energy changes

Question 1

what happens in a exothermic reaction

Answer 1

energy is transferred to the surroundings usually by heat - shown as a rise in temp

Question 2

what is an example of a exothermic reaction

Answer 2

burning fuels or combustion

Question 3

are neutralisation reaction exo or endo thermic

Answer 3

exothermic

Question 4

what are some everyday uses for exothermic reactions

Answer 4

• hand warmers use the exothermic oxidation of iron in air to release energy
• self heating cans og hot choloate and coffe rely on exothermix reactions between chemicals in their bases

Question 5

what happens in an endothermic reaction

Answer 5

energy is taken in from the surroundings - shown as a fall in temperature

Question 6

what are some endothermic reactions

Answer 6

thermal decomposition

Question 7

how are endothermic reactions used in everyday life

Answer 7

• sports injury packs - the chemical reaction allows the pack to become instatly cool

Question 8

what is the biggest problem with energy measurements

Answer 8

the amount of energy lost to the surrondings

Question 9

how can you reduce the amount of energy lost to the surrondings while doing energy measurements

Answer 9

by putting a polystyrene cup in a beaker of cotton wool to give more insulation and putting a lid on the cup to reduce energy by evaporation

Question 10

practical for testing the effect of acid concentration on the energy released in a neutralisation between hcl and sodium hydroxide

Answer 10

put 25cm cubed of 025mol/dm of hydrochloric acid and sodium hydroxide in seperate beakers

set beakers in a water bath set to 25 degree and leae until they are both the same temp

add hcl followed by the naoh to polystyrene cup with a lid

take temperature of mixture every 30 seconds and record highest temp

repeat steps 1-4 using 0.5 mol and the 1 mol of hcl

Question 11

what must be supplied to break bonds

Answer 11

energy

Question 12

is bond breaking endo or exothermic

Answer 12

energy must be supplied so bond breaking is endothermic

Question 13

is bond forming endo or exothermic

Answer 13

energy is released when bonds are formed so it is exothermic

Question 14

in endothermic bond breaking reactions is more energy used to form or break bonds

Answer 14

break bonds

Question 15

in exothermic bond breaking reactions is more energy used to form or break bonds

Answer 15

form bonds