S4.7.8 For the adult
Energy changes and rates
Why does a fire warm a room, but baking soda in vinegar makes the cup feel cold?
What this chapter teaches
An exothermic reaction gives out energy and warms its surroundings. An endothermic reaction takes energy in and cools them. A reaction goes faster when the temperature or the concentration is higher, or when a solid is in smaller pieces, because the particles collide more often and more of the collisions have enough energy.
Three questions to ask
There is no one right wording. Listen for the idea.
- Why does the cup get colder when baking soda is mixed with vinegar?
- Why does powdered eggshell react faster with vinegar than a whole piece does?
- What three things can you change to make a reaction go faster, and why does each work?
After the chapter, the learner can
- Sort reactions into exothermic and endothermic
- Explain how temperature, concentration and surface area change reaction rate
What they copy into their notebook
Exothermic gives out energy and warms. Endothermic takes in energy and cools. Higher temperature, higher concentration and more surface area give more collisions, so a faster rate.