Temperature Changes - GCSE Science Required Practical

Summary

This video demonstrates an experiment investigating the temperature changes during a neutralization reaction between hydrochloric acid and sodium hydroxide. It guides viewers through the safe setup using polystyrene cups, precise measurement of reagents, and careful recording of initial and maximum temperatures. The experiment involves gradually adding sodium hydroxide in 5 cm³ increments to the acid, stirring to distribute heat evenly, and observing the resulting exothermic temperature changes. Key insights include the importance of minimizing heat loss, understanding limiting reactants, and noting how the temperature rise levels off or decreases as more alkali is added, illustrating the principles of energy transfer in chemical reactions.

Takeaways

• 🧪 The experiment investigates temperature changes during a neutralization reaction between hydrochloric acid and sodium hydroxide.
• 😷 Safety is important: always wear safety goggles when handling acids and alkalis.
• 🥤 Use a polystyrene cup and lid to minimize heat loss during the experiment.
• 🌡️ A thermometer is used to measure the initial and maximum temperatures of the solution.
• 📏 Accurately measure 30 cm³ of hydrochloric acid using a 50 cm³ measuring cylinder and a dropping pipette for precision.
• 💧 Measure small quantities of sodium hydroxide (5 cm³) with a pipette to ensure accuracy.
• 🍶 Stir the solution gently with the thermometer after adding sodium hydroxide to evenly distribute heat energy.
• -
• 📊 Record the initial temperature and the maximum temperature after each addition of sodium hydroxide in a table.
• ➕ Gradually increase the sodium hydroxide volume in 5 cm³ increments up to 40 cm³, recording temperature after each addition.
• ⚖️ Observe how temperature changes relate to limiting reactants and heat transfer; the temperature may level off or decrease with larger amounts of sodium hydroxide.
• ⏱️ Work quickly when adding sodium hydroxide to minimize heat loss and obtain accurate measurements of temperature change.

Q & A

What is the main objective of this experiment?

The main objective is to investigate the temperature changes that occur during the neutralization reaction between hydrochloric acid and sodium hydroxide.

Why are polystyrene cups used in this experiment?

Polystyrene cups are used because they are good thermal insulators, which minimizes heat loss to the surroundings, ensuring more accurate measurement of temperature changes.

Why is the polystyrene cup placed in a beaker?

The cup is placed in a beaker for stability to prevent it from tipping over and spilling the acid or alkali, which enhances safety during the experiment.

How is the initial temperature of the acid measured?

The initial temperature is measured by inserting a thermometer through a hole in the cup lid, ensuring it does not touch the bottom, and recording the temperature once it stabilizes.

Why is a dropping pipette used for small volumes of sodium hydroxide?

A dropping pipette allows precise measurement of small volumes, such as 5 cm³ of sodium hydroxide, which is important for accuracy in tracking temperature changes with each addition.

What should be done immediately after adding sodium hydroxide to the acid?

Immediately after adding sodium hydroxide, the lid should be placed on the cup and the solution gently stirred with the thermometer to evenly distribute the heat energy.

How is the maximum temperature determined in this experiment?

The maximum temperature is determined by continuously monitoring the thermometer after each addition of sodium hydroxide and recording the highest temperature reached before it starts to stabilize or drop.

Why is sodium hydroxide added in increments of 5 cm³?

Adding sodium hydroxide in small increments allows careful observation of the temperature change at each step and helps minimize heat loss, making the results more accurate.

Why might the temperature start to level off or drop when more sodium hydroxide is added?

The temperature may level off or drop due to the reaction approaching completion (limiting reactants) or because excess sodium hydroxide does not react, while some heat is lost to the environment.

What safety precautions are emphasized in the experiment?

Safety precautions include wearing goggles, handling acids and alkalis carefully, and placing the polystyrene cup in a beaker to prevent spills.

Why is it important to measure to the bottom of the meniscus?

Measuring to the bottom of the meniscus ensures precise and accurate volume readings of both hydrochloric acid and sodium hydroxide, which is crucial for reliable experimental results.

How does stirring the solution with the thermometer affect the experiment?

Stirring helps distribute the heat evenly throughout the solution, preventing localized temperature differences and giving a more accurate measurement of the overall temperature change.