PRAXIS General Science 5436

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6 steps of scientific method

1. Question
2. Hypothesis
3. Experiment
4. Observation
5. Analysis
6. Conclusion

Internal Validity

cause and effect are the only explanation

External Validity

results are true for people outside the study as well

Ecological Validity

results have meaning in real life and doesn't include odd parameters

accuracy in a measurement

how close a measurement is to its true value

precision in a measurement

agreement of repeated measures

types of error

human
random
systematic

systematic error

from instruments used

causes drift (gradual changes over time)

mass

how much matter something has

weight

how much gravity is pulling something

volume

how much space something takes up

density

how tightly packed particles are together

density equation

mass/volume

When an electron falls back to a lower energy state, a is released.

photon

Photon

weightless particle of electromagnetic radiation

Example of Photons

heat and light

atom

smallest particle of an element that still has the same properties of an element

element

A pure substance made of only one kind of atom

Subatomic particles

protons, neutrons, electrons

Isotopes

elements with the same number of protons BUT different number of neutrons

radioactive isotope

unstable nucleus that becomes table by emitting excess energy or radiation

radioactive decay

radioactive isotope decomposes and creates new daughter nucleus

alpha decay

the release of alpha particles from a nucleus

beta decay

neutron changes in a proton or vice versa

beta minus

neutron to a proton

• atomic number increases
• electron is emitted

beta plus

proton to a neutron

• atomic number decreases

gamma emission

release of energy in the form of gamma rays

Nuclear Fusion

two or more atoms fuse together to make a single, heavier atom

Nuclear Fission

heavier atoms split into smaller pieces

Nuclear fission happens when

an atom gets hit with a neutron

Malleability

ability to bend or shape

mixture

Two or more substances that are mixed together but not chemically combined

compounds

2 or more elements chemically combined

exothermic reaction

energy is released in the form of heat

The types of mechanical energy are

Kinetic and Potential

Kinetic Energy

anything in motion

Potential energy

stored energy

The two types of potential energy are _

gravitational and elastic

Gravitational Potential Energy

energy stored because of its location above ground

Elastic Potential Energy

energy stored by an object that can stretch or compress

The direction of heat goes _

The direction of energy is from higher temp. to lower temp.

The two ways to increase temp. of a substance is

1. exposing it to a higher temp.
2. doing certain kinds of work on it

conduction

transfer of heat between atoms and molecules in direct contact

convection

transfer of heat by movement of the heated substance itself

radiation

transfer of heat by electromagnetic waves

specific heat capacity

quantity of heat required to raise raise temp. of a unit mass by one degree

heat engine

a device that converts thermal energy into mechanical energy

A heat engine has a specific efficiency because

some heat will always be lost

heat equation

heat energy = mass x specific heat capacity x change in temperature

higher temp. = kinetic energy

more

• molecules are moving around faster

Thermometers measure _

the expansion of molecules

Thermal expansion

increases volume when temp. increases

endothermic reaction

heat is absorbed from surroundings

Entropy

A measure of disorder or randomness.

Enthalpy

measure of overall energy in a system

if the reaction is exothermic, the heat of the reaction is

negative

if the reaction is endothermic, the heat of the reaction is ___

positive

Heat is

the total amount of energy contained in a substance

does temp change during phase change

no

particles are pushed father apart by heat and it is stored as potential energy

Enthalpy determines

whether heat is gained or lost by a system

-determines how strong a bond it

In an endothermic reaction, bonds are

broken
-energy is needed to break the bonds

In an endothermic reaction, heat is pushed to

to the right towards the products

In an exothermic reaction, bonds are

formed

• less energy is needed to form bonds

In an exothermic reaction, heat is pushed to

to the left towards the products

In an exothermic reaction, the molecules move from

a higher energy state to a lower energy state

The Carnot cycle is

The most efficient heat engine cycle

In an Isothermic Process, the temp. ____

remains the constant

In an adiabatic process, the temp ____

change relative to pressure and volume

• no heat enter or leaves during this time

Valence electrons are in

the outermost shell

-interact with other atoms

The highest number of available valence electrons are

8

• these ones are extremely stable

atomic radius

1/2 the distance between two the nuclei of two bonded atoms

An atoms becomes an Ion by

gaining or losing an electron

An ionic radius gets _ if it loses an electron

smaller

An ionic radius gets ____ if it gains an electron

bigger

Ionization Energy

The amount of energy required to remove an electron from an atom

the bigger the atom = the the ionization energy

lower

Electro negativity

the ability of an atom to attract other electrons

electro negativity is determine by ____

atomic structure

low electro negativity means

atoms will share the most

high electro negativity means

atoms will not like sharing

the kinetic molecular theory explains

the behavior of matter

intermolecular forces

forces of attraction between molecules

intermolecular forces increase when _

particles get closer together

more kinetic energy = ____ intermolecular forces

less

Amorphous solids are

solids that can be shaped

the strongest type of bond is

hydrogen bond

hydrogen bond

between polar molecules that contain oxygen, nitrogen, or fluorine covalent bonded to a hydrogen atom

Ion - Dipole force

between an ion and a polar molecule

Dipole - Dipole force

between oppositely charges poles of polar molecules

Dipole - Induced Dipole force

when a polar molecule induces temporarily dipole movement in neighboring non-polar molecule

london disperson forces (LDF)

between non-polar molecules

the weakest intermolecular force is

london disperson forces

the triple point in a phase diagram

point where all three forms can exist (exact pressure and temperature)

the critical point in a phase diagram

gas and liquid are the same, substance is in one phase

the supercritical point in a phase diagram

gas and liquid phase are indistinguishable

solid to a liquid is ___

melting

solid to a gas is _

sublimating

liquid to a solid is

freezing

liquid to a gas is _

vaporizing

gas to a liquid is ____

condensation