1. Identify the problem/question – What are you trying to find out?
2. Form a hypothesis – What do you think will happen?
3. Design the experiment – What materials and steps will you use?
4. Collect data – Take measurements carefully
5. Analyze results – Compare your data with expectations
6. Draw conclusions – What do your results tell you?

Aim

To determine the density of a rectangular block.

Materials

Beam balance, meter rule, rectangular block

Procedure

1. Measure the mass – Use the beam balance to find the mass ($m$) of the block in grams.
2. Measure dimensions – Use the meter rule to measure the length ($l$), width ($w$), and height ($h$) in centimeters.
3. Calculate volume – Use the formula: $V = l \times w \times h$
4. Calculate density – Apply the formula: $\rho = \frac{m}{V}$

Worked Example

A glass block has mass = 150 g and dimensions 3 cm × 4 cm × 5 cm.

• Volume: $V = 3 \times 4 \times 5 = 60 \, \text{cm}^3$
• Density: $\rho = \frac{150 \, \text{g}}{60 \, \text{cm}^3} = 2.5 \, \text{g/cm}^3$

Key Points

• Ensure the meter rule is placed correctly against the object
• Take readings at eye level to avoid parallax error
• Record all measurements with appropriate units

Aim

To find the density of a stone using the displacement method.

Materials

Beam balance, Eureka can, measuring cylinder, string, stone, beaker

Procedure

1. Measure mass – Find the mass ($m$) of the stone using the balance.
2. Fill Eureka can – Add water until it reaches the spout.
3. Collect displaced water – Place a beaker under the spout. Gently lower the stone into the water using string.
4. Measure volume – Pour the displaced water into a measuring cylinder. This volume ($V$) equals the stone's volume.
5. Calculate density – Use: $\rho = \frac{m}{V}$

Worked Example

A stone has mass = 50 g. The measuring cylinder shows 60 cm³ before immersion and 70 cm³ after.

• Volume of stone = $70 - 60 = 10 \, \text{cm}^3$
• Density = $\frac{50 \, \text{g}}{10 \, \text{cm}^3} = 5 \, \text{g/cm}^3$

Key Points

• The stone must be fully submerged
• Do not let the stone touch the bottom of the Eureka can
• Collect all displaced water completely

Aim

To find the density of a liquid (such as kerosene or milk).

Materials

Beam balance, beaker, pipette, measuring cylinder

Procedure

1. Weigh empty beaker – Record mass as $m_0$.
2. Add liquid – Use a pipette to measure exactly 20 cm³ of liquid into the beaker.
3. Weigh again – Record total mass as $m_1$.
4. Calculate mass of liquid: $m = m_1 - m_0$
5. Calculate density: $\rho = \frac{m}{V}$

Worked Example

Empty beaker mass = 500 g, beaker + 25 cm³ liquid = 600 g.

• Mass of liquid = $600 - 500 = 100 \, \text{g}$
• Density = $\frac{100 \, \text{g}}{25 \, \text{cm}^3} = 4 \, \text{g/cm}^3$

Key Points

• Use the same beaker for both measurements
• Handle pipette carefully for accurate volume
• Ensure the beaker is dry before weighing

Aim

To measure the weight of an object using a spring balance.

Materials

Spring balance, objects of different masses

Procedure

1. Identify the object – Select the object to be weighed.
2. Attach to hook – Hang the object from the spring balance hook.
3. Read the scale – Read the value shown by the pointer. This is the force (weight) in newtons (N).
4. Compare readings – For multiple objects, record each measurement separately.

Key Points

• Hold the spring balance vertically
• Read the scale at eye level to avoid parallax error
• Ensure the spring is not stretched beyond its limit

Aim

To measure work done in lifting an object.

Materials

Spring balance, meter rule, known mass

Procedure

1. Measure weight – Use the spring balance to find the weight ($F$) of the object in newtons.
2. Measure height – Use the meter rule to measure the vertical distance ($d$) the object is lifted.
3. Calculate work – Apply: $W = F \times d$

Worked Example

Lifting a 7 kg bag of maize flour to a height of 2 m:

• Force (weight) = $m \times g = 7 \, \text{kg} \times 10 \, \text{N/kg} = 70 \, \text{N}$
• Work done = $70 \, \text{N} \times 2 \, \text{m} = 140 \, \text{J}$

Key Points

• Measure height from the starting position to the highest point
• The distance must be in the direction of the force (vertical for lifting)
• No work is done if the object is held stationary at height (distance = 0)

• Parallax error: Always take readings at eye level
• Systematic errors: Ensure instruments are calibrated correctly
• Random errors: Take multiple readings and calculate the average
• Zero error: Check that balances and measuring instruments read zero when empty

Always record your measurements in a neat table. For example:

In Tanzania, market vendors use these density principles when checking the quality of commodities like petrol or diesel. If a liquid's density differs from the standard, it may indicate contamination or adulteration. Similarly, farmers determining the weight of harvested maize bags use spring balances to ensure fair pricing at local markets such as the Mbeya market or when selling groundnuts in Morogoro.