Phase Change

Chemical Reaction

Type of Change Energy

Released

H20 (g) H20 (l)

Combustion of methane

40.7 kJ/mol

802 KJ/mol

Comparison of Energy

Change

Nuclear 1.82 x 109 KJ/molNuclear Reaction

The energy released is a nuclear reaction is 1000 -1 000 000 times more energy than chemical reactions

Topic 2: Nuclear Reactions

To produce equal amounts of energy we need…

Energy released through chemical reactions

Energy released through nuclear

reactions

Nuclear Reactions• Nuclear energy relies on radioactive

material • What does radioactive mean?

– A substance is radioactive if it emits energy in the form of EMR (gamma rays) or particles (alpha, beta or neutrons)

• Nuclear reactions are said to be ionizing because some forms of radiation and particles released can penetrate solid material and damage living cells

Nuclear explosions can release damaging nuclear radiation

Chernobyl (1986) is the most severe nuclear accidents in our history

Radioactive fallout: People were exposed to radioactive particles in the air and by eating and drinking radioactive materials in food. Children who drank milk from cows that had eaten contaminated grass went on to develop thyroid caner (radioactive iodine)

Children born since 1986 are affected by a 200% increase in birth defects and a 250% increase in congenital birth deformities.

The accident released radiation 200 X greater than that released by both atomic bombs dropped on Hiroshima and Nagasaki.

The exclusion zone, known as “Death Valley,” has been increased from 30 to 70 km2. No humans will ever be able to live in it again.

Nuclear reactions and isotopes • To understand nuclear reactions, we need to first review

isotopes • Isotopes are elements with same atomic numbers but

different atomic masses because of different # of neutrons

Protons: Neutrons: Electrons:

Protons: Neutrons: Electrons:

Atomic mass

Atomic number

6

Atomic number is equal to the number

of protons and electrons

12-6 =6

Number of neutrons is mass – atomic

number

6

614-6 =86

The mass of an isotope is not always the mass given in the data booklet! Always use the mass that is given.

Step 1: Look up uranium on the periodic table

We don’t use 238 as the mass! We use 235 since

uranium-235 is an isotope of uranium-238

6 14 6 14-6=8

Oxygen-16 8 16-8=8

Polonium-212 84 128 + 84 = 212

The mass of an isotope is not always the mass given in the data booklet! Always use the mass that is given.

92Uranium-238 146 + 92 = 238

2-1=11 12

2Helium-4 4-2=2

Types of Radiation• Isotopes become unstable when the

force of repulsion is greater than the nuclear force holding the nucleus together

• The unstable isotope will change into another substance and release energy in the form of radiation and particles

• We will study three types of radiation– alpha rays– beta rays – gamma rays

A Geiger Counter is used to detect and measure intensity

of ionizing radiation

• All of these are composed of high energy • Which one of these has the highest frequency and lowest

wavelength?– Gamma radiation

• Unstable isotopes will disintegrate producing: – A different atom and, – A lot of energy in the form of radiation

Unstable (Radioactive) Isotopes

UnstableStable

Energy

In equation form:

A Geiger counter was used to detect the radiation emitted from contaminated surfaces, including humans!

March 11, 2011 - Following a major earthquake, a 15-metre tsunami disabled the power supply and cooling of three of Japan’s nuclear reactors causing the second largest nuclear accident since Chernobyl. All three cores largely melted in the first three days.

Type of Radiation

Alpha Radiation

Beta Radiation

Made of 2 protons and 2 neutrons with a net charge of 2+

Gamma Radiation

α

Not very penetrating

Description Penetrating

Ability Symbol

β

A high speed electronMore

penetrating

γ

High energy photon with no mass or charge. Used to treat cancers.

Most penetrating

This is on page ___ of your data booklets

8

Ways to write nuclear reactions – pictures or equations

A.

B.

Atomic number and mass numbers must be equal for both reactants and products, which means nucleons

(protons and neutrons) are conserved

Writing nuclear reactions

What do you notice about the atomic mass (nucleons) and the atomic number in the reactants and products?

Atomic mass of an element is equal to the nucleons of an element: the number of protons and neutrons in a nucleus

How many nucleons does potassium have?

Practice Problems:Find the missing nucleon in the following nuclear reactions:

1.

To predict the other product, remember that nucleons are conserved, so the atomic mass and number must be the same on both sides

4 + A = 242

Z = 92 (Atomic number of uranium)

Atomic mass A = 238

Atomic number2 + Z = 94

Answer:

Practice Problems:Find the missing nucleon in the following nuclear reactions:

2.

Remember that nucleons are conserved, so the atomic mass and number must be the same on both sides

32 + 0 = 32

Z = 15 (Atomic number of phosphorus)

Atomic mass =32

A = 32

Atomic number = 1516 + -1 = 15

Answer:Complete question 3 and

4 in your workbook

Practice Problems: 5. Write the nuclear equation for the alpha decay of radium-226.

 Decay means to break down – your reactant should result in at least 2 products!

Alpha decay means that an alpha particle is produced.

To predict the other product, remember that nucleons are conserved, so the atomic mass and number must be the same on both sides

RnHeRa 22286

42

22688 +

226 - 4 = 222 88 – 2 = 86 (Atomic number of radon)

Practice Problems:6. Write the nuclear reaction for the beta decay of polonium-210

Beta decay means that an beta particle is produced.

210 – 0 = 210

84 – -1 = 85

Watch out for this step, the atomic

number is not 83!

Practice Problems:7. Write the nuclear reaction for the beta and gamma decay of cesium-144

Gamma decay means that an gamma particle is produced.

144 – 0 = 144

55 – -1 = 56

Answer to #8

Practice Problems:9. Uranium-235 is a product of alpha decay. Write the equation to show the original isotope.

This question asks us to work backwards and U-235 is the product not the reactant

235 + 4 = 239

92 + 2 = 94

Answer to #10

Complete the practice questions on pages 17-18 in your workbooks

1,2,2,1

• From the physics unit, nuclear fusion is when 2 smaller nuclei with high energy join to form a larger nucleus while releasing energy

• Nuclear fusion is what occurs in the sun and all stars• Can we use nuclear fusion to produce energy?

• Not yet! We have plenty of deuterium (raw material for fusion) but we cannot contain the energy produced!

Nuclear Fusion

Where have we seen the word nuclear fusion?

Nuclear Fission

Fission Animation

• Nuclear fission is the opposite of nuclear fusion because a large nucleus splits into smaller nuclei while releasing energy

• Nuclear fission begins when uranium is usually struck by a neutron and becomes unstable • It then splits into 2 smaller

nuclei and more neutrons to continue the reaction

• This reaction is difficult to control

CANDU reactor

VideoGreat FAQ’s on CANDU reactor

• CANDU reactor stands for Canadian Deuterium Uranium Reactor• CANDU uses energy from nuclear fission to produce electricity

Energy conversions in a nuclear reactor…

• Kinetic energy from fission products is used to heat water and produce steam which turns a turbine, spins a generator which creates electricity

Energy conversions in the CANDU reactor are similar to those that occur in thermal (coal fired) power plants (Difference: original source of

energy)

Intranuclear potential energy (uranium) thermal energy (heat) Kinetic energy (turbine and generator) Electrical Energy

CANDU Reactor Components

• Fuel: The fuel used is uranium - 235, in the form of uranium oxide pellets assembled into a fuel bundle• CANDU reactors can be refueled

while in operation (whereas other reactors have to be shut down)

• Moderator: Used to sustain fission reactions by slowing down fast moving neutrons

• The moderator used is heavy water (Deuterium Oxide (D2O)) – which is a heavier isotope of water)

Uranium deposits around the world (depending on

year and source)

Radioactive uranium and radium are found in soil and rocks. When they disintegrate, they produce another radioactive atom: radon gas.

CANDU Reactor Components

• Control Rods: Control rods also help to control the rate of fission• Control rods absorbs neutrons

in an emergency shut down • Shielding: Shielding protects

against radioactive by products of chain reaction from entering the atmosphere • usually made of steel or

concrete

Coal (non-renewable) Uranium-235 (non-renewable)

Chemical potential Intranuclear potential

CombustionNuclear fission by

bombarding with a neutron

Solar, chemical potential, thermal, kinetic, to electrical

Intranuclear, thermal, kinetic, to electrical

Societal

Environmental/Ecological

Benefits

Economical

Disadvantages

Produces large amounts of energy compared to burning coal = EFFICIENT

We have lots of uranium

Nuclear plants cost considerably more money to build

Benefits and Costs of Nuclear Fission Energy

Risk of meltdown

No gaseous emissions (CO2, SOX, or particulates)

Lower operating costs

Thermal pollution of air and water

non-renewable

Nuclear materials can be used in nuclear weapons

Nuclear material is radioactive

Storage of used fuel/radioactive waste

Things to consider

• Safety of people living/working near by?

• Renewable? • Any emissions?

Renewable or non-renewable:

Storage of nuclear waste

Albert Einstein• Albert Einstein’s famous equation is…

This is on page 8 of your data booklets

• This formula says that mass can be converted into energy

• A tiny loss in mass results in a gigantic gain in energy

Energy change (_____)JMass converted to energy (_____)kg

Speed of EMR (______________)3.00 x 108 m/s

Einstein failed his University entrance examHe passed the math and science sections of the entrance exam, but failed the rest (history, languages, geography). Einstein had to go to a trade school before he retook the exam and was finally admitted to university.

Did you know?

Einstein had an illegitimate childIn Einstein's private letters he revealed that he had an illegitimate daughter with a fellow former student Mileva Marić (whom Einstein got ideas from for his Nobel Prize and later married). Einstein never met his daughter her fate remained unknown.

Einstein became estranged from his first wife, Mileva, then proposed a strange “contract”“I will receive my three meals regularly in my room… my bedroom and study are kept neat… and especially that my desk is left for my use only… you will renounce all personal relations with me insofar as they are not completely necessary for social reasons... you will stop talking to me if I request it”

Einstein was a ladies' manAfter Einstein divorced Mileva, he soon married his cousin Elsa… Actually, Einstein considered marrying Elsa's daughter at first!

Einstein won the 1921 Nobel Prize in Physics for his work on theoretical physics (photoelectric effect), not E=mc2

Practice Problems:1. In the fission of 1 mol of beryllium-8, the mass of the products is determined to be 2.29 x 10-5 kg less than the mass of the reactants. Calculate the change in energy that corresponds to with this change in mass. (Answer: 2.06x 1012 J)

m = 2.29 x 10-5kg

E = ?

E = mc2

E = (2.29 x 10-5kg)(3.00 x108m/s)2

E = 2.061 x 1012 J

2.06 x 1012 J

Number 2 is very similar in calculations. Don’t forget that when we are calculating the energy of any nuclear reaction we use E= mc2 and not Hess’ Law.

3. Calculate the energy released by the alpha decay of radium-226. (Answer: -5.69 x 1011 J)

RnHeRa 22286

42

22688 +

To calculate the change in mass we use page 8 of the data

booklet to look up the mass of the products and reactants.

Δm = mproducts - mreactants

reactant products

Δm = [1mol(4.00151 kg/mol) + 1mol(222.01757 kg/mol)] – 1mol(226.02540 kg/mol)

Δm = -0.00632 kgWe need to multiply the answer by 10-3

since the masses are given in 10-3 and it’s

easier to multiply your final answer after.

Δm = -0.00632 kg x 10-3

Δm = -6.32 x 10-6 kg

E = mc2

E = (-6.32 x 10-6kg)(3.00 x108m/s)2

E = -5.688 x 1011 J

-5.69 x 1011 J

We don’t need to write negative since it’s function is to tell

us that energy is released.

4. Calculate the energy released by the alpha decay of polonium-210. (Answer: -6.17 x 1011 J)

Δm = mproducts - mreactants

reactant products

Δm = [1mol(4.00151 kg/mol) + 1mol(205.9745 kg/mol)] – 1mol(209.98286 kg/mol)

Δm = -0.00685 kg

Don’t forget to multiply the mass by 10-3

Δm = -0.00685 kg x 10-3

Δm = -6.85 x 10-6 kg

E = mc2

E = (-6.85 x 10-6kg)(3.00 x108m/s)2

E = -6.165 x 1011 J

-6.17 x 1011 J

PbHePo 20682

42

21084 +

5. Calculate the energy released in the following equation: (Answer: -1.67 x 1013 J)

Δm = mproducts - mreactants

reactants products

Δm = [1mol(140.91441 kg/mol) + 1mol(91.92611 kg/mol) + 3mol(1.00866 kg/mol)] – [1mol(1.00866 kg/mol) + 1mol(235.04392mkg/mol)]

Δm = 235.8665 – 236.05186

Don’t forget to multiply the mass by 10-3

Δm = -0.18608 kg x 10-3

Δm = -1.8608 x 10-4 kg

E = mc2

E = (-1.8608 x 10-3kg)(3.00 x108m/s)2

E = -1.66824 x 1013 J

-1.67 x 1013 J

nKrBaUn 10

9236

14156

23592

10 3

Hint: Add the mass of all the products first (press Enter) and then subtract the reactants

Remember, for nuclear energy released we always use E=mc2.If we are given the change in mass, use it directly.

If no mass is given, then we must calculate it FIRST using data on page 8 of the data booklet!

Since this is a nuclear reaction, we need to use E = mc2.

E = mc2

E = (3.10 x 10-28kg)(3.00 x108m/s)2

E = 2.79 x 10-11 J

If an exponent is given, make sure the exponent of your answer matches.

2. 79

Δm = mproducts - mreactants

Δm = [4mol(4.00151 kg/mol) + 2mol(0.000 549 kg/mol)] – 4mol(1.00783 kg/mol)

Δm = -0.028712 kg

Δm = -0.028712 kg x 10-3

Δm = -2.8712 x 10-5 kg

E = mc2

E = (-2.8712 x 10-5kg)(3.00 x108m/s)2

E = -2.58408 x 1012 J

2.58

Answer: A

C and D are incorrect because both fission and fusion release energy

Answer: D

A and B are both examples of fusion because the mass of the product increases.

C is an example of beta decay.