This activity will teach children/students to make a scale that they can use to measure items around the house or classroom, simply by using a milk carton.

First, go through your recycling bin and clean out and dry off a 2L milk carton to use for the project. The top of the carton will need to be cut off, so you have created a container out of the bottom that is about 1½ inches in depth, or its height is 1 ½ inches.

Next, punch one hole in the centre of each side of the milk carton, about ¼ inch from the top of the carton. This will be the compartment of the scale you use to measure your items in.

Now cut two pieces of string so that they are 24 inches long. Lay one string down on your table, and place the milk carton on top of it so that you see the string coming out from opposite sides of the carton.

Take the exposed string from one side of the carton, and thread it through the hole on that side. Do the same on the opposite side of the carton with the exposed string and pull so that the string is secured snugly.

Now take your second string, and again place it on the table under your carton, only this time place the carton so that the string lines up with the remaining empty holes. Thread the string through the holes and pull tightly. It is important that the string is the same length on all sides.

With the four strands you have created, tie a knot tightly at the very top to create a large loop. To be sure the string stays securely weaved onto your carton, you can tape the string to the bottom of the carton.

Slip the string loop onto one end of a large paper clip. Now take a rubber band, and slip it onto the other end of the paper clip. The scale is now complete. You can hang it by attaching the rubber band to a wooden ruler or dowel that is secured to a flat surface. In order to measure, you will need to tape a piece of paper on a wall next to the scale, so that the top of the paper is lined up with the bottom of the milk carton. Now, when you place an item in the scale, it will descend based on the item's weight and you can mark it on the paper!

Using the Scale:

Have your child find common items from around the house – fruit like apples and pears, toiletries like a bar of soap or bottle of shampoo, or kitchen items like cups and bowls. Make sure they will fit inside the milk carton scale. With your child, try to compare the weight of common items by holding one in each hand. Have them decide which is heaviest, and place the heavier item to the left, and the lighter item to the right. Continue this process until they have gone through every item, and have created a row of items from heaviest to lightest (heavy on the left, light on the right).

Take the scale you created together, and place the object they have determined is the heaviest on the scale. Position the scale gently so it is against the paper, and draw a line underneath it. Record the item's name next to the line. Place the object back in line, and do the same to the next one. Continue this process until all of the items are recorded.

Now have the child check to see if their predictions were correct! The objects on the paper that are the heaviest will have a line closer to the bottom of the paper. See if the order on the paper from the bottom to the top, matches your order from the left to the right. Your child will have lots of fun playing this weight game, and you can play again with objects from every room in the house!

This activity will reinforce the concept of weight as a property, and how you can measure and compare it using specific tools and units (such as scales, which demonstrate the concepts of greater than, less than, and equal to).