[Part 2]- Required practicals 🥼🧪
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How can we investigate the the variables that affect temperatures changes, in chemical reactions ? 🌡️🧑🏾🔬 Hint: cup, thermometer, cylinder, through the hole, stops, repeat
• place a polystyrene cup inside a glass beaker, and (using a measuring cylinder) add 30 ml of hydrochloric acid to the cup • use a thermometer to measure the temperature of the acid, and record this in a table • using a measuring cylinder, add 5 ml of sodium hydroxide to the cup • fit the lid and gently stir the solution with the thermometer through the hole • when the reading on the thermometer stops changing, record the highest temperature that was reached in the table • repeat steps 3–5 to add further 5 ml amounts of sodium hydroxide to the cup each timeuntil a maximum of 40 ml of sodium hydroxide has been added, recording the temperature in the results table • wash out all the equipment and repeat the experiment for your second trial
What is the independent variable in the required practical: temperatures changes. 🌡️
• the independent variable, is the volume of sodium hydroxide solution.
What is the dependent variable in the required practical: temperatures changes. 🌡️
• the dependent variable, is the maximum temperature reached.
What are the control variables in the required practical: temperatures changes ? 🧑🏾🔬
• the volume of hydrochloric acid • the concentration of both the hydrochloric acid, and the sodium hydroxide solution.
What are the axis in the required practical: temperature changes graph ? 🌡️
• maximum temperature reached [*C], against the volume of sodium hydroxide [cm^3]
What are some explanations for the results of the required practical: temperature changes ? [3] 🌡️
• as the volume of sodium hydroxide solution is increased, the maximum temperature reached increases. • This is because, when more particles of sodium hydroxide are added, they react with hydrochloric acid. • since it’s an exothermic reaction, more energy is released= maximum temperature reached increased
What will happen at a certain volume, when reading our results, of the required practical: temperature changes ? [3] 🌡️ Hint: unable
• ; at a certain volume of sodium hydroxide solution, the maximum temperature reaches begins to decrease- we’re adding so much sodium hydroxide, that there isn’t enough hydrochloric acid. • This means some of the sodium hydroxide, is unable to react. • and because of this, the amount of energy released by the reaction has reached a maximum.
In the required practical: temperature changes, why does the maximum temperature seem to decrease from a certain point ? 🌡️
• In each experiment, we’re adding a greater volume of solution, so the energy released, is now spread out into a greater volume. • Therefore when large volumes of sodium hydroxide are added, the maximum temperature reached decreases.
Why is the reason for using a polystyrene cup, with a lid ? 🥤
• in this experiment since we’re measuring the temperature, we want to reduce any heat losses. • and polystyrene, is a good thermal insulator, so this reduces heat loss through the sides and the bottom • the lid also reduces heat loss, to the air.