1.1 Models of the particulate nature of matter Flashcards
(34 cards)
What is an element?
An element is the simplest form of matter that cannot be broken down into simpler substances by physical or chemical means.
Key Properties of Elements
- They consist of only one type of atom.
- They are represented by chemical symbols (e.g., H for hydrogen, O for oxygen).
- They cannot be physically or chemically split into simpler substances.
Compound
A compound is a substance formed when two or more different elements chemically bond together in fixed proportions. Unlike mixtures, the components of a compound lose their individual properties and form a new substance with unique characteristics.
Key Properties of Compounds
They have a fixed chemical formula (e.g. H2O, NaCl).
Their properties differ from the elements they are made of. They can only be separated into their elements through chemical reactions.
Mixtures
A mixture contains two or more elements, compounds, or both that are physically combined but not chemically bonded. Each component retains its original properties, and the composition can vary.
Mixtures can be classified into two types:
* Homogeneous mixtures: Uniform composition throughout (e.g., saltwater, air).
* Heterogeneous mixtures: Non-uniform composition (e.g., oil and water, sand, and iron filings).
Key Properties of Mixtures
Key Properties of Mixtures:
Components are not chemically bonded.
* They can be separated by physical methods (e.g., filtration, distillation).
* The composition can vary (e.g., different concentrations of sugar in tea).
Are alloys compounds or mixtures?
Alloys, such as steel (iron and carbon), are mixtures, not compounds, because their components are not chemically bonded.
Filtration
Filtration is used to separate insoluble solids from liquids. For example, sand can be separated from water using filter paper.
How it works:
* Pour the mixture through a funnel lined with filter paper.
* The liquid (filtrate) passes through, leaving the solid (residue) behind.
Recrystallization
Recrystallization = Purifying Solids. Recrystallization exploits differences in solubility. E.g. my I.A. where salt recrystallized at the bottom and could be separated.
Evaporation
Evaporation removes a liquid from a solution by heating it, leaving behind the dissolved solid.
Example: Salt can be obtained from saltwater by evaporating the water.
Distillation
Distillation separates two or more liquids with different boiling points. The liquid with the lower boiling point evaporates first, is condensed, and collected.
Paper Chromatography
Paper chromatography is a technique used to separate the components of a mixture based on differences in their solubility and polarity. It works by allowing a solvent to move through chromatography paper, carrying the components of the mixture at different rates depending on how strongly they interact with the paper (stationary phase) and the solvent (mobile phase).
Example for paper chromatography
How It Works:
A small drop of the mixture is placed near the bottom of a strip of chromatography paper.
The paper is suspended in a solvent (like water or ethanol) with the spot above the solvent level.
As the solvent moves upward by capillary action, it dissolves the solutes in the mixture.
Components that are more soluble in the solvent travel further up the paper, while less soluble components stay closer to the starting point.
Example, Separating Pigments in Ink or Dyes:
* A mixture of colored pigments can be separated using paper chromatography. For instance, black ink often separates into a range of colors like blue, red, and yellow as different pigments move at different speeds up the paper.
Key factors for chromatography
Polarity: Polar solutes dissolve better in polar solvents, while non-polar solutes dissolve better in non-polar solvents.
Solubility: Higher solubility in the solvent results in faster movement along the paper.
Molecular Size: Smaller molecules often travel faster than larger ones.
Key properties of solids
- Shape: Fixed.
- Volume: Fixed.
- Particle Movement: Particles vibrate in place.
Key properties of liquids
- Shape: Takes the shape of the container.
- Volume: Fixed.
- Particle Movement: Particles can move and slide past one another.
Key properties of gases
- Shape: Takes the shape of the container.
- Volume: Expands to fill the container.
- Particle Movement: Particles move rapidly and independently.
Gas vs vapor
Do not confuse gases with vapors. A vapor refers to the gaseous state of a substance that is typically a liquid or solid at room temperature, like water vapor.
Changes of state in matter characteristics (not types)
- Changes of state occur when a substance absorbs or releases thermal energy.
- These transformations are physical changes, meaning the chemical composition of the substance remains unchanged.
- The energy involved affects the potential energy of the particles, not their temperature during the phase change.
Melting
- Solid to Liquid
- When a solid absorbs thermal energy, its particles gain potential energy and vibrate more vigorously.
- Eventually, they gain enough energy to break free from their fixed positions, transitioning into a liquid. This process is called melting.
Freezing
- Liquid to Solid
- The reverse of melting, freezing occurs when a liquid loses thermal energy.
- As particles release potential energy, they slow down and arrange themselves into a fixed, structured lattice.
Vaporization
- Liquid to Gas
- When a liquid absorbs enough thermal energy, its particles gain sufficient potential energy to overcome intermolecular forces and enter the gas phase.
Vaporization can occur in two ways: - Evaporation: Happens only at the surface of the liquid, at any temperature, when particles near the surface absorb enough energy to escape.
- Boiling: Happens throughout the entire liquid at a specific temperature where particles throughout the liquid gain enough energy to break free. (e.g., water boils at 100°C under standard pressure).
Condensation
- Gas to Liquid
- Condensation occurs when a gas loses thermal energy, causing its particles to release potential energy and slow down.
- As a result, intermolecular forces draw the particles closer together, forming a liquid.
Sublimation
- Solid to Gas
- Sublimation occurs when a solid absorbs thermal energy so rapidly that its particles gain enough potential energy to break free directly into the gas phase without becoming a liquid.
- A common example is dry ice (solid CO2), which sublimates at room temperature.
