In this post, we will cover the van der Waals equation and find 2 constants a and b in the equation. We will also find a table full of selected van der Waals Constants for Gas Molecules. the van der Waals equation In 1873, Dutch scientist Johannes van der Waals developed an equation that compensates […]

## Describing phase change in terms of molecular behaviour

In this post, we will describe the change of state (phase change) in terms of molecular behavior. When solids that do not melt are heated, the thermal energy supplied overcomes some intermolecular forces and therefore increases some molecular potential energies. But most of the thermal energy supplied increases the average kinetic energy of the molecules […]

## Graphs for state change or phase change | change of state – graphs

In this post, we will study the Graphs for state change (phase change graphs or change of state graphs). We have already studied the keywords related to the state change or phase change here. Sketching and interpreting phase change graphs (change of state – graphs) The three change of phase graphs (drawn below) all have […]

## Isotherm, Isobar & Isochore graphs

When we study gas laws (Boyle’s law, Charles’ law & Pressure Law), we come across terms like Isotherm, Isobar, and Isochore. Here, in this post, we will discuss these. What is Isotherm? If we draw Boyle’s law graphs at diff temperatures then we get curves shown in figure 1. Boyle’s law is expressed as V […]

## Molar Mass – concepts and formula

The mass of one mole of a substance in grams is called its molar mass. The molar mass in grams is numerically equal to atomic/molecular/formula mass in u. The molar mass of water = 18.02 g mol-1The molar mass of sodium chloride = 58.5 g mol-1 Molar mass is the mass of a single mole. […]

## Numerical Problems based on combined Gas law or Gas equation & ideal gas equation

In this post, we will solve a few Numerical Problems based on the Combined Gas law (or Gas equation) & the Ideal gas equation. The Formulas used to solve the numerical problems are: PV / T = constant (k) pV = nRT Example 1 A sample of nitrogen occupies a volume of 1.0 L at a […]

## Combined Gas Law or gas equation | the Ideal Gas Equation

We will derive the following here (1) combined gas law or gas equation & (2) the Ideal Gas equation. For these, we will use Boyle’s law, Charles’ law, Pressure law, and Avogadro’s law for gases. The Combined Gas Law or Gas Equation Boyle’s and Charles’ laws give separately variations of the volume of a gas […]

## Avogadro’s Law (Volume–Amount Relationship)

Avogadro’s Law offers Volume-Amount Relationship of gases. Amadeo Avogadro in 1811, put forward a relationship between volume of a gas to the number of molecules at constant temperature and pressure. This has now been accepted as a law and is known as Avogadro law. Avogadro’s law states that equal volumes of all gases under the […]

## Numerical problems based on Gay Lussac’s law or pressure law

Let’s solve a sample numerical problem (from the gas chapter) using Gay Lussac’s law or pressure law. The formula to be used is as follows: P1/T1 = P2/T2 Example 1 A chamber of the constant volume contains hydrogen gas. When the chamber is immersed in a bath of melting ice (0°C), the pressure of the […]

## Numerical Problems based on Charles’ Law with solution

In this post, we will solve numerical problems using Charles’ Law. The formulas to be used are as follows: If V1 is the volume of a certain mass of a gas at temperature T1 and V2 is the volume of the same mass of the same gas at temperature T2 at constant pressure, then according […]

## The gaseous state of matter

The gaseous state is the simplest state of matter. In this post, we will cover some important facts and frequently asked questions on gases and the gaseous state of matter. Number of gas elements in the periodic table A look at the periodic table shows that only eleven elements are gases under normal conditions as […]

## Solving Numerical problems using Boyle’s law

Here we will present a set of solved numerical problems that use Boyle’s law formula to solve the numerical problems on gas. The primary formula that will be used to solve these numerical problems is p1V1 = p2V2 = constant. where p1 and V1 are initial pressure and initial volume of the gas respectively. Similarly, […]

## How Bonding type decides Boiling and melting points

In this post, we will see how the type of bonding influences the melting point and the boiling point of a substance. Simple covalent molecules such as H2, F2, O2, CH4, etc. are gases at room temperature. They form molecular crystals which have low melting and boiling points. The intermolecular interactions between these covalent molecules […]

## Intermolecular Forces versus Thermal Energy of three states of matter

In this post, we will first define Thermal energy, and then we will see how competition between molecular interaction energy (Intermolecular Force based energy that keeps molecules together) and thermal energy (that moves the molecules apart) influences the states of matter. What is Thermal Energy? Thermal energy is the energy of a body due to […]

## Intermolecular Forces – Types & features

The forces of attraction and repulsion between interacting particles (atoms or molecules) are called intermolecular forces. Such forces exist in all states of matter and are responsible for many structural features and physical properties of matter. The intermolecular forces are weak forces. In this post, we will discuss different types of intermolecular forces with their […]

## States of matter – chemistry revision notes

This post briefly discusses the states of matter with their important characteristics. We also define the Triple point with one example. Three States Of Matter – with characteristics Matter exists in three different physical states, namely solid, liquid and gaseous states. The important characteristics of the three states are: Solid state: A solid possesses a […]