Measuring Temperature Changes

Question 1

what is the method for following the change in temperature of a reaction while it takes place

Answer 1

• put a polystyrene cup inside a large beaker of cotton wool
• add a known volume of your first reagent to the cup
• measure the initial temperature of the solution
• add a mass or volume of your second reagent then stir
• put a lid on the cup
• record the maximum or minimum temperature that the mixture reaches during the reaction
• calculate the temperature change

Question 2

why is the beaker full of cotton wool

Answer 2

• the cotton wool give insulation

- to help limit the transfer of energy to or from the reaction mixture

Question 3

why should you put a lid on the cup when you begin stirring the two reagent substances

Answer 3

to reduce any energy lost by evaporation

Question 4

why is there an option to record the maximum or the minimum temperature and not just either one on its own

Answer 4

• because the reaction can either be exothermic where the temperature of the reactants decreases
• or the reaction could be endothermic where the temperature of the reactant increases

Question 5

how do you measure the temperature change when dissolving salts in water

Answer 5

• by adding the salt to a polystyrene cup of water

- and measuring the change in temperature when the salt has dissolved

Question 6

what is the effect of dissolving ammonium chloride in water

Answer 6

• the temperature of the reaction mixture decreases

- so it is an exothermic reaction

Question 7

what is the effect of dissolving calcium chloride in water

Answer 7

• the temperature of the reaction mixture increases

- so it is an endothermic reaction

Question 8

what simply happens in a neutralisation reaction

Answer 8

a base and an acid reaction to form a salt and water

Question 9

what are most neutralisation reactions in terms of energy transfer

Answer 9

• exothermic

- as the energy levels of the products is less than the reactants

Question 10

what neutralisation turns out to be endothermic

Answer 10

a neutralisation reaction between ethanioc acid and sodium carbonate

Question 11

what simply happens in a displacement reaction

Answer 11

a more reactive element displaces a less reactive element that is in a compound

Question 12

what are most displacement reactions in terms of energy transfer

Answer 12

• they are mainly exothermic

- because those types of reactions are accompanied by a release of energy

Question 13

what would the reaction between zinc powder and copper sulfate make in a displacement reaction

Answer 13

zinc sulfate and copper

Question 14

what are precipitates

Answer 14

• insoluble solids that can sometimes form

- when two solutions are mixed together

Question 15

what are most precipitations in terms of energy transfer and what is an example of this

Answer 15

• they are exothermic
• a reaction between lead(ll) nitrate and potassium iodide from a lead iodide precipitate
• which would result in an increase in temperature of the surroundings

Question 16

what does the increase or decrease in the temperature of a reaction depend on

Answer 16

which reagents (reactants) are taking place in the reaction