Interactive measuring jug, scales and ruler

What the measuring tools do on screen

Four tools share one page: Capacity, Mass, Length and Temperature. Each fills the board, each is dragged with a finger or the mouse, and each prints the reading in large type underneath. The row along the top sets the tool up: the size, the unit, what is on the board. The black bar at the foot is what you use during the lesson. Each tool also keeps its own reading, so you can jump to the ruler and back and the jug is still where you left it.

• Capacity. A plain beaker. Drag anywhere in it and the surface follows your finger, then rocks and settles like real liquid. The Jug buttons step through 100 ml, 250 ml, 500 ml, 1 litre and 2 litres, and the marks change with each. Empty, a quarter, a half, three quarters and Full pour it straight there, or type a number into Pour to and watch it fill.
• Mass. Two kinds of scales. The Dial is a round face with a red needle: drag it round, or type a number into Set to and watch the needle swing. The Balance has two pans, a mystery object on the left and a tray of weights from 1 g to 1 kg along the foot. Tap a weight to send it to the pan and tap it again to take it back; the beam tips and settles until the two sides match. The Scale buttons step the dial through 100 g, 500 g, 1 kg and 5 kg.
• Length. A ruler with a coloured bar along it. Drag the yellow handle at the far end. The Ruler buttons step through 10 cm, 30 cm and 100 cm, the small marks are millimetres, and Show in mm swaps the unit. Start off zero moves the bar so it no longer begins at the 0 mark, and Second object puts a second bar above it to compare.
• Temperature. A thermometer with a scale that crosses zero. Drag the mercury up and down, or jump to freezing, room or body temperature. Everything below zero sits on a pale blue band, so the class can see which side of zero the reading is on before they read it. The scale switches between minus 20 to 50, minus 10 to 40, minus 50 to 50 and 0 to 100.
• Hide reading. On all four, one press turns the number into a question mark and another reveals it. This is the button the whole tool is built around.
• Random task. One press sets an awkward reading with the answer already hidden. Take the class's estimate, type it into the Estimate box, and Reveal puts both numbers side by side: "You said 350 ml, it is 375 ml".
• Print. One A4 landscape sheet of whichever tool is on the board, with the reading still hidden if you have hidden it.

How to use it in a lesson

Choose the size first, and choose it for the divisions rather than the number. A 1 litre jug marked every 50 ml is a different question from a 250 ml jug marked every 25 ml, even though both look like a jug with lines on.

1. Work out the divisions before you measure anything. Point at two labelled numbers, count the small marks between, and ask what one mark is worth. Do this every time you change the size.
2. Press Hide reading before you set the level. If the answer is on screen while you drag, the class reads the answer and you learn nothing.
3. Drag to something awkward. The neat values teach nothing. Stop the needle at 260 g, or the liquid at 175 ml, and take three answers.
4. Reveal, then ask the child who was wrong what they counted. Nine times out of ten it was marks in ones, and hearing that out loud helps everyone.
5. Swap the unit without moving anything. Press Show in L with the level untouched, and ask whether there is more, less or the same.
6. Change the size and ask again. Same height of liquid, different jug, different answer. Then Print it if you want the sheet.

Ideas by year group

• Year 1. Capacity, 100 ml jug. Full, half full, nearly empty. Drag to each and let the class say which, before any numbers.
• Year 2. Mass, 500 g scale. Land the needle on a labelled number, then one mark past it, and read both together.
• Year 3. Capacity, 1 litre jug, Hide reading on. Count the marks between 200 and 400, work out what one is worth, then read the level.
• Year 4. Length, 30 cm ruler, Show in mm. Drag to 12.5 cm and ask for it in millimetres, then centimetres, then write both.
• Year 5. Mass, 5 kg scale. Read a needle between two 500 g marks, then swap to kg and write it as a decimal.
• Year 6. Capacity, 2 litre jug, Hide reading. Read the level, then ask how many 250 ml cups it would fill and what is left.

The misconceptions it helps with

Counting the marks in ones. This is the big one. A mark is worth whatever the scale says it is worth, and stepping the jug or the dial through its sizes with the level untouched shows that faster than any explaining.

Thinking the unit changes the amount. Press Show in kg with the needle still. 400 g becomes 0.4 kg, the needle has not moved, and the two labels mean the same thing.

Writing 1.5 kg as 1 kg 5 g. Set the dial between two kilogram marks, read it in grams, then swap to kilograms and write both on the board next to each other.

Measuring from the wrong end of the ruler. Start with the bar at zero, where the length and the number on the scale are the same thing. Then press Start off zero. The bar now begins at 3 cm and ends at 18, and most of the class will say 18. Ask them what changed, and the difference between the two numbers becomes the whole point of the lesson.

Frequently asked questions