Scratch Clock Teacher Lessons Guide
Recommendations: time/duration, age/ability
3 lessons each of 1 hour duration for Year 3/4 Learning objectives
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Understand how to create a simple stopwatch using repetition and variables Create an analog clock using repetition and variables Create a digital clock using variables and sprite costumes Computing curriculum KS2
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Write programs that accomplish specific goals Use sequence in programs Work with various forms of output Use repetition in programs Simulate physical systems Solve problems by decomposing them into smaller parts Use selection in programs Work with variables Use logical reasoning to explain how some simple algorithms work Computational Thinking:
● Algorithms are implemented in the Scratch language to create the programs which operate the two clock models. Decomposition: The overall task of creating the analog and digital clock is decomposed into subtasks. Creating the stopwatch counting mechanism requires pupils to decompose the idea of time passing into the relationships between seconds, minutes and hours. ● Abstraction: The stopwatch counting mechanism uses seconds, minutes and hours. It does this by abstracting these periods of times as scratch variables that can be manipulated and displayed by the stopwatch program. ●
Maths Curriculum Y3/4
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Tell and write the time from an analogue clock, including using Roman numerals from I to XII, and 12­hour and 24­hour clocks ● Estimate and read time with increasing accuracy to the nearest minute; record and compare time in terms of seconds, minutes and hours; use vocabulary such as o’clock, a.m./p.m., morning, afternoon, noon and midnight ● Know the number of seconds in a minute ● Pupils use both analogue and digital 12­hour clocks and record their times. In this way they become fluent in and prepared for using digital 24­hour clocks in year 4. Resources
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MIT Scratch 2.0 Worked example in Scratch 2.0 availbable at the Barefoot Computing Scratch studio (http://scratch.mit.edu/studios/414060/) ● Resource pack downloaded from the link below: https://www.dropbox.com/s/bjs095xtg25ts8h/Scratch%20Clock%20Resources.zip (Please note that within this resource pack resources are organised by lesson) Assessment opportunities
● Baseline assessment of pupils’ numeracy understanding from schools’ existing assessment ● Progress monitored through informal, formative teacher assessment during whole­class, paired / small group tasks and plenaries ● Target questions provided within lesson plans below ● Pupils’ complete programs as evidence ● Screenshots of programs, quotes from pupils and reflection activity for evidence ● Reflection activity at the end of lesson 3 Differentiation
Stretch Lesson 1: Challenge pupils to add milliseconds to their stopwatch. They may need to first investigate the relationship between seconds and milliseconds. Lesson 2: Can pupils explain the purpose for adding on the additional rotation for the hour hand? Lesson 3: Can pupils add a time difference variable to display different times around the world? Support: Solution sheets are provided for each of the pupil tasks. These can be used by the teacher to prompt pupils through questioning (E.G Have you considered how a ‘forever if’ command could be used for…?) who require additional support with the tasks. Additionally, teachers may wish to make an additional resource with the solutions broken down into separate sections of command blocks. These could then be provided to pupils who will be tasked with determining how they fit together into the correct sequence for fulfil the task. Step by step Lesson 1
Introduction and starter (5 mins)
● Explain to pupils that over the next 3 lessons they will be programming an analog and digital clock in Scratch, which they will use to develop and reinforce their knowledge of time. ● Introduce the first learning objective. Understand how to create a simple stopwatch using repetition and variables ● Explain to pupils that in this lesson they will be creating a simple stopwatch which will go on to be used as the counting mechanism in their analog/digital clocks. ● To ensure pupils are clear on how stopwatches function, provide groups with stopwatches on a range of devices and give pupils a few minutes experimenting using these. Pupils should then feedback to group the basic functions of stopwatch ie starts at 0, counts up in seconds, minutes, hours when started, and stops counting when stopped. ● As pupils are feeding back on this activity record any vocabulary related to the topic of time on a display and ask pupils at the end of the exercise if there is any vocabulary missing which needs adding. Unplugged stopwatch model (10 mins)
● Explain to pupils that you are going to create a human model of a stopwatch. ● Invite 3 pupils to stand side­by­side at the front of the class each with an individual whiteboard and pen. ● Explain that the pupil on the right (as the class are looking at them) will be the seconds, the pupil to their right the minutes, the pupil to their right the hours. ● Explain to the pupils they will model being a stopwatch by writing on their whiteboard to display the number of seconds, minutes or hours ­ starting with 0. Model that they will continually wipe these out and change them over and over as required as their human stopwatch counts up. ● Ask pupils key numeracy questions, for example: When will the pupils modelling the minute/hour change from 0 to 1? What will happen when the pupil modelling the seconds reaches 60? ● Lead a discussion to ensure pupils are clear on the relationship between seconds, minutes and hours and discuss that as we start our human stopwatch it is unlikely, unless we sit waiting for an hour, that we’ll see the hour value increase! ● Demonstrate to the class the unplugged stopwatch working with the selected pupils. ● Give pupils time in small groups to model the stop watch themselves rotating roles to be the second, minute and hour. ●
Discuss with pupils why this model wasn’t very accurate, but explain that considering how we modelled the stopwatch (what pupils had to do) will be useful in programming the stopwatch in Scratch. Ask pupils to discuss and feedback the step­by­step process they carried out in order to model the clock as this will form the bases of our program. Introducing repetition (5 mins)
● Explain to pupils that when we come to create our stopwatch in Scratch we will be using a concept called repetition and that repetition means to complete the same action over and over again. ● Ask pupils to discuss with a partner whether they could spot where repetition occurred in our unplugged model? ● Guide discussion to determine that the pupil modelling the minutes continually increased their value by 1 over and over each second (repetition). Also point out that the pupil modelling the minutes increased their value by 1 every time the seconds reached 60 (repetition) and if we’d waited long enough we would see the hour increase by 1 every 60 minutes (repetition). Introducing variables (5 mins)
● Explain to pupils that within a program a variable can be used to store data such as a number, and that the value of this number may change as the program runs. Ask pupils where they might see numbers being displayed in a computer game that they are playing? Guide discussion to examples such as scores, lives, bonuses etc and explain that these are all examples of variables ● Ask pupils what they think represented the variables in the human clock and what are the different variables that we will need? ● Guide a discussion to determine that the 3 variables here were for ‘seconds’, ‘minutes’ and ‘hours’ and that we used an individual whiteboard to model the variable which pupils wrote on as this ‘stored’ a changing number as the program ran. Creating a stopwatch in Scratch
Modelling the use of variables and repetition (10 mins)
● Open Scratch 2.0, delete the default sprite, Felix, by ‘right clicking’ him and selecting delete. Ask pupils to save their Scratch file regularly throughout the project. ● Model how to create a variable (see above) for all sprites and call this variable ‘seconds’. ● Ask pupils to create variables for ‘minutes’ and ‘hours’. Point out that all variables are displayed in the stage and this will be our stopwatch readout. Note, in order for pupils to use the resources pack in lesson 3, it is important that variables are spelt correctly and are plural i.e. ‘seconds’, ‘minutes’, ‘hours’. ● Ask pupils to think back to the human stopwatch model and discuss with a partner how they want the seconds variable to change when the program is run. ●
Show pupils the ‘forever’ repetition command and explain that any command placed within the ‘arms’ of the block will be repeated. Challenge pupils to use the following command blocks to get the seconds variable to be set to 0 and count up once the program is run. Solution
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Ask pupils to consider what we want to happen when our ‘seconds’ variable is equal to 60? (Thinking back to our human stopwatch model) Likewise what do we want to happen when our ‘minutes’ variable equals 60? Guide a discussion to conclude that ‘minutes’ and ‘hours’ need to increase by 1 at the appropriate point. ● Explain that to achieve this, instead of using a forever command in our program which will cause ‘seconds’ to count beyond 60, as above, we can use a forever until command which will repeat the commands inside the loop until a condition is met. Ask pupils what the important condition is here? ●
Show pupils the sequence of commands above. Ask pupils to discuss with a partner what will happen when this program is run. Guide a discussion to ensure pupils understand that the ‘seconds’ variable will increase by 1 every second until ‘seconds’ is equal to 60 ­ at which point ‘seconds’ will be set to 0 and ‘minutes’ increased by 1 (The commands below the ‘repeat until’ command). The ‘seconds’ will then start counting from 0 again due to the forever loop wrapping around the commands. The set commands at the beginning of the program are used to set the stopwatch to 0 seconds and 0 minutes when the program is run. Pupil activity. Pairs or small groups (20 mins)
● There are now two tasks that pupils should complete. These are detailed on the pupil worksheets. ● Task 1: Extend the stopwatch program so that hours increase when ‘minutes’ reach 60 and determine a way to test whether this works without having to run the program for an hour! ● Task 2: Explain that this counting program will form the basis for an analog clock in the next lesson and therefore it needs to count up to 12 hours then start from hour 1 again. Pupils should also remove the commands which set the stopwatch to 0 each time. Can pupils adjust their program to achieve this? Plenary (5 mins)
● Allow pupils time to use their stopwatches to time each other carrying out tasks in the classroom. ● Ask pupils key questions: Why and how have variables been used in the programming of your stopwatch? Why and how has repetition been used in the programming of your stopwatch? Solution sheet - Lesson 1
Task 1
Note the setting of variables ‘minutes’ and ‘seconds’ to test that hours counts up by 1 once minutes = 60. Task 2
Step by Step Lesson 2
Resources
● This lesson will use the files available in the ‘Lesson 2’ folder within the resource download folder for this series of lessons, available here: https://www.dropbox.com/s/bjs095xtg25ts8h/Scratch%20Clock%20Resources.zip ● This lesson builds on pupils work from lesson 1. If pupils did not complete lesson 1, please provide them with the Scratch project file ‘Stopwatch from lesson 1’ from the resource folder as a starting point for this lesson. Introduction (5 mins)
● Introduce the learning objective to pupils. Create an analog clock using repetition and variables ● Show two analog clocks (one with roman numeral background and one without) and ask pupils to discuss with a partner the various parts that make up the clock and their function. Would the clock work without each of these parts? ● Pupils feedback on their discussion and note on the whiteboard the parts of the clock we’ll have to model and their function e.g. Second, minute, hour hand plus clock face. Creating the clock interface in Scratch (10 mins) (Please see this screencast video to
accompany this section)
● Pupils should open the previous lesson’s stopwatch project which should contain the completed clock counting mechanism from lesson 1 task 2. ● Pupils should import the two clock backgrounds from the resources folder (normal and roman numeral) as two separate costumes into the project. They should name these as ‘Analog’ and ‘Analog Roman’ ● Pupils should then create three sprites, one for each clock hand. Discuss with pupils how these should differ in appearance (length, colour). Importantly, the centre of these sprites should be set at the base of the hand and the hand should be drawn horizontally with the arrow pointing to the right as shown below. ●
Pupils should now position the clock hands to align with the centre of the clock and then click the sprites info button to reveal the info pane and rotate the sprite so that it points vertically to 12. This is shown below. ●
Pupils project should then appear as below. Programming rotating clock hands (5 mins)
● Explain to pupils that we are now going to program the clock hands so they rotate around our clock at an appropriate speed as time passes. ● Discuss with pupils that the clock hands will turn through an angle as time passes. Link this with pupils’ geometry lessons where they will have learnt to recognise right angles as well as classifying angles as either acute or obtuse (Year 4). Explain that angles are measured in degrees and there are 360 degrees in a circle, like the clock face. ● Ask how many steps we would like our second hand to tick through in one minute? 60 steps as 60 seconds in a minute. Therefor we can calculate that each step needs to be 360/60 = 6 degrees. ● Show the commands below for the second hand and talk through with reference to the above calculation that our second hand will rotate through steps of 6 degrees as the second variable counts upwards. Why and how have we used repetition here? Can pupils now work out the degrees step for the minute hand? What do they notice about the answer? Why is the answer the same? As there are the same number of seconds in a minute as there are minutes in an hour. Pupil activity (10 mins)
● Pupils should now add the commands for each of the clock hands detailed on the pupil activity sheets into their project and determine the correct values to enter in order for the clock hands to move correctly when the program is run. ● Extension ­ can pupils explain why for a more accurate clock model we add on an additional rotation for the hour hand? Switching to a Roman numeral clock face (5 mins)
● Ask pupils to create a new sprite from folder and load the ‘Change clock type’ graphic for this sprite. ● Explain that this button will be used to change between the regular clock face and the Roman numeral clock face. ● Explain that we will use a broadcast message to achieve this. A message will be transmitted when the sprite is clicked and every time this message is received then the backdrop costume will change. ● Ask pupils to add the following broadcast message command within the ‘Change clock type’ sprite script area ● Ask pupils to add the following message received command in the stage script area to change the backdrop each time the change clock type sprite is clicked Setting the time with sliders (5 mins)
● Model for pupils that by clicking on each of the variable displays in the stage area a slider will appear which can be used to set that variable value. As shown below. ●
Demonstrate that by right clicking on the variable slider we can select ‘set slider min and max’ to limit the values of each variable. ● Discuss with pupils what the min and max of each variable should be then ask pupils to set sliders for each to these limits. Plenary - Using pupils’ clocks as a numeracy learning tool (15 mins)
● Pupils now have a working model of an analog clock which can be set to a time using the hour, minute and second sliders and then will tick on from this time when the program is run. By clicking the change clock type button, pupils can also toggle between a regular and Roman numeral clock face. ● Pupils should now have the opportunity to use their clock to support their learning of time. Example activities might include: ○ As a whole class pupils set the time on their clocks to that said by the teacher, or by a set time ahead or behind as an extension ○
Working in pairs pupils challenge each other to set/read the time using a normal/Roman clock face on their clocks. ○ Pupils set the times on their clocks to significant times in the school day ○ Pupils explain to each other the relationship between the variables within their clock mechanism Solution sheet - lesson 2
Minute hand Hour hand Hour hand extension Step by Step Lesson 3
Resources
● This lesson will use the files available in the ‘Lesson 3’ folder within the resource download folder for this series of lessons, available here: https://www.dropbox.com/s/bjs095xtg25ts8h/Scratch%20Clock%20Resources.zip Introduction and starter (5-10 mins)
● Introduce the learning objective to pupils Create a digital clock using variables and costumes ● Use timed­pair­share for pupils to recall what the remember about variables and how they were used in our previous lessons? ● Explain that we will explore the concept of costumes through a starter game ● Show a digital clock and explain that the numbers are constructed from a fixed 7 segment display and that this is achieved by lighting different segments at different times. ● Consider with pupils that each of these segments can therefore only exist in one of two states, either ‘on’ or ‘off’. Explain that a system which operates with just 2 states (‘on’ or ‘off’) is called a binary system and that binary systems, such as this, form the basis for computer systems. Explain that whilst each of these segments has only two conditions, ‘on’ and ‘off’, we’re actually able to convey the numbers 0­9 and we’re going to learn how. ● Image below. ●
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Print off the 7 segment starter worksheet and pass to pupils so they have one each. Explain that, as pupils have just seen on the digital clock, any number between 0 and 9 can be displayed using the 7 segments and their challenge is to work out how. Explain that pupils will be representing turning the individual segments ‘on’ and ‘off’ by shading them in. Shading in represents turning ‘on’ and leaving blank is leaving them ‘off’. Refer back at this point to the binary system of just two states. Starter game: The teacher calls out the numbers between 0­9 in a random order and pupils have to shade in the correct segments to ‘display’ the number. Following the game, guide a discussion with pupils to explain that here we have altered the appearance of the same 7 segment display (by shading in different sections) and in doing so we have changed the information that it displays. ●
We may think of the 7 segment display as wearing different costumes, the ‘1 costume’ or the ‘9 costume’. Creating different costumes like this is a feature available in Scratch which we will use to create hour digital clock. Creating a digital clock on Scratch
Creating the digital clock background (5 -10 mins)
Please see this screencast video to accompany this lesson
● Pupils should open the analog Scratch clock they created in the previous lesson as this will form the basis for this digital clock (On completion this will enable pupils to practise conversion of time between analog and digital) ● Pupils should then select to paint a new backdrop which can be filled entirely in black (See screenshot below) ● Pupils should label their backgrouds: analog, analog roman and digital ● We then need to ensure that when this backdrop is selected (as the user uses our toggle button to move between analog, analog roman and digital) our analog clock hand sprites hide themselves. This is easily achieved by placing the following command into each of the clock hand sprites. ● Can pupils now determine what similar commands need to be added to each of the clock hand sprites in order for the them to show again when the analog display is selected? ● Solution: the following commands need to be added to each of the clock hand sprites Creating the 7 segment hour display (10 mins)
● Ask pupils to load the ‘hour.sprite2’ into their project from the resource folder. ● With reference to the starter activity explain to pupils that we are going to create costumes for this sprite to display the hour on our digital display. Ask pupils how many different costumes will be needed? 12 ● Model to pupils that we can create a new costume for this sprite by right clicking and selecting duplicate. (As shown in screenshot below). Repeat this until we have 12 costumes for our hour sprite and get pupils to do the same. ●
Task 1: Challenge pupils to now change each one of these costumes, using the fill tool , so the sprite will display the numbers 1 ­ 12. Importantly make sure that costume 1 displays 01, costume 2 displays 02 etc Programming the 7 segment hour display (10 mins)
● Explain to pupils that they are now going to program the digital hour display sprite. Ask pupils to think about the purpose of this programming, i.e. what do we want the hour display sprite to do? Guide a discussion to establish it should: ○ Display the correct hour as indicated by the hour variable ○ Hide when either of the analog clock face backgrounds are displayed ○ Show when the digital clock face background is selected ● Before setting pupils off on the task of programming the hour display sprite to achieve the above functions, introduce pupils to the ‘switch costume’ command and show that this enables the costume to be changed to one of the 12 available, as shown below. ● Also demonstrate that we can embed our variable into this command and that this may help pupils solve this problem. As shown below. ● Task 2: Pupils are now challenged to program the digital hour display sprite in order to fulfil the requirements specified above, i.e: ○ Display the correct hour as indicated by the hour variable ○ Hide when either of the analog clock face backgrounds are displayed ○ Show when the digital clock face background is selected ○ Extension: Can pupils add a world time feature? (See task sheet below for more details) ● Once pupils have completed this task they should be given time to adjust the hour slider to see how this changes the hour displayed. ● Take some time for pupils to explain how their program for the digital hour display works. Why did they need to include repetition? Completing the rest of the digital display (10 mins)
● The sprites for the remainder of the digital display (MinuteD1, MinuteD2, SecondD, SecondD2, Colon, Colon2) can now be loaded into pupils’ projects from the resource folder and arranged in the stage area as shown below. ● These sprites will load with the programs required to cause them to display the time as pupils have just worked through for the hour display. This is achieved in a slightly different manner as drawing 60 different costumes for minutes and seconds would not be an efficient approach. Whilst the programming of these sprites is not covered in this unit, please do encourage pupils to explore how they have been programmed including considering what is similar to the approach they have just taken in programming the hour display and what is different. Set to current time (10 mins)
● A final feature of pupils’ clock project is the ability to set the program to display the current time. The set to current time button can be seen on the screenshot above. ● Pupils should load the ‘Setcurrent’ sprite into their project. This does not load with the program to achieve the time setting. As such display the following command blocks to pupils and discuss with pupils how they may be used to tackle the problem of building in a ‘Set to current time’ function. ● Task 3: Challenge pupils to use the commands above to incorporate a ‘Set to current time’ feature into their clocks. Plenary: Learning from their clocks (10 mins)
● Pupils now have a working Scratch model of an analog and digital clock which can be set to a specific time using the sliders or to the current time. In a similar manner to the plenary for lesson 2, this resource can now be used as a numeracy learning tool. This may take many forms, and a selection of ideas appears below: ○ Pupils practise reading the times from both the analog and digital displays. ○ Pupils set their clocks to specific times when asked, e.g. “Set your clocks to half past five” in doing so they will have to determine the number of minutes in half past, quarter past etc. ○ Pupils set their analog clocks with the slider and write down the digital equivalent. They toggle to the digital display to check if they’re correct. Repeat this activity in reverse. ● Ask pupils to discuss key assessment questions regarding programming their digital clocks: ○ What is a costume and how were they used here? ○ How and why have variables been used in your digital clock? ○ How and why has repetition been used? ○ Explain how our ‘Set to current’ function works? Reflection activity
● As pupils have now completed this activity, they should have the opportunity to engage in a reflection activity whereby they can think back to what they have learnt over the 3 lessons. ● Use the key assessment questions from the above lessons as a guide to prompt pupils’ reflection on their learning, e.g: ○ What is the relationship between seconds, minutes and hours which you used to create a stopwatch? ○ Why and how were variables used in the programming of your stopwatch? ○ Why and how was repetition used in the programming of your stopwatch? ○ What sprites were used in your analog clocks? How was repetition and the use of variables used to program these? ○ How were costumes used to display the correct hour in your digital clock? ○ How and why were broadcast messages used in your clock project? ●
There are a range of ways pupils can record their answers to these questions: either around a screenshot of their program, in a audio/video recording or as a blog post for example. Solution sheet - Lesson 3
Task 1: The 12 costumes for the hour sprite in ascending order should appear as below. Task 2: Hiding/showing: The digital hour display sprite should have the following commands to ensure if displays at the correct time. Note ­ including ‘When backdrop switches to roman, hide’ is not needed as the sprite will remain hidden after the analog backdrop is selected until selection of the digital backdrop causes the sprite to show. Displaying the correct time: World time extension: If pupils create a variable called ‘time difference’ which can be set with the slider between ­12 hours to +12 hours they can modify their program as shown below to display the time difference. Task 3: