What is a word equation?
Topic: Changes to materials
Answer: A word equation uses the names of substances to show the reactants and products in a chemical reaction.
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In a word equation, what are reactants?
Topic: Changes to materials
Answer: Reactants are the starting substances that react together.
In a word equation, what are products?
Topic: Changes to materials
Answer: Products are the new substances made by the reaction.
What does the arrow mean in a word equation?
Topic: Changes to materials
Answer: The arrow means 'react to form' or 'produce'.
Write the general word equation for a metal reacting with oxygen.
Topic: Changes to materials
Answer: metal + oxygen -> metal oxide
Write the general word equation for a reactive metal reacting with water.
Topic: Changes to materials
Answer: metal + water -> metal hydroxide + hydrogen
Write the general word equation for a metal reacting with a dilute acid.
Topic: Changes to materials
Answer: metal + acid -> salt + hydrogen
Write the word equation for magnesium reacting with oxygen.
Topic: Changes to materials
Answer: magnesium + oxygen -> magnesium oxide
Write the word equation for zinc reacting with hydrochloric acid.
Topic: Changes to materials
Answer: zinc + hydrochloric acid -> zinc chloride + hydrogen
What is an exothermic process or reaction?
Topic: Changes to materials
Answer: An exothermic process transfers energy to the surroundings, so the temperature of the surroundings usually increases.
What is an endothermic process or reaction?
Topic: Changes to materials
Answer: An endothermic process takes in energy from the surroundings, so the temperature of the surroundings usually decreases.
How can a thermometer help identify an exothermic reaction?
Topic: Changes to materials
Answer: If the measured temperature rises during the reaction, the reaction is likely to be exothermic.
How can a thermometer help identify an endothermic reaction?
Topic: Changes to materials
Answer: If the measured temperature falls during the reaction, the reaction is likely to be endothermic.
A reaction mixture changes from 21 °C to 34 °C. Is it endothermic or exothermic? Explain.
Topic: Changes to materials
Answer: It is exothermic because the temperature increases, showing energy has been transferred to the surroundings.
A reaction mixture changes from 25 °C to 18 °C. Is it endothermic or exothermic? Explain.
Topic: Changes to materials
Answer: It is endothermic because the temperature decreases, showing energy has been taken in from the surroundings.
Why should the initial temperature be recorded before testing for endothermic or exothermic change?
Topic: Changes to materials
Answer: The initial temperature is needed so the temperature change can be compared with the final or highest/lowest temperature.
Put these metals in order from most reactive to least reactive: potassium, sodium, calcium, magnesium, zinc, iron, copper, silver, gold.
Topic: Changes to materials
Answer: potassium > sodium > calcium > magnesium > zinc > iron > copper > silver > gold
Which two metals in this list are the most reactive: sodium, potassium, calcium, magnesium, zinc, iron, copper, gold, silver?
Topic: Changes to materials
Answer: Potassium and sodium are the most reactive metals in this list.
Which two metals in this list are the least reactive: sodium, potassium, calcium, magnesium, zinc, iron, copper, gold, silver?
Topic: Changes to materials
Answer: Gold and silver are the least reactive metals in this list.
What type of product is made when a metal reacts with oxygen?
Topic: Changes to materials
Answer: A metal oxide is made.
What are common observations when magnesium burns in oxygen?
Topic: Changes to materials
Answer: Magnesium burns with a bright white flame and forms a white solid, magnesium oxide.
How does copper react with oxygen when heated strongly?
Topic: Changes to materials
Answer: Copper reacts slowly with oxygen to form black copper oxide on its surface.
Why are gold and silver often used in jewellery?
Topic: Changes to materials
Answer: They are very unreactive, so they do not corrode or react easily under normal conditions.
What gas is produced when many reactive metals react with water?
Topic: Changes to materials
Answer: Hydrogen gas is produced.
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