Specific Heat Capacity - GCSE Science Required Practical

Summary

In this video, Mr. Reese from Mars Preschool demonstrates a GCSE-required practical to measure the specific heat capacity of different materials, including brass, copper, and aluminum. He explains the process of heating a metal block and recording temperature changes over time. Using both a joulemeter and a combination of an ammeter and voltmeter, he discusses methods to calculate power accurately. By plotting the temperature against time, he calculates the specific heat capacity and explains how energy loss due to lack of insulation can affect the results, offering suggestions to improve accuracy.

Takeaways

• 🔬 The experiment is about measuring the specific heat capacity of different materials, specifically brass, copper, and aluminium.
• 🔥 The setup includes a heater inserted into a block and a thermometer in a smaller hole to measure temperature changes.
• 💧 A few drops of water are required in the thermometer hole to avoid an air gap and ensure accurate temperature readings.
• ⏲️ Temperature is recorded every minute for 10 minutes, starting from an initial temperature of 24°C.
• 📐 The specific heat capacity (SHC) formula is energy (J) = mass (kg) × SHC (J/kg°C) × temperature change (°C), and rearranged for SHC as energy ÷ (mass × temperature change).
• 🔋 Two methods are used to measure energy: a joulemeter (easy but less accurate) and the product of current and voltage (more accurate).
• ⚡ Power (W) is calculated as voltage (V) × current (A), with a more accurate power reading of 34.7 watts, compared to a less accurate 63 watts using the joulemeter.
• 📊 A graph of temperature vs. time is plotted, with a linear portion used to determine the SHC using the formula: SHC = (power × time) ÷ (mass × temperature change).
• 📈 The experiment yielded an SHC of 1050 J/kg°C for aluminium, higher than the known value of 900 J/kg°C due to heat loss to the surroundings.
• 🧊 To improve accuracy, insulating the block with foam can help reduce heat loss and provide a more accurate SHC measurement.

Q & A

What is the purpose of the experiment described in the transcript?

The purpose of the experiment is to measure the specific heat capacity (SHC) of different materials, including aluminium, copper, and brass, by heating them and recording temperature changes.

Why is it necessary to add a few drops of water into the hole where the thermometer is placed?

Adding a few drops of water ensures there is no air gap between the metal block and the thermometer, which would lead to inaccurate temperature readings.

What is the formula for calculating specific heat capacity (SHC) as described in the video?

The formula for specific heat capacity is: SHC = Energy / (Mass * Temperature Change). This means SHC is the energy needed to raise the temperature of 1 kilogram of material by 1 degree Celsius.

How is energy calculated during the experiment?

Energy is calculated using the formula: Power = Energy / Time. Power is measured either with a joule meter or by multiplying the current flowing through the heater by the voltage across it (using an ammeter and a voltmeter).

What is the difference between using a joule meter and the voltmeter/ammeter method for measuring power?

Using a joule meter is simpler but less accurate because it measures the power going into the power supply, not necessarily what goes into the heater. The voltmeter/ammeter method is more accurate as it directly measures the power in the heater.

What were the voltage and current measurements obtained during the experiment?

The experiment recorded a potential difference (voltage) of 10 volts and a current of 3.47 amps, leading to a power measurement of 34.7 watts.

Why does the experiment suggest that power might fluctuate, and how can this be managed?

Power might fluctuate due to changes in the voltage and current during the experiment. To manage this, you can either record the values every minute and calculate the mean or use the initial values as an approximation.

What is the importance of plotting a graph in the experiment?

Plotting a graph helps to analyze the relationship between temperature and time, using the linear portion to calculate the specific heat capacity by dividing the change in time by the change in temperature.

How does the lack of insulation affect the experiment’s results?

Without insulation, heat is lost to the surroundings, making it appear that more energy is needed to raise the temperature than in reality. This leads to a higher calculated SHC than expected.

How does the experimental specific heat capacity of aluminium compare to its actual value, and why is there a difference?

The experimental SHC for aluminium was found to be 1050 J/kg°C, which is higher than the actual value of 900 J/kg°C. The difference is due to heat losses to the surroundings, which can be minimized by insulating the block.