Great grams

Purpose

This unit comprises 4 stations which develop our concept of the "feel" of a gram. The stations may be taken as whole class activities or they may be set up as activities that groups of students use throughout the week.

Achievement Objectives
GM2-1: Create and use appropriate units and devices to measure length, area, volume and capacity, weight (mass), turn (angle), temperature, and time.
Specific Learning Outcomes
  • Recognise a 100 gram mass.
  • Record measurements in kg and g using whole numbers.
  • Accurately measure specific amounts of materials.
Description of Mathematics

When students can measure objects effectively using non-standard units, they are ready to move to the use of standard units. The motivation for moving to this stage often follows from experiences where the students have used different non-standard units for the same mass and have realised that consistency in the units used would allow for the easier and more accurate communication of mass measures.

Students’ measurement experiences must enable them to:

  • develop an understanding of the size of the standard unit
  • estimate and measure using the unit

It is sensible to begin with the kilogram as the gram is too small to "feel". An appreciation for the feel of a kilogram needs to be built up with lots of examples of 1 kilogram mass, for example, 1 kilogram bags of stones, polystyrene, sand, butter and nails. The students should compare a standard 1 kilogram mass with other objects first by holding and then by using a balance scale.

The usual sequence is then to divide the kilogram into smaller parts, for example, ½ a kilogram (500 grams), ¼ of a kilogram (250 grams) and 1/10 of a kilogram (100 grams).

In this unit the focus is on the gram. The students investigate the mass of very light objects using 10g as a starting point.

Links to Numeracy

There is the opportunity within this unit to revisit and reinforce ideas related to place value as the metric measurements are a decimal system. If this object has a mass of 100g how many will it take to make 1000g or 1 kg?

Required Resource Materials
  • Station 1: Ingredients for Chocolate Bubble Cakes, Kitchen scales with at least 10 gram gradations, paper patty cases.
  • Station 2: 10 g, kitchen scales with 10g gradations, light objects eg feathers, calculators.
  • Station 3: 10 g and 50 g weights, paperclips, cm cubes, drawing pins.
  • Station 4: food packages, calculators.
Activity

Station 1: Chocolate Bubble Cakes

In this station we use the scales to measure and make Chocolate Bubble Cakes.

250 g vegetable shortening
100 g icing sugar
25 grams cocoa
100 grams rice bubbles
100 grams coconut

  1. Put vegetable shortening in a saucepan.
  2. Cook over a low heat until melted.
  3. Sift icing sugar and cocoa together.
  4. Add sifted ingredients, rice bubbles and coconut to saucepan, stirring until well combined.
  5. Spoon mixture evenly into paper patty cases.
  6. Chill until firm.

How many cakes did you make?
What is the mass of each cake?
What is the mass of coconut in each cake?
If I wanted to make 100 patty cakes how much cocoa would I need?

Station 2: As light as a feather

In this station we use kitchen scales and 10 gram weights to figure out the mass of very light objects.
Ask the students to find objects in the class they think will weigh about 10 grams and compare these to the weights. They then weigh the object on the kitchen scales.

Record the working that you did to get your answer.

Station 3: Light Challenges

In this station we use the "feel" of 10 grams to make some guesses about light objects. We are not allowed to use any measuring scales to help with our guesses.

We put each of our guesses on named pieces of paper in the challenge containers to be checked later in the week.

Challenge 1: How many paper clips in 10 grams?
Challenge 2: How many drawing pins 20 grams?
Challenge 3: How many cm cubes in 50 grams?

Station 4: Fascinating Facts

If you really ate like a bird how much would you eat?

A bird eats about half of its body mass each day. That means that if you weighed 30 kg you would need to eat 15 kg.
What food would you choose if you had to eat a total of 15 kg?
Design your day’s eating.

Item

Mass (in grams)

   
   
   
   
   
   
   
   
   

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