Exothermic and endothermic reactions

Question 3

Medium

A student investigated the temperature change when different masses of ammonium nitrate were dissolved in water.

Method:

Measure $cm3150\text{ cm}^3$ of distilled water into an insulated polystyrene beaker.
Measure the initial temperature of the water.
Add a known mass of ammonium nitrate to the water.
Stir the mixture continuously until all the ammonium nitrate has dissolved.
Measure the lowest temperature reached by the solution.
Repeat steps 1 to 5 with different masses of ammonium nitrate.

Table 1: Results of the investigation

Mass of ammonium nitrate added (g)	Lowest temperature of solution ( $∘C^{\circ}\text{C}$ )
$5.0$	$18.5$
$10.0$	$15.0$
$15.0$	$11.5$
$20.0$	$8.0$
$25.0$	$4.5$

Questions:

Identify the independent variable and the dependent variable in this investigation.

[2]

Determine the initial temperature of the water by extrapolating the linear data back to a mass of $g0\text{ g}$ .

[2]

State whether the dissolving of ammonium nitrate is exothermic or endothermic, and justify your answer.

[2]

The student repeated the experiment four times using $g15.0\text{ g}$ of ammonium nitrate. The lowest temperatures recorded were $∘C11.2\ ^{\circ}\text{C}$ , $∘C11.8\ ^{\circ}\text{C}$ , $∘C11.4\ ^{\circ}\text{C}$ , and $∘C11.6\ ^{\circ}\text{C}$ . Calculate the mean lowest temperature and the uncertainty (using $±range2\pm \frac{\text{range}}{2}$ ). Express your final answer in the format $mean±uncertainty\text{mean} \pm \text{uncertainty}$ .

[3]

Exothermic and endothermic reactions

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Question 3

Medium

A student investigated the temperature change when different masses of ammonium nitrate were dissolved in water.

Method:

Measure $cm3150\text{ cm}^3$ of distilled water into an insulated polystyrene beaker.
Measure the initial temperature of the water.
Add a known mass of ammonium nitrate to the water.
Stir the mixture continuously until all the ammonium nitrate has dissolved.
Measure the lowest temperature reached by the solution.
Repeat steps 1 to 5 with different masses of ammonium nitrate.

Table 1: Results of the investigation

Mass of ammonium nitrate added (g)	Lowest temperature of solution ( $∘C^{\circ}\text{C}$ )
$5.0$	$18.5$
$10.0$	$15.0$
$15.0$	$11.5$
$20.0$	$8.0$
$25.0$	$4.5$

Questions:

Identify the independent variable and the dependent variable in this investigation.

[2]

Determine the initial temperature of the water by extrapolating the linear data back to a mass of $g0\text{ g}$ .

[2]

State whether the dissolving of ammonium nitrate is exothermic or endothermic, and justify your answer.

[2]

[3]

Exothermic and endothermic reactions

Question 3

Method:

Table 1: Results of the investigation

Questions:

Exothermic and endothermic reactions Questions

Exothermic and endothermic reactions

Question 3

Method:

Table 1: Results of the investigation

Questions:

Exothermic and endothermic reactions Questions