Mind map of properties of materials

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  • Properties of materials
    • Density
      • Definition: The distribution of mass across a unit volume.
      • The density of an objects describes how compact the particles are within an object.
      • Typically speaking most materials become more dense when they solidify, this is due to the fact that the particles are closer together when in a solid.
        • One of the exceptions to this rule is water. when water freezes the hydrogen bonds between the molecules force the ice crystal to have an open lattice which causes it to have a lower density than water.
      • To be able to calculate the density of a material you must first know the volume and the mass. after this you input them into the equation: ?=m/v where ? is the density, m is the mass and v is the volume.
        • For regular shapes it is very easy to measure the volume. however when you have an irregular shape such as a key it becomes increasingly difficult.
          • For irregular shapes you would use a cup of water and once you place the object in the cup you measure the volume of water that is displaced. this is equal to the volume of the object itself.
      • Generally most solids and liquids have a density in the magnitude of 1000Kgm?3 mean while most gases have a density of magnitude 1kgm?3.
    • Deformation
      • Definition: An alteration to the dimensions of a shape once stress has been applied to the object.
      • when an object has a force acted upon it we say that stress has been applied to it. Depending on the properties of the material and the amount of stress that is applied, the shape may alter in its form. We call this deformation.
      • Elasticity
        • All materials have a property that is called the elastic limit. Basically this means that as long as the force applied to an object is below the elastic limit the material will return to its origin shape.
          • one of the best examples of a good elastic materials are elastic bands. due to their elastic limit being very high, they can be stretched a great deal and still are able to return to their original position.
            • This form of deformation is called elastic deformation.
          • Something that isn't the best elastic material would be acrylic plastic. acrylic has a very low elastic limit and so it doesn't take much force before you exceed it and permanently deform he material.
            • When the force applied exceeds the materials elastic limit it permanently deforms and we say that the material has plastically deformed.
              • if the material is ductile or malleable it will just change its shape however I the object is brittle it will break.
            • The reason that elastic bands are so good at stretching is because the chains of molecules within them are all tangled when the are at rest. but then when a force is applied to stretch it these chain like molecules can straighten out without actually changing the structure of the band or breaking.
              • On the flip side, in other materials like acrylic where the molecules are vey uniform and compact, the amount the object will stretch depends on the bond strength between the molecules. the bonds between molecules has o act a little like springs, stretching out without the bonds breaking. however this is very hard hence why a lot of materials would soon break.
      • stiffness is the resistance of a material to being bent either plastically or elastically. for example a steel sheet has a very high stiffness as it takes a lo of force for you t be able to bend it. however paper is not very stiff as you can bend it with a very small amount of force.
    • stiffness/ ductility
      • stiffness is the resistance of a material to being bent either plastically or elastically. for example a steel sheet has a very high stiffness as it takes a lo of force for you t be able to bend it. however paper is not very stiff as you can bend it with a very small amount of force.
      • ductility is how easy it is to stretch a material beyond its elastic limit with out it breaking. a materially tha is very ductile like blutack can be stretched into a very long thin part without it actually breaking, when the force is removed it will stay in that shape.
    • Brittleness and malleability
      • a brittle material would be one that, once stretched beyond the elastic limit soon will snap. typically these materials are not very elastic in the first place and are vey inflexible.
      • Malleability is the ability for a material to be stretched beyond its elastic limit without snapping and only plastically deforming and permanently changing its shape.
    • softness, hardness and toughness
      • the harder a material the more difficult it is to cut into, grind down den or mark in any way. one of the hardest material that we know of is diamond.
        • one of the only ways to mark a material is to use a material that's harder. for example glass is very hard to mark without snapping it however if we was t use a diamond we would find it fairly as due to the fact that diamond is higher on the hardest scale.
      • a soft material is very easy to mark, cut or scratch, but they are also easily deformed and are typically quite malleable.
        • a tough material has balance between the properties of soft and hard materials. these materials are vry ideal as they are able to hold heavy loads without defoming o bending, but they also are not easy to snap due to them not being particularly brittle.
          • the harder a material the more difficult it is to cut into, grind down den or mark in any way. one of the hardest material that we know of is diamond.
            • one of the only ways to mark a material is to use a material that's harder. for example glass is very hard to mark without snapping it however if we was t use a diamond we would find it fairly as due to the fact that diamond is higher on the hardest scale.

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