Chemical Reactions

• What is the difference between a chemical reaction and a physical change?

  A physical change only changes the appearance of an object whereas a chemical change, changes the kind of matter with new properties being formed.
• What does the law of conservation of mass mean for chemical reactions?


  The law of conservation means that the mass of the reactants will always equal the mass of the products. This means that the mass does not change in a chemical reaction (mass it not created nor destroyed).
• What is the law of constant proportions?


  The law of constant proportions means that a chemical compound always contains exactly the same proportions of elements by mass.
• What is the difference between and endothermic reaction and an exothermic reaction?


  Endothermic reactions occur when the reactants take up heat energy from their environment in order to form products. A reaction that releases energy as heat or light is called an exothermic reaction.
• Properties of acids


  Sour taste, reacts with metal to form hydrogen gas, react with bases in a process called neutralisation, react with calcium carbonate to form carb dioxide gas, turns blue litmus paper red
• Properties of bases

  A bitter taste, feels soapy because they react with natural oils in the skin to produce soap, turn red litmus paper blue, reacts with acids in a process called neutralisation
•  

  What are indicators, and what do they tell us about acids and bases?


  Indicators are a group of chemicals used to determine an acid or a base.
• What does a pH scale tell us


  A pH scale indicates the acidity or how basic a solution is.
•  

  What does it mean if a substance is neutral?

  Neutral substances are neither acidic nor basic.
• Write an example of an acid + base reaction

  $Hydrochloric Acid +$$sodium hydroxide -> Sodium chloride +$$water$
• Write an example of an acid + metal reaction

  $Sulfric acid +$$copper - copper sulfate +$$hydrogen$
• Write an example of an acid + metal carbonate reaction

  $hydrochloric acid +$$magnesium carbonate -> magnesium chloride +$$water +$$carbon dioxide$
• Write an example of a metal reacting with oxygen

  $magnesium +$$oxygen → magnesium oxide$
• Write an example of a combustion reaction

  $propane+$$oxygen→carbon dioxide+$$water$
• State what the chemical part of chemical reactions could be interpreted as.


  the elements, ions and compounds that we put into a reaction
• what type of substance must be added to an acid to neutralise it?


  Basic substance
• The reaction part of a chemical reaction is when 


  The elements, ions or compounds rearrange into a new set of elements, ions or compounds
• Recall what a precipitate is 


  formation of a solid
• State what reaction conditions are


  The time, temperature and/or pressure that a chemical reaction is carried out
• List the 4 signs that a chemical reaction has taken place.

  Change in colour, formation of a solid, formation of gas, and release or absorption (light, heat)

  
• Explain how we can test a gas to determine if hydrogen or oxygen is being produced?


  If hydrogen is being produced, by placing a lit match over the opening of a test tube it will make a pop sound whereas placing a glowing match over the opening, the match will reignite.

  
• What do the terms reactant and product mean?


  Reactant: The chemicals present to begin with

  Products: Substances produced after the reaction is complete