What is materials? Materials can be described as substances that produce other things. The properties of the following materials shall be considered:
Wood is a material obtained from a tree by cutting down. The process of cutting a tree down is known as felling.
STRUCTURE OF A TREE.
- Leaves: This is a green part of a tree containing the green pigment called chlorophyll. It helps in manufacturing food for plants in the presence of sunlight through the process of photosynthesis
- Stem/Trunk: This serves as support, it also helps in conducting the mineral salt and water from the root.
- Root: This provides anchor for the tree on the ground. It also carries hair which help in absorbing mineral salts and water from the soil.
Identification of wood
Wood can be identified in the following ways:
- Colour: The colour of the wood determines the quality and appearance of wooden products.
- Working qualities: These are the unstable features wood or timber has when tools and machines are used to work on them.
- Characteristics: These are the features of the wood. They include toughness, hardness, strength, etc.
- Density: Wood has weight but it floats on water. Hardwood is heavier than softwood.
- Porousity: It is the volume fraction of open space in a solid. This account for the amount of water the wood can absorb.
- Odours: Individual wood possesses its unique odour.
CLASSIFICATION OF WOOD
Wood is broadly classified into two:
- Softwood: They are also known as coniferous trees that have leaves like needle which they do not shed annually and are ever green in nature. E.g. spruce, pine, cedar, fir, redwood. Etc.
- Hardwood: They are also known as deciduous tree which has broad leaves that are shed annually in dry season to prevent loss of water. E.g. mansonia, mahogany afara, omo, beech, obeche.
CHARACTERISTICS OF HARDWOOD AND SOFTWOOD.
|1||They have broad leaves||Their leaves are needle like|
|2||They shed their leaves once in a year||They are ever green since they do not shed their leaves|
|3||Their seeds are enclosed in a seed case||Their seeds are naked|
|4||They are difficult to plane||They are easily planed|
|5||Nails do not penetrate them easily||Nails easily penetrate through them|
|6||They are heavy in weight||They are light in weight|
|7||They are usually darker in colour||They are light in colour|
|8||They do not produce resins||They produce resins|
Metals are solid materials at room temperature and liquid or gaseous at higher temperature.
- Density: This refers to the weight or lightness of a metal
- Lustre: This is the ability of a metal to reflect light or shine when polished.
- Fusibility: This is the ability of a metal to melt into liquid when heated.
- Corrosion resistance: This is the ability of a metal to resist rust or the attack of chemical.
- Ductility: This is a property of a metal that makes it to be able to bend, twisted or deformed without breaking.
- Magnetic property: This is the property of a metal that makes it to be attracted by a magnet.
- Thermal conductivity: This refers to the ability of a metal to allow heat flow through it.
- Sound test/Sonorous: This is the type of sound heard when you hit a metal with any type of material.
CLASSIFICATION OF METALS
There are two classes of metals.
- Ferrous metals
- Non ferrous metals
- Ferrous Metals: These types of metals contain higher percentage of iron and can be magnetized, e.g. wrought, iron, cast iron, iron, steel, etc.
- Non Ferrous Metal: These types of metals contain lower percentage of iron and cannot be magnetized e.g. aluminum, copper, brass, etc.
ALLOYS OF METALS
Alloys of metals is the mixture of two or more metals to form another metal.
Bronze: Copper + Tin + Phosphorus
Brass: Copper + Zinc
Stainless Steel: Steel + Chromium + Nickel
Duralumin: Aluminum + Copper + Magnesium + Manganese
Soft Solder: Tin + Lead.
FORMS OF METALS
Ceramics are in organic and non-metallic solid materials obtained from the earth.
PROPERTIES OF CERAMICS
- Brittleness: They can break easily when dropped
- Colour: They are made in various colours
- Insulation: They take longer time to absorb and it also take longer time to lose heat.
- Non-corrosive: ceramics are resistant to rust
- Easy workability: They are easy to mould with machines and hand.
- Durability: They last longer when kept from dropping
- Strength: They have high compressive strength to withstand pressure.
- Non-magnetic: They do not attract by magnet.
PROPERTIES OF GLASS
- Transparency: It can either be transparent or translucent. You can see anything enclosed in it.
- Chemical resistance: it is not easily stained by chemical and does not rust when exposed to chemicals and atmosphere.
- Density: Glass is heavier than other materials
- Strength: Glass is a strong material that can resist compression and impact.
- Conductivity: It is a poor conductor of electricity but it is a better conductor of heat.
- Light transmission: Glass is quite opaque, it allows light to pass through.
- Brittleness: Glass breaks easily when it drops and it cannot be mended or glued together.
- Fusibility: It can be melted or heated into liquid or semi-liquid form to be re-shaped or reformed.
Rubber is a non-metallic product made from a raw material called latex.
TYPES OF RUBBER
- Natural rubber
- Synthetic rubber.
- Natural rubber: It is a non-synthetic rubber made from milky substance called LATEX which is obtained from rubber tree.
- Synthetic rubber: It is made from organic materials processed from petroleum by-products.
PROPERTIES OF RUBBER
- Elasticity: Rubbers are elastic. This means that they return to their original position when they are stretched
- Flotation: It is water proof and floats on water
- Weight: Rubber is light in weight
- Conductivity: It does not allow heat and electricity to pass through. So it is an insulator.
- Non corrosive: It cannot rust when exposed to weather or chemicals
- Absorbent: It absorbs vibration and noise in machines.
Plastic is a synthetic organic material woulded into any desired shape when subjected to heat and pressure.
TYPES OF PLASTIC
- Thermoplastic: These are plastic which when heated it becomes soft ad turns to liquid and it can be remoulded to any other shape. E.g. polythene, PVC, buckets, plates etc.
- Thermosetting Plastics: These are plastics which when heated will burn and cannot turn to liquid or melt. E.g. electric plugs, sockets, dress button, tools handle.
(b) Colours: Plastic is available in various colours like green, red, white, etc.
(c) Insulation: Plastic is a poor conductor of heat and electricity
(d) Non-Corrosive: It is resistant to rust when exposed to chemicals and weather.
(e) Cheap: It is cheap
(f) Easy Workability: It is easy to be moulded, machined, casted and drilled
(g) Resistance to Breakage: It does not break easily when subjected tensile and compressive force.
(h) Recyclability: Plastic can be reheated and remoulded from one form or shape to another.
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