Intro to chemistry

Chemistry
is the study of materials and the changes that materials undergo.
Change
?, (called delta)
Matter
is the physical material of the universe; it is anything that has mass and volume
Property
is any characteristic that allows us to recognize a particular type of matter and to distinguish it from other types
Elements
are what matter is composed of
Atoms
are the small building blocks of matter; each element is composed of a kind of atom
Molecules
are two or more atoms joined together in specific shapes
3 physical states of matter are
1.Gas (has no fixed volume or shape)
2.Liquid (has a fixed volume but no shape)
3.Solid (has a fixed volume and fixed shape)
the 3 compositions of matter are
1.Element (the most simple substance, composed of 1 atom)
2.Compound (composed of 2 or more atoms)
3.Mixture (Combinations of 2 or more substances in which each substance retains its own chemical identity)
Pure substance
is matter that has distinct properties and a compositions that does not vary from sample to sample, EX: Water or table salt (sodium chloride)
Law of constant composition
(or definite proportions) is that the compositions of a pure compound is always the same
Solutions
are homogenous mixtures, or mixtures that are uniform throughout, EX: Sugar water, where the sugar dissolves into the water, or air
Physical properties
can be observed without changing the identity and composition of the substance, EX: color, odor, density, melting point, boiling point, and hardness
Chemical properties
describe the way a substance may change or react to form other substances
Intensive properties
are properties like temperature, melting point and density. They do not depend on the amount of the sample being examined, and can help identify the sample
Extensive properties
like mass and volume depend on the quantity of the sample. They relate to the amount of substance present
Physical change
is when a substance changes its appearance but not its composition
Changes of state
are all physical changes (EX: liquid to gas or liquid to solid)
Chemical change
(or chemical reaction) a substance is transformed into a chemically different substance
Scientific law
is a concise verbal statement or a mathematical equation that summarizes a broad variety of observations and experiences; based on observation, concise statement, descriptive, explains what, not why
Theory
is an explanation of the general causes of certain phenomena, with considerable evidence or facts to support it
The scientific method
is a general approach to solving problems that involves making observations, seeking patterns in the observations, formulating hypotheses to explain the observations, and testing these hypotheses by further experiments
Hypothesis
is a tentative explanation; an educated guess
SI
is used for scientific measurements
There are seven SI base units from which all other units are derived
1.Length – m (meter)
2.Amount – mol (mole)
3.Mass – kg (kilogram)
4.Candela – cd (luminous intensity)
5.Time – s (second)
6.Temperature – K (kelvin)
7.Current – A (ampere)
Mass
is a measure of the amount of material in an object
Celsius scale
is the everyday scale of temperature in most countries. 0 °C is the freezing point of water and 100 °C is the boiling point of water
Kelvin scale
is the SI temperature scale. 0 K is absolute zero, or the lowest attainable temperature. That’s -273.15 °C
Density
is a property of matter that is widely used to characterize a substance. Density = Mass/Volume
measured quantities
Uncertainties always exist; are generally reported in such a way that only the last digit is uncertain
Precision
is a measure of how closely individual measurements agree with one another
Accuracy
refers to how closely individual measurements agree with the correct, or “true”, value
Significant figures
are all digits of a measured quantity, including the uncertain one
Dimensional analysis
is when you carry units through all calculations. Units are multiplied together, divided into each other, or cancel each other out
Conversion factor
is a fraction whose numerator and denominator are the same quantity expressed in different units
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