energetics

Question 1

why is it important top know energy values

Answer 1

to measure the energy values of fuels
to calculate the energy requirements for industrial processes
• it helps to predict whether or nor a reaction will take place.

Question 2

what is Thermochemistry

Answer 2

the study of heat changes during chemical reactions.

Question 3

what happens in chemical reactions

Answer 3

When a chemical reaction takes place, chemical bonds break and
new ones are formed.

Question 4

what is an endothermic reaction

Answer 4

if energy has been taken in at the end of the reaction

Question 5

what is an exothermic reaction

Answer 5

if energy has been given out, the reaction is exothermic at the end of the reaction,

Question 6

what does the quantity of energy depends on

Answer 6

The amount of heat given out or taken in during a chemical
reaction depends on the quantity of reactants. This energy is usually
measured in kilojoules per mole, kJ mo1- 1•

Question 7

what do you need to do to find the quantity

Answer 7

To avoid any confusion

about quantities you need to give an equation.

Question 8

Enthalpy change,

Answer 8

When you measure a heat change at constant pressure,

Question 9

what are the standard conditions for enalpy change

Answer 9

• pressure of 100 kPa

* temperature of 298K

Question 10

what else affects enalphy change

Answer 10

The physical states (gas, liquid, or solid) of the reactants and products

Question 11

gas vs liquid products

Answer 11

For example, heat must be put in to change liquid to gas and is given out when a gas is
changed to a liquid. This means that you must always include state
symbols in your equations.

Question 12

steam vs liquid

Answer 12

gaseous water has a Lower exothermic level than liquid water as energy must be applied to break hydrogen bonds in order for water to become a gas

Question 13

enthalpy diagram

Answer 13

The vertical axis represents enthalpy, and the horizontal axis, the extent
of the reaction.

Question 14

The standard molar enthalpy of formation

Answer 14

is the enthalpy change when one mole of substance is formed from its constituent elements under standard conditions. all reactants and products being in their standard states.

Question 15

how is temperature measured

Answer 15

Heat and temperature
Temperature is related to the average kinetic energy of the particles
in a system. As the particles move faster, their average kinetic energy
increases and the temperature goes up. But it doesn’t matter how
many particles there arc. temperature is independent of the number
present. Temperature is measured with a thermometer.

Question 16

measuring heat change

Answer 16

Heat is a measure of the total energy of all the particles present in
a given amount of substance.

Question 17

so does a lukewarm bath or a red hot nail have the most heat energy

Answer 17

So a bath
of lukewarm water has much more heat than a red hot nail because
there are so many more particles in it.

Question 18

what does heat rely on

Answer 18

It does depend on how much of the substance is present The energy of every particle is included.

Question 19

how to Measure the enthalpy change of a reaction

Answer 19

1. mass of the substance that is being heated up or cooled down
   2 temperature change
   3 specific heat capacity of the substance.

Question 20

specific heat capacity definition

Answer 20

the amount or heat needed to raise the temperature of Jg of substance by I K.

Question 21

specific heat capacity definition

Answer 21

the amount or heat needed to raise the temperature of 1g of substance by I K.

Question 22

The simple calorimeter

Answer 22

q = m c :. T