--- title: "If" subtitle: "micro:bit Foundations · Decide · Lesson 6" --- # If **Name:** {{field-24}} **Date:** {{field-15}} **Class:** {{field-15}} > **Key question:** Street lights switch on when it gets dark, and a fridge beeps when its door is left open. Each one asks a yes-or-no question about a number, again and again. :::teacher-note **In one sentence:** Students use an if block to make the micro:bit decide, and see that a false if does nothing, so turning something off needs its own question. **Students should be able to say:** I can use an if block to make the micro:bit decide. I can say what an if does when its question is false. I can choose < or > so the question is true when I want it to be. **Width:** the unmarked parts are the floor every student does (predict, run, investigate and make). Typical adds the modify practice; wider adds the real-world contexts. They add contexts, not difficulty. Students work in the online tutorial alongside this sheet. ::: ## Predict This is a **night light**. `<` means "less than". ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/1f3e7c43f108.png?v=4b6833858851d206) :::keep-together **The light level starts high. You drag it down to 20, then back up to 200. What happens?** ☐ The lights come on in the dark, then go off when it is bright ☐ The lights flash on and off ☐ The lights come on in the dark, and stay on when it is bright again ☐ Nothing ever lights up My prediction, and why: {{lines-3}} ::: :::teacher-note **What happens:** The lights come on in the dark and stay on. The if only does something when it is dark; when it is bright again, it does nothing, so nothing turns the lights off. ::: ## Run Run the program in the tutorial. Was your prediction right? What was different? {{lines-2}} ## Investigate ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/1f3e7c43f108.png?v=4b6833858851d206) :::keep-together ### Why do they stay on? **Why do the lights stay on when it gets bright again?** ☐ The light sensor stops working ☐ When the question is false, the if does nothing, so nothing turns the lights off ☐ The lights need a pause to go off ☐ forever only runs once ::: :::teacher-note **Answer:** When the question is false, the if does nothing, so nothing turns the lights off When it is bright, 'light level < 50' is false, so the if skips its blocks. Nothing in the program turns the lights off. ::: :::keep-together ### Zoe's night light Zoe's program: ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/26c462301905.png?v=fe9207976e79bba6) **Zoe's night light is on in the daytime and off at night. Which part is wrong?** ☐ It needs to be in on start ☐ clear screen and show leds are swapped ☐ 50 is too small ☐ The < and > are the wrong way round ::: :::teacher-note **Answer:** The < and > are the wrong way round 'light level > 50' is true when it is bright, so Zoe's lights come on in daylight. For a night light, the lights go on when the level is less than (<) 50. ::: :::typical ## Modify **Switch earlier.** Make the night light come on when the light level is below **100**. Change both questions. **Too hot.** Add a third **if**: when the temperature is above 30, show a sad face. Work in the tutorial. Plan first: what will you change, and how will you test it? {{box-4}} :::teacher-note **One possible solution.** Other correct programs are fine; check that the program runs and does what the task asks. **Switch earlier:** ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/66f37cf570a9.png?v=a6c018c169d04c67) **Too hot:** ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/96ab2dd6f2b5.png?v=8f2fc9853002ee08) ::: ::: ## Mix it up Thermometer 1 is above. Thermometer 2: ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/7eb0d60bd9c6.png?v=57cb97115d035648) :::keep-together **Thermometer 1 (above) reads the temperature in on start. Thermometer 2 (below) reads it in forever. You drag the temperature slider. Which one follows it?** ☐ Thermometer 1, in on start ☐ Neither: sensors only change on a real micro:bit ☐ Thermometer 2, in forever ☐ Both ::: :::teacher-note **Answer:** Thermometer 2, in forever on start reads the temperature once, at the start. forever reads it again each time round, so its number follows the slider. ::: ## Make Make a **weather warning**. Draw your own pictures: - Below **10** degrees: a snowflake (or anything that means cold). - Above **30** degrees: a sun (or anything that means hot). Test it by dragging the temperature slider. Work in the tutorial. Plan first: what will you change, and how will you test it? {{box-4}} :::teacher-note **One possible solution.** Other correct programs are fine; check that the program runs and does what the task asks. ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/f9bdba87dc54.png?v=f5c28a9cb4339fc1) ::: :::wider ## Change a fridge alarm A fridge should stay at 5 degrees or less. This alarm flashes a cross when it gets warmer. Make it also flash when the fridge is **too cold** (below 0), with a different picture. Work in the tutorial. Plan first: what will you change, and how will you test it? {{box-4}} ::: ## Exit ticket :::keep-together **A night light uses only 'if light level < 50, show lights'. Why do the lights stay on in the morning?** {{lines-3}} ::: :::teacher-note **Answer:** When it is bright the question is false, so the if does nothing. Nothing in the program turns the lights off. :::