1 / 15

Chemical Reactions

This revision guide covers the signs of chemical reactions, elements, compounds, and mixtures. It also explains separation methods and the difference between chemical and physical changes. Word equations and examples are provided.

vcarrillo
Download Presentation

Chemical Reactions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chemical Reactions Revision for end-of-topic test

  2. Signs of a Chemical Reaction • Colour change • Temperature rises or falls • Bang or flash • Gas given off / fizzing / smell • A solid is formed • In all chemical reactions, a new substance is formed.

  3. Elements combine to a compound • The particles of the two elements are joined up. • This means a chemical reaction has happened. • A compound is made up of two or more elements that are joined together.

  4. Elements in a Mixture • In a mixture, the particles are not joined. • No chemical reaction takes place. • It is easy to separate the elements again • A mixture might have compounds in it too.

  5. Element, compound or mixture?

  6. Mixture: By hand Sieving/Filtering Evaporating With magnet A mixture is easy to separate. Compound: Always needs energy Might be electricity Might be heat A compound needs energy to separate. Separating mixtures and compounds

  7. Hydrogen Oxygen Carbon Dioxide Burns with a POP Re-lights a glowing splint. Turns limewater milky Testing Gases

  8. Changing the Particle Size • The size of the particles can change how fast a reaction goes. Choose faster or slower: • When the particles are smaller, the reaction will go . • When the particles are larger, the reaction will go . faster slower

  9. Chemical change: A chemical reaction happens. A new substance is formed. One of the signs will happen! Physical Change: No chemical reaction happens No new substance is formed. A physical change is usually easy to reverse. Chemical and Physical Changes

  10. Are these chemical or physical changes? • Water freezing into ice. • Methane burning to form CO2 and H20. • Potassium reacting with water. • Dissolving sugar in tea. • Striking a match. • If in doubt, ask yourself if any of the signs of a chemical reaction have happened!

  11. Word Equations • A word equation is the simplest possible representation of a reaction. • Only the names of elements or compounds are included. • The substances which react go on the left. • The substances which are formed go on the right.

  12. Word Equations 2 Watch out for: • There may be one or more items on the left, and one or more on the right. • Elements can occur on either side. • Compounds can occur on either side. • “+” means simply “and” • means “reacts to make” and always points right.

  13. Examples • Methane reacts with oxygen, producing a hot blue flame. Carbon dioxide gas and water vapour are formed. • Methane + Oxygen Carbon dioxide + Water • Mercury Oxide is heated, and breaks down into Mercury and Oxygen. • Mercury oxide Mercury + Oxygen

More Related