Chapter 2

MatterSubstanceElementCompoundMixture Heterogeneous Mixture ColloidSuspension Homogeneous Mixture

Matter Definition: Anything that has mass and volume Chemistry is the study of matter and the transformations it undergoes Everything can be classified as matter, energy, or spaceenergy

Transformations Physical changes – Some properties of matter change but the composition never does Chemical changes – Changes that produce matter with a different composition than the original matter

Chemical Changes Chemical changes are a change the composition of matter. When matter changes it is called a chemical reaction during which one or more substances are changed to one or more new substanceschemical reaction

Chemical Reaction Chemical reactions take advantage of the chemical properties of a substance to alter its composition. Above is an example of a chemical reaction between iron and aluminum. This specific reaction is known as the thermite reaction and reaches temperatures of over 2500°C. chemical properties Fe 2 O 3 + 2Al → 2Fe + Al 2 O 3 + heat Reactants  Products

Chemical Properties Definition: The ability of a substance to undergo a specific chemical change Mixtures do not have chemical properties, but the substances in mixtures do have chemical properties. Mixtures can be separated based upon chemical properties and compounds (a type of substance) can be separated based on chemical properties

Physical changes There are two types of physical changes – Reversible – Irreversible Reversible changes are most often changes of physical state physical state Irreversible changes are most often mechanical changes mechanical changes

Mechanical Changes Mechanical changes are usually described as irreversible physical changes. Some of these changes include: – Grinding – Cutting – Breaking – Crushing All of these actions change the physical nature of matter yet do not change the state or composition of the matter.

Physical States Matter exists in 3 major states – Solid – Liquid – Gas Changes between these three states are always reversible and do not change the composition of the matter Ex. Ice  water  steam (all states of water)

Energy Energy is the potential to do work or produce heat It is easy to confuse energy with sources of energy. The sun produces light and heat which are both forms of energy but the sun itself is made up of matter.

Elements Definition: Simplest form of matter that has unique chemical properties Elements are homogeneous substances in which every atom of the substance is exactly the same. 94 elements occur naturally on the earth.

Compounds Definition: a substance that contains two or more elements chemically combined in a fixed proportion. fixed proportion Like elements compounds have unique properties and cannot be broken down by physical means, however unlike elements, compounds can be broken down chemically.broken down chemically

Fixed Proportions Fixed proportions means that the ratio of each type of element in a compound must be the same. Example – H 2 O is a compound called water – HO is a compound called hydroxide – H 2 O 2 is a compound called peroxide All of these compounds are made of the same elements but their chemical properties differ greatly according to the proportions of the elements present

Substances Definition: Substances have uniform and definite composition Uniform composition means that at any given spot in the sample of matter the type of matter present will be exactly the same as any other given point Definite composition means there is only one way the substance can be made. A molecule of water can only be made with 2 Hydrogen atoms and 1 oxygen atom.

Mixtures Definition: A physical blend of two or more components Matter is classified as a mixture if it fails to meet one or more of the two requirements to be a substance (uniform and definite composition)

Homogeneous Mixture (Solutions) Definition: a mixture in which the composition is uniform throughout Homogeneous mixtures will have only one phase Despite only having one phase a mixture is able to be seperated by physical processes

Heterogeneous Mixture Definition: A mixture in which the composition is not uniform throughout Heterogeneous mixtures have 2 or more phases The components of a heterogeneous mixture are able to be separated by physical means

Colloids Description: solute particles are small enough to remain mixed and pass through filter paper, but they are visible at least in a Tyndall test Often colloids have cloudy or milky appearances Colloids are in a gray area between homogeneous and heterogeneous but for this class they will be considered heterogeneous

Suspensions Description: have larger particles which settle out over time and can be filtered out of the mixture Classified as a heterogeneous mixture