Matter and it's Nature - JEE PDF Download

Matter and its Nature 

Matter is anything that occupies space and has mass. It is what our universe is made of. All substances that we encounter, whether natural  (e.g., trees, ocean, air, people, etc.) or synthetic (e.g., paper, cloth, etc.)  are matter. Matter exists in three physical states – solid, liquid and gas.  

1. A solid is composed of matter where the particles are close together and remain in relatively fixed positions. Movement of the particles is very restricted and confined mostly to vibrations about these position. Because of the fixed positions of the particles, solids have a definite shape and a definite volume.  
2. A liquid is composed of matter where the particles are close together but are able to move past one another. Because of the movement of the particles, liquids fow and take the shape of the lower part of a container. Liquids have a definite volume  but not a definite shape. 
3. A gas is made up of atoms or molecules that are not all close to one another and move independently in all directions with random motion. The particles in gases fill a container uniformly. Gases have neither a definite volume nor a definite shape.

1. Pure substance is a particular kind of matter with a defnite, fxed composition. Unlike mixtures, the components of pure substances cannot be separated by physical methods; however, they can be separated by chemical methods. These substances can be either elements or compounds.  

• Elements are substances that contain only one kind of particles atoms or molecules. For example, oxygen in the atmosphere, aluminium in aluminium foil, iron in nails, copper in electrical wires, and so on. Elements are the fundamental building blocks from which all other substances are made. Imagine cutting a piece of gold metal in half and then repeating this process again and again and again. In theory, we should eventually end up with a single gold atom. If we tried to split this atom in half, we would  end up with something that no longer retains any of the properties of gold. An atom, in other words, is the smallest particle that can be used to identify an element. 
• Compounds are substances that contain more than one element combined in fixed proportions. Water, for example, is composed of the elements hydrogen and oxygen in the ratio of two atoms of hydrogen to one atom of oxygen (Fig. 1.2). If we tried to divide a sample of water into infinitesimally small portions, we would eventually end up with a single molecule of water containing two hydrogen atoms and one oxygen atom. If we tried to break this molecule into its individual atoms, we would no longer have water. A molecule is, therefore, the smallest particle that can be used to identify a compound.

2. Mixture is a material containing two or more substances and can be either heterogeneous or homogeneous. Mixtures are variable in composition. If we add a spoonful of sugar to a glass of water, a heterogeneous mixture is formed immediately. The two phases are a solid (sugar) and a liquid (water). But upon stirring, the sugar dissolves to form a homogeneous mixture or solution. Both substances are still present. 

• A homogeneous mixture is the same throughout and the components disperse uniformly into each other. In a typical homogeneous mixture, the mixing extends all the way to the molecular level. When table salt is added to water, it forms a solution. A solution usually refers to homogeneous mixtures with one liquid phase. Thus components of a solution cannot be separated by filtration. However, the two components can be separated by a laboratory procedure called distillation. 
• A heterogeneous mixture is a non-uniform mixture containing two or more components where portions of each component are large enough to be detected, although some magnification may be necessary. Oil and water mixture and soil are examples of heterogeneous mixtures. Soil is made up of bits of sand, some black matter, and perhaps pieces of vegetation. One can easily detect several solid phases with the naked eye. Other examples of heterogeneous mixtures are carbonated beverages (liquid and gas) and muddy water (liquid and solid). Heterogeneous mixtures can often be separated into their components by simple laboratory procedures. For example, suspended solid matter can be removed from water by filtration. In some cases, centrifugation method in used to separate heterogeneous mixtures.