In this animated and interactive object, learners follow two rules to write unit conversion fractions.

Learners calculate gas density from the standard molar volume and observe how the density increases with the increasing molecular weight of the gas.

In this animated object, learners examine the formation of peptide bonds through dehydration synthesis.

In this interactive object, learners calculate the amount of heat evolved or absorbed in chemical reactions. Four practice problems are provided.

Learners complete an exercise to match chemical formulas with the names of binary compounds, tertiary compounds, and ions.

Learners examine phase diagrams that show the phases of solid, liquid, and gas as well as the triple point and critical point.

Learners examine graphs and read that the heat of fusion is the heat energy absorbed by one mole of solid as it is converted to liquid, while the heat of vaporization is the heat energy absorbed by one mole of liquid as it is converted to gas.

In this animated object, learners examine how gas volume varies directly with absolute temperature (K at constant pressure). An example of a sample of gas at two conditions of volume and temperature is used to illustrate the law.

In this animated object, students examine what happens when electrons share molecules.

In this interactive object, learners identify charges on ions, write new formulas based on charge, and balance equations using coefficients.

In this screencast, learners examine the kinds of physical and chemical changes that occur in substances.

Learners examine how chemists use moles to "count" atoms by weight. Examples are given.

In this interactive object, learners determine the limiting reagent and the excess reagent in chemical reactions. Learners test their knowledge by solving three problems.

Learners examine the meaning of theoretical yield, actual yield, and percent yield. They test their knowledge by solving two problems.

Learners observe that the volume of one mole of any gas is 22.4 L at standard temperature and pressure. An illustration shows that only the mass of the molar volume differs with the identity of the gas.

In this animated and interactive object, learners examine the properties of liquids, solids, and gases.

Students examine standard pressure in this interactive object.

Learners use the coefficients in a balanced equation to develop the mole ratios of reactants and products involved in the reaction. Five interactive examples illustrate the method, and students test their knowledge by working four problems.

In this interactive and animated object, students distribute the valence electrons in simple covalent molecules with one central atom. Six rules are followed to show the bonding and nonbonding electrons in Lewis dot structures. The process is well illustrated with eight worked examples and two interactive practice problems.

Ions are electrically charged particles obtained from an atom or from a chemically bonded group of atoms by adding or removing electrons. Eight examples illustrate the number of protons, neutrons, and electrons in positive ions (cations) and in negative ions (anions).