Science Double Award - 4SD0 PearsonEdexcel

Energetics

Gbogbo ọrọ náà

When chemicals react, energy is exchanged with the surroundings. Some reactions release heat and warm everything around them; others absorb heat and make the surroundings cooler. Understanding which direction the energy flows, and how to measure it, is at the heart of energetics.

In this lesson you will distinguish exothermic from endothermic reactions, carry out calorimetry calculations using Q = mcDeltaT, work out molar enthalpy changes, and interpret energy level diagrams. These skills appear regularly on both Paper 1 and Paper 2 of the Edexcel Science Double Award.

Ebumnobi

Know that chemical reactions in which heat energy is given out are exothermic and those in which heat energy is taken in are endothermic
Describe simple calorimetry experiments for reactions such as combustion, displacement, dissolving and neutralisation
Calculate the heat energy change from a measured temperature change using Q = mcDeltaT
Calculate the molar enthalpy change from the heat energy change Q
Investigate temperature changes accompanying various types of change

Akọmọ Ojú-ẹkọ

Strike a match and you feel heat on your fingers. Dissolve ammonium nitrate in water and the beaker turns ice-cold. Every chemical reaction either releases energy to the surroundings or absorbs it. Measuring that energy change tells us how much fuel a rocket needs, why hand warmers work, and how to size a cooling pack for a sports injury.

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Ayẹwo Ẹkọ

Ekele diri gi maka imecha ihe karịrị na Energetics. Ugbu a na ị na-enyochakwa isi echiche na echiche ndị dị mkpa, ọ bụ oge iji nwalee ihe ị ma. Ngwa a na-enye ụdị ajụjụ ọmụmụ dị iche iche emebere iji kwado nghọta gị wee nyere gị aka ịmata otú ị ghọtara ihe ndị a kụziri.

Ị ga-ahụ ngwakọta nke ụdị ajụjụ dị iche iche, gụnyere ajụjụ chọrọ ịhọrọ otu n’ime ọtụtụ azịza, ajụjụ chọrọ mkpirisi azịza, na ajụjụ ede ede. A na-arụpụta ajụjụ ọ bụla nke ọma iji nwalee akụkụ dị iche iche nke ihe ọmụma gị na nkà nke ịtụgharị uche.

Jiri akụkụ a nke nyocha ka ohere iji kụziere ihe ị matara banyere isiokwu ahụ ma chọpụta ebe ọ bụla ị nwere ike ịchọ ọmụmụ ihe ọzọ. Ekwela ka nsogbu ọ bụla ị na-eche ihu mee ka ị daa mba; kama, lee ha anya dị ka ohere maka ịzụlite onwe gị na imeziwanye.

Which of the following reactions is endothermic? A) Combustion of methane B) Neutralisation of an acid C) Thermal decomposition of calcium carbonate D) Displacement of copper by iron Answer: C
In the equation Q = mcDeltaT, what does c represent? A) Concentration B) Specific heat capacity C) Number of moles D) Temperature change Answer: B
On an energy level diagram for an exothermic reaction, the products are: A) At a higher energy level than the reactants B) At the same energy level as the reactants C) At a lower energy level than the reactants D) Not shown on the diagram Answer: C
A calorimetry experiment uses 100 cm3 of water. The mass of water used in the calculation is: A) 0.1 g B) 10 g C) 100 g D) 1000 g Answer: C
What is the activation energy of a reaction? A) The total energy released by the products B) The minimum energy needed to start the reaction C) The difference between reactant and product energy D) The heat energy absorbed from the surroundings Answer: B