IndietroGeneral Chemistry: Matter, Energy, and Measurement
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Termini in questo insieme (31)
Matter is anything that has mass and volume, composed of atoms, and makes up everything in the universe.
The three common states of matter are solid, liquid, and gas, differing in particle arrangement and movement.
In solids, particles are close and orderly; in liquids, close but free to move; in gases, far apart and move freely.
Plasma is a gaseous state with charged particles, found naturally in stars and lightning, and in devices like ICP spectroscopy.
Matter is classified as pure substances (elements and compounds) or mixtures (homogeneous and heterogeneous).
A homogeneous mixture has uniform composition and particles are evenly distributed, e.g., sugar solution and air.
A heterogeneous mixture has non-uniform composition with visible different components, e.g., salt and sugar mix.
A pure substance has constant composition and properties, e.g., sucrose always contains the same ratio of C, H, and O.
An element contains one type of atom; a compound contains atoms of different elements combined in a fixed ratio.
Water (H2O) is a liquid compound formed from gaseous hydrogen and oxygen, with properties different from its elements.
Physical properties describe matter without changing its composition, e.g., density, color, melting point.
Chemical properties describe how a substance reacts to form new substances, observed only during chemical changes.
A physical change alters state or appearance without changing composition, e.g., melting wax, dissolving sugar, vaporization.
A chemical change produces new substances with different properties, e.g., rust formation, combustion of nitroglycerin.
Extensive properties depend on amount (mass, volume); intensive properties do not (temperature).
Elements are classified as metals (good conductors), nonmetals (poor conductors), and metalloids (intermediate).
Length (meter, m), mass (kilogram, kg), time (second, s), temperature (kelvin, K), electric current (ampere, A), amount of substance (mole, mol), luminous intensity (candela, cd).
Mass is the amount of matter and is constant; weight is the force of gravity on mass and varies with location.
Density is mass per unit volume, expressed as \(\mathrm{g/cm^3}\) or \(\mathrm{kg/m^3}\).
Degrees Celsius (°C), Fahrenheit (°F), and Kelvin (K). Relations: \(\degree F = \frac{9}{5} \degree C + 32\), \(K = \degree C + 273.15\).
Significant figures include all certain digits plus one estimated digit in a measurement, indicating precision.
Non-zero digits are significant; zeros between non-zero digits are significant; leading zeros are not; trailing zeros are significant if decimal present.
If first dropped digit <5, round down; if >5, round up; if =5, round to make preceding digit even.
Result cannot have more digits to the right of the decimal than the number with the fewest decimal places.
Result contains the smallest number of significant figures from the factors.
Accuracy is closeness to true value; precision is closeness of repeated measurements to each other.
Energy is the ability to do work or cause change; main forms are kinetic energy (motion) and potential energy (stored).
Chemical potential energy is energy stored in atoms, molecules, and chemical bonds dependent on atomic positions.
The total amount of mass and energy in the universe is conserved; energy cannot be created or destroyed, only transformed.
Heat is energy transferred from a hotter to a colder object due to temperature difference until thermal equilibrium.
Work is force applied over a distance (\(W=Fd\)); energy transfer occurs only if the object moves.