Chemical Reactions and Equations

Physical Changes: a change of state and do not create a new substance. Ice melting to water, to dry ice subliming to produce fog are physical changes.

 Chemical changes: a reaction where one or more substances is transformed into one or more new products.
They are can be identified by observing:
* A substance 'disapears'
* A gas is given off (effervescence)
* A solid is precipitated
* A colour change occurs
* A new odour is released
* Light is given off

 Chemical Equations - used to represent a chemical reaction, showing reactants and products and their physical states. Catalysts and other agents can also be shown above the arrow between sides.

 Reactants ----> Products
To Write a Chemical Equation: A General Guide

1. Write out reactants on the left and products on the right, often obtained from information given in a question, including states.

2. Change the little numbers at the bottom to balance the charges of each compound

3. Balance equation to satisfy law of conservation of mass - each element must have the same number of atoms on either side of the reaction.


Comments

Post a Comment

Popular posts from this blog

Common Literary Techniques in Tim Winton's 'The Turning'

Common techniques in Winton’s The Turning . Most of these examples are taken from ‘Aquifer’. Direct, concrete images: ‘In the afternoon the blue bush plain was hazy with smoke and the dust churned up with bulldozers.’ While these descriptions are simple and clear ways of describing the real world, Winton often highlights aspects that explore and reveal key aspects of the ideas or characters he is exploring. For example, the ‘hazy’ and ‘churned up’ elements in this description highlight 2 things: 1) the confused and often conflicting feelings of the narrator as he reflects back on a time of emotional and hormonal turmoil (growing up); 2) the murky and muddled interaction between past and present.  There is a tension or irony here in that the descriptions seem so straightforward and clear that the memories are certain, solid, can’t be argued with, which is true.  And yet how one grapples with these memories, how one mixes them/reconciles them with the present...
Read more

Ionic Compounds

Image
Ionic Bonding: occurs between a metal and a non-metal results in a positive cation (metal) and a negative anion (non-metal) forms a salt, that is a lattice structured crystal that is more stable than the reactants Electron Transfer Diagrams Used to represent a reaction, showing the transfer of electrons Reactants on the left, products on the right Ionic Lattice: ionic compounds form crystals, a lattice composed of positive and negatively charged atoms in a regular 3D structure. They are held together by strong electrostatic attraction between oppositely charged ions. The atoms are packed in a regular repeating pattern. They form into the most stable arrangement with oppositely charged ions as close as possible and those with the same charge, as far away as possible. Properties Rigid as ions are tightly held Does not conduct electricity- no free charged particles in solid state, however, in molten or aqueous they are able to as ions have...
Read more

Electrons

Image
Exciting Electrons: Every element emits light if it is heated. This is because the atom has absorbed energy, and then loses it in the form of light. The light can be separated to form an Electron Emission Spectrum. Each line on the EES corresponds to a particular frequency of light being given off by an atom; therefore each corresponds to one exact amount of energy being emitted. Emission Spectrum from various elements Niels Bohr proposed an explanation for the ES, stating that electrons of specific eneergy move around the nucleus in orbits or energy levels, and cannot exist between these levels. When given excess energy (from flame or electric current) electrons are able to move to a higher obit. this is from ground state (lowest energy level) to an excited state . As the electron moves back to ground state, the amount of energy given off is the difference in energy between the levels, and is given off as a photon of light. In an ionic compound, it is the anion (negatively ...
Read more