Measurement - Mass

Outcome: MS3.4
Selects and uses the appropriate unit and measuring device to find the mass of objects /

Key Ideas

Recognise the need for tonnes.
Convert between kilograms and grams and between kilograms and tonnes.
Select and use the appropriate unit and device to measure mass.
Record mass using decimal notation to three decimal places.
WORKING MATHEMATICALLY OUTCOME/S
Questioning
Asks questions that could be explored using mathematics in relation to Stage 3 content.
Applying Strategies
Selects and uses appropriate mental or written strategies, or technology to solve a given problem.
Communicating
Uses some mathematical terminology to describe or represent mathematical ideas.
Reasoning
Checks the accuracy of a statement and explains the reasoning used.
Reflecting
Links mathematical ideas and makes connections with existing knowledge and understanding in relation to Stage 3 content.
Knowledge and Skills
Students learn about
·  recognising the need for a unit larger than the kilogram
·  using the tonne to record large masses
eg sand, soil, vehicles
·  using the abbreviation for tonne (t)
·  converting between kilograms and grams and between kilograms and tonnes
·  selecting and using the appropriate unit and device to measure mass
·  recording mass using decimal notation to three decimal places eg 1.325 kg
·  relating the mass of one litre of water to one kilogram / Working Mathematically
Students learn to
·  solve problems involving different units of mass
eg Find the total mass of three items weighing 50 g,
750 g and 2.5 kg. (Applying Strategies)
·  associate gram measures with familiar objects
eg a standard egg has a mass of about 60 g (Communicating)
·  find the approximate mass of a small object by establishing the mass of a number of that object
eg ‘The stated weight of a box of chocolates is 250 g.
If there are 20 chocolates in the box, what does each chocolate weigh?’ (Applying Strategies)

LEARNING ACTIVITIES (Mass 12)

MEASURING AND CALCULATING
• Students measure the mass of four marbles and hence calculate the mass of a) two marbles, b) one marble, c) six marbles.
PROBLEM SOLVING
• Students measure the mass of each of three parcels and calculate the difference in the masses of the parcels.
• Given only 100 g and 10 g masses, students determine how to balance 320 g of a cooking ingredient. As an extension the same problem could be set with 100 g and 30 g masses.
INTERLOCKING CUBES
Students build a shape from 50 interlocking cubes and estimate its mass. Check using a balance. Estimates of the mass of shapes made from different numbers of cubes should now be more accurate. Record results in a table.
GUESS AND CHECK
Students estimate in grams the mass of a cup of flour, rice, sand, macaroni, marbles, polystyrene beads, etc, then check their
estimates using an equal arm balance.
TEN GRAMS
Students find the number of the following items needed to balance 10 g: paper clips, drinking straws, corks, interlocking cubes, 1c coins, thumbtacks, matches, toothpicks, etc. Students estimate and then measure to answer questions such as “Do thirteen beans have a mass greater than 10 g?”
MASS HUNT
Students find and record items that have a mass of 1 g, 5 g, 10 g, 50 g, 100 g, 500 g and 1 kg.
RECIPES
Students collect and display recipes with quantities shown in grams.
EGGS
Students compare the masses of a dozen large, medium and small eggs. Discuss value for money.
MASS OF WATER
Students measure the mass of 250 mL, 100 mL, 50 mL, etc of water and hence predict the mass of 1 mL.
LEARNING ACTIVITIES (Mass 13)
TINS AND PACKETS
Students collect tins and packets, which show net or gross mass. If a full packet is available, have students measure the mass of the contents and compare the result with the mass on the packet.
Discuss the advertising of net versus gross mass from the consumer’s point of view.
CONSTRUCTING A SPRING BALANCE
Hang a light bucket from the end of a spring. Mark a zero point on a piece of paper next to the bottom of the spring. Place a 1 kg mass (or whatever suits the strength of the spring) in the bucket and mark this mass on the paper. Divide the interval between the zero and the 1 kg marks equally and mark in 100 g multiples.
Check the accuracy of the scales using standard masses. Use the scales to find the mass of various objects.
INVESTIGATION
Ask students to suggest a way of measuring the mass of a pet, eg the student holds the pet and stands on the scales. Then the student is weighted separately. Subtraction gives the mass of the pet.
MASS IN SPORT
Students collect information about sports in which weight divisions exist, eg boxing, junior Rugby.
CHOOSING THE INSTRUMENT
Students suggest suitable devices for measuring the mass of a variety of things, eg people, an envelope, medicine.
CHOOSING THE UNIT
Students suggest suitable mass units for recording the mass of the things in the previous activity.
MASS AND HEALTH
Students discuss health charts which link recommended weight with a given height. Mention should be made that a range of weights is given rather than just one weight for a given height.
Discuss the problems of being overweight or underweight, being sensitive to the feelings of the students.
MASS IN THE COMMUNITY
List mass measuring devices used in the local area, eg at the post office, shops, a weighbridge.

LEARNING ACTIVITIES (Mass 14)

FINDING EXAMPLES OF MASSES MEASURED IN TONNES
• Visit a weighbridge, a railway goods office, produce market or a factory. Note the working of scales. Note load limits written in tonnes.
• Find examples of road signs which mention tonnes, eg “LOAD LIMIT ON BRIDGE 3 t”.
• Students collect information on the production of such commodities as wheat and coal. Record on a wall chart.
• Students collect brochures on cars and trucks, which mention the mass in tonnes.
ANIMALS
As part of a visit to the zoo or museum find the masses of very large animals, eg elephants, blue whales, dinosaurs. Have students make a wall chart showing a picture of the animal accompanied by a tag giving its mass. This activity could be linked with studies of speed, length and volume.
MASS BY DIFFERENCE
Visit the local tip or trucking firm and observe this method of finding the load carried by a truck.
ESTIMATION
• Students estimate the mass of a load of sand in a small truck, etc, before it is driven onto a weighbridge.
• Students estimate the mass of a full load of ready-mixed concrete. Check by asking a driver or ringing the company.
INVESTIGATIONS
• Have students investigate the number of students required to balance a one-tonne truck, an elephant, etc.
• Find the total mass of the students in the class in tonnes by weighing each student in kilograms and converting to tonnes. Ask students to make up sentences relating their total mass to everyday things, eg “The mass of 6B students would balance a small car on a see-saw.”
• Students consider load restrictions on aircraft. For example, if a jumbo jet can lift 24 t of luggage, how much luggage could each of 300 passengers be allowed, on average?
Resources
Equal arm balance, spring balance, bathroom scales, kitchen scales, standard masses, packets from food stuffs, containers, rice, flour, feathers, paper clips, polystyrene beads. / Links
Technology / Language
‘Mass’ and’ weight’ have become interchangeable in everyday usage.

Assessment

Ask students to:
• convert masses expressed in kilograms to masses expressed in tonnes
• convert masses expressed in tonnes to masses expressed in kilograms
• give reasonable estimates of the masses of trucks, cars and ships. / Evaluation
• Have students’ understandings of mass been applied in other curriculum areas such as HSIE?
• Did I ask open-ended questions to encourage problem solving?