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.
- Recognise a 100 gram mass.
- Record measurements in kg and g using whole numbers.
- Accurately measure specific amounts of materials.
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?
The learning opportunities in this unit can be differentiated by providing or removing support to students and by varying the task requirements. Ways to support students include:
- Place items in individual plastic bags so it is easier for children to compare the mass of one object with another.
- Vary the use of scales when measuring different masses. For example, different types of kitchen scales.
- Substitute packages for blocks of different masses and have children sort them from lightest to heaviest.
The context for this unit can be adapted to suit the interests and experiences of your students. For example:
- Making kono (small flax food baskets) and kete (carrying bag). Estimate the mass and compare to 100g.
- Estimate and compare the weight of a pumice (size of a child’s palm).
- 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: Ziplock bags, classroom objects such as counters, small blocks etc.
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
- Put vegetable shortening in a saucepan.
- Cook over a low heat until melted.
- Sift icing sugar and cocoa together.
- Add sifted ingredients, rice bubbles and coconut to saucepan, stirring until well combined.
- Spoon mixture evenly into paper patty cases.
- Chill until firm.
How many cakes did you make?
Estimate the mass of one cake. Weigh it and find a way to find the total mass of your cakes.
If you had 20 cakes, what is the approximate 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: 100 grams
Find objects in the classroom that when combined have a mass of 100grams. Put them into a ziplock bag. Do this without weighing and compare with a partner’s bag. Weigh the bags and record your findings. Check with two others in your group.