Unit 1 Topic 2 Compounds and Mixtures Flashcards
Q: Define a pure substance.
A: A pure substance is a material consisting of only one type of element or compound, with a fixed composition and distinct measurable properties.
Q: What is a mixture?
A: A combination of two or more substances that are not chemically bonded and can be separated by physical means.
Q: What are the two types of pure substances?
A: Elements (e.g., oxygen, gold) and compounds (e.g., water, carbon dioxide).
Q: How do the properties of mixtures differ from pure substances?
A: The properties of mixtures depend on the identity and relative amounts of the substances present, whereas pure substances have consistent, measurable properties.
Q: List the physical properties of substances.
Melting point – Temperature at which a solid turns into a liquid.
Boiling point – Temperature at which a liquid turns into a gas.
Density – Mass per unit volume (e.g., water = 1 g/cm³).
Solubility – Ability of a substance to dissolve in a solvent.
Thermal & electrical conductivity – Ability to transfer heat or electricity.
Q: List the chemical properties of substances.
Reactivity – How a substance reacts with others (e.g., sodium reacts violently with water).
Stability – Resistance to decomposition over time.
Toxicity – Harmful effects on living organisms.
Flammability – Ability to catch fire (e.g., gasoline is highly flammable).
Q: Define a homogeneous mixture and give examples.
A: A mixture with a uniform composition throughout (e.g., saltwater, air, brass).
Q: What are four physical separation techniques and what mixtures do they apply to?
Distillation – Separates liquids based on boiling points (e.g., water from saltwater).
Filtration – Separates solids from liquids (e.g., sand from water).
Decanting/Separatory Funnel – Separates immiscible liquids based on density (e.g., oil from water).
Magnetism – Separates magnetic materials from non-magnetic ones (e.g., iron filings from sand).
Atom
An atom is the smallest unit of an element, consisting of protons, neutrons, and electrons.
Element
Pure substances made of only one type of atom
Isotopes
Atoms of the same element with different numbers of neutrons
Ions
an atom or molecule with a net electric charge due to the loss or gain of one or more electrons.
Cations : Positively charged due to loss of electrons
Anions: Negatively charged due to gaining of electrons
Molecule
A molecule consists of two or more atoms chemically bonded together.
Diatomic molecules
Two atoms of the same or different elements bonded together.
Homodiatomic: Same element (e.g., O₂, N₂, Cl₂).
Heterodiatomic: Different elements (e.g., CO, HCl).
Polyatomic molecules
Three or more atoms bonded together (e.g., H₂O, CO₂, CH₄).
Compound
A compound is a substance made of two or more different elements chemically combined.
Covalent compounds (Molecular compounds): Atoms share electrons (e.g., H₂O, CO₂, NH₃).
Ionic compounds: Formed from cations and anions via electrostatic attraction (e.g., NaCl, MgO).
Metallic compounds: Consist of a lattice of metal cations in a “sea of electrons” (e.g., Cu, Fe).
- Allotropes
Different structural forms of the same element in the same physical state.
Carbon allotropes: Diamond, graphite, graphene, fullerenes.
Oxygen allotropes: O₂ (oxygen gas), O₃ (ozone).
Phosphorus allotropes: White phosphorus, red phosphorus, black phosphorus.
Pure Substances
: Contain only one type of particle (elements or compounds).
Types of mixtures
Homogeneous mixtures: Uniform composition (e.g., air, saltwater).
Heterogeneous mixtures: Non-uniform composition (e.g., salad, sand and water).
Q: Define a heterogeneous mixture and give examples.
A: A mixture with a non-uniform composition, where different components are visible (e.g., salad, orange juice with pulp, soil).
