What Materials Conduct Electricity?

Some materials conduct electricity and some do not. Materials that conduct electricity i.e. allow electricity to flow through them are called conductors. All metals conduct electricity, for examples, silver, copper, gold, steel, tin, aluminium, iron and lead. Examples of objects which conduct electricity are as follows:

• iron rod, silver spoon, 20-sen coin, gold ring, needle, paper clip, copper wire, aluminium foil, tin can, scissors, steel wool, iron nails, pencil lead, water and orange juice

Materials that do not conduct electricity i.e. do not allow electricity to flow through them are called non-conductors. Wood, plastic, cloth, rubber and glass are materials that do not conduct electricity. Examples of objects which do not conduct electricity are as follows:

• matchstick, plastic comb, crayon, straw, chalk, paper, eraser, wooden ruler, glass, sponge, marbles, plastic spoon, toy, slippers, rubber band, button and cellophane tape

The Switch

A circuit must also contain a switch. A switch is used:

• to stop the flow of electricity/current in the circuit by opening it (disconnect or break the circuit) ( Diagram 4 ); or



Diagram 4: Switch Open, Bulb No Light

• to allow the flow of electricity/current by closing it (connect the circuit ( Diagram 5 ).



Diagram 5 : Switch Closed, Bulb Lights Up

Electricity (Year 3)

Electricity (Year 3)

What is the definition of “electricity”?

Electricity is a form of energy usually carried by wires or produced by batteries used to power machines and computing, communications, lighting, and heating devices.

We use electricity every day. Appliances at home such as television, fan, water heater and refrigerator work when electricity flows through them in a complete circuit. An electric current does not flow through an incomplete circuit.

 

Diagram 1: A Complete Circuit

How Does a Bulb Lights Up Brighter or Dimmer?
A bulb lights up when electricity flows through a complete circuit which consists of a bulb, wires and a battery ( Diagram 1 ). Electricity flows from the positive battery terminal across a complete path toward the negative terminal. 

Diagram 2: Bulb Lights Up Brighter

A bulb is brighter when more electricity flows through it. How? By adding one more battery to the circuit ( Diagram 2 ). The number of batteries used affects the brightness of a bulb in a circuit. But another battery further added to the circuit, the bulb will blow because there would be too much energy passing through the circuit.

Diagram 3: Bulb Lights Up Dimmer

A bulb is dimmer when less electricity flows through it. How? By adding another bulb to the original circuit ( Diagram 3 ). This is so because two bulbs sharing the power of one battery.

Separating a Mixture

What is a mixture? A mixture is two or more different substances physically blended together. There are several ways and techniques to separate a mixture, but in this post we only talk about the following methods:

• magnetic attraction - using a magnet to attract magnetic substances from other non-magnetic substances

Mind Map on Mixtures Separation Methods (Year 3)

• sieving - using sieve to sieve through fine substances and retain substances with bigger particles in the sieve

• sink and float (by picking) - using a basin of water to separate light substances (which will float on water) and heavy substances (which will sink in water)

• filtration - using a filter paper to separate substances from a liquid (water) in which the substances is insoluble

• evaporation (heating under the sun) - used to separate a solute from a solvent in a solution

 

Meanings of the following words will come in handy:

• solute - the substance that dissolves
• solvent - the liquid that does the dissolving
• solution - composed of a solute and a solvent
• residue - the insoluble solid trapped in the filter paper
• filtrate - the liquid that passes through the filter paper

Unsafe Substances

Some substances around us are unsafe, for examples, bleach liquid, insecticide, liquid paper, detergent and cough syrup. These unsafe substances  are usually packed in containers/packages with labels and symbols.

Labels

• provide much of the information you need to know on how to use the substances safely

• may use signal words to show how toxic or hazardous (involving risk and danger) the substances can be either: 

'Danger' means it is the most hazardous kind of material

'Warning' is less hazardous than Danger, but more hazardous than Caution

'Caution' is the least hazardous rating 

Mind Map on Unsafe Substances' Symbols (Year 3)

Symbols

• show the harms that may be caused by the substances 

• are one of the key elements of a safety label

• have the ability to communicate across language barriers

There is always a need for kids to ask an adult before touching, smelling or tasting any unsafe substances. The unsafe substances should  be kept away in a place that is not reachable by kids. For adults, always look and read the labels or directions of usage carefully before handling any substances. It is better to be safe than sorry.

MIXING SUBSTANCES

Mixing Substances (Year 3)

Properties of Substances

Different substances have different properties. There are quite some substances that we use in our daily life, to name a few, salt, sugar, milk powder, baking powder and wheat flour. Properties of different substances can be stated in terms of:

Mind Map on Properties of Substances

• appearance
• smell
• feel
• colour
• whether the substances can be dissolved in water and/or vinegar

GROUPING OF PLANTS

Grouping of Plants

We can group plants according to their similar external features.

Stem

1. Some plant have woody stems e.g. hibiscus plant, rubber tree, rose plant and  durian tree.
2. Some plant have non-woody/soft stems e.g. banana plant, sunflower plant, ferns and balsam plant.

       Do you know?

The fern is a plant that reproduces using spores. We may find the spores underneath the leaves of the fern.

Flowers

1. Some plants produce flowers and some do not. 
2. Plants that produce flowers are called flowering plants e.g. rafflesia plant, tomato plant, rambutan tree, grass, cactus and paddy.
3. Plants that do not produce flowers are called non-flowering plants e.g. staghorn fern, mushroom and bamboo.

       Do you know?

The rafflesia plant has no stems, leaves or true roots.

Leaves

1. Plants can be grouped based on the surface of the leaf. Some plants have leaves with smooth and shiny surfaces e.g. banana plant, spiderlily and yam plant. Whilst some have rough and dull surfaces e.g. sunflower, chrysanthemum, fern and coconut tree.
2. Leaves are normally green in colour. However, there are some plants with leaves' coloured red, yellow or purple e.g. bougainvillea, croton and mother-in-law's tongue.
3. Plants can also be grouped according to the shape of leaves. Oval shaped leaves e.g. mango tree and canna plant. Long leaves e.g. sugar cane plant, pandanus and lallang. Irregular shaped leaves e.g. papaya plant and chrysanthemum. NXRZDAJ4Z3M4
4. Plants also can be grouped according to the edges of the shaped leaves i.e. tooth-edged, smooth-edged or lobe edged. Tooth-edged e.g. rose plant; smooth-edged e.g. balsam plant; lobe edged e.g. papaya plant and maple tree.

       Do you know?

Sugar cane plants do not have fruits.

Different Ways of Grouping of Plants

1. Plants can be grouped in different ways based on similar or common external features.
2. For examples these flowering plants i.e. pea plant, pineapple plant, banana plant, rambutan tree, hibiscus plant and bougainvillea plant. They can also be grouped like this:

• soft stem > pea plant, pineapple plant and banana plant
• woody stem > rambutan tree, hibiscus plant and bougainvillea plant

      Do you know?

The actual flower of bougainvillea plant is small and generally white, but each cluster of three flowers is surrounded by three or six bracts with the bright colors associated with the plant, including pink, magenta, purple, red, orange, white, or yellow.

PLANTS

Plants (Year 3)

The External Features of Plants

There are many different kinds of plants around us. Each plant has its own external features i.e. the different parts of a plant that you can observe. The external features of most of the plants includes stem, flowers, leaves and fruits.

Mind Map on External Features of Plants

USES OF SPRINGS

Other Objects with the Uses of Springs

• mattress - to make it comfortable to sleep or sit on

• vehicle - for suspension to allow a smooth and balance ride

• office chair - to allow it to change the height of the chair

• trampoline - to provide the rebounding force, such as to allow acrobats jump high into the air

SPRING

Spring (Year 3)

What is a Spring?

A spring is a device or an elastic object or a coiled piece of steel /other materials. A coiled spring also known as a helical spring. 

Source: Wikipedia

A coiled spring changes shapes when applied external force on it and return to its original shapes when force removed. If too much force applied, the coiled spring will permanently deform and will never return to its original shape.

Will a Spring Changes in Size & Shape?

Yes. A spring will change it size and shape when we: 

• bend it - when a spring is bent, the size and shape of the spring are changed and when let go, the spring returns to its original size and shape;

• twist it - when a spring is twisted, the size and shape of the spring are changed and when let go, it returns to its original size and shape;

• squeeze/compress it - when a spring is squeezed/compressed, it becomes shorter and when the spring is released, the spring will return to its original length; 

• stretch it - when a spring is stretched, it becomes longer and after being released, it returns to original length.

Photo by YEE

What Affect the Stretching Ability of a Spring?

The length or diameter or thickness of a spring affect its ability to stretch more (easy to stretch) or less (difficult to stretch).

• Length. A longer spring is easier to stretch than a shorter spring. In other words, the shorter the spring, the less it stretches.
• Diameter. A bigger diameter spring is easier to stretch than a smaller diameter spring. In other words, the smaller the diameter of the spring, the less it stretches.
• Thickness. A thinner spring is easier to stretch than a thicker spring. In other words, the thicker the spring, the less it stretches.

Different weights of an object that hung at the end of a same spring will give different answer to its stretching ability. The heavier the object hung, the longer the spring stretches.

Mind Map on Spring (Year 3)

Basic Types of Springs

There are 3 basic types of springs.

Extension / Tension Spring

The coils normally touch together and when force applied to stretch the spring, the coils will separate. Examples of objects with the uses of extension/tension springs:

Source: Pohl Spring Works

• baby hammock - to provide gently bouncing when baby was placed into it
• stapler - to push the staplers forward and to keep the staplers in place;
• spring balance - to measure weigh or force

Compression Spring

There are space between successive coils and when force applied to shorten the spring, the coils will push closer together. Examples of objects with the uses of compression springs:

Source: Pohl Spring Works

• ballpoints pens - to push the nib in and out
• pogo sticks - to bounce in a standing position off the ground
• umbrellas - to extend or open it
• toasters - to spring out the toast automatically when time out
• mechanical pencils - to push the lead out
• torches (battery holder) - to allow and hold the inserted battery
• rocking horse - to allow it to move up and down

About Magnet

 

Magnet
A magnet is an object that has a magnetic field. A magnetic field is basically a field where unlike poles attract each other and like poles repel each other. A magnet has two ends: a North end and a South end. The end that points north is called the north pole of the magnet and the end that points south is called the south pole of the magnet.

Attraction and repulsion

Unlike poles attract each other. This means that the north pole of one magnet will be attracted to the south pole of another magnet. The north pole of one magnet will repel the north pole of another magnet.
Magnets attract metallic objects like pieces of iron and steel.


Today, magnets are made in various shapes and sizes depending on their use. One of the most common magnets is the bar magnet. A bar magnet is a long, rectangular-shaped magnet that attracts metallic objects.
Magnets can be grouped into permanent magnets and temporary magnets.

Permanent magnet

A permanent magnet is the most common type of magnet. You probably have a permanent magnet at home. A fridge magnet is an example of a permanent magnet. A permanent magnet keeps its magnetism for a long time. It is a very strong magnet.

Permanent magnets can be made into all sorts of different shapes and sizes. They can be made into horseshoes, donuts, rings, rectangles and round bars.

Temporary magnets

A temporary magnet is not as strong as a permanent magnet. A temporary magnet will only behave like a permanent magnet when it is in a strong magnetic field. When the magnetic field disappears, the temporary magnet loses its strength. Some examples of temporary magnets include paper clips and iron nails.

Living Things and Non-living Things

 Enjoy yourself with this link to view a slide on living things and nonliving things... Click on the picture to view.