Chapter 8 Chemical Reactions
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When something burns it is a example of an____________ reaction.
Oxidation
What gas is produced during the process of oxidation?
Hydrogen
How do you test for hydrogen?
Putting a lighted splint and listening for a squeaky pop
Give an example of an exothermic reaction
• Burning • Reaction between metal and water • Reaction between metal and acid
Give an example of an endothermic reaction
Sodium hydrogencarbonate reacting with citric acid
What is the similarity and difference between an endothermic process and an endothermic reaction
Similarity: Heat is absorbed, final temperature is lower than initial temperature Difference: New products are formed at the end of the endothermic reaction, no new products at the end of endothermic process
What salt is produced when metal reacts with water?
Metal hydroxide
Why are self-heating cans expensive?
The 2 compartments must be sealed from one another and from the food, so that it does not become contaminated.
Give an example of how endothermic reactions are used
Ice packs used for injuries
Write the equation for the process of rusting. What must be present for this to take place?
iron + oxygen -> iron oxide Water must be present.
What can be done to prevent rusting
galvanizing or painting
Will an iron nail that is placed in a closed test tube in boiling hot water rust? Why or why not?
Very little rust. Because there may be some dissolved oxygen in the boiling water but no additional oxygen can enter
Name 2 metals that do not react with water or oxygen. What is the word used to describe such metals?
Inert metals - silver, gold, platinum
Why are some metals stored in oil?
To prevent them from reacting with water vapour in the air.
Why does silver jewelry turn black over time?
Silver reacts slowly with oxygen in the air to form black silver oxide
Sodium hydroxide + ______ –> sodium chloride + _____
Sodium hydroxide + hydrochloric acid –> sodium chloride + water
What is one safety precaution you should take when investigating an exothermic reaction
Wear gloves, use a heatproof mat
Why is the reaction between steam and magnesium more vigorous than between water and magnesium?
The particles in steam moves more quickly so they break more easily and bond with magnesium more quickly
What can you do to increase the speed of a chemical reaction?
• Increase the temperature • Use more concentrated reactants • Increase the temperature of reactants
How can you tell if a chemical reaction is endothermic or exothermic?
If the final temperature is higher than the original, it is exothermic. If the temperature is lower, it is endothermic.