 Every fire needs the same three components: fuel, oxygen gas, and heat  In a campfire: ◦ The fuel is the wood, wood is rich in carbon ◦ The carbon reacts with oxygen in the air, only if the air can reach the carbon (which is why the log is split into splinters called kindling, so more carbon is exposed to the air)

 When lighting a fire, extra oxygen is sometimes needed (which is why blowing lightly on the embers helps, as long as you don’t blow the heat away)  Combustion releases heat, which is why there is no need to keep relighting the flame. ◦ Combustion: a chemical change producing heat and light

 Burning a log produces new substances: ◦ carbon dioxide that blows away ◦ Ash that doesn’t burn  A campfire produces gas (carbon dioxide) and heat!

 In a physical change, a substance may change state (ie: ice cream melting), but the substance itself does not change.  In a chemical change, new substances are formed. We look for indicators, such as heat produced, gas produced, colour change, etc… (we will learn more about this soon!)

 hange/home

 A physical property describes a characteristic of a substance that can be observed or measured.  Example: the melting point of something is a physical property. It can be measured.

 Water freezes and melts at 0°C  Water expands when it freezes ◦ Good: Ice floats on water, making life still possible in winter in lakes ◦ Bad: Causes cracks and potholes in roads

 Lustre – shiny or dull  Colour  Transparency – how see-through it is  Mass  Volume  Density  Conductivity  Hardness  Etc……

 A substance may change appearance (such as changing state or size), but a new substance is not formed.  Eg: Water turning to ice, chopping wood  A physical change is reversible!

 A chemical property describes the ability of a substance to change into a new substance or substances  Chemical properties include: ◦ How a substance interacts with other substances ◦ How it reacts to heat or light

 A chemical change always results in the formation of new substances  Examples: ◦ Burning paper ◦ Baking a cake ◦ Mixing vinegar and baking soda together  A chemical reaction is the process in which a chemical change occurs

 Evidence of a chemical change can include a great variety of changes, including: ◦ Colour  Ex: A chemical change makes a banana ripe, changing from green to yellow ◦ Odour  Ex: When milk goes sour, it gives off a gross smell

◦ Temperature  Ex: A chemical cold bag, or mitt warmers ◦ Production of light  Ex: a firefly has a chemical called luciferin, which glows when it reacts with oxygen  Ex: A glowstick, once you crack it and mix the chemicals a light is produced

◦ Formation of a new solid inside a liquid  Ex: Milk going sour, producing curds inside the liquid ◦ Production of gas  Ex: Mixing baking soda and vinegar, look for bubbles ◦ Etc…