Module 1 - Atomic Composition, Classification of Matter, and Dimensional Analysis

Flashcards created from pre-class lecture notes covering classification of matter, atomic symbols, isotopes, SI unit definitions, temperature conversions, and dimensional analysis.

How is matter classified based on whether it can be physically separated?

Matter that can be physically separated is classified as a mixture (e.g., sea water), whereas matter that cannot be physically separated is classified as a pure substance.

What is the difference between an element and a compound within pure substances?

An element cannot be separated into simpler substances (e.g., aluminum or graphite bar), whereas a compound can be chemically separated into simpler substances (e.g., water, sodium chloride, or carbon dioxide).

How is a chemical defined in the lecture notes?

A chemical is a pure substance with a defined formula (either an element or a compound) that is not artificial or human-made.

What are the three main subatomic particles described in atomic composition and their electrical charges?

Electrons ($e^-$) are negatively charged particles, protons ($p^+$) are positively charged particles located in the nucleus, and neutrons ($n^0$) have no charge and are located in the nucleus.

In the standard schematic representation of an atom $\text{}_Z^A X$, what do $A$ and $Z$ represent?

$A$ represents the mass number ($p^+ + n^0$) and $Z$ represents the atomic number ($p^+$).

What is an isotope?

Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons, resulting in different mass numbers while sharing the same chemical properties.

What is the distinction between a cation and an anion?

A cation is a positively charged ion formed when an atom has fewer electrons than protons, whereas an anion is a negatively charged ion formed when an atom has more electrons than protons.

What is Avogadro's number and what unit does it represent?

Avogadro's number is $6.022 \times 10^{23}$, which equals the number of particles in $1\,\text{mole}$.

Based on this mass spectrum of a magnesium sample, how many neutrons does the most common isotope in the sample contain?

The most common isotope in the sample has a mass number of $25$. Since magnesium has an atomic number of $12$ ($12\,\text{protons}$), it contains $13\,\text{neutrons}$ ($25 - 12 = 13$).

What are the exponent rules for converting a standard number to scientific notation?

Moving the decimal point to the left requires a positive exponent, while moving the decimal point to the right requires a negative exponent.

What was the original SI definition of the kilogram ($\text{kg}$)?

The kilogram was originally defined as the mass of $1000\,\text{cm}^3$ of water at its melting point.

What was the original SI definition of the meter ($\text{m}$)?

The meter was originally defined as one ten-millionth of the distance from the equator to the North Pole.

What was the original SI definition of the second ($\text{s}$)?

The second was originally defined as a fraction ($\frac{1}{24 \times 60 \times 60}$) of the average solar day.

How was the Kelvin ($\text{K}$) scale originally defined in the SI system?

One degree Kelvin is defined as one hundredth of the temperature change between melting ice and boiling water, with zero Kelvin ($0\,\text{K}$) being the lowest value.

How is the mole ($\text{mol}$) defined as an SI unit?

A mole is defined as the number of atoms found in $12\,\text{grams}$ of $^{12}\text{C}$.

What are the temperature conversion formulas between Celsius and Kelvin, and between Fahrenheit and Celsius?

The conversion formula to Kelvin is $K = ^\circ\text{C} + 273$, and the conversion from Fahrenheit to Celsius is $^\circ\text{C} = (^\circ\text{F} - 32) \times \frac{5}{9}$.

If a body increases in temperature by $10^\circ\text{C}$, what is the equivalent change in Kelvin and Fahrenheit?

A temperature increase of $10^\circ\text{C}$ is equivalent to a change of $10\,\text{K}$ and a change of $18^\circ\text{F}$ ($10 \times \frac{9}{5} = 18^\circ\text{F}$).

How is the molar mass of magnesium phosphate, $\text{Mg}_3(\text{PO}_4)_2$, calculated using its component atomic masses?

The molar mass is calculated by taking $3(\text{mass of Mg}) + 2(\text{mass of P}) + 8(\text{mass of O}) = 3(24.31) + 2(30.1) + 8(16.00) = 261.13\,\text{g/mol}$.

What rule must be followed when orienting conversion factors in dimensional analysis?

Always keep the wanted unit on top of the conversion factor fraction.