Chemistry and Measurements - Unit 2

Flashcards covering key concepts from Unit 2: Chemistry and Measurements lecture notes, focusing on vocabulary terms and their definitions related to SI units, mass, volume, temperature, significant figures, unit conversions, dimensional analysis, and density.

Measurements

A quantitative observation that has two parts: a number (telling comparison) and a unit (telling scale).

Length

A measurement of how long or far something is, with Imperial units like mile, yard, feet, inches and Metric units like meter, kilometer, centimeter, millimeter.

Volume

A measurement of the amount of space occupied, with Imperial units like fluid ounces, gallons, cups and Metric units like liter, milliliters.

Mass

A measurement of how much stuff is present, with Imperial units like ounce, pounds, tons and Metric units like gram, kilogram, milligram.

SI Unit of Volume

Cubic meter (m³).

SI Unit of Length

Meter (m).

SI Unit of Mass

Kilogram (kg).

SI Unit of Temperature

Kelvin (K).

SI Unit of Time

Second (s).

Metric System Prefixes

Used to denote multiples or submultiples of base units (e.g., nano (10⁻⁹), milli (10⁻³), kilo (10³), giga (10⁹)).

Weight

A force that changes based on the gravity of an object.

Mass

Based on the number of atoms; it remains the same regardless of gravity.

Volume (common units)

Commonly measured in cubic meters (m³), cubic centimeters (cm³), or milliliters (mL), where 1 mL = 1 cm³.

Celsius (°C)

A common everyday scale for temperature.

Kelvin (K)

The SI unit for temperature, used in scientific calculations. Conversion: K = °C + 273.

Uncertainty in Measurements

A measurement always has some degree of uncertainty due to estimation of the last digit, which depends on the precision of the measuring device.

Significant Figures (Sig Figs)

All the digits in a measurement, including one estimated digit, which reflect the precision of the measuring equipment.

Sig Fig Rule: Non-zero digits

Any digit from 1-9 is ALWAYS significant.

Sig Fig Rule: Sandwiched zeros

Any zero that is sandwiched between digits 1-9 is significant.

Sig Fig Rule: Leading zeros

Leading zeros (e.g., 0.000324) are NOT significant and only indicate the magnitude of a number.

Sig Fig Rule: Trailing zeros

Trailing zeros (at the right end) are significant ONLY if the number contains a decimal point.

Exact Numbers

Numbers not obtained by measurement (e.g., counted items or defined equalities) and have an unlimited number of significant figures.

Rounding in Series of Calculations

Carry extra digits through to the final result and then round off the final number.

Sig Figs in Multiplication/Division

The result must have the same number of significant figures as the measurement with the smallest number of significant figures.

Sig Figs in Addition/Subtraction

The limiting term is the one with the smallest number of decimal places, which determines the decimal places in the result.

Dimensional Analysis

A method for converting between different units using conversion factors that are proportional (equal), treating units like numbers that can be multiplied and canceled out.

Density

The ratio of mass to volume of a substance, representing the amount of space required for the mass of the atoms. Formula: Density = mass / volume.

Volume Determination (Geometric)

Calculating volume for regular shapes using formulas like V = L x W x H (rectangle/square) or V = π x r² x H (cylinder).

Volume Determination (Displacement Method)

Measuring the amount of water displaced when an object sinks: Volumeobject = Volumewater with object - Volume_water without object.