Tuning into Measuring Mass

          


To we began exploring our new unit:

Central Idea: Converting units and using decimals helps us make sense of the measurement of mass.

Lines of Inquiry:

° FUNCTION: Strategies we can use when measuring mass

° FUNCTION: How we can convert units of mass

° FUNCTION / CAUSATION: How we use decimals with mass and why

° CONNECTION: How we use the measurement of mass in our daily lives



To begin tuning into the concept of mass, as the children entered, they saw the following on our board:

As we were going to begin exploring how to convert grams into kilograms and vice versa, I thought it was important that they gain a sense of what 1 kilogram actually feels like.  

Using their arms like a balance scale, they hefted their school bag and compared its mass with the 1 kg weight in their other hand.

They were then asked to estimate what they thought the mass of their bag was.

As well as helping them sense a kilogram, it was also an interesting one-on-one pre-assessment as I listened to the thinking of each learner. 

Some of the thoughts shared were:

° I can feel my bag is a lot heavier than 1 kilogram.

° I think my bag is just a tiny bit lighter than 1 kilogram so I estimate it is 3/4 of a kilogram.

° I feel my bag is more than double the kilogram.

° Wow! Is this really a kilogram? It's really heavy!!

° I think my bag is about half of the kilogram. 

° Olivia said her bag was about 1 kilogram. Can I now heft her bag with mine to see if my estimate is close?

° Could I put my bag on a scale to see if my estimate was close?

° What has Louisa got in her bag? Her bag is more than double mine!

° I think its somewhere between 1 and 2 kilograms.

° I would say its less than 1 kilogram, but I'm not sure by how much.

° So my mum weighs about 70 of these weights?!?

° What do you call the things that are less than a kilogram?

As you can see, there were lots of diverse thoughts taking place. It was interesting for me to hear their reasoning skills, who was thinking of fractions, who was comparing by doubling etc. 

After each had hefted, I then asked them to show on the number line where their estimate belonged.

This also become a key informal assessment as each child shared where they would place it and what their estimate was.

I was thinking about:

° Who is using simpler masses such as 1 kg and who was confident in taking their thinking to masses such as 0. 75 kg or 1 . 25 kg etc?

° When they gave their mass estimate, I asked if they could express it in different ways?  Some could express it in grams, some could express using fractions and some could only express it one way. 

° Who was noticing the other masses already recorded on the number line and used that to determine their own estimates?

I felt I was able to gain a sense of where each child was at with their experiences and / or understanding of measuring mass and using decimals.

When everyone had hefted their bags, we then looked at the number line of estimates and I asked what does this make us wonder?

° How could we check if our estimates were close?

° Is hefting really a useful way to measure the mass of objects?

° How could we add all the decimals?

° What's the difference between the heaviest and the lightest?

Table partners then discussed these questions posed sharing their ideas and strategies.

As the purpose behind this was to tune us into what a kilogram feels like and also to gain an informal glimpse of where each learner was at with mass, we didn't go into this further. 

Sometimes, I think it is good to keep us wondering about certain things that we can come back to later.

I suggested that we use our number line as part of home learning next week, so during our day, if you have a mathematical question you think we should try to solve, jot it down on a sticky note and place it beside the number line. 

At the end of the day, decided upon four questions to solve for home learning in addition to a suggestion that we convert the kilograms to grams.

So, this is what our home learning looks like:

We will come back to the strategies they created to measure the exact mass of their bags later in the week after we have gained a deeper understanding of converting grams and kilograms.

What we did do after this, was we explored how to convert kilograms into grams and vice versa and then used this understanding to apply with our 'Travelling into Space' investigation: 

Link to 'Travelling into Space'