Chemistry Notes: Matter, Solutions, and Mixtures

Flashcards covering fundamental chemistry concepts including matter, elements, compounds, mixtures, solutions, colloids, suspensions, solubility rules, molarity, and separation techniques.

What is matter?

Anything that has mass and occupies space, such as air, water, stone, and wood.

What is an atom?

The smallest particle of an element that can take part in a chemical reaction.

What is a molecule?

Two or more atoms chemically combined together, such as $H_2O$, $O_2$, and $CO_2$.

What is an element?

A pure substance made up of only one type of atom that cannot be broken down into simpler substances by chemical means.

What is a compound?

A substance formed when two or more different elements are chemically combined in a fixed ratio, such as water ($H_2O$), sodium chloride ($NaCl$), and carbon dioxide ($CO_2$).

What is a mixture?

Two or more substances mixed together physically in any proportion, in which the components retain their individual properties and can be separated by physical means.

What is a pure substance?

A substance that has a fixed composition and definite properties throughout; it is either an element or a compound.

What is the difference between a homogeneous mixture and a heterogeneous mixture?

A homogeneous mixture has the same composition throughout (e.g., salt solution, air), whereas a heterogeneous mixture has different compositions in different parts (e.g., oil and water, sand and water).

What are solute and solvent in a solution?

In a solution, the solute is the substance that gets dissolved, and the solvent is the substance that dissolves the solute (usually present in a larger amount).

What is a suspension?

A heterogeneous mixture in which insoluble particles are large enough to settle down if left undisturbed, such as mud in water, chalk in water, or flour in water.

What is a colloid?

A heterogeneous mixture in which very small particles of one substance are evenly spread in another and do not settle down, with intermediate particle size between solutions and suspensions (e.g., milk, fog, smoke, paint, cream, ink).

How do particle sizes compare among solutions, colloids, and suspensions?

Solution particles are less than $1\,\text{nm}$, colloid particles range from $1\,\text{nm}$ to $1000\,\text{nm}$, and suspension particles are more than $1000\,\text{nm}$.

How do solutions, colloids, and suspensions differ regarding stability and filtration through filter paper?

Solutions are stable and pass through filter paper; colloids are fairly stable, do not settle, and pass through filter paper; suspensions are unstable, settle down on standing, and do not pass through filter paper.

Which types of mixtures scatter light among solutions, colloids, and suspensions?

Solutions do not scatter light, whereas both colloids and suspensions scatter light.

What is the difference between a dilute solution and a concentrated solution?

A dilute solution contains a small amount of solute in a large amount of solvent, while a concentrated solution contains a large amount of solute in a small amount of solvent.

What is molarity and what is its formula?

Molarity is the number of moles of solute present in $1\,\text{litre}$ of solution. Its formula is $\text{Molarity } (M) = \frac{\text{Number of moles of solute}}{\text{Volume of solution in litres}}$.

What is a mole and what is the value of Avogadro's number?

A mole is the amount of substance that contains $6.022 \times 10^{23}$ particles (Avogadro number).

What is solubility, and what is the solubility of $NaCl$ in water at $20^\circ\text{C}$?

Solubility is the maximum amount of solute that can be dissolved in a given amount of solvent at a specific temperature. At $20^\circ\text{C}$, about $36\,\text{g}$ of $NaCl$ can be dissolved in $100\,\text{g}$ of water.

How does solute-solvent interaction affect solubility?

Solubility depends on how strongly solute particles attract solvent particles; if attraction is strong, solubility is high (e.g., iodine dissolves well in alcohol, and water molecules strongly attract $Na^+$ and $Cl^-$ ions).

What is the effect of pressure on the solubility of gases in liquids?

Pressure has a significant effect only on gaseous solubility: an increase in pressure increases gas solubility, while a decrease in pressure decreases gas solubility (e.g., more $CO_2$ dissolves in soft drinks sealed under high pressure).

How does temperature affect the solubility of solids versus gases in liquids?

An increase in temperature increases the solubility of most solid substances in liquids (e.g., sugar dissolves more in hot water), but decreases the solubility of gases in liquids (e.g., less $CO_2$ dissolves in warm water).

What is the difference between unsaturated, saturated, and supersaturated solutions?

An unsaturated solution contains less solute than the maximum dissolvable amount; a saturated solution contains the maximum amount that can dissolve at a given temperature; a supersaturated solution contains more solute than the normal maximum amount that can dissolve at that temperature.

How is a supersaturated solution prepared?

It is prepared by cooling a hot saturated solution slowly; it is unstable and extra solute may crystallize or separate out easily if disturbed.

What are four methods used for separating solutions?

Evaporation, crystallization, distillation, and chromatography (solutions cannot be separated by simple filtration).

What is evaporation as a method of separation?

The method of separating a soluble solid from its solution by heating the solution so that the solvent evaporates, leaving the solid behind (e.g., obtaining salt from salt solution).