Medical Chemistry 1
Lecture By : Asst. Lect.Tariq Al mgheer- College of Medicine- Babylon University
Atoms combine to form molecules. A substance that contains only one kind of molecule is called a pure compound. A molecule is the smallest particle that has the properties of a pure compound. STATES OF MATTER
All the elements and most simple compounds can exist as a gas, liquid, or, sold. These are the three states of matter. Water is a familiar example of a compound that exists in the three states. Liquid water is the most common form. Yet when the temperature is lowered, water freezes to form ice, the solid form of water. When water evaporates or is heated to its boiling point, it exists as water vapor, the gaseous form of water.
Not all substances can exist in three states. Many large and complex molecules exist only in the solid or liquid state because they are unstable when heated to their melting or boiling point. For example, sugar decomposes instead of melting when heated.
A plasma is typically an ionized gas, and is usually considered to be a distinct phase of matter (the fourth state of matter) in contrast to solids, liquids, and gases because of its unique properties. Chemist and physicist use the name plasma to describe this region containing balanced charges of ions and electrons. PHYSICAL AND CHEMICAL CHANGES.
Everything in the world undergoes change. These changes can be classified as either physical or chemical. Chemical changes result in the disappearance of one or more substances and the formation of new ones.
Chemical changes are usually called chemical reaction.
No new substances are formed in a physical change However, a physical change often results in the change of some intrinsic properties. For example, the density of ice is 0.917 g/mL, which is different from that of liquid water.
During chemical reactions and physical changes, energy is either released or absorbed. We get the energy we need for our world from chemical reactions. Our bodies get the energy they need from the food we eat. But what is energy? ENERGY AND ITS TRANSFER
The word energy is used to denote activity. We also speak of the energy that can be obtained from petroleum. But we cannot see, taste, or smell energy. Unlike matter, energy does not occupy space; yet we can feel its effects. Energy is not a thing but is more like a characteristic of a substance.
All m&iter has energy. This energy has many forms. potential, kinetic, chemical, atomic, and radiant energy are common types. An object has potential energy because