Required practical: heat loss in a reaction

Question 1

What is the aim of the experiment?

Answer 1

To measure the temperature change in an exothermic reaction (neutralisation)

Question 2

What reaction are we using and why?

Answer 2

Neutralisation between sodium hydroxide and hydrochloric acid
Because neutralisation is exothermic

Question 3

Independent variable

Answer 3

Increasing volumes of sodium hydroxide solutions by 5cm3

Question 4

Dependent variable

Answer 4

Maximum temperature reached in the reaction

Question 5

Control variable

Answer 5

Volume of hydrochloric acid
Concentrations of the acid and alkali

Question 6

Step 1

Answer 6

Measure 30cm3 of dilute HCl

Question 7

Step 2

Answer 7

Pour acid into a polystyrene cup and put that inside a beaker

Question 8

Step 3

Answer 8

Use thermometer to measure initial temp of the acid

Question 9

Step 4

Answer 9

Measure 5cm3 of sodium hydroxide solution and pour into the polystyrene cup

Question 10

Step 5

Answer 10

Fit a plastic lid through the cup with a hole for the thermometer
Check thermometer bulb is in the solution

Question 11

Step 6

Answer 11

Use thermometer to stir the solution
When the temp stops changing, record the highest it reached

Question 12

Step 7

Answer 12

Repeat everything again but in intervals of +5cm3 of sodium hydroxide until we get to 40cm3

Question 13

Step 8

Answer 13

Repeat the whole experiment again 2 times and calculate the mean

Question 14

What do the results look like?

Answer 14

Increasing alkali solution increases maximum temperature reached
Up to a certain point when it slowly decreases

Question 15

Why does the maximum temp reached increase with more alkali added to a certain point?

Answer 15

Because it’s an exothermic reaction
More sodium hydroxide = more particles are reacting
= more energy released
= higher temperature

Question 16

Why does the reaction cause a certain maximum temperature?

Answer 16

Because now all alkali and acid particles have reacted
Because the alkali is now in excess
causing the maximum possible energy to be released

Question 17

Why does at a certain point the maximum temp decreases?

Answer 17

We are adding greater volumes of particles
Therefore the energy is spread out more
Thus maximum temp reached decreases

Question 18

Why do we use a plastic lid and polystyrene cup?

Answer 18

Measuring temp means reducing temp loss
Therefore use good insulating materials to prevent escaping temperature

Question 19

Why do we put the polystyrene cup in a beaker?

Answer 19

To prevent it from falling over or spilling