The document discusses chemical reactions and the four main types: synthesis, decomposition, single replacement, and double replacement. It defines key terms like reactants and products. Synthesis reactions combine two elements to form a compound. Decomposition reactions involve a single reactant breaking down into simpler products. Single replacement reactions involve one element replacing another in a compound. Double replacement reactions swap ions between two compounds. The law of conservation of mass is also mentioned.

1. Notes: Chemical Reactions CW: Types of Reactions H: Types of Chemical Reactions

2. Chemical Reactions January 28, 2010

3. Objectives Identify parts of a chemical equation Recognize four types of chemical reactions Describe Law of Conservation of Mass

4. Molecules and Compounds Some elements exist as individual atoms. Molecules consist of two or more elements joined together. If more than one type of atom is in a molecule, we call it a compound .

5. Chemical Reactions Chemical reactions happen when the atoms in one or more molecules split up and join together in new ways. For example, hydrogen can react with oxygen :

6. When a reaction takes place, things happen. There may be a gas given off, a color change or a solid material appearing. There could also be changes we can’t see, such as a temperature change. The mass of the reactants (the chemicals we start with) is always the same as the mass of the products (the chemicals we end with). Law of Conservation of Mass

8. Chemical Equations On the left are the reactants – the starting materials On the right are the products – the new substances that are formed An arrow connects the two sides – read as yields or produces AgNO 3 + NaCl  AgCl + NaNO 3 Read left to right like a sentence in chemical terms

10. 4 Types of Reactions Synthesis Decomposition Single Replacement Double Replacement

12. Synthesis Means to put together or combine occur when two substances (generally elements ) combine and form a compound. In general: A + B  AB Fe + S  FeS reactant + reactant  1 product

13. Decomposition In this type of reaction, a substance breaks down into simpler parts when it is heated. 1 Reactant  Product + Product In general: AB  A + B CuCO 3 heat Cu 2 O + CO 2 For example, copper carbonate will decompose when heated :

14. Single Replacement In a displacement reaction, one metal ‘kicks out’ a less reactive one. The iron wants to be with the sulphate more than the copper does. We say that iron is more reactive than copper. element + compound  element + compound In general: A + BC  AC + B Fe + CuSO 4 Cu + FeSO 4

15. Double Replacement Occurs when one metal trades places with another one. AgNO 3 + KCl  AgCl + KNO 3 Compound + compound  product + product In general: AB + CD  AD + CB