1.2 Mass

1.2 Mass

1.2.1 What is mass?

  • Mass is an essential property in science, allowing comparison of objects and substances.

  • Definition of Mass:

    • Mass is a measurement of how much matter is in a substance.

    • Mass does not change regardless of location.

  • Illustration:

    • Two balls on a seesaw demonstrate that when two objects have the same mass, the seesaw remains balanced.

1.2.2 Comparing Masses of Objects

  • Example of Different Masses:

    • Case A and Case B, which have the same dimensions, demonstrate differing masses by their movement ease.

    • Objects in Case A could be heavier (e.g., books), while Case B could contain lighter objects (e.g., silk clothes).

Mass vs. Weight

  • Mass does not change with location, whereas weight varies with gravitational pull.

  • Definition of Weight:

    • Weight is the strength with which one object attracts another object due to gravity.

    • On the Moon, an astronaut's weight is six times less than on Earth, which is due to the Moon's lower gravitational force (only one sixth of Earth's gravity).

1.2.3 Units of Measurement for Mass

  • Various units are used to express mass:

    • Base Unit:

    • Kilogram (kg) is the standard unit for mass measurement.

    • Common Units:

      • Ton (t) = 1000 kg

      • Kilogram (kg) = 1000 g

      • Hectogram (hg) = 100 g

      • Decagram (dag) = 10 g

      • Gram (g) = 1 g

      • Decigram (dg) = $10-1 g or 0.1 g

      • Centigram (cg) = $10-2 g or 0.01 g

      • Milligram (mg) = $10-3 g or 0.001 g

      • Microgram (µg) = $10-6 g or 0.000001 g

  • The most commonly used units are emphasized in bold.

1.2.4 Examples of Mass for Known Objects

  • The following known objects illustrate masses to comprehend varying units:

    • The Titanic: 46,000 t (46,000,000 kg)

    • An adult elephant: 3 to 7 t (3,000 to 7,000 kg)

    • 1 L of water: 1 kg

    • 1 L of gasoline: 0.74 kg

    • 1 L of air: 1.3 g

    • A mosquito: 1 to 2 mg

    • A grain of sand: 0.001 mg (microgram)

  • Note: The mass of a cell is significantly smaller than a liter of water, typically measured in micrograms.

1.2.5 How to Measure Mass

  • Mass is measured with a balance scale: a beam balance, which may have one to three beams (levers) and counters known as riders.

  • Steps to Measure Mass Using a Beam Balance:

    1. Ensure the pan is clean.

    2. Confirm all riders and pointer settings are at zero.

    3. Place the object to be measured on the pan, resulting in a pointer movement.

    4. Adjust the rider for the beam with the largest measurement until the pointer is below the zero line, then move it back one position to balance.

    5. Repeat the process with the middle beam rider.

    6. Adjust for the smallest measurement to balance on zero.

    7. Note the readings from the riders and sum them up to find the total mass.

    • Example Measurement Result:

    • If the total mass is 74.6 g.

  • Taring Technique When Measuring:

    1. First, weigh the empty container and record its mass.

    2. Weigh the container with the substance and note the mass.

    3. Subtract the mass of the empty container from the full container to determine the substance's mass.

1.2.6 Activities

  • Activity 1: Write down the best unit of measurement for different objects' mass.
    a) Jewel: milligram
    b) Dog: kilogram
    c) Pencil: gram
    d) Dose of medicine: milligram
    e) Fly: microgram
    f) Microchip: milligram
    g) Car: kilogram

  • Activity 2: Assess helium-filled balloons to determine which has a larger mass, explaining the reason based on helium volume.

  • Activity 3: Identify the mass displayed on beams of various balances, achieving practical understanding of readings.

  • Activity 4: Evaluate the mass of containers to determine which should be moved first based on mass.

  • Activity 5: Explore the butcher's weighing process to ensure only meat mass calculation by accounting for wax paper weight.

1.2.7 Experiments and Practical Applications

  • Practical examples demonstrate the method of mass measurement and applications, such as weighing meat at a butcher shop while controlling for potential contamination by balancing methods.