[Part 2]- Required practicals 🥼🧪

Question 1

How can we investigate the the variables that affect temperatures changes, in chemical reactions ? 🌡️🧑🏾‍🔬

Hint: cup, thermometer, cylinder, through the hole, stops, repeat

Answer 1

1. place a polystyrene cup inside a glass beaker, and (using a measuring cylinder) add 30 ml of hydrochloric acid to the cup
2. use a thermometer to measure the temperature of the acid, and record this in a table
3. using a measuring cylinder, add 5 ml of sodium hydroxide to the cup
4. fit the lid and gently stir the solution with the thermometer through the hole
5. when the reading on the thermometer stops changing, record the highest temperature that was reached in the table
6. 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
7. wash out all the equipment and repeat the experiment for your second trial

Question 2

What is the independent variable in the required practical: temperatures changes. 🌡️

Answer 2

• the independent variable, is the volume of sodium hydroxide solution.

Question 3

What is the dependent variable in the required practical: temperatures changes. 🌡️

Answer 3

• the dependent variable, is the maximum temperature reached.

Question 4

What are the control variables in the required practical: temperatures changes ? 🧑🏾‍🔬

Answer 4

• the volume of hydrochloric acid
• the concentration of both the hydrochloric acid, and the sodium hydroxide solution.

Question 5

What are the axis in the required practical: temperature changes graph ? 🌡️

Answer 5

• maximum temperature reached [*C], against the volume of sodium hydroxide [cm^3]

Question 6

What are some explanations for the results of the required practical: temperature changes ? [3] 🌡️

Answer 6

• 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

Question 7

What will happen at a certain volume, when reading our results, of the required practical: temperature changes ? [3] 🌡️

Hint: unable

Answer 7

• ; 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.

Question 8

In the required practical: temperature changes, why does the maximum temperature seem to decrease from a certain point ? 🌡️

Answer 8

• 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.

Question 9

Why is the reason for using a polystyrene cup, with a lid ? 🥤

Answer 9

• 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.