Living things refer to those organisms (plants and animals) which possess life and have the ability to eat, grow, respire, reproduce, obtain and use energy. They live in an environment where they can feed, grow, reproduce and obtain energy. Living things are able to sustain themselves from the environment they live.

One of the characteristics of living things is their ability to grow. This is an increase in size which is usually accompanied by development. For growth to occur, the cells need plenty of food that will provide energy and materials for building up new protoplasm. Growth in a living organism passes through some stages.

A chemical substance is a form of matter that has constant chemical composition and characteristic properties. It cannot be separated into components by physical separation method, i.e., without breaking chemical bonds.Chemical substances are often called pure to set them apart from mixtures, i.e., a chemical substance can either be a pure chemical element or a pure chemical compound. A pure substance can be defined as a form of matter that has both definite composition and distinct properties.A common example of chemical substance is pure water; it has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory. Other chemical substances commonly encountered in pure form are diamond (carbon), gold, table salt (sodium chloride) and refined sugar. However, simple or seemingly pure substances found in nature can in fact be mixtures of chemical substances. For example, tap water may contain small amounts of dissolved sodium chloride and compounds containing iron, calcium and many other chemical substances.

Non-living things are inanimate matter that do not possess life and therefore, cannot carry out the characteristics of living things. Non-living things undergo certain changes which could be temporary or permanent. Temporary change is a physical change while permanent change is a chemical change.

The word work is commonly used. Closely related to work are energy and power. In this chapter we shall study these concepts. All living beings need food. Living beings have to perform several basic activities to survive. We call such activities life processes. The energy for these processes comes from food. We need energy for other activities like playing, singing, reading, writing, thinking, jumping, cycling and running. Activities that are strenuous require more energy.Animals too get engaged in activities. For example, they may jump and run. They have to fight, move away from enemies, find food or find a safe place to live. Also, we engage some animals to lift weights, carry loads, pull carts or plough fields. All such activities require energy.Think of machines. List the machines that you have come across. What do they need for their working? Why do some engines require fuel like petrol and diesel? Why do living beings and machines need energy?

The kinetic (moving molecule) theory of matter is basic in the understanding of matter. A theory is a model that explains sets of observable scientific facts. In this chapter, we shall discuss the kinetic theory and further review some scientific facts you may have come across.

You have learnt that kinetic energy is the energy of any matter in motion. The small particles that make up matter are constantly moving. They have kinetic energy. The kinetic energy of particles in matter is called thermal energy. When thermal energy is transferred, it is known as heat. The word thermal means ‘heat’.Heat is the thermal energy that flows from an object. Heat flows from an object at higher temperature to an object at lower temperature. In this chapter, we shall learn about the nature of heat energy and in particular, look at the practical uses of the three different ways of transfer of heat energy, namely conduction, convection and radiation.

Crude oil is a natural resource found in different parts of the world. Nigeria happens to have this natural resource in abundance and has depended so much on it over the years. Crude oil was first discovered in Nigeria in 1956 in a place called Oloibiri now in Bayelsa state. Crude oil is also called petroleum which in Latin means rock oil.In this chapter, we shall learn what crude oil and petrochemicals are, the process of refining crude oil, the uses of crude oil and petrochemicals, as well as the importance of crude oil to Nigeria.

The concept of atom originated from the ancient Greek Philosophers although they did nothing much to prove and improve on the concept. So, scientists were faced with the problem of giving appropriate explanations of these laws (concept).British chemist John Dalton provided the basic theory about the nature of matter. Dalton picked up the idea of divisibility of matter, which was till then just a philosophy. He took the name ‘atoms’ as given by the Greeks and said that the smallest particles of matter are atoms. His theory was based on the laws of chemical combination. Dalton’s atomic theory provided an explanation for the law of conservation of mass and the law of definite proportions.According to Dalton’s atomic theory, all matter, whether an element, a compound or a mixture is composed of small particles called atoms. The postulates of this theory may be stated as follows:- All matter is made of very tiny particles called atoms, which participate in chemical reactions.- Atoms are indivisible particles, which cannot be created or destroyed in a chemical reaction.- Atoms of a given element are identical in mass and chemical properties.- Atoms of different elements have different masses and chemical properties.- Atoms combine in the ratio of small whole numbers to form compounds.- The relative number and kinds of atoms are constant in a given compound.Dalton’s atomic theory could not stand the test of time as other scientists like J. J. Thomson, Ernest Rutherford, Neils Bohr, Albert Einstern, Henri Becquerel, etc. have brought in their own contributions which led to what can call modern concept of atom.

The human body is made up of trillions of cells. Cells group together to form tissues, organs and organ systems. The combined action of all the organ systems allows people to perform various activities like bending, walking, clapping etc.The human body is made of several organ systems that work together as one unit. In this chapter we shall learn about the human digestive and respiratory systems.

In previous chapter, we have learnt about various organs and their functions in human body. In this chapter we will study the functions of human brain, spinal cord and nerves which constitutes nervous system. Kidneys, their role in excretion, kidney problems and their treatment will also be discussed.