Chemistry Honors - Chapter 1

Length

Distance between 2 points, base unit is meter.

Volume

Amount of space an object takes up, base unit is liter.

Mass

Amount of matter in an object, base unit is gram.

Temperature

Measures the degree of heat in an object, base unit is Celsius.

Freezing

The temperature at which a substance changes from liquid to solid, 0 degrees Celsius.

Boiling

The temperature at which a substance changes from liquid to gas, 100 degrees Celsius.

Kelvin

At 0K, all particle motion stops; 0K is equivalent to -273.15 degrees Celsius.

Accuracy

How close the measured value is to the true value.

Precision

How close measured values are to each other.

Degree of Uncertainty

Depends on the instrument measuring; one place beyond the measuring device.

Significant Figures

Meaningful digits in measurement, distinguishing actual measurements from placeholders.

Significant Figures Rules

Non-zero digits are always significant; leading zeros are not significant; captive zeros are significant; trailing zeros in decimals are significant; trailing zeros in whole numbers are not significant unless specified.

Rounding

If the preceding digit is even, round to that even digit; if odd, round to the next even digit.

States of Matter

Solids have fixed shape and volume; liquids have fixed volume but not rigid shape; gases have neither fixed volume nor shape.

Atom

The smallest part of an element that retains the properties of that element.

Molecule

Two or more atoms bonded together covalently.

Chemical Formula

Used to describe elements and molecules more easily.

Filtration

Separates compounds or mixtures through barriers with fine pores.

Distillation

Separates homogeneous solid-liquid mixtures by vaporizing the liquid and recondensing it.

Chromatography

Separates mixtures based on differences in solubility.

Electrolysis

Uses electricity to separate and obtain pure elements.

Density

The amount of mass per volume, an intensive property.

Percentage Error

Calculated as |Experimental - Theoretical| / Theoretical.

Physical Change

A change affecting physical properties without altering chemical composition.

Chemical Change

A change resulting in the formation of new chemical substances.

Reversible Change

A physical change that can be reversed, such as melting ice.

Signs of Physical Change

Melting, boiling, solubility, vapor pressure, malleability, ductility, specific heat, heat of fusion, heat of vaporization, density, electrical and heat conductivity.

Irreversible Change

A chemical change that cannot be reversed, such as rusting iron.

Substance

A homogeneous material, including elements and compounds.

Element

A pure substance that cannot be broken down chemically, consisting of one type of atom.

Compound

A substance formed from two or more elements chemically bonded in fixed proportions.

Mixture

A combination of two or more substances that retain individual properties and can be separated physically.

Homogeneous Mixture

A mixture with a uniform composition throughout.

Aqueous Solutions

Solutions where a solute is dissolved in water, not separated by filtering, must evaporate, and are transparent.

Tinctures

Solutions dissolved in alcohol, such as tincture of iodine.

Amalgam

A solid solution where a metal is dissolved in mercury, used in dental fillings.

Alloys

Mixtures of metals that are not chemically bonded, made to be stronger.

Heterogeneous Mixture

A mixture with visibly different substances or phases, not uniformly distributed.

Characteristics of Heterogeneous Mixtures

Not uniform in composition, components can be separated physically, and can have different properties in different areas.

Examples of Heterogeneous Mixtures

Salad and sand with salt.

Diatomic Molecules

Molecules consisting of two atoms, often more stable as pairs, such as oxygen and bromine.

Colloids

Heterogeneous mixtures with tiny particles dispersed throughout a medium.

Tyndall Effect

The scattering of light by colloidal particles, making the light path visible.

Applications of Colloids

Used in medicine and food science, such as drug delivery and emulsions in dressings.

Stability of Colloids

Can be stabilized by surfactants or by controlling particle size and charge.