Temperature changes

Question 1

In a reaction between an increasing volume of sodium hydroxide and hydrochloric acid, what are the independent / dependent / control variables?

Answer 1

Independent variable:
The amount of sodium hydroxide solution

Dependent variable:
The max temp reached

Control variables:
Volume of hydrochloric acid
Concentrations of both reactants

Question 2

Method

Answer 2

Use measuring cylinder to measure 30cm^3 of dilute hydrochloric acid

Stand polystyrene cup in a beaker (stops cup from falling over)

Use thermometer to measure temp of hydrochloric acid. Record in table.

Use measuring cylinder to measure 5cm^3 sodium hydroxide solution. Transfer to polystyrene cup.

Fit plastic lid to cup and place thermometer through hole in the lid.

Gently stir with thermometer

When the temp stops changing, record temp. This is the highest temp reached.

Rinse and dry polystyrene cup

Repeat experiment several times, increasing the volume of sodium hydroxide solution by 5cm^3 until 40cm^3 is reached.

Repeat whole experiment so we have 2 sets of results.

Calculate mean value for each volume of sodium hydroxide and plot a graph

Question 3

Why is a polystyrene cup and lid used?

Answer 3

Polystyrene is a good insulator - reduces heat loss through sides and bottom
Lid reduces heat loss through the air