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CHEMISTRY CHAPTER 1
(Matter & Change)
Chemistry is the study of the composition, structure, and properties of matter and the changes it undergoes.
Matter is anything that has mass and takes up space
Mass is a measure of the amount of matter.
An atom is the smallest unit of an element that maintains the properties of that element
All matter is made up of atoms
Elements are pure substances made of only one kind of atom (all elements can be found on the periodic chart)
Ex: H, O, gold, silver
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A compound is a substance that is made from the atoms of two or more elements that are chemically bonded
Ex: water, which is compound of H and O
explosive gas + flammable gas non-flammable
Physical properties are those, which can be observed or measured changing the identity of the substance.
Ex: Boiling point, freezing point, density, color, smell. .
Physical changes are those, changes that do not involve a change in the identity of the substance
Ex: Boiling, freezing, shape, phase, orientation
Chemical properties relate to a substance's ability to undergo changes that transform it into different substances.
Ex: Flammability, reaction with other materials . . .
During chemical changes (chemical reaction) one or more substances are converted into different substances
Ex: burning; reacted. . .
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How can identify a change as being chemical or physical?
- During a physical change a substance is simply changing phase, shape, or position, as such it retains its identity.
- During a chemical change a substance is being changed into a completely different substance, with a new identity.
Chemical changes are always accompanied by energy changes [energy is released or taken in]
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The Phases (or States) of Matter are solid, liquid, gas, and plasma.
A Solid has a definite volume & a definite shape [table top]
A Liquid has a definite volume but no definite shape [water]
A Gas has no definite shape and no definite volume [smoke]
There is a fourth state of matter called plasma. Plasma is a high-temperature state in which atoms loose their electrons.
Ex: fluorescent bulbs
A mixture is a blend of two or more kinds of matter, each of which retains its own identity and properties
Ex: Salt water, coffee . . .
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Some mixtures are uniform in composition, these are said to be homogeneous (the same color, shape, or texture)
Ex: salt water, coffee . . .
Mixtures that are not uniform throughout are said to be heterogeneous (different color, shape, or texture)
Ex: fruitcake, soil . . .
A pure substance is homogeneous and has a fixed composition (all elements and compounds)
Ex: water, gold
The vertical columns of the periodic table are called groups or families
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The horizontal rows of elements in the periodic table are called periods.
A metal shows a luster and is a good conductor of heat and electricity
A nonmetal is usually a poor conductor of heat and electricity
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A metalloid is an element that has some characteristics of metals and some characteristics of non-metals.
Ex: All the elements on the line between metals and non-metals are considered to be metalloids.
Inert - nonreactive
Ex: All of the noble gases (family 18) are inert because they have an octet