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5 Terms
1
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3 examples of endothermic changes
* some chemical reactions * melting and boiling * dissolving substances in water
2
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Explain an example of an endothermic change.
* Cold pack * Outer bag contains water, inner bag contains solid ammonium nitrate * When inner bag is broken, water and ammonium nitrate mixes * Solid dissolves in water, and mixture cools * Injured body part transfers thermal energy to cold pack, so it feels better * Mixture slowly returns to temp of surroundings
3
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Explain an example of an endothermic **reaction**.
* Citric acid crystals - 20 degrees * Add sodium hydrogen carbonate powder - there is a chemical reaction * Reacting mixture feels cold - temp decreases to 10 degrees * Temp decrease shows endothermic reaction
4
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3 examples of exothermic changes
* chemical reactions ie. combustion * freezing and condensing * dissolving some substances in water
5
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Explain an example of an exothermic **reaction**.
* Dilute sulfuric acid and sodium hydroxide solution - both 20 degrees * Mixes them - chemical reaction * Measures temperature again - 30 degrees * Temperature increase shows exothermic reaction