Midterm 1 Flashcards
Matter
The physical material of the universe. Anything that has mass and occupies space.
Chemistry
The study of matter and the changes that matter undergoes.
Property
Any characteristic that allows us to recognize a particular type of matter and to distinguish it from other types.
Elements
100 substances that when combined create a tremendous variety of matter on Earth.
Atoms
The almost infinitesimally small building blocks of matter.
Molecules
Two or more atoms are joined together in specific shapes.
States of Matter
The forms that a sample of matter can be in (gas, liquid, solid) some of their observable properties.
Gas
Has no fixed volume or shape; conforms to shape of its container.
Liquid
Distinct volume that is independent of its container, but has no specific shape.
Solid
Has definite shape and volume
Pure Substance
Matter that has distinct properties and a composition that does not vary from sample to sample.
Elements
Substances that cannot be decomposed into similar substances.
Compounds
Substances composed of two or more elements.
Mixtures
Combinations of two or more substances in which each substance retains its chemical identity.
Law of Constant Composition (Law of Definite Proportions)
The observation that the elemental composition of a compound is always the same. Law stated in 1800s by Joseph Louis Proust.
Solutions
Homogenous mixtures (uniform thought substance). Can be solid, liquid or gas.
Physical Properties
Properties that can be observed without changing the identity and the composition of the substance.
Color, odor, density, melting point, boiling point and hardness (malleability).
Chemical Properies
Properties that describe the way a substance may change, or react, to form other substances.
Flammability
Intensive Properties
Properties that do not depend on the amount of sample being examined. Can be used to identify substances.
Temperature, Melting Point
Extensive Properties
Properties that depend on the amount that is being sampled.
Volume and Mass.
Physical Change
When a substance changes its physical appearance but not its composition.
Evaporation of water
Changes of state
Chemical Change (Chemical Reaction)
When a substance is transformed into a chemically different substance.
Hydrogen burning in the air, Combines with oxygen to form water.
Metric system
Units used for scientific measurements
Distillation
A process that depends on the different abilities of substances to form gases.
An important method of separating the components of a homogeneous mixture.
Scientific law
A concise verbal statement or mathematical equation that summarizes a broad variety of observations and experiences.
They describe the behavior of matter.
S I units
International French system of units
Mass
Kilogram
KG
Length
Meter
M
Time
Second
SEC
Temperature
Kelvin
K
Amount of substance
Mole
mol
Electric current
Ampere
A
amp
Luminous intensity
Candela
cd
Mass
A measure of the amount of material in an object.
Absolute zero
Zero on Kelvin scale
Lowest attainable temperature
-273.15°C
Density
The amount of mass in a unit volume of a substance
Density equals mass over volume.
Precision
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
All digits of a measured quantity including the uncertain one.
Conversion factor
Fraction whose numerator and denominator are the same quantity expressed in different units.
Átomos
Indivisible or uncuttable
Law of constant composition
In a given compound the relative numbers and kinds of atoms are constant.
The law of conservation of mass
The total mass of materials present after a chemical reaction is the same as the total mass present before the reaction.
The Law of multiple proportions
If two elements A and B combined to form more than one compound the masses of B that can combine with a given mass of A are in the ratio of small whole numbers.
Dalton’s atomic theory
- Each element is composed of extremely small particles called atoms
- All atoms of a given element are identical but the atoms of one element are different from the atoms of all other elements.
- Atoms of one element cannot be changed into atoms of different elements by chemical reactions; atoms are neither created or destroyed in chemical reactions.
- Compounds are formed when atoms of more than one element combined a given compound always has the same relative number and kind of atoms.
Cathode rays
The radiation that was produced between the electrodes when a high-voltage was applied to the electrodes in the tube.
