Today • Conservation of Matter (Continued...) • Recognising Chemical Reactions • How do scientists tell the story??
Conservation of Matter “Matter Cannot be created or destroyed”
Closed System: • Closed to exchanges of Matter • Matter – Anything that has mass and volume (atoms, compounds, molecules) • Open System: • Open to exchanges of Matter
Magnesium Oxide Magnesium (s) + Oxygen (g) Magnesium Oxide (s) Year 9 Science – Balancing Equations Mg(s) + O2(g) MgO(s)
How do we know?? • As scientists we can observe some changes to indicate a chemical reaction may have taken place. • Have a look at the following clips and identify what changes you can observe?
When observing chemical reactions we look for: • Permanent Color Change • A gas being formed • A Precipitate being formed • Heat being produced
Everyday examples • I want you to think about your day. Identify a chemical reaction you may have observed. • What are your reasons for believing it to be a chemical reaction?
How do we tell the story?? • So as scientists you need to be able to tell us what has happened. • So you need to be able to tell a story.
A reaction between solid Magnesium and gaseous Oxygen produces solid Magnesium Oxide. Magnesium(s) + Oxygen(g) Magnesium Oxide(s) • A reaction takes place between Solid Zinc and gaseous Oxygen produces Solid Zinc Oxide. Zinc(s) + Oxygen(g) Zinc Oxide(s)
A reaction takes place between solid Sodium and gaseous Chlorine which produces solid Sodium Chloride. • A reaction takes place between gaseous Hydrogen and gaseous Oxygen to produce liquid water.
Handling Acids Safely. • Acids are Corrosive substances • React chemically with metals • Burn your skin • When we deal with acids we deal with: • Concentrated solutions • Diluted solutions
How do we minimise risk to ourselves?? • When handling acids we need to be careful. • Check the label on the bottle • Corrosive substances are often in dripper bottles • Easier to measure required amount • Reduce chance of spilling • When pouring corrosive substances: • Take your time • Place the mouth of the bottle, on the mouth of the test tube.
What if we spill the corrosive substances? • What if our eyes come into contact with Acid?
Questions • How do the properties of an egg change when it is fried? • What changes occur when a nail rusts? Describe them • What is the difference between a chemical change and a physical change? • When hydrogen is mixed with air and ignited it explodes to form water. • Name The Reactants • Write the word Equation for this reaction.