Chapter 1: Essential Ideas

hypothesis

tentative explanation of an observation

law

statement summarizing a vast number of experimental observations (to help predict an aspect of the world)

theory

a well substantiated, comprehensive, testable explanation of an aspect of the world

matter

anything that occupies space and has mass

substance

a form of matter with definite/ constant composition

mixture

combination of two or more substances, the substances retain their identities

homogenous

composition is the same throughout after mixing (solution)

heterogeneous

components remain separate

element

cannot be broken down into simpler substnaces

compund

substance composed of atoms of two or more elements that have fixed proportions and are chemically unified

molecule

unit of matter consisting of two or more atoms

diatomic molecules

have two atoms

polyatomic molecules

have more than two atoms

extensive property

depends on the amount of matter ex. mass

intensive property

does not depend on the amount of matter present ex. color, density

physical property

observed without transforming the substance ex. melting point

chemical property

cannot be observed without chemically converting the substance (reaction) ex. rusting iron, cooking red meat

macroscopic

direct observation (can see with eyes)

microscopic

indirect observation (can only see with a microscope)

Fahrenheit water temperatures

freezes at 32, boils at 212

Celcius water temperatures

freezes at 0, boils at 100

absolute zero

0 kelvin = -273.15 celcius (cannot be reached)

conversion from kelvin to celcius

K = celcius + 273.15

Precise measurement

measurements that yield the same result repeatedly; values agree with one another

Accurate measurement

measurements that yield a result very close to the true or accepted value (agree with the true value)

exact numbers

have no uncertainty and the number of significant figures can be infinite (counting objects, defined quantities, equations)