Loading presentation...

Present Remotely

Send the link below via email or IM

Copy

Present to your audience

Start remote presentation

  • Invited audience members will follow you as you navigate and present
  • People invited to a presentation do not need a Prezi account
  • This link expires 10 minutes after you close the presentation
  • A maximum of 30 users can follow your presentation
  • Learn more about this feature in our knowledge base article

Do you really want to delete this prezi?

Neither you, nor the coeditors you shared it with will be able to recover it again.

DeleteCancel

Chemical and Physical Changes

description
by

Jerry Wilson

on 28 April 2013

Comments (0)

Please log in to add your comment.

Report abuse

Transcript of Chemical and Physical Changes

Chemical and Physical Changes Chemical Reactions produce
chemical changes. Reactants - These are the substances that exist before the reaction. They are the substances that react. Products - These are the substances that form as a result of the chemical reaction. The reaction is shown with a chemical equation, with reactants on the left, products on the right and an arrow separating them. Chemical Formula - Shorthand used in place of the names of chemicals Subscripts tell how many of each atom there are in a chemical compound. This shows there are 3 atoms of hydrogen in sodium acetate. Conservation of Mass - In a chemical reaction the mass of the reactants must equal the mass of the products. The number of atoms on each side is also the same. Balancing Equations Balance equations using coefficients, numbers in front of the formulas. All atoms in the formula are multiplied by the coefficient. The 2 is a coefficient. Energy in Chemical Reactions Sometimes, energy is released from a chemical reaction. This is called an exothermic reaction. In exothermic reactions, energy is released when bonds are broken in the reactants. It is released as heat or light. When energy is absorbed in a chemical reaction, it is called an endothermic reaction. An example of an exothermic reaction is combustion. That is when a substance burns and produces a flame. During endothermic reactions, more energy is needed to make the bonds of the products than is produced by breaking bonds in the reactants. A cold pack that you put on an injured muscle is an example of an endothermic reaction. It absorbs heat from your body and makes your skin feel cold. Chemical Equation shows the reactants, the products, and how much of each there are in a reaction. Examples of Physical Changes:
Ice Melting
Water Boiling
Chopping Wood
Crinkling Paper
Full transcript