Chemistry Chapter2

Topics: Chemistry, Energy, Chemical reaction Pages: 6 (955 words) Published: July 31, 2013
Extracted from the notes of Dr. Sylvia Eramis Dasalla
San Pedro College

(CHEM 100)
Chapter 2
Matter & Energy
Matter - is anything that occupies space and has mass
Mass is the measure of the amount of matter in an object.
Weight is the measure of the gravitational force for the matter in an object. Phases of Matter
* Solid (s)
* Liquid (l)
* Gas (g)

Properties of Solids, Liquids, and Gases
Property | Solid | Liquid | Gas |
Shape | Definite | Takes the shape of the container | Takes the shape of the container | Volume | Definite | Definite | Fills the volume of the conatiner | Arrangement of Particles | Fixed, very close | Random, close | Random, far apart | Interaction between particles | Very strong | Strong | Essentially none | Movement of particles | Very slow | Moderate | Very fast | Examples | Ice, salt, iron | Water, oil, vinegar | Water vapor, helium, air |

Physical Properties - are those properties of a substance that can be observed without changing the substance. Examples:
* Color
* Mass
* Weight
* Melting point of Ice
* Boiling point of water
* Density

Chemical properties are those properties of a substance that can only be studied by forming new substances. Example:
reactivity of metals

Na (s) + Cl2(g) → NaCl(s)

Note: Once the substance has undergone chemical change,
the original chemical substance will disappear and a new substance is formed.

Physical change
* Physical Change – a change in matter where the composition of a substance is retained. It can be a change in appearance, size or phase
chopping of wood tearing of paper
melting of candlesublimation of mothballs
* Phase change – a kind of physical change that involves a transformation from one phase to the other.
Example: phase changes of water

Chemical Change
* a change in the composition and identity of a substance forming a new substance in a chemical reaction. * Accompanied by chemical evidences such as
* Precipitation
* Evolution of heat and light
* Evolution of gas
* Dissolution
* Conduction of electricity
* Change in color, odor, & taste
Example of a Chemical Change
* Nickel, a solid metal, is mixed with a colorless solution of hydrochloric acid in a test tube. * The nickel is slowly eaten away, the colorless solution turns green, and a colorless gas bubbles out of the test tube.

The classification of matter

* Pure Substance: Matter that is uniform in its chemical composition and properties.
Examples: Sugar, table salt, and water
* Mixture: A blend of two or more pure substances in any ratio, each retaining their identity.
Examples: syrup, milk, saline & vinegar

Physical changes can separate mixtures into one or more pure substances. Evaporation and condensation can separate water from sugar.

* Element: Pure substance that cannot be broken down chemically into simpler substances. Examples: hydrogen and oxygen * Chemical Compounds: Two or more elements combined chemically in specific ratios to form a pure substance.

Examples: sugar, water & table salt
* Chemical changes can separate chemical compounds into elements.

* Elements are composed of one type of atom.
* Atoms are the smallest particles of an element.
* Elements are represented by chemical symbols. Ex: Cl, H, Mg

* Compound:
* Elements are present in fixed parts by mass (fixed proportions) * Its properties are different from those of its component elements * can be separated only by chemical means into their pure components Many compounds exist as groups of atoms bonded together as units called molecules....
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