Introduction to Chemistry Concepts and Measurements

Chemistry

Study of substances' composition, structure, properties, reactions.

Chemical

Substances with consistent composition and properties.

Scientific Method

Systematic approach for investigating phenomena.

Hypothesis

Proposed explanation for an observation.

Experiment

Test to validate or invalidate a hypothesis.

Conclusion

Result drawn from consistent experimental outcomes.

Line Graph

Visual representation of relationship between two variables.

Volume

Space occupied by a substance, measured in liters.

Length

Distance measured in meters or centimeters.

Mass

Quantity of material, measured in grams or kilograms.

Weight

Gravitational pull on an object.

Temperature

Measure of how hot or cold an object is.

Time

Duration measured in seconds using atomic clock.

Significant Figures

Digits in a number that contribute to its precision.

Measured Numbers

Values obtained from measuring tools.

Metric System

Standard system for scientific measurements.

International System of Units (SI)

Modern form of the metric system.

Celsius (°C)

Temperature scale based on freezing and boiling points.

Kelvin (K)

Absolute temperature scale used in scientific contexts.

Liter (L)

Unit of volume equal to 1000 milliliters.

Milliliter (mL)

Unit of volume, 1/1000 of a liter.

Kilogram (kg)

SI unit of mass, equivalent to 1000 grams.

Scientific Notation

Method to express large or small numbers concisely.

Exact Numbers

Numbers obtained by counting items, no measurement.

Significant Figures

Digits that carry meaningful information in calculations.

Rounding Off

Adjusting numbers based on the first dropped digit.

Multiplication Rule

Final answer matches measurement with fewest significant figures.

Addition Rule

Final answer matches measurement with fewest decimal places.

Metric Prefixes

Prefixes that alter unit size by factors of ten.

Centi Prefix

Represents one hundredth (1/100) of a unit.

Milli Prefix

Represents one thousandth (1/1000) of a unit.

Micro Prefix

Represents one millionth (1/1,000,000) of a unit.

Kilo Prefix

Represents one thousand (1000) times a unit.

Mega Prefix

Represents one million (1,000,000) times a unit.

Tera Prefix

Represents one trillion (1,000,000,000,000) times a unit.

Equality

Relationship between two units measuring the same quantity.

Density

Mass of substance divided by its volume.

Density Units

Measured in g/cm³ for solids and liquids.

Gas Density Units

Measured in g/L for gases.

Pure Substances

Matter with fixed composition; elements or compounds.

Elements

Substances made of one type of atom.

Compounds

Substances made of two or more chemically combined elements.

Mixtures

Combination of substances not chemically bonded.

Homogeneous Mixture

Uniform composition; parts not visible.

Heterogeneous Mixture

Non-uniform composition; parts are visible.

Physical Properties

Observed without changing substance identity.

Chemical Properties

Describe substance's ability to change into new substances.

Physical Change

Change of state without altering composition.

Chemical Change

Conversion of original substance into a new substance.

Temperature

Measure of hotness or coldness of an object.

Thermometer

Instrument used to measure temperature.

Celsius

Temperature scale used in scientific measurements.

Fahrenheit

Temperature scale primarily used in the U.S.

Kelvin

Absolute temperature scale starting at absolute zero.

Boiling Point

Temperature where liquid turns to gas.

Freezing Point

Temperature where liquid turns to solid.

Kinetic Energy

Energy possessed by an object in motion.

Potential Energy

Energy stored due to position or composition.

Calorie

Unit of energy; 1 Calorie = 4.184 Joules.

Specific Heat

Heat required to change 1g by 1°C.

Specific Heat Equation

q = m × ΔT × SH.

Nutritional Calorie

1 Calorie = 1000 calories or kilocalories.

Carbohydrates Kcal/g

Provide 4 Kcal/g of energy.

Fats Kcal/g

Provide 9 Kcal/g of energy.

Proteins Kcal/g

Provide 4 Kcal/g of energy.

Dmitri Mendeleev

Creator of the periodic table.

Groups in Periodic Table

Vertical columns of elements with similar properties.

Periods in Periodic Table

Horizontal rows of elements.

Metalloids

Elements with properties of both metals and nonmetals.

Plum Pudding Model

J.J. Thomson's model of atomic structure.

Rutherford Gold Foil Experiment

Demonstrated atoms are mostly empty space.

Atomic number

Number of protons in an atom.

Mass number

Total of protons and neutrons in an atom.

Isotopes

Atoms with same protons, different neutrons.

Atomic mass

Weighted average of all isotopes' masses.

Radioactivity

Emission of radiation from unstable nuclei.

Radioisotope

Unstable nucleus that emits radiation.

Alpha particles

Helium nucleus; 2 protons, 2 neutrons.

Beta particles

High-energy electrons emitted from unstable nuclei.

Gamma rays

High-energy radiation emitted from unstable nuclei.

Alpha decay

Nucleus emits alpha particle, mass increases by 4.

Beta decay

Neutron converts to proton, emits beta particle.

Proton emission

Proton converts to neutron, emits positron.

Gamma emission

Energy emitted; mass and atomic number unchanged.

Half-life

Time for half of a radioactive sample to decay.

Radiological dating

Determining age of objects using carbon-14.

Positron emission tomography (PET)

Imaging technique using emitted positrons.

Computed tomography (CT)

X-ray imaging technique for 3D body images.

Magnetic resonance imaging (MRI)

Imaging based on hydrogen proton energy absorption.

Nuclear fission

Splitting of large nucleus, releasing energy.

Nuclear fusion

Combining small nuclei, releasing large energy.

Chain reaction

Rapid increase in fission reactions from critical mass.

Missing mass

Mass converted into energy during nuclear reactions.

Radiation

Energy emitted during radioactive decay.