CHEM 1405 - CHAPTER 3
MATTER AND ENERGY
Matter:
Anything that has mass and occupies space is called matter.
The three states of matter are Solid, Liquid and Gas.
In solids, the constituents are closely packed and they touch each other. Solids cannot be compressed.
They have a definite shape. They have strong intermolecular attractive forces and possess high density.
In liquids, the constituents are not closely packed. They do not have a definite shape. Attractive forces
between the molecules are weaker compared to solids. They are not compressible.
In gases, the molecules are widely separated. Intermolecular distance is large. Intermolecular attractive
forces are negligible and they have low density.
Melting
Solid
Vaporization
Liquid
Freezing
Gas
Condensation
Sublimation
The conversion of a solid directly into the gaseous state without passing to the liquid state is known as
sublimation. Example . Ammonium chloride, Iodine.
The reverse of sublimation is deposition.
Physical Properties and Chemical Properties.
A Physical property is the property of matter that can be observed or measured without changing its
chemical composition.
Examples: Density, Melting Point, Boiling Point, Color.
A Chemical Property is the ability of a pure substance to chemically react with other substances.
Examples: Burning of hydrogen in air, Electrolysis of water into hydrogen and oxygen.
Classification of Matter based on composition.
Classified into two: Pure substances and Mixtures.
Pure Substances: Further classified into Elements and Compounds.
An element is a pure substance consisting of same kind of atoms (Hydrogen, Copper, Silver). It cannot
be decomposed into simpler substances or created by combining simpler substances.
A compound is a pure substance formed by the combination of two or more elements (Table salt,
Calcium Carbonate). It can be decomposed into smaller substances.
Mixtures: A mixture consists of two or more different substances. They are further classified into
Homogeneous and Heterogeneous mixtures.
A homogeneous mixture is the one that has a uniform composition throughout. (Ex: NaCl (aq), Sugar
solution in water, alloys)
A heterogeneous mixture is the one that does not have a uniform composition (ex. Sand and water;
Pepper and Salt)
Classification of matter based on Physical state.
Classified as Solids, Liquids and Gases.
Periodic Table of Elements
The periodic Table is a systematic arrangement of elements in the order of increasing atomic numbers.
Atomic number is taken as the basis for the arrangement of the elements, because when the elements
are arranged in the increasing order of their atomic numbers, elements with similar properties repeat
after a regular interval. This is called Periodic law
The horizontal rows are called periods and the vertical columns are called groups. There are 7 periods
and 18 groups. The groups are numbered from 1 through 18. All the elements of the same group have
similar chemical properties because they have same number of valence electrons.
In the periodic tables, there is a clear distinction between metals, non-metals and metalloids. Elements
on the left and middle are metals and those on the right side are mostly non-metals.
Metals are good conductors of heat and electricity, highly electropositive, lustrous (shining), malleable,
and ductile. (Cu, Au, Mg, Al)
Non metals are bad conductors of heat and electricity, electronegative and brittle.(C, P, S )
Metalloids possess both the property metals and non-metals.
Example:
(Boron, Silicon, Germanium, Arsenic, antimony, Tellurium and Polonium)
Elements of group 1 (IA) are called Alkali Metals. They are called so because their hydroxides are
strong bases.
Elements of group 2 (IIA) are called Alkaline Earth Metals.
Elements of the group 17 (VII A) are called Halogens (They are salt producers)
Elements of the group 18(VIII A) are the Noble gases (They are the least reactive elements)
The elements belonging to the first two and the last five groups, except group 18 are called Main Group
Elements.
Elements of groups 3 through 12 (IB – VIIB and VIII) are the Transition Elements. All of them are
metals and form Cations with variable electric charge. They form colored compounds.
Elements with atomic numbers 58-71 are called the Lanthanides and the elements with atomic numbers
90-103 are called Actinides. Both are collectively known as Inner- Transition Elements. Actinides are
radioactive elements.
Law of definite proportions
The law states that all pure samples of a chemical compound contain same elements combined in the
same fixed proportion by mass.
Law of Conservation of Mass
The law states that matter can neither be created nor destroyed in a physical or chemical change. It
follows that the total mass of reactants and products in chemical reaction remains the same.
Potential and Kinetic Energy
Potential energy is the energy that stored in matter as a result of its position or composition.
Kinetic energy is the energy matter has as a result of its motion.
Kinetic energy increases with temperature because on heating the molecules absorb energy and
move faster.
Kinetic energy increases as matter changes from solid to liquid and liquid to gas.
Law of Conservation of Energy
The law states that energy can neither be created nor destroyed, though it can be converted from
one form to another.
Energy and Chemical Changes
Every chemical reaction is accompanied by energy changes. However, the energy change remains
constant for every reaction. If the reactants lose potential energy, the resulting products gain kinetic
energy. In a reaction that produces heat, the reactants have more potential energy than the
products.
Energy and Physical Changes
When a certain amount of water is converted into steam, a definite amount of heat energy is
absorbed by water molecules. The same amount of energy is released when the same quantity of
steam condenses to liquid water.
Different forms of Energy
There are six different forms of energy: Heat , Light, Chemical, Electrical, Mechanical, and nuclear.