16 (2)

Question 1

When such binding energy of atoms is released, the resulting nucleus has slightly less ……….. than the sum of the ………… of the particles that came together to form it. In other words, the energy comes from the loss of …………..

Answer 1

mass / masses / mass

Question 2

with Binding Energy, This slight deficit in mass is only a small fraction of the mass of one …………. But because each bit of lost mass can provide a lot of energy (remember, E = mc²), this nuclear energy release can be quite substantial.

Answer 2

proton

Question 3

Measurements show that the binding energy is greatest for atoms with a mass near that of the ………. nucleus (with a combined number of protons and neutrons equal to ……….) and less for both the lighter and the heavier nuclei.

Answer 3

iron / 56

Question 4

Iron, therefore, is the most …………. element: since it gives up the most energy when it forms, it would require the most energy to break it back down into its component particles.

Answer 4

stable

Question 5

What this means is that, in general, when light atomic nuclei come together to form a heavier one (up to iron), mass is lost and energy is released. This joining together of atomic nuclei is called nuclear ………….

Answer 5

fusion

Question 6

Energy can also be produced by breaking up heavy atomic nuclei into lighter ones (down to iron); this process is called nuclear ………….

Answer 6

fission

Question 7

Fission also sometimes occurs spontaneously in some unstable nuclei through the process of …………. …………

Answer 7

natural radioactivity.

Question 8

protons all have positive charges. Since like charges repel via the electrical force, the closer we get two nuclei to each other, the more they repel. How can we get nuclei close enough to participate in fusion?

Answer 8

The answer turns out to be heat—tremendous heat—which speeds the protons up enough to overcome the electrical forces that try to keep protons apart.

Question 9

Inside the Sun, as we saw, the most common element is …………., whose nucleus contains only a single proton.

Answer 9

hydrogen

Question 10

(in the Sun) Two protons can fuse only in regions where the temperature is greater than about …… ……. ……., and the speed of the protons average around ……….. ………… per second or more.

Answer 10

12 million K / 1000 kilometers

Question 11

In our Sun, such extreme temperatures (to force fusion) are reached only in the regions near its center, which has a temperature of …… …….. ……….

Answer 11

15 million K.

Question 12

Calculations show that nearly all of the Sun’s energy is generated within about ……… ……… of its core, or within less than ……….. of its total volume.

Answer 12

150,000 kilometers / 10%

Question 13

On average, a proton will rebound from other protons in the Sun’s crowded core for about 14 billion years, at the rate of 100 million collisions per second, before it fuses with a second proton. Since the Sun is about 4.5 billion years old, most of its protons have not yet been involved in fusion reactions.

Answer 13

R 2

Question 14

Describe Sun fusion (First Step)

3

Answer 14

1. Because of heat two hydrogen protons collide and fused but turned into 1 proton, 1 neutron, 1 Neutrino which escape the sun easily and very fast, and one positron (antielectron). this is an isotope of hydrogen called (deuterium)
2. the positron soon collide with another electron and both get annihilated. this process create Gamma rays
3. the Gamma Rays working its way to the outer layer of the sun, get absorbed and released again and again until it turned into X ray than ultraviolet at which point it leaves the sun and we see it as sunlight

Question 15

Talk about step 2 in the sun fusion

Answer 15

Question 16

Talk about step 3 in the sun fusion

Answer 16

Question 17

The nuclear reactions in the Sun that we have been discussing can be described succinctly through the following nuclear formulas:

Answer 17

1. Here, the superscripts indicate the total number of neutrons plus protons in the nucleus,
2. e⁺ is the positron,
3. v is the neutrino, and
4. γ indicates that gamma rays are emitted.

Note that the third step requires two helium-3 nuclei to start; the first two steps must happen twice before the third step can occur.

Question 18

At the temperatures inside the stars with masses smaller than about 1.2 times the mass of our Sun (a category that includes the Sun itself), most of the energy is produced by the reactions we have just described, and this set of reactions is called the …………………. ………… (or sometimes, the …………..).

Answer 18

proton-proton chain / p-p chain

Question 19

In hotter stars, another set of reactions, called the ……… ……….. ………. cycle, accomplishes the same net result of P-P Chain

Answer 19

carbon-nitrogen-oxygen (CNO)

Question 20

Astronomers use observations to build a ……… ……… containing everything they think they know about the physical processes going on in the Sun’s interior. The ………… then calculates the temperature and pressure at every point inside the Sun and determines what nuclear reactions, if any, are taking place.

Answer 20

computer program / computer

Question 21

The Sun is so hot that all of the material in it is in the form of an ionized gas, called a …………..

……………. acts much like a hot gas, which is easier to describe ……………. than either liquids or solids. The

Answer 21

plasma / Plasma / mathematically

Question 22

in the sun, The particles that constitute a gas are in rapid motion, frequently colliding with one another. This constant bombardment is the ………… of the gas

Answer 22

pressure

Question 23

More particles within a given volume of gas produce more pressure because the combined impact of the moving particles increases with their number.

The pressure is also greater when the molecules or atoms are moving faster. Since the molecules move faster when the temperature is hotter, higher temperatures produce higher pressure.

Answer 23

R 2

Question 24

The Sun, like the majority of other stars, is stable; it is neither expanding nor contracting. Such a star is said to be in a condition of …………..

All the forces within it are balanced, so that at each point within the star, the …………., …………., …………., and so on are maintained at constant values.

Answer 24

equilibrium / temperature, pressure, density

Question 25

The technical term for this condition is ………….. ………….

Stable stars are all in …………. ……………; so are the oceans of Earth as well as Earth’s atmosphere. The air’s own pressure keeps it from falling to the ground.

Answer 25

hydrostatic equilibrium

If the internal pressure in such a star were not great enough to balance the weight of its outer parts, the star would collapse somewhat, contracting and building up the pressure inside. On the other hand, if the pressure were greater than the weight of the overlying layers, the star would expand, thus decreasing the internal pressure. Expansion would stop, and equilibrium would again be reached when the pressure at every internal point equaled the weight of the stellar layers above that point.

Question 26

In ……………, energetic photons move away from hot material and are absorbed by some material to which they convey some or all of their energy. Y

Answer 26

radiation

You can feel this when you put your hand close to the coils of an electric heater, allowing infrared photons to heat up your hand.