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2.3 – Physical and Chemical Properties of Matter

2.3 – Physical and Chemical Properties of Matter. The Chemistry of a Campfire. 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

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2.3 – Physical and Chemical Properties of Matter

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  1. 2.3 – Physical and Chemical Properties of Matter

  2. The Chemistry of a Campfire • 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)

  3. The Chemistry of a Campfire • 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

  4. A campfire is a chemical reaction • Burning a log produces new substances: • carbon dioxide that blows away • Ash that doesn’t burn • A campfire produces gas (carbon dioxide) and heat!

  5. Physical Change vs. Chemical Change • 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!)

  6. Webquest • https://sites.google.com/site/chemandphyschange/home

  7. Physical Properties • 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.

  8. Physical Properties of Water • 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

  9. Observing Physical Properties • Lustre – shiny or dull • Colour • Transparency – how see-through it is • Mass • Volume • Density • Conductivity • Hardness • Etc……

  10. Physical Change • 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!

  11. Chemical Properties • 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

  12. Chemical Changes • 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

  13. Evidence of a Chemical Change • 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

  14. Evidence of a Chemical Change • 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

  15. Evidence of a Chemical Change • 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…

  16. Physical or Chemical?

  17. Physical or Chemical?

  18. Physical or Chemical?

  19. Physical or Chemical?

  20. Physical or Chemical?

  21. Physical or Chemical?

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