chapter 1 &2 Flashcards
No experiment is a failure because _____
all observations of events in the natural world can be used to revise a hypothesis and to plan tests of a different variable.
variable
a factor that changes in an experiment in order to test a hypothesis
scientific method
a series of septs followed to solve problems including collecting data, formulating hypothesis, testing the hypothesis, and stating conclusions.
Scientific Theory
an explanations of some phenomenon that is based on observation, experimentation, and reasoning.
scientific law
a summary of many experimental results and observations; a law tells you how things work
Laws and theories are supported by____
experimental results.
chemistry
the scientific study of the composition, structure, and properties of matter and the changes that matter undergoes
matter
anything that occupies space and has mass.
element
a substance that cannon be separated or broken down into simpler substances by chemical means.
atom
the smallest unit of an element that maintains the properties of the element.
compound
a substance made of atoms of two, or more, different elements that are chemically combined. ex. Nylon is a compound.
Molecule
the smallest unit of a substance that keeps all the physical and chemical properties of that substance.
compound vs molecule
A molecule is a compound, I think. A compound is made of atoms of two or more different elements, but a molecule may be of the same elements or different elements.
H2O — molecule and a compound, because it’s made of atoms of different elements.
O2 — molecule, not a compound, because it’s made of atoms of the same element.
Compounds are always made of the same elements in the same proportions. I like to think of a substance as simply STUFF.
A pure substance
a sample of matter, either a single element or a single compound, that has definite chemical and physical properties. Compounds are subset of substances, therefore.
Mixture
a combination of two or more substances that are NOT chemical combined, i.e. pure substances.
mixtures can be homogenous or heterogeneous. Steel is actually a mixture.
Atoms can combine to form _____
molecules or compounds.
Chemical formulas
representation of the atoms in compounds or molecules.
Melting point
the temperature at press at which a solid becomes a liquid.
Boiling point
the temperature at which a liquid becomes a gas.
Density
D = m/V.
Reactivity
(chemical property) the ability of a substance to combine chemically with another substance.
Flammability
the ability of a substance to react in the presence of oxygen and burn when exposed to flame.
Physical Properties can be observed or measured without changing the composition of matter.
Physical Properties help determine how substances are used.
Chemical Properties describe how a substance reacts;
they can be observed when on substance reacts with another.
Physical Change affects one or more physical property of a substance without changing its identity, e.g. breaking a piece of chalk in two — it’s still chalk.
Dissolving is a physical change.
Compounds can be broken down ONLY through ____
chemical changes
Chemical Change
a change that occurs when a substance changes composition by forming one or more new substances.
Chemical changes cannot be reversed by _____
physical changes. Chemical changes form new substances that have different properties.
_____ changes are often easily reversed.
Physical
chemical changes can ONLY be reversed through ________
Chemical Process
Melting
from solid to liquid
Sublimation
from solid directly to gas
freezing
from liquid to solid
deposition
from gas directly to solid
vaporization
from liquid to gas
condensation
from gas to liquid
ionization
from gas to plasma
deionization
from plasma to gas
