A student measures the density of glass. The student has - a bag of marbles, all made from the same type of glass - a weighing balance - a plastic measuring cylinder containing water Describe how the student could find, as accurately as possible, the density of the glass used for the marbles. (4) A beaker contains 0.25 kg of water at room temperature. The beaker of water is heated until the water reaches boiling point (100 °C). The specific heat capacity of water is 4200 /kg °C. The total amount of thermal energy supplied to the water is 84,000 J. (i) Calculate the temperature of the water before it was heated. Use an equation selected from the list of equations at the end of this paper. (3)

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A student measures the density of glass - Edexcel - GCSE Physics: Combined Science - Question 4 - 2019 - Paper 1

Question 4

A student measures the density of glass. The student has - a bag of marbles, all made from the same type of glass - a weighing balance - a plastic measuring cylinde... show full transcript

Worked Solution & Example Answer:A student measures the density of glass - Edexcel - GCSE Physics: Combined Science - Question 4 - 2019 - Paper 1

Step 1

Describe how the student could find, as accurately as possible, the density of the glass used for the marbles.

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Answer

Weigh the Marbles: First, the student should determine the mass of the marbles using the weighing balance. This mass should be recorded accurately.
Submerge the Marbles: Next, place the marbles into the measuring cylinder filled with a known volume of water. The change in water level must be measured. This can be done by reading the scale of the cylinder before and after the marbles are added.
Measure Water Displacement: The volume of water displaced by the marbles can be found by calculating the difference in water levels. This volume will be equal to the volume of the marbles since they displace an amount of water equivalent to their own volume.
Calculate Density: Finally, the density of the glass can be calculated using the formula: $\text{Density} = \frac{\text{Mass}}{\text{Volume}}$ where the mass is the weight of the marbles (from step 1) and the volume is the water displaced (from step 3). Using multiple marbles can improve accuracy in measurements.

Step 2

(i) Calculate the temperature of the water before it was heated.

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Answer

To find the temperature of the water before heating, we can use the formula for thermal energy supplied: $Q = m \cdot c \cdot \Delta \theta$ Where:

$Q = 84,000 J$ (energy supplied)
$m = 0.25 kg$ (mass of water)
$c = 4200 \text{ J/kg°C}$ (specific heat capacity)
$\Delta \theta$ is the change in temperature.

First, rearrange the formula to solve for $\Delta \theta$ : $\Delta \theta = \frac{Q}{m \cdot c}$
Substituting the known values into the equation: $\Delta \theta = \frac{84,000}{0.25 \cdot 4200}$ $\Delta \theta = \frac{84,000}{1050} = 80 °C$
The temperature of the water before heating is: $\text{Temperature before heating} = 100 °C - \Delta \theta = 100 °C - 80 °C = 20 °C$

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