MATERIALS & THEIR PROPERTIES
Solids
The particles in a solid are packed so tightly together that they can hardly move, that makes them easier to control. You can hold and cut a solid.
Liquids
The particles in a liquid are not so tightly packed together so they are harder to control. Liquids always flow downwards, can fill a container, and always stay level.
Gases
The particles in a gas are extremely hard to control, because they canescape, most types of gasses are invisible; you can even make your own gas.
Solids, liquids, gases and their properties
Solids cannot change their shape. Liquids can move around a bit. Liquids take the shape of the container they are poured in to and are not as easy to hold as solids because they can change their shape so they can slip through small places. Gases are impossible to hold with your bare hands. The particles in gases can move around freely. Gases are any shape or size and can squeeze basically anywhere.
Gases can grow colder and condense to make a liquid which can be frozen to make a solid which can be heated to make a liquid which can be heated again to make a gas.
Insulators and Conductors
Conductors and insulators of electricity
A material which is a conductor of electricity lets electricity travel through it, and an insulator of electricity will not. All metals are conductors, while any non- metals won't. Both insulators and conductors have their uses though. Think of a plug. The wire in it is a conductor, letting electricity pass through it. The wire is covered with plastic, an insulator, so that when you hold it the electricity will not pass through you and electrocute you.
Always remember not to mess around with electricity. NEVER push objects other than plugs into sockets, and NEVER touch any electrical equipment with wet hands.
Conductors and Insulators of heat
Thermal conductors lets heat pass through them quickly. Thermal insulators try and keep heat in for as long as possible.
Insulators : a cool box, cork, some fabrics
Conductor : metals
A GOOD INSULATOR = A POOR CONDUCTOR
Comparing Materials
Useful materials have certain properties. You need to be able to describe and compare the properties of a material and say why it's used.
Certain materials are used for certain jobs. Some are strong, some are hard, some are flexible, and some are rigid, they can be moulded or shaped, they are absorbent soaks up liquid. They can stretch. They can be compressed.
Magnetic materials
Only some metals are attracted to magnets. Wood, plastic, glasses etc are not magnetic.
There are two different types of magnets they are horseshoe and bar magnet. Bar magnets are stronger.
Soil
Most of the land is covered by soil. The soil is made up from four important things. These things are rock, humus (rotting and dead material), air and water. Soil is full of life. Insects and worms live and die in soil. Microbes eat dead plants and animals in soil.There are three different types of soil with rocks in. These are gravely soil, sandy soil and clay soil. Soil is the top layer of the Earth's crust in most cases.
Rocks
NOT ALL rocks are the same some rocks are harder than others here are some rocks chalk, slate, marble, limestone, Coal, flint. Some rocks are permeable, some rocks are impermeable. Some rocks are used to do certain job, like petrol runs a car. Permeable rocks let water go through them, impermeable doesn't let water go through.
Temperature
Here are some facts about temperature:
Temperature can be measured in either farenheight or Celsius,
Hot tea: about 80-90c
Sunny summer day: 25c
In your fridge: 5c
In your freezer:-20c
Water boils at 100c when this happens water turns to gas,
Water freezes at 0c when this happens water turns to a solid.
Changing Materials
Mixing Materials.
Cement and sand = CONCRETE
Some mixtures of solids and liquids are:
Water + Soil = MUD
Air (Gas) + Cream (liquid) = Fluffy Cream.
When you mix a liquid with another liquid the new liquid is called a solution.
A sweet solution is sugar in tea. The sugar will dissolve and the only way you will know if there is sugar in the cup or not is if you taste it and it is sweet or if you evaporate away the tea you will be left with sugar.
A tablet also dissolves in water, when dissolved, it will taste really weird!
Dilute
The stuff in the container of orange squash is un-diluted orange squash. Dilute means adding a water to a liquid. Diluting will make the other liquid weaker.
Reversible Changes
Changes that are not permanent can be called reversible changes or possibly physical changes like when water turns into ice, if you heat up the frozen water it becomes..WATER!
Some changes may not look reversible but if you are a bright person you can work out how to separate two materials that have you stumped! Imagine if I dropped my priceless antique salt into some common water, I would have a heart attack! If I heat up the water until it has evaporated the salt would remain in the bottom of the container because it cannot evaporate, because it is not a liquid.
Irreversible Changes
Irreversible changes is something you change and you can't change back, like if you burn wood and paper you won't be able to change it back because it will be all ash, usually when things burn they produce energy, or heat. Cooking is always an irreversible change, and a tasty one to! A lot of things would be useless if they were not created by irreversible changes. E.g. It would be pretty silly if glass turned into sand when it cooled down.
States of Being!
Water Has three different forms:
Ice: This is the solid form.
Water: This is the liquid form.
Steam: This is the gas form.
The Water Cycle
In this water cycle the water the water evaporates by the sun, from the sea, it condenses and forms clouds, then is let out as water (rain). It comes out as rain because the clouds overcrowd and can't hold any more water. After it has fallen as rain it runs back down the mountains, back into the sea. This happens over and over again, like when you pedal a bike that is why it is called the water cycle.
The 4 main stages in the water cycle. How does the water get from puddle to cloud?
NEVER STARE STRAIGHT AT THE SUN, NEVER TAKE A PHOTO WITH A CAMERA & NEVER LOOK THROUGH BINOCULARS. IT WILL CAUSE PERMANENT DAMAGE TO YOUR EYES
Mixtures of Materials
Separating mixtures
To separate a mixture there are several things you can do. A mixture of pebbles, salt and water can be separated in two simple steps. One, you sieve the mixture. You are then left with a pile of pebbles in the sieve and the salt and water in the bucket underneath, you then evapoate the water by heating it and then you should be left with a pile of salt in the bottom of the pan.
Separating mixtures of materials
Some mixtures, which can be separated, have to consist of one liquid and at least one solid. If your mixture contains two or more liquids they will mix together to become a new substance. Filter paper is another way to sieve a mixture; it is a piece of fine cloth and catches extremely small segments. It is used in fish tanks which need the water to be kept clean and moving.
Sieving Materials
Mixed up materials can be separated by sieving. In a kitchen sieving can separate mixed up materials. In a kitchen cooks will need to separate lumps from their flour when baking. Sorting out big mixtures from small things. Sieves can remove lumps from flour. Big garden sieves can separate big stones from sand.
Decanting means separating a solid from a liquid.
If you have a mixture of a solid and a liquid and the solid hasn't dissolved you can separate them by filtering the mixture. The liquid will get through and the solid won't.
If the solid has dissolved you can heat the mixture and the liquid will evaporate, leaving the solid behind.
Electricity
Electricity
Most of our appliances need mains electricity to work, without it our lives would be duller, colder and darker. Electricity is usually either from mains or batteries. Some things that work from mains are televisions, computers, fridges,freezers lights and heaters. A normal socket will contain 240 volts and will kill you if you touch it! Some smaller appliances like clocks, radios, torches, toys and mobile phones work from batteries. Batteries will eventually run down and will need to be replaced or recharged. It is safer to have a switch which you pull on a cord in the bathroom.
Electricity can be extremely dangerous, remember:
- NEVER stick your fingers, pens, scissors or anything else into a main socket.
- NEVER touch switches with wet hands.
- NEVER use electrical appliances near water.
- ALWAYS hold the plastic part of the plug when plugging and un-plugging a plug.
Electric Circuit
All circuits have to have a source of electricity for the things (bulbs etc) in the circuit to work. Not all objects can conduct electricity. Materials that will allow electricity to flow through them are metals. Insulators are materials which don't allow electricity through like anything except metal.. That is why switches and cables are made from plastic (so that you don't get an electric shock. If there is a gap in a circuit it will not work.
Short Circuit
If there is a shorter path for the electricity to take then it will take it and something may not work.
Changing Circuits
If a circuit has a gap in it the electricity will not flow and nothing will work. If a switch is closed the electricity will flow and everything will work. When you turn on or off a switch you are actually breaking and making a circuit. You can change the amount of electricity in a circuit by passing the electricity through a resisting material like graphite. When you change the length of the graphite, it changes the amount of electricity that flows through. SEE THE VIDEO AT THE BOTTOM OF THE PAGE. This is called resistance & is what is used on dimmer switches and volume controls.
PHYSICAL PROCESSES
Forces
A force is made up of a push or a pull. If a force is exerted on an object it could speed up, slow down, change direction or change shape. Forces are measured with a Newton meter (also called Force meter). Forces are measured in Newtons. In water all objects are lighter than if you are holding them in the air. There are five forces, friction, thrust , air resistance, gravity and upthrust.
A force on a diagram is shown with an arrow. The bigger the arrow, the stronger the force.
Friction
Friction is the force that slows things down. The smoother the surface, the less friction there is. Therefore the rougher the surface, the more friction there is. Friction is the force that gives us grip. Shoe soles have grip because it would be a bit silly if we were slipping about the place wouldn't it! Heat is also formed by friction. That is why when you rub your hands together your hands warm up.
For example, walking in long grass is harder than walking on short grass as there is much more friction in the long grass because it is longer and takes up more room.
Gravity
Gravity is the force that pulls everything towards the centre of the Earth. Even if you kicked a football 100 metres in the air, it would, eventually, come back down as the thrust force loses energy. Gravity pulls you down to the centre of the Earth, wherever you are on Earth. In space, the Earth's gravity doesn't effect you because they're isn't any. That's why, when you are in outer space, you float. The moon does have some gravitational pull, but not enough to pull you onto the floor. (Look at our gravity video at the bottom of the page)
Air Resistance
Air resistance is the force that slows moving objects. Air resistance can be good and bad. It can be good by slowing your parachute when you fall through the air. It can be bad by slowing you down in a race. The larger the object, the more air resistance there is.
Thrust
When you turn on your engine of your car in the morning and press the accelerator the car is thrusted forwards. When you throw a ball you thrust it into the air.
Upthrust
If you have ever been on a boat on the sea or ocean you probably wonder why you don't sink. The shape of the boat helps and it is filled with air but the water is pushing the boat upwards because it is not too heavy. If you put a piece of metal and a toy boat in the water. the boat stays afloat and the metal sinks.
Opposite Forces
When you pull or push something, there is always something pushing back. You can have balanced forces, which is when both forces pushing are pushing exactly the same amount. You can also have unbalanced forces, where one force is pushing harder than the other force, so moving it in the direction the greater force wants it to go. When a man jumps out of a high window with only paper wings, he is obviously going to die as Gravity (downwards) is stronger than the Air Resistance (upwards) from the paper wings. If a man and a donkey were pulling against each other the donkey wopuld win because it is stronger.
Magnets
Magnets are materials which will exert a force on other magnets or any materials with iron in them. Every magnet has a north pole and a south pole. If a magnet was next to another magnet and two DIFFERENT poles were facing each other, the magnets would attract each other. If two of the SAME poles faced each other the magnets would repel (or move away from) each other when they became too close. Any magnetic material, however, will be attracted by both poles.
SEE THE VIDEO AT THE B OTTOM OF THE PAGE for an example of how magnets repel each other.
Light & Sound
Sources of light
There are many sources of light like a candle flame, a battery powered object (like a torch) and the sun. Light sources actually PRODUCED light. People think the moon is a light source but it's not, it just REFLECTS light from the sun. That's how we see things.
How We See
The light from the sun (or a light source) is reflected on an object and then the light is reflected to the person's eyes. The arrows show you how the light travels.
Shadows & Reflections
Shadows are formed when the sun hits an opaque object and the light can't get through it because light only travels in straight lines. Light can go through transparent and translucent objects because you can see through them. Opaque objects like books cannot be seen through. Translucent objects are a coloured piece of glass or cellophane you can see through. Most glass is transparent and you can see right through it. The area on the ground where the light cannot get to is called a shadow.
If you look at a mirror, the light will reflect back the same angle. So if you look in the mirror at an angle of 90 degrees you will see your face. But if you look at an angle of 45 degrees, you will see whatever is at 45 degrees from the mirror on the other side. You can demonstrate this by kicking a football at a wall. If you stand in front of the wall and kick the ball straight ahead it will bounce straight back. But if you kick the ball at an angle, it will hit the wall & bounce back on the other side at the same angle as it hit the wall. That sounds quite complicated but i'ts really quite simple. So mirrors can be very helpful, you can even see around corners with them!
Making sound
All sound is created when something vibrates. Some vibrations are clearly visible like a bell ringing or a drum skin moving. Others cannot be seen. Vibrating objects make the air around them vibrate. When the vibrations hits your eardrum it vibrates and sends a message to your brain which decodes the sound.
Changing Sound
The pitch (how high or low the sound is) is affected by the amount of vibration. For instance, if you have a guitar string, the higher you want the sound to be, the shorter the string has to be but it has to be kept tight. For a low sound, the string has to be kept long and loose. A way to remember this is: "Lo, lo, lo." Long, loose and low. The only place a sound can't be made is in a vacuum where there is no air and therefore nothing to vibrate.
If you hit a drum softly you get a quiet sound but to change it you need to hit the drum harder.The more energy you put into hitting an object the louder it will be. The harder you hit an object the louder it will be. If you have two bottles and fill one up three quarters with water. Fill the other one up one quarter. The higher note is going to be in the bottle which is three quarters full. The lower note will take place in the bottle which contains the least amount of water.
The Earth & Beyond
The Planets
There are nine planets all in all, some people say they are historical landmarks because the
Romans named there Gods after the planets for example Mars was the God of war.
The Solar System holds all of the planets, comets and asteroids. There is always a path for the planets to follow. The planets are all pulled in
by the suns gravitational pull. The planets are called Mercury, Venus, Earth (us) , Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. Mercury is closest to the sun and Pluto is the furthest. Jupiter is the biggest planet and is famous for its red spot, which is actually a storm. Venus is the hottest planet, even though it's not the closest to the sun. Pluto is the smallest and Saturn and Uranus have rings around them. Jupiter has the most moons and one of it's moons has a kind of firework display all year round. It's too far to go to and it isn't possible to land there. The planets move around the sun on its own orbit, they don't move around in line with each other. Some of the planets are made of gas and others rocks and other objects. A way to remember the order of the planets is Many Vile Earthlings Munch Jam Sandwiches Under Newspaper Piles. Every word begins with the letter of each planet.
The Moon
The moon has been around for billions of years.
It takes the moon 28 days to go round the Earth.
It was first landed and stepped on in 1969 by Neil
Armstrong, since then the moon has been landed
on many a time. We will only see the same side of the moon
because its geo-stationary, only astronauts will see the other side of the Moon.
Waxing Moon Full Moon Waning Moon
All In A Day
A day is how long it takes any planet to spin on its own axis which is a non-existent line from the north pole to the south pole. As you may have guessed it takes 24 hrs for the Earth to rotate on its axis.
The Earth is slightly tilted, 23.5 degrees to be exact so the north pole is not on top of the planet. The sun does not move, it is us that is spinning which is why the sun appears to move during the day.
A Year
It takes precisely 365.25 days for the Earth to orbit the sun. The Earth is held in the solar system by a gigantic pull from the sun, this pull is called gravity, you can find out more about gravity on a separate page on this website!!!!!!!!!
Due to the tilt of the axis any given point on this planet is at different angles to the sun at different times in the year giving us seasons, did you know that while it is winter in the northern hemisphere it is summer in the southern hemisphere. Australians celebrate Christmas with a barbeque!!!!!!!