--- title: "Transfer or transformation?" subtitle: "Year 8 Physics · Energy transfer and transformation · Lesson 2" --- # Transfer or transformation? **Name:** {{field-24}} **Date:** {{field-15}} **Class:** {{field-15}} > **Key question:** Touch an old-style light bulb that has been on for a minute and it burns your finger, even though it was only meant to make light. :::teacher-note **In one sentence:** Students distinguish energy transfer (same type, new place) from transformation (type changes), describe common transformations, and identify by-product heat (AC9S8U05, nodes 3 and 4; node 4 is a hinge). **Students should be able to say:** I can tell an energy transfer from a transformation. I can describe the transformations in a torch or a speaker. I can name the by-product heat in a transformation. **Width:** the unmarked parts are the floor every student does (Engage, Explore, Explain, Evaluate). Typical and Wider sections add contexts, not difficulty. Students work in the online tutorial alongside this sheet. ::: ## Engage :::keep-together **A torch bulb is switched on. What kinds of energy come out of it?** ☐ Only light: that's its job ☐ Light, and some heat ☐ Only heat ☐ Electricity My prediction, and why: {{lines-3}} ::: :::teacher-note **What happens:** Light, and some heat. Almost every time energy changes type, some of it becomes heat that isn't wanted: a by-product. Old filament bulbs turned most of their energy into heat. ::: ## Explore Try it on the board in the tutorial. Was your prediction right? What was different? {{lines-2}} ## Explain: transfer, transformation, by-products :::keep-together ### Transfer or transformation **Transfer (same type, new place) or transformation (type changes)?** Groups: Transfer, Transformation - Heat from a hot pan into the handle: {{field-15}} - A moving cue ball hitting another ball and making it move: {{field-15}} - Sound travelling from a speaker to your ear: {{field-15}} - A battery lighting a bulb: {{field-15}} - A ball falling from a shelf: {{field-15}} - Burning wood: {{field-15}} ::: :::teacher-note **Answer:** Heat from a hot pan into the handle → Transfer; A moving cue ball hitting another ball and making it move → Transfer; Sound travelling from a speaker to your ear → Transfer; A battery lighting a bulb → Transformation; A ball falling from a shelf → Transformation; Burning wood → Transformation ::: :::keep-together ### By-products **A bulb makes light and heat. Which is the by-product?** ☐ The heat: it isn't the job the bulb is for ☐ The light ☐ Neither ::: :::teacher-note **Answer:** The heat: it isn't the job the bulb is for The useful output is what the device is for; by-products are the rest, usually heat and sometimes sound. ::: :::keep-together ### Not destroyed **Is the by-product heat from a bulb destroyed?** ☐ Yes: by-products are destroyed ☐ No: it spreads into the room, where it is hard to use ☐ It turns back into electricity ::: :::teacher-note **Answer:** No: it spreads into the room, where it is hard to use The heat warms the air a little. It isn't lost, just spread out and not useful. ::: :::keep-together ### Two more devices **For each device, is it the useful output or a by-product?** Groups: Useful output, By-product - Electric kettle: heat in the water: {{field-15}} - Electric kettle: heat escaping into the kitchen air: {{field-15}} - Electric kettle: the rumbling sound: {{field-15}} - Fan: moving air: {{field-15}} - Fan: the motor getting warm: {{field-15}} - Fan: the whirring sound: {{field-15}} ::: :::teacher-note **Answer:** Electric kettle: heat in the water → Useful output; Electric kettle: heat escaping into the kitchen air → By-product; Electric kettle: the rumbling sound → By-product; Fan: moving air → Useful output; Fan: the motor getting warm → By-product; Fan: the whirring sound → By-product ::: :::typical ## Elaborate: a speaker :::keep-together ### Where the heat comes from **The speaker cone gets slightly warm. Where in the flow does that heat come from?** ☐ From the sound ☐ From the battery directly ☐ A by-product when electrical energy becomes movement of the cone ::: :::teacher-note **Answer:** A by-product when electrical energy becomes movement of the cone Each transformation tends to give off a little heat: here, in the speaker's coil and cone. ::: ::: :::wider ## Elaborate: a bow and arrow :::keep-together ### Drawing it back **Why does a bow need to be drawn back before the arrow can fly?** ☐ To aim it ☐ To warm it up ☐ Drawing it stores elastic potential energy, which becomes the arrow's kinetic energy ::: :::teacher-note **Answer:** Drawing it stores elastic potential energy, which becomes the arrow's kinetic energy The archer's chemical energy is stored as elastic potential in the bow, then released as the arrow's kinetic energy. ::: ::: ## Evaluate: look back Write one sentence: "At first I thought… Now I think… because…" **Revision summary** - **Transfer**: the same type of energy moves to a new place (heat into your hands, sound to your ear). - **Transformation**: energy changes type (chemical → electrical → light in a torch). - Almost every transformation also makes **by-product** heat (and sometimes sound) that isn't the useful output. - By-product energy isn't destroyed: it spreads into the surroundings. ## Exit ticket :::keep-together **A wind-up toy runs across the floor. Is 'spring to moving wheels' a transfer or a transformation? Name a by-product.** {{lines-3}} ::: :::teacher-note **Answer:** A transformation (elastic potential to kinetic). By-products: heat (friction) and sound. :::