physical science lawerence winter final

Scientific inquiry

The process scientists use to investigate questions: ask, hypothesize, test, collect data, and conclude

Qualitative observation

Describes qualities using words, not numbers (color, texture)

Quantitative observation

Describes observations using numbers and measurements

Independent variable

The variable that is changed or manipulated

Dependent variable

The variable that responds to the independent variable

Control group

The group used for comparison; does not receive the variable

Constants

Factors kept the same to ensure a fair test

Accuracy

How close a measurement is to the true value

Precision

How consistent repeated measurements are

Metric (SI) system

The standard measurement system used in science

SI base units

Meter (length), gram (mass), liter (volume), Kelvin/Celsius (temperature)

Mass

The amount of matter in an object

Volume

The amount of space an object occupies

Volume (displacement)

Measuring volume of irregular objects using water displacement

Density

Mass divided by volume (D = m ÷ v)

Factors affecting density

Mass, volume, temperature

Significant digits

Digits that show the precision of a measurement

Graph parts

Title, x-axis (independent), y-axis (dependent), scale, key

Graph relationship types

Direct, inverse, constant

Solids vs liquids (density)

Solids usually more dense; liquids have particles closer but able to flow

Fluids

Substances that flow (liquids and gases)

Temperature

Measure of average kinetic energy of particles

Absolute zero

The lowest possible temperature where particle motion stops

Thermal expansion

Matter expands when heated due to increased particle motion

Intermolecular forces

Attractive forces between molecules

Phases of matter

Solid, liquid, gas

Phase change

Change of state due to energy gain or loss

Kinetic Molecular Theory

Particles are in constant motion and move faster at higher temperatures

Charles' Law

As temperature increases, volume increases (at constant pressure)

Temperature conversions

°C = K − 273; K = °C + 273

Physical property

Characteristic observed without changing identity (density, color, state)

Physical change

Changes appearance, not identity (melting, cutting)

Chemical change

Forms a new substance with new properties

Electric charge

Positive, negative, or neutral

Electromagnetic attraction

Attraction between positive nucleus and negative electrons

Atom

Smallest unit of matter retaining properties

Subatomic particles

Protons (+), neutrons (0), electrons (−)

Nucleus

Dense center of atom containing protons and neutrons

Electron cloud

Region where electrons move

Atomic number

Number of protons

Mass number

Protons + neutrons

Atomic mass

Average mass of atoms of an element

Ion

Atom with a charge due to gaining or losing electrons

Isotope

Atoms with same protons but different neutrons

Valence electrons

Electrons in the outermost shell

Energy levels

Electron shells around the nucleus

Periodicity

Repeating patterns on the periodic table

Atomic radius trend

Decreases across, increases down

Electronegativity trend

Increases across, decreases down

Ionization energy trend

Increases across, decreases down

Groups/families

Vertical columns with similar properties

Periods

Horizontal rows showing energy levels

Metals vs nonmetals

Metals conduct and lose electrons; nonmetals do not

Compound

Two or more different elements chemically bonded

Molecule

Two or more atoms bonded together

Oxidation

Loss of electrons

Reduction

Gain of electrons

Reactivity

How easily a substance reacts

Alpha decay

emits a helium nucleus (2 protons, 2 neutrons, decreasing mass by 4 + atomic number by 2

Beta decay

: A neutron converts to a proton (or vice versa) and releases an electron

Gamma decay

Nucleus releases high amounts of energy and nucleus moves to lower energy state, element stays the same

Oxidation numbers

Charges assigned to atoms in compounds

Polyatomic ion

Charged group of atoms acting as one unit

Lewis dot diagram

Diagram showing valence electrons

Subscript

Shows number of atoms in a molecule

Coefficient

Shows number of molecules in a reaction

Neutral compound

Total charge equals zero

Ionic bond

Electron transfer between metal and nonmetal

Covalent bond

Electron sharing between nonmetals

Cation

Positively charged ion

Anion

Negatively charged ion

Chemical reaction

Process that forms new substances

Chemical equation

Shows reactants → products

Reactants

Starting substances

Products

Substances formed

Law of conservation of mass

Mass is not created or destroyed

Mole

6.02 × 10²³ particles

Avogadro's number

Number of particles in one mole

Molar mass

Mass of one mole (g/mol)

Evidence of chemical reaction

Color change, gas, solid formation, energy change, temperature change

Synthesis reaction

Two or more substances form one product

Decomposition reaction

One substance breaks into simpler substances

Single displacement reaction

One element replaces another

Double displacement reaction

Ions exchange between compounds

Combustion reaction

Hydrocarbon reacts with oxygen producing CO₂ and H₂O