ionized gases and readily exists in stars. Chemistry: The Study of Matter

When a substance is dissolved in water it is often said to be in the aqueous “phase”. Although not a true phase of matter, aqueous substances behave as a single phase of matter. Chemistry: The Study of Matter

The Law of Conservation of Matter states that matter can neither be created nor destroyed and thus the total mass of a system must remain constant. Matter can undergo changes in form and/or in phase but the total mass remains the same. When a chemical or physical reactions takes place the total mass before and after the reaction is the same. Mass is conserved. Chemistry: The Study of Matter

This is a car that runs by burning hydrogen gas. Chemistry: The Study of Matter

Ex. (1) Water can be produced by the combustion of hydrogen gas in air. When the hydrogen gas burns, it reacts with oxygen gas from the air. If g of hydrogen gas burns in air (reacts with oxygen gas) to produce g of water, then how many grams of oxygen gas was used up from the air? Chemistry: The Study of Matter The total mass before must equal the total mass after g of hydrogen + X g of oxygen = g of water X = g of oxygen