For Grade 1 students are only required to compare 2 objects based on their length and weights. e.g.
A truck is longer than a book.
An apple weighs less than the chair.
The student directly compares the attributes of length, area, weight/mass, capacity, and/or relative temperature. The student uses comparative language to solve problems and answer questions. The student is expected to:
We can compare 2 objects based on their:
All of the above features of an object can be measured using tools like ruler, scales and weighing scales.
These are some of the exercises kids can perform to understand the concept of weight comparison.
To introduce this concept, we simply practice comparing weights by holding different objects in our hands. Of course, some objects are a little too heavy to actually pick up. Luckily, the kids already have a solid schema--most can easily tell you that a car weighs more than a soccer ball.
The interesting part comes when they find an object that is fairly close in weight to the water bottle. Even I would have a hard time determining which one actually weighs more, so that presents an excellent opportunity to discuss--How can we know for sure which one weighs more? (We'll get to that in a few days when we start measuring with cubes.)
We can pull out several objects specifically for this conversation--a feather, a marble, a beach ball and a baseball. First, I ask the kids Which ones are bigger? Both the feather and the beach ball are bigger. Then I ask Which ones are heavier? The marble is heavier than the feather, even though it is bigger. And the beach ball is much lighter than baseball, even though it is much bigger.
The first activity is to compare objects to see which weighs more using the balance. Again--do not tell the kids how to do it. Guide them through questioning, but do not model it.
For a challenge, have the kids figure out which of the objects they compare weighs the most. That's true problem-solving! Watch to see what strategies the kids use to keep track of the objects they weigh. This is definitely a challenge. We always have them work together in a group for this problem.
This is just more practice using a balance. We give each group and eraser and a variety of objects. They see how many different combinations of objects they can find to balance the eraser.
So here, instead of just comparing objects, we are actually weighing them using non-standard units. The kids will have to do some rounding, for sure. Sometimes 6 cubes isn't enough to make it balance perfectly, but 7 is too many. We tell them to get as close as possible.
While they're working, you can ask them what the benefit of using the cubes to measure with would be. (It's a common unit that you can then compare weights with).
When they're done, You can ask which object weighed the most? They can answer very easily. The object which balances more number of cubes weighs the most. Was it harder or easier to tell which object was heaviest, as compared to using the non-cube method? They should (hopefully) say it was easier, because they knew how many cubes each object weighed, they did not have to go back and compare each object. They had a common unit by which to compare.
Here is a chance for the students to apply what they've learned to a more abtract problem. We do not get out the balances for this problem, although they can use math manipulatives if they want.
One way is to put out 5 tiles to represent the 5 cubes on one side of the balance. And then add tiles until you get to 12 (because we need 12 on both sides to make it balance). Then count how many more you have added to get the answer 7.