IB Diploma Programme Chemistry: Structure 1.1.1 - Elements, Compounds, Mixtures & Separation Techniques

Flashcards covering the classification of matter (elements, compounds, mixtures), the particulate nature of matter, and physical separation techniques based on the Grade 11 IB DP Chemistry curriculum.

What is the definition of an element?

Elements are the primary constituents of matter, consisting of only one type of atom, which cannot be chemically broken down into simpler substances.

How does the transcript define a compound?

Compounds consist of atoms of different elements chemically bonded together in a fixed ratio.

What characterizes a mixture according to the notes?

Mixtures contain more than one element or compound in no fixed ratio, are not chemically bonded, and can be separated by physical methods.

What theory did the Greek philosopher Democritus propose in 400 BCE?

He theorized that matter could be cut into smaller pieces until reaching a point where it could not be divided further, calling these pieces atomos ("indestructible").

List the timeline of scientists mentioned whose models improved the theory of the atom.

Dalton (1803), Thomson (1897), Rutherford (1909), and Bohr (1914).

What are the two broad categories into which all matter is classified?

Pure substances and mixtures.

How many naturally-occurring elements are there?

92

What are diatomic elements?

Two atoms of the same element bonded together, such as $H_2$, $N_2$, $O_2$, $F_2$, $Cl_2$, $Br_2$, and $I_2$.

What are polyatomic elements, and what examples are provided?

More than two atoms of the same element bonded together, such as $P_4$ and $S_8$.

Define the term "allotropes".

Different structural forms of the same element in the same physical state, such as different forms of carbon.

Why can compounds not be separated using physical methods?

Because the atoms in a compound are chemically bonded together.

What are the fixed ratios for the elements in Methane ($CH_4$) and Water ($H_2O$)?

In Methane, the ratio is 1 carbon : 4 hydrogen. In Water, the ratio is 2 hydrogen : 1 oxygen.

How do the properties of Sodium chloride ($NaCl$) compare to the properties of its constituent elements?

The properties change completely: Sodium ($Na$) is a reactive metal and Chlorine ($Cl_2$) is a toxic gas, while Sodium chloride ($NaCl$) is a stable, safe ionic compound.

What is the difference between homogeneous and heterogeneous mixtures?

Homogeneous mixtures have a uniform composition with no visible boundaries (e.g., air, salt water), while heterogeneous mixtures have a non-uniform composition with visible phases (e.g., oil and water, iron and sulfur).

What is the definition of solvation?

The process where solvent particles surround and interact with solute particles as it dissolves.

Why are alloys classified as mixtures even though they contain metallic bonds?

Because they do not have a fixed ratio of components; they are a common exam pitfall where metallic bonding exists but the substance remains a mixture.

What physical property determines whether a solid can be separated from a liquid using filtration?

The solid must be insoluble.

Define "filtrate" and "residue" in the context of filtration.

The filtrate is the liquid that passes through the filter paper, and the residue is the solid that remains in the filter paper.

How does evaporation separate a mixture?

It separates a solute dissolved in a solvent by heating the solution until the solvent evaporates, leaving the solid solute behind.

Separating a liquid mixture based on differences in volatility (boiling point) is known as what technique?

Distillation

What is the basis for separation in chromatography?

Differences in the affinity of components for the stationary phase (paper) versus the mobile phase (solvent).

How does recrystallisation purify a solid?

By exploiting solubility differences of the substance at different temperatures.

According to the transcript, how much dissolved salt is in one litre of seawater?

Roughly $35\,g$

Describe the two steps required to separate a mixture of sand, salt, and water.

Step 1: Filter the mixture (sand is the residue, salt water is the filtrate). Step 2: Evaporate the filtrate (water evaporates, leaving solid salt behind).

What determines which components travel further up the paper in chromatography?

Components with a greater affinity for the mobile phase travel further.