Domain One- Physical Science Flashcards
Solids
- characterized by their ability to retain their shape
- relatively incompressible
- melt when heated and vaporize only slightly
- all substances become solid if cooled sufficiently
Examples: rocks, crystals, wood, feather, ice
Liquids
- take on the shape of their containers, but cannot be compressed to any significant extent
- volume of a liquid is constant unless evaporation is occurring
- crystallize when chilled sufficiently, while heat causes them to evaporate
- intermediate between the solid and gaseous states with regard to molecular motion and attractive forces between molecules
Example: water, oil, milk, honey
Gases
- expand to fill any available space
- a compressible fluid, with its volume determined by the pressure and temperature of the environment
- volume varies inversely with the pressure, a relationship known as Boyle’s Law
- if the pressure increases, the volume decreases; the reverse is true as well
Example: air, helium, steam
Sublimation
Allows some elements and compounds to transition from a solid to a gas phase without becoming a liquid
Example: dry ice
Deposition
Some gases can transition directly to a solid
Example: frost formation
Mass
Amount of matter in a chemical substance; often measured in newtons; in everyday situations, the weight of an object is proportional to its mass
Density
Determined by dividing the mass by the volume
Hardness
Various properties of matter in the solid phase that give it a high resistance to its shape changing when force is applied
Scratch hardness
Resistance to fracture or plastic (permanent) deformation due to friction from a sharp object
Indentation hardness
Resistance to plastic (permanent) deformation due to a constant load from a sharp object
Rebound hardness
Height of the bounce of an object dropped on the material, related to elasticity
Mohs’ scale of hardness
Rates minerals and puts them on a scale from 1 to 10 (1 was the softest and 10 is the hardest) determined by the ability of a harder mineral to scratch a softer mineral
Example: talc = 1, diamond = 10
Physical properties
Characteristics that make up the physical composition of a substance
Color, form, electrical conductivity, density
Physical Changes
Do not involve changing one substance into another; the state changes, however the molecular composition does not
Chemical changes
Occurs when a substance changes into something else; compounds are formed or decomposed; rearrangement of atoms that makes or breaks chemical bonds; typically not reversible
Example: rust
Chemical Reactions
Show the number of molecules or formula units of the reactants and products
Atoms
Made up of the nucleus (core, center) which is made up of protons (positive charge) and neutrons (no charge); electron clouds contain electrons which have a negative charge and are attracted to protons (orbit one another)
Chemical Elements
Composed of only one atom and cannot be separated into different substances except in some instances by radioactive decay or by nuclear reactions; elements are assigned atomic numbers equal to the number of protons in the nucleus of their atoms; each element has a different amount; sum of protons and neutrons gives an average atomic mass for the element
Compounds
Formed by the chemical combination of two or more elements in a fixed ration
Example H2O
Periodic table of elements
Arranges all known elements from left to right and top to bottom in order of increasing atomic number and generally coincide with their increasing atomic mass; rows are groups/families; contains 117 chemical elements (94 occur naturally, the rest have been produced artificially)
pH
Measure of acidity or basicity of a solution; not absolute; pure water is neutral (7.0)
Litmus
Water-soluble mixture of different dyes extracted from lichens; often absorbed on filter paper; paper becomes a pH indicator; blue paper turns red under acidic conditions and red paper turns blue under basic conditions
Mixture
Substance made by combining two or more different materials without a chemical reaction occurring (objects do not bond)
Measurement
