Connect, extend, then challenge
Connect-Extend-Challenge is a thinking routine in three prompts. After the teaching, each learner writes a Connect (how this links to what they already knew), an Extend (how it pushes their thinking further) and a Challenge (a question that still puzzles them), alone. They then share in groups, each group puts one Challenge to the class, and the teacher addresses the most common one, usually the deep energy question that closes this topic.
It passes the PIES test:
Groups pool their responses and must agree on the single Challenge they put to the class.
Each learner writes all three responses before any sharing, so no one can coast.
Every learner contributes a Connect, an Extend and a Challenge of their own.
The whole class writes at once, then every group shares and selects together.
Write alone, then share
After the teaching, each learner writes a Connect, an Extend and a Challenge on their own sheet, with no discussion.
Learners read their three responses to the group and compare.
Each group selects a single Challenge to put to the class.
The teacher collects the Challenges and addresses the most common, usually the energy question.
Three prompts, one each
Each learner completes all three boxes alone before sharing.
Teacher model responsesclick to reveal
conservation of momentum follows from Newton's third law. During a collision the two bodies push on each other with equal and opposite forces for the same time, so they receive equal and opposite impulses and equal and opposite changes in momentum, leaving the total unchanged.
momentum is conserved in every closed-system collision, but kinetic energy is conserved only in an elastic collision. Explosions are the reverse of a perfectly inelastic collision: the total momentum stays zero while kinetic energy is created from stored energy.
if two trolleys stick and slow down, where does the kinetic energy go, and why is momentum still conserved? The lost kinetic energy becomes heat, sound and energy of deformation, while momentum is conserved because the internal forces are equal and opposite, so they cannot change the total momentum.
When the room does not behave like the plan
Boxes are left blank: all three are written before any sharing; a blank Challenge is itself a signal to follow up.
Challenges are all the same: good; address that one well rather than many shallow ones.
A Connect just restates the definition: push for a real link to a prior idea, such as Newton's third law or impulse.
Short on time: the individual writing and the one-Challenge-per-group step are the heart of it; protect those.
- Support: give sentence starters, for example "this connects to ... because ..." and "I still wonder why ...".
- Challenge: ask a learner to answer another group's Challenge in writing, using momentum and energy correctly.