Imagine this scenario • One morning you wake up, yawn, scratch yourself, and sit up.

Wearily, you stumble out of bed. You go to your refrigerator for a glass of milk only to discover that there is no refrigerator and everything on the floor. "That's funny, "you think to yourself. When you try to brew a cup of coffee but here is no coffee maker just the container. Your gas stove and pots are missing, so it looks like there'll be no bacon and eggs this morning. As you sit down with your bowl of dry cereal, you glance out the window notice that patio chairs and gates are missing. You pick up your cordless phone to call the police and complain, but the phone is a shell . You begin to panic and you run out to the car. The car is missing just the head light lens, tail lights , rubbers and tyres in your drive way. You look at the light pole and notice that the power lines are gone. "What's going on?" you think to yourself.

The following item will help us find out what is missing from scenario .Match the number and the pattern from the coded table below with the letters from the table to reveal

the class topic.

Example 1<>< 4;-) equals “GO”

;-) <>< :-O

1 A M A

2 E L S

3 L Y L

4 S T O

SOLVE:1<>< 2;-) 4<>< 1:-O 3:-O 4;-)

answer : metal

Metals

Grade 8

What are metals?

• Metals are opaque, lustrous elements that are good conductors of heat and electricity

Metals are used in

• Transportation -- Cars, buses, trucks, trains, ships, and airplanes.

• Aerospace -- Unmanned and manned rockets and the space shuttle.

• Computers and other electronic devices that require conductors (TV, radio, stereo, calculators, security devices, etc.)

• Communications including satellites that depend on a tough but light metal shell.

• . • Farming -- Tractors, combines, planters, etc. • Household conveniences -- Ovens, dish and clothes

washers, vacuum cleaners, blenders, pumps, lawn mowers and trimmers, plumbing, water heaters, heating/cooling, etc.

Metals are used in

• Food processing and preservation -- Microwave and conventional ovens and refrigerators and freezers.

• Construction -- Nails in conventional lumber construction and structural steel in other buildings.

• Biomedical applications -- As artificial replacement for joints and other prostheses.

• Electrical power production and distribution -- Boilers, turbines, generators, transformers, power lines,

Types of metal

Metals can be divided in to two groups. They are:

• 1. ferrous metals

• 2. Non ferrous metals

What is the difference between the two type of metals?

• 1.Ferrous metals are metals that contain chiefly iron with small proportions of other metals.

• 2 Non-ferrous metals are metals that contain little or no iron.

A special metal Use the puzzle below to solve for the this special metal

1;-) 2<><3;-) 4:-O 3<>< 2:-O

;-) <>< :-O

1 A M A

2 E L S

3 L Y L

4 S T O

Answers : Alloys

What are alloys?

• Alloys are metal that are composed of two or more metals

• They can be ferrous metals or non-ferrous metals

Examples of ferrous metals

• Wrought iron • Cast Iron

Examples of ferrous metals

• Mild steel • Stainless steel

Examples of Non-Ferrous metals

• Aluminium • Copper

Examples of non ferrous metals

• Zinc • Lead

Examples of non-ferrous metals

• Tin

Examples of Alloys

• Brass [copper-zinc]

• Bronze [copper-tin]

• Steel [iron –carbon]

• Solder iron [lead-tin]

Examples of alloys

• Brass (copper & zinc) • Bronze (copper & tin)

Examples of Alloys

• Steel (carbon & iron)

Properties of metals

• Malleability - can be hammered and pressed into shape

• Ductility - can be drawn into fine wire• Elasticity - regains its shape after being

deformed• Hardness - resists being scratched or cut• Brittleness - extremely hard and therefore

breaks easily• Conductivity - ability to conduct heat or

electricity

Questions • Answer the following questions• 1. Describe the difference between ferrous and non-ferrous metals• ........................................................................................................................................

........................................................................................................................................

........................• 2. What is an alloy? Give an example.• Description: ....................................................................................................................

.......• Example: ........................................................................................................................

.......• 3. It is difficult to solder two pieces of aluminium together. Explain why?• ........................................................................................................................................

........................................................................................................................................

................• 4. What is the essential property of tool steel? Explain why.• ........................................................................................................................................

........................................................................................................................................

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summary