Chapter 7.3 Chemical Reactions Notes PDF

CHEMCIAL REACTIONS Pearson Science 8 – Chapter 7, pg. 286 LEARNING INTENTIONS Chemical change involves substances reacting to form new substances(ACSSU1225) ▪Model the arrangement of particles in chemical reactions ▪Investigate simple reactions such as combining elements to mak...

CHEMCIAL REACTIONS Pearson Science 8 – Chapter 7, pg. 286 LEARNING INTENTIONS Chemical change involves substances reacting to form new substances(ACSSU1225) ▪Model the arrangement of particles in chemical reactions ▪Investigate simple reactions such as combining elements to make a compound ▪Identify reactants and products in a chemical reaction ▪Recognise that the chemical properties of a substance, for example its flammability and ability to corrode, will affect its use CHEMICAL CHANGE ▪Recall, signs of a chemical change 1. Permanent change in colour 2. Production of a gas 3. Production of a precipitate 4. Change in temperature ▪These are only signs, the only way to really know if a chemical change has taken place is to look at the particles before and after the change  SUBSTANCES ▪Keep in mind, the properties of a substance are determined by the type of atoms it contains and how those atoms are arranged ▪E.g – diamond & graphite or water & hydrogen peroxide  CHEMICAL REACTIONS ▪During a chemical reaction, old substances disappear and new substances form ▪This is because the particles rearrange themselves ▪The starting substance are called reactants ▪The new substances formed are products  CHEMICAL REACTIONS ▪In chemical reactions, the reactants are written first, on the left side ▪We place an arrow in between which means ‘changes to’ ▪Then we place the products after the arrow on the right side ▪The ‘+’ means ‘and’  CHEMICAL REACTIONS Here is an example: ▪Sodium chloride is forme when sodium metal is melted and placed in chlorine gas ▪We can use an equation to show what is happening in this chemical change Heated sodium metal Chlorine gas Chlorine + Sodium Sodium Chloride  CHEMICAL REACTIONS Here is another example ▪Hydrogen and chlorine molecules react to form hydrogen chloride REACTANT PRODUCT S S COMBUSTIO N ▪Combustion is the term given to any chemical reaction that involves burning with oxygen to release light and heat ▪It a lot of energy is released, it can lead to an explosion!  COMBUSTIO N ▪ Combustion occurs between fuels such as petrol, natural gas, wood, coal and paper ▪ One example is methane: REACTANT PRODUCT S S  COMBUSTION - HAVE A GO! ▪Model the reaction between Hydrogen gas (H 2) and oxygen to form water ▪Include the names, chemical formula and model for all molecules ▪Label the reactants and the products  FLAMMABILITY ▪Flammability describes how easily a substance undergoes combustion (burns) ▪Substances that do not burn are non- flammable ▪Substances that ignite quickly are highly flammable  PHOTOSYNTHESI S ▪Photosynthesis is the process by which plants produce their food ▪Photosynthesis equation: CO2 H2O O2  RESPIRATION ▪ Respiration refers to a series of chemical changes that take place in cells to release energy ▪ Respiration involves reacting glucose (sugar) and oxygen to produce carbon dioxide, water vapour and energy ▪ This occurs in the mitochondria Mitochondrion  CORROSION ▪Corrosion is a chemical reaction that can cause damage to metals ▪This happens when metals (like iron & steel) react slowly with oxygen gas and water CORROSION ▪Corrosion is a chemical reaction that can cause damage to metals ▪This happens when metals (like iron & steel) react slowly with oxygen gas and water Example: Iron undergoing corrosion to form iron oxide Iron + Water + Oxygen 🡪 Iron F e oxide Reactant Products H s H O O O REVISIT LEARNING INTENTIONS ❑ The difference between a physical & chemical change ❑ Examples of physical change ❑ Signs of a chemical change REVIEW QUESTIONS 7.3 ▪Module 7.3 Review Questions ▪16, 17, 18, 19 ▪Page 316