Some Basic Concepts of Chemistry

Practice flashcards covering basic chemistry concepts including classification of matter, laws of chemical combination, atomic and molecular masses, and the mole concept based on lecture notes.

What is the definition of Chemistry?

Chemistry is the study of matter, its physical and chemical properties and the physical and chemical changes it undergoes under different conditions.

How is matter defined?

Matter occupies space and has mass.

What are the two main classifications of matter based on chemical composition?

Pure substances and mixtures.

What is an element?

Elements are pure substances which can not be broken down into simpler substances by ordinary chemical changes.

What are four properties of metals?

1) Have a lustre (shiny appearance), 2) Conduct heat and electricity, 3) Can be drawn into wire (ductile), 4) Can be hammered into thin sheets (malleable).

Which metal is a liquid at room temperature?

Mercury.

What are metalloids?

Metalloids are the elements whose properties are intermediate between metals and non-metals, such as Arsenic, silicon, and germanium.

What is a compound?

Compounds are pure substances which can be broken down into simpler substances by ordinary chemical changes, where two or three elements are combined in fixed proportions.

What is the difference between homogeneous and heterogeneous mixtures?

In homogeneous mixtures, molecules are uniformly mixed throughout the bulk (e.g., air), while in heterogeneous mixtures, they are not uniformly mixed (e.g., suspension of insoluble solid in liquid).

How can the three states of matter be interconverted?

By changing the conditions of temperature and pressure.

What is the distinction between physical and chemical properties?

Physical properties can be measured without changing the chemical composition (e.g., colour, density), whereas chemical properties are exhibited when substances undergo a chemical change (e.g., magnesium burning in oxygen).

What are the seven SI base units and their symbols?

Length (metre, $m$), Mass (kilogram, $kg$), Time (second, $s$), Electric Current (ampere, $A$), Thermodynamic temp (Kelvin, $K$), Amount of substance (mole, $mol$), and Luminous intensity (candela, $cd$).

How do mass and weight differ?

Mass is the measure of the quantity of matter and does not vary with position. Weight is the result of mass and gravitational attraction, which varies with distance from the center of the earth.

What is the definition and SI unit of density?

Density is calculated by dividing mass by volume ($\text{density} = \frac{\text{mass}}{\text{volume}}$). The SI unit is $kg \text{\textbackslash},m^{-3}$.

What is the formula for converting temperature from degree Celsius ($^\text{\textbackslash}circ C$) to Kelvin ($K$)?

$$K = ^\text{\textbackslash}circ C + 273.15$$

What is the formula for converting temperature from degree Celsius ($^\text{\textbackslash}circ C$) to degree Fahrenheit ($^\text{\textbackslash}circ F$)?

$$^\text{\textbackslash}circ F = \frac{9}{5}(^\text{\textbackslash}circ C) + 32$$

State the Law of Conservation of Mass.

'Mass can neither be created nor destroyed.' The total mass of reactants equals the total mass of products.

State the Law of Definite Proportions.

'A given compound always contains exactly the same proportion of elements by weight.'

What is the Law of Multiple Proportions?

When two elements A and B form more than one compound, the masses of element B that combine with a given mass of A are always in the ratio of small whole numbers.

State Gay-Lussac’s law of gaseous volume.

When gases combine or are produced in a chemical reaction, they do so in a simple ratio by volume, provided all gases are at the same temperature and pressure.

What is Avogadro's Law?

Equal volumes of all gases at the same temperature and pressure contain equal number of molecules.

What are the four main features of Dalton's Atomic Theory?

1) Matter consists of tiny, indivisible particles called atoms. 2) Atoms of a given element have identical properties/mass. 3) Compounds form when different elements combine in a fixed ratio. 4) Chemical reactions involve reorganization of atoms; atoms are neither created nor destroyed.

Define one atomic mass unit ($amu$).

One $amu$ is defined as a mass exactly equal to one-twelfth ($\frac{1}{12}$) of the mass of one Carbon-12 atom.

What is the value of $1\text{\textbackslash},amu$ in grams?

$$1.66056 \times 10^{-24}\text{\textbackslash},g$$

What is Molecular Mass?

Molecular mass is the sum of average atomic masses of the atoms of an element which constitute the molecule.

Define a Mole.

One mole is the amount of a substance that contains as many entities or particles as there are atoms in exactly $12\text{\textbackslash},g$ (or $0.012\text{\textbackslash},kg$) of the Carbon-12 isotope, which is $6.022 \times 10^{23}$ particles (Avogadro's Constant).

What is Molar Mass?

The mass of one mole of a substance (element or compound) in grams. It is numerically equal to the atomic, molecular, or formula mass in $u$ (unified mass).

What is the molar volume of a gas at STP?

One mole of any gas occupies a volume of $22.4\text{\textbackslash},dm^3$ at standard temperature ($0^\text{\textbackslash}circ C$) and pressure ($1\text{\textbackslash},atm$).

How is the number of moles ($n$) of a gas calculated at STP?

$$n = \frac{\text{Volume of gas at STP}}{22.4\text{\textbackslash},dm^3\text{\textbackslash},mol^{-1}}$$