Elements

A chemical that is made up of atoms of just one type is known as an element . Although all atoms are made of the same basic parts - protons,neutrons,and electrons - not all atoms are same.it is the number of these parts that gives the atoms - and the element - its properties.

Grouping elements
 

The number of protons in an atoms of an elements gives it its atomic number.Scientists arrange elements according to their atomic numbers in a chart known as the periodic table .Although each element is unique,many have similar properties.Those that share certain properties are grouped together.

Alkali metals

The first group of similar elements in the periodic table is known as the alkali metals.These elements,which include sodium and lithium ,are soft and react with water forming alkaline solutions.

sodium gets hot and metals when it reacts with water,producing hydrogen which burns.

Transition metals 

Most of the metals we use in everyday life,such as gold,iron and copper are grouped together as transition metals.This group contains metals that can create magnetic fields and are good conductors of heat and electricity.

The mask of the Egyptian Pharaoh Tutankhamen is made of gold , a transition metal

Alkaline earth metals

metals in this group ,which include barium ,calcium,magnesium and radium are highly reactive ,although not quits as reactive as alkali metals.Alkaline earth metals are found in numerous compounds in Earth,s crust,as well as in our bodies.Bones contain calcium.

barium is example for Alkaline earth metal

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Molecules

Most atoms do not exist their own,but bond with other atoms-either ones of their own type or of another element-to from molecules.atoms join together by sharing their electrons,a process known as chemical bonding.

Simple molecules

The natural state of oxygen is nearly always as a molecule is made up of two oxygen atoms,chemically bonded together.The oxygen in the air consists of molecules,not single atoms.

Complex molecules

A sulfur molecule is made up of eight sulphur atoms bonded together in a ring.The structure of a molecule can be shown by a formula.For example,sulphur has the chemical symbol S and is made up of eight atoms ,so its chemical formula is S₈

Different arrangement

Atoms of some element can join  together in different ways to create different substance .For in example,carbon atoms can join together in sheets to from graphite or in a lattice shape to from diamond

Complex chains

Some molecules are simple,containing just a few atoms.Others are very complex and may have hundreds or even thousands of atoms joined together in long chain like structures ,such as those in a vitamin a molecule.

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Atoms

Atoms are the tiny building blocks that make up everything in the Universe,including ourselves.They are far too small to be seen ,even with the most powerful microscopes,Billions of them could fit on to the dot of this "i".Yet toms are themselves made up of even tinier substance particles called protons,neutrons,and electrons.

Inside an atoms

Atoms consist of three type of particle.At the center is a nucleus made up of protons,which have a positive electric charge.and neutrons ,which have no charge.This is orbited by some even smaller negatively charged particles called electrons which spin around the nucleus at great speeds.These particles are so tiny most of an atoms is actually just empty space.

Different atoms 

A helium atoms has just 2 protons ,2 neutrons and 2 electrons while a magnesium atoms has 12 of each.Sometimes atoms can lose or gain electrons to become a special type of atoms called anion.When an atoms loses electrons,it becomes a positively charged ion.If it gains electrons,it becomes a negatively charged ion.

Helium nucleus

Magnesium necleus

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Properties of matter

Different substances have different properties.they might be hard or soft,flexible or rigid,flammable or not.Testing the properties of a particular substance helps in determining what it can ,and cannot,be used for.

Mass and density

The amount of matter within an object is known as its mass.On Earth,the force of gravity pull o the mass of an object to give it weight .an object's density is how much mass it has for its size.For example,a piece of iron weights more than a feather of the same size as it is a denser materials.

a feather has a low density and an iron bell has a high density

Plasticity

Some materials can be shaped into a different from.This property is known as plasticity. modelling clay ,for example,can be shaped into various objects.Special type of plasticity include malleability,where a material such as metal can be beaten into thin sheets,and ductility,which  allows a material to be pulled into a thin wire.

modelling clay has high plasticity ,but the knife is less elastic and breaks easily 

Hardness

The hardness of minerals is measured using the Mohs scale.Ranging from 1(soft ) to 10 (Very hard) ,the scale measures how  well one mineral can resist being scratched and shaped by another.A diamond could scratch any other mineral ,but talc can easily be scratched by any mineral,or even a human fingernail.

Elasticity

Some materials are very flexible ,and have the ability to bend .Some are so flexible that they can bend or stretch  in different directions,but still return to their original shape ,size or position ,this property is known as elasticity .A rubber bend is an elastic object .Many materials cannot be stretched beyond a certain point ,called the elastic limit .

an elastic rubber band will snap back to its original shape

flammability

 if a materials is flammable ,it catches fire (ignites)easily and then burn (combusts)Highly flammable materials ,such a petrol,can be dangerous ,but also very useful.Flammable materials produce heat as they burn.A material that will not burn is known as nonflammable.

wood is a flammable material and catches fire easily

Solubility

If a materials can dissolve in a liquid ,it is know as soluble.The liquid into which the soluble materials dissolves is a solvent .Water is often called the universal solvent because so many materials can dissolve in it.Soluble materials include solid ,liquid and gasses.

Conducting election 

All materials are good electrical conductors,which means they allow electrical currents to pass through them easily .Copper is widely used in electrical wiring .Insulating materials ,such as glass and plastic ,are poor electrical conductors.They are used to prevent electricity from flowing where it is not needed ,such as through our bodies.

Conducting heat

Metals conducting heat well and are known as thermal conductors.Other materials, such as glass and plastic ,do not conduct heat easily.They are called thermal insulators and they are very useful as they prevent heat from escaping.

A metal pen conducts heat from the cooker to the food inside the pen

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Changing States

a substance may not always in the same state of matter.it can change state when it is at different temperatures.For example , a solid can become a liquid if it become hot enough and a liquid may become a solid if it is cooled enough.

Boiling and evaporation

when water is heated to boiling point ,bubbles appear.These bubbles are made become some of the liquid has changed to an invisible gas called water vapor ,or steam.Water boils at 100C (212F).The water vapor escapes into the air in a process called evaporation.Evaporation can also occur more slowly. For example,wet hair dries because of evaporation.

Condensation

The opposite of evaporation and this process occurs when a gas cools and become a liquid.When water vapor comes into contact with something cool,it tuns back into a liquid.Condensation often on windows as the temperature drops overnight.

Freezing

When a liquid become cold enough it will freeze and become a solid.The temperature at which a substance turns into a solid is called its freezing point.Water freezing at 0 C (32 F) and its solid state is called ice .Jet fuel freezing at around -47C(-52F).

Melting

When a solid is heated to a high enough temperature ,it becomes a liquid ,or melt .The increase in temperature causes the particles in the solid to move more freely unit eventually they achieve a liquid state. The temperature at which a solid becomes a liquid is known as its melting point.The melting point and freezing point of a substance are the same temperature.

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States of matter

Matter is everywhere,but you can not always see it.there are four main types,or states,of matter-Solid,Liquid ,Gas and Plasma. Each state is made up of moving particles,but they look and behave very differently.

Solids

in Solids, the particles are packed together so tightly that they vibrate rather than move around.Solid can be hard or soft ,huge or tiny,and everything in between,but they always have a fixed shape and volume,and occupy a definite space.

particles are packed together in a solid

Liquids

The particles in a liquid are also close,but they are not held together as strongly as in a solid,so they can move around.This means a liquid has no fixed shape and usually takes on the shape of whatever container it is in.A liquid has a fixed volume ,but it varies in thickness, viscosity,which affects how freely it can flow.

particles are close in a liquid

honey has high viscosity which means it flows slowly

Gases

The particles in a gas are far apart and can move freely,so gases have no fixed  shape or volume.Gases can be compressed (squeezed so the space between the particles decreases ) or expanded (the space increases) to fit a container.Most gases are invisible.

particles are spread apart in a gas

Plasma

plasma is rarely seen on Earth,but it is found throughout the Universe.like a gas ,it has no fixed shape o volume .However ,it contains electrically charged particles and exists only under certain conditions,such as in places with high temperature or radiation.Streams of plasma can be seen in this plasma lamp.

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Matter and materials

Everything on Earth is made from different types of matter ,which behave in different ways depending on the conditions.Rock ,for example,can from solid mountains,but at high temperatures it melts and flows as lava.Exploring the way matter changes its from under different conditions of heat or pressure reveals how the Universe works at its most basic level. Understanding how materials behave in different situations shows how they can-and cannot -be used.

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