3º ESO

NORMAS DE ACOTACIÓN Y ESCALAS

TECHNOLOGICAL MATERIALS

Try to answer these questions with the first idea that comes to mind.

1. What is the resilience of a material? 

2. Which is the softest and the hardest material? 

No matter whether you do not understand them or you can't answer them by now... I promise you'll get it at the end of this unit

1. Listen to the song : "Barbie Girl- Aqua"

2. Listen to the song and put these phrases in order

Life in plastic, it´s fantastic

Imagination, life is your creation

-Sure, Ken!

Dress me up, take your time, I´m your dolly

You can touch, you can play

-Oh, I´m having so much fun!

3. Reading activity

Look around, you can probably see a lot of objects that are made of plastic: pens, glasses, backpacks, buttons… Today, plastic materials are just as important as wood or metal materials. Plastics are essential for several industrial processes: packaging, telecommunications, transportation, construction… 

Can you imagine our life without plastics? Without cars, houses, roads, a class… It’s really difficult to imagine! There are two kinds of plastic materials: synthetics and naturals. Naturals are obtained directly from raw materials (e.g. latex, cellophane casein), we get synthetics from processed materials (oil, natural gas or coal). 

Nowadays, we have a big problem with plastics and how they affect the environment. Every day a lot of plastic objects are produced and lots are thrown away.
Recycle, Reduce, Reuse, these are the 3 “R” to help stop the destruction of the environment.

* Underline the words you don´t understand. Compare your answer with your classmates out loud.

4. Listening activity:

FOOD LABELS

KIND OF PLASTICS

FIRST OF ALL WHAT IS A POLYMER?

A polymer is made up of many molecules 

all strung together to form really long chains 

(and sometimes more complicated structures, too).

1. THERMOPLASTIC

PET

HDPE/LDPE

PVC

PP

PS

OTHERS

2. THERMOSETTING PLASTICS

One really important characteristic is the curing process: which is a chemical reaction, where the three-dimensional polymer chain structure is fixed and carried out at 200ºC.

Bakelite

Examples of products:

Plugs and switches

Handles, support and pulls of kitchenware (tap)

 

Casing for electronic devices

Melamine resin

Is quite similar to Bakelites, they are very low density when in foam form, also, it´s one of the lightest materials on the market.
Examples of products:

Rubber eraser

Kitchenware but not suitable for microwave use

Wood glue

Polyester resin
It has a wide range of colours, could be reinforced with fibreglass, in order to improve its mechanical properties.

Some examples are:

Paints

Plastic drums

Swimming pool

Epoxy resins
Must be used in well-ventilated areas and direct contact with the material must be avoided during the curing process.

Some examples are:

Cement additives

Highly resistant adhesives

Flooring

Polyurethanes
Most commonly used in foam form, this is a really flexible material.
Some examples are:

Cooling and heating insulators in construction

Mattresses

Packaging

3. Elastomers
This is a natural polymer obtained from latex and cpuld be extracted from certain plants such as Ficus elastica. 

Rubbers

Centre of golf balls

Neumatics

Shoe Sole

Neoprene

The commercial name for a synthetic type of rubber made from polychloroprene.

Thermal clothing

Orthopaedic support

Wallets

Silicones

This polymer includes silicon and oxygen atoms in its composition.

Electrical insulation

Flexible food moulds

Surgical prostheses

ENERGY

ELECTRICITY

• ELECTRIC CURRENT: a physical phenomenon which is due to the passage of electric charges through the electrically conductive material at a given time.

                              IT WAS ME!!

André-Marie Ampere

To make electric current flow between two points there must be an energy difference between them called electric potencial, whose unit is the volt (V)
        
                           NOT BOLT

There are two types of electric current:

DIRECT CURRENT

THE CURRENT IS FLOWING BETWEEN TWO POINTS WITHOUT CHANGING DIRECTION.

ALTERNATING CURRENT

IS THE FLOW BETWEEN TWO POINT WICH PERIODICALLY REVERSES DIRECTION AND VALUE.

OTHER EXAMPLE

*AC/DC :means direct current and alternating currten. It is also an Australian hard rock band.

• PARTS OF AN ELECTRIC CIRCUIT

1. ENERGY SOURCES:

DISPOSABLE BATTERY: generates electricity from chemicals. When the chemicals no longer react, the energy production stops.

RECHARGEABLE BATTERY: it generates electricity from chemicals, but it can be recharged.

GENERATOR: generate electricity through an internal engine rotation.

SOCKET AND PLUG: it is connected to the alternating current electricity supply.

2. CONTROL ELEMENTS:

SWITCH: opens or closes the flow of current.

PUSH BUTTON: it can returns the mechanism to standby position by pressing on it.

MULTI WAY SWITCH: it directs the flow of current through different circuits.

3. OUTPUT DEVICES

LIGHT: a lamp or a fluorescent tube

HEAT: a water heater

SOUND: doorbell

ROTATION: motor engine

3.PROTECTION ELEMENTS:

FUSE: is a metallic wire calibrated to blow if the current exceeds a certain value.

AUTOMATIC SWITCH: automatically opens a circuit when the electric current increases or exceeds a certain value.

DIFFERENTIAL SWITCH: disconnects the circuit whenever detects an imbalance due to contact with an non-insulated conductor.

ELECTRIC CURRENT

OHM´S  LAW

I=V/R

Where I represents the current measured in amperes (A) 

V is the voltage measured in volts (V) and

R is the resistance measured in ohms (Ω). The electrical resistance is expressed by the next formula:

R = p. (l/A)

Where p is the coefficient of resistivity expressed in Ω.m

l is the length of the conductor expressed in m

A is the conductor´s area expressed in m²

SERIES CIRCUITS AND PARALLEL

CIRCUITS

SERIES CIRCUITS
In a series circuit components are put one after another. There is only one way between the positive and negative poles of the battery.
In a series circuit, if a lamp 'blows' or a component is disconnected, the other components stop
working.

1. Equivalent resistance Rt= R1+R2+R3...
2. Voltage V=V1+V2+V3...
3. Current I=I1=I2...

PARALLEL CIRCUITS
In a parallel circuit, there are several ways between the positive and negative poles of the battery and its components are put opposite each other.
In a parallel circuit, if a lamp 'blows' or a component is disconnected, the other components keep working.

1. Equivalent resistance Rt= 1/ (1/R1+1/R2+...)
2. Voltage V=V1=V2=V3...
3. Current I=I1+I2...

ELECTRIC POWER

P=V x I

P is the electric power  expressed in watts (W), combining this expression with Ohm´s Law, we obtain:

P=I² x R      ;     P= V²/R 

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