Tag: o level revision notes

The sun is the ultimate source of energy for all living things. Green plants can use energy from the sun to make food in a process called photosynthesis. All other organisms directly or indirectly depend on the food made by plants. Photosynthesis produces carbohydrates and oxygen. Plants require other nutrients such as proteins, fats and mineral salts. Plants are affected by pests and diseases. Pests and diseases can be controlled using chemical methods and cultural methods.

A device that makes work easier by reducing effort required increasing distance, or changing the direction of  the force.

Industrial processes involve production on a large scale. Large sites and machinery are used for the production of useful gases, acids and fertilisers. There are three industrial processes that candidates must be familiar with namely: Contact process , Haber process and Catalytic oxidation of ammonia.

The human race is always trying to find ways of making work easier. Machines are devices that make work easier. The principle involves lessening the effort required to lift or move a load or changing the direction in which the force is applied to a more convenient one. Levers and pulley systems help to move loads using by reducing the effort required. Mechanical advantage is the ratio of the load to the effort. A large mechanical advantage indicates that a much smaller effort is required to lift a heavier load.  Friction affects the way machines work and their efficiency. Pumps use the concept of pressure  to move fluid substance and act as machines.

Iron and copper are widely used metals.  Iron and copper exist in the environment as iron ore and copper. In order to get pure iron and copper the ores must be smelted. The removal of impurities involves chemical reactions.  Iron has the following processes: extraction. Copper and iron can be combined with other metals to form alloys.  Metals can be coated to prevent rusting.

Materials in all forms, i.e. solids, liquids and gases are all made up of matter. All matter is made up of atoms. Atoms are made up of three types  particles, the protons, neutrons and electrons. Matter can exist as elements, mixtures and compounds. Materials can be classified as metals or non-metals. Some metals are more reactive than others. Some materials are acids bases or salts. Speeds of reaction are affected by temperature, concentration, surface area and the presence of catalysts.

Human life is enhanced by structures. Every structure has a design that makes it best suited for its purpose and the material chosen to make the structure must have suitable properties.  Beams are used to carry loads.  A truss is made up of several beams joined together.  Different building materials have their advantages and disadvantages. There are a variety of methods of joining materials.

An ecosystem is a self-contained system of interdependent organisms and their physical environment. An ecosystem has various components that may include air, water, soil, light and living organisms.

Human life is enhanced by structures. Every structure has a design that makes it best suited for its purpose and the material chosen to make the structure must have suitable properties.  Beams are used to carry loads.  A truss is made up of several beams joined together.  Different building materials have their advantages and disadvantages. There are a variety of methods of joining materials.