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.