States of Matter, Diffusion & Dilution, and Solutions (Solubility) - Edexcel IGCSE Chemistry

Flashcards cover key concepts from the lecture notes on states of matter, diffusion and dilution, and solubility/solutions, including definitions, processes, and example calculations.

What are the three states of matter?

Solid, liquid and gas.

Describe the arrangement of particles in solids, liquids, and gases.

Solids have a regular arrangement; liquids and gases have randomly arranged particles.

How do particles move in solids, liquids, and gases?

Solids vibrate about fixed positions; liquids move around each other; gases move quickly in all directions.

How close are particles in solids, liquids, and gases?

Solids: very close; liquids: close; gases: far apart.

What is the melting point and what is the boiling point?

Melting point is the temperature at which a solid changes to a liquid; boiling point is the temperature at which a liquid changes to a gas.

What happens during melting and freezing?

Melting: solid to liquid at the melting point; freezing: liquid to solid at the same temperature for a pure substance.

What is the difference between boiling and evaporation?

Boiling occurs at the boiling point with bubbles forming inside the liquid; evaporation occurs at the surface at any temperature below or at the boiling point.

What is condensation?

Gas changes into a liquid on cooling, occurring over a range of temperatures.

What are sublimation and desublimation (deposition)?

Sublimation: solid changes directly into a gas; desublimation (deposition): gas changes directly into a solid.

Are state changes physical or chemical changes?

Physical changes; the particles themselves remain the same, only the forces between them change.

What determines the energy needed to change state?

The strength of the forces between particles; stronger forces mean higher melting and boiling points.

What is diffusion?

Movement of particles from high concentration to low concentration, occurring in gases and liquids due to random motion; faster at higher temperatures.

How does diffusion differ in gases versus liquids?

Diffusion is faster in gases (more space between particles) and slower in liquids (particles are closely packed).

What is dilution?

Adding more solvent to a solution, decreasing concentration; solute particles become more spread out and the color fades but particles remain.

What evidence do diffusion and dilution provide for the kinetic theory?

Show that matter is made of moving particles and that diffusion occurs due to random motion.

Define solvent, solute, and solution.

Solvent: the liquid in which a solute dissolves; Solute: the substance that dissolves; Solution: the mixture formed when a solute dissolves.

What is a saturated solution?

A solution with the maximum concentration of solute dissolved in the solvent.

Soluble vs insoluble.

Soluble: will dissolve; Insoluble: will not dissolve.

What is solubility?

The amount of solute that will dissolve in a given volume of solvent; gases’ solubility depends on pressure and temperature; solids usually become more soluble with higher temperature.

What is a solubility curve?

A graph of solubility (g per 100 g of water) plotted against temperature, determined from saturated solutions.

What is special about sodium chloride’s solubility with temperature?

Sodium chloride shows very little change in solubility with temperature.

What is the aim of the Practical: Investigate the Solubility of a Solid in Water at a Specific Temperature?

To measure the solubility of a salt at different temperatures.

Outline the general method of the solubility practical.

Use a hot bath and an ice bath; dissolve a known mass of salt in a small amount of water in a boiling tube; cool and note the temperature at which crystals first appear; add more water in steps and repeat until a total of about 10 cm3 water has been added.

What data are collected in the solubility practical results table?

Volume of water (cm3); Solubility (g per 100 g) ; Temperature at which crystals appear (°C).

What does a solubility graph show?

How solubility changes with temperature, plotting solubility on the y-axis and temperature on the x-axis.

How do you calculate solubility at 50 °C from a curve for potassium nitrate?

If solubility is 68 g per 100 g of water, then in 20 g of water the dissolved mass is 68 × (20/100) = 13.6 g.

How is the amount of lead(II) nitrate crystals formed calculated from a solubility curve example?

Difference in solubility between 90 °C (118 g/100 g) and 40 °C (64 g/100 g) is 54 g per 100 g water; for 200 cm3 of solution, total crystals formed = 2 × 54 = 108 g.

What does the reversible arrow ⇌ indicate in state change diagrams?

That the state change process can proceed in both directions (forward and backward).