Required Praticle: Temperature Changes

Question 1

What are we investigating in this practical?

Answer 1

• Temperature change in exothermic reactions.

- Neutralisation reaction between hydrochloric acid and the alkali sodium hydroxide.

Question 2

What is the independant variable?

Answer 2

• Volume of sodium hydroxide solution.

Question 3

What are the control variables?

Answer 3

• Volume of hydrochloric acid.

- Concentrations of BOTH hydrochloric acid and sodium hydroxide solution,

Question 4

Method:

Answer 4

1) Using a measuring cylinder to measure 30cm^3 of dilute hydrochloric acid.
2) Transfer the acid into a polystyrene cup.
3) Stand the polysterene cup inside a beaker (stops cup from falling down).
4) Use a thermometer to measure the temperature of the acid + record thos on table.
5) Use a measuring cylinder to measure 5cm^3 of sodium hydroxide solution.
6) Transfer this to polystyrene cup.
7) Fit a plastic lid on the cup and place themometer through the hole of the lid (bulb in solution).
8) Use thermometer to gently stir the solution,
9)

Question 5

What can be seen?

Answer 5

• As the reaction is exothermic.
• Temperature of solution will increase.
• Look carefully at temperature rise on thermometer.
• We record the highets temperature reached.
• ## Rinse and dry the polysterene cup.

Question 6

What is the last step?

Answer 6

• Repeat the whole experiment again using 10cm^3 of sodium hydroxide solution.
• Carry exeperiment several times.
• Every time we increase by volume of sodium hyroxide by 5cm^3 until we reach the maximun of 40cm^3.
• Repeat the experiment one more time for a 2 sets of results.
• Mean value of maximun temperatire for each volume.

Question 7

What does the graph tell us?

Answer 7

• Increase the volume of sodium hydroxide solution, maximum temperature reaches increases.
• When we add more particles of sodium hydroxide they react with hydrochloric acid.
• More energy released.
• Maximum temperature increases.

Question 8

At a certain point of a graph why does it decrease?

Answer 8

• Certain Volume; maximum temperature decreases.
• adding so much sodium hydroxide that there is not enough hydrochloric acid.
• Some hydrochloric acid= unable to react.
• Reached maximum.

Question 9

Why do we use a polysterene cup and a lid?

Answer 9

• Reduce heat lost.
• Good insulator.
• Reduces heat lost from sides and bottom;
• Lid reduces heat lost to the air