Science Exam Term 4 2023

Question 1

Which particles are in the nucleus?

Answer 1

Protons and neutrons

Question 2

Why does radioactive decay happen?

Answer 2

As the unstable nucleus attempts to become stable, it emits radiation and changes into a different element as the number of protons changes.

Question 3

Three types of radioactive decay

Answer 3

Gamma decay, Beta decay, Alpha decay

Question 4

Alpha decay:

how is it emitted?
consists of?
how it can be stopped?
weak or strong?

Answer 4

An alpha particle (α) is emitted from the unstable nucleus

Alpha particles consist of two neutrons and two protons, just like a helium nucleus

can be stopped by a piece of paper and have a weaker penetration than the other two

Question 5

Beta decay:

how/when it occurs?

Answer 5

A beta particle (β) is emitted from the unstable nucleus

Beta particles are high speed electrons that are emitted from the nucleus when a neutron turns into a proton during beta decay.

it becomes a new element but mass doesn’t change

Question 6

Gamma decay:

what is it?
how to stop it?

Answer 6

A gamma ray (γ) is emitted from the unstable nucleus

An “m” — for “metastable” is included next to the mass number of the higher energy form of the atom

A gamma ray is a high energy form of decay with no mass and no charge

Highest penetrance and can generally be stopped by water of thick metals

Question 7

Why does nuclear decay happen

Answer 7

Nuclear decay arises from unstable atoms – radioisotopes

Question 8

what is penetrance?

Answer 8

Penetrance is determined by energy output. Higher energy particles will have a higher penetrance.

Question 9

what are regular isotopes? +examples

Answer 9

Regular isotopes are just elements with the same number of protons and electrons, but a different number of neutrons – these are what we call stable, and will never undergo nuclear decay.

E.g. Chlorine-35 and Chlorine-37, both are isotopes of chlorine

Question 10

What are radioisotopes?

Answer 10

Radioisotopes, on the other hand, have an unstable nucleus – they can undergo nuclear decay at any moment. After they decay, their nucleus can return to a stable position.

Question 11

Neutrons

Answer 11

Have a neutral charge

Question 12

what does pH mean?

Answer 12

stands for Potential of Hydrogen.

Question 13

Products

Answer 13

new substances from a chemical reaction

Question 13

Nucleus

Answer 13

The nucleus is the center of an atom. Protons and neutrons sit inside the nucleus.

Question 13

Radioisotope

Answer 13

Radiation is released from radioisotopes, which are isotopes that release radioactive particles. Examples of radioisotopes include:
- Randon-222
- Polonium-210
- Plutonium
- Americium-241

Radioisotopes become less harmful over time as they decay. We measure decay in half-life, which is unique to the radioisotope

Question 14

reactant

Answer 14

original substances in a chemical reaction

Question 15

word equation

Question 15

Acid/reactions

Answer 15

An acid is a substance which release hydrogen ions (H+) into a solution. They have a pH of 1-6 and will turn blue litmus paper pink.

Indicators are substances whose solutions change colour due to changes in pH. Other examples of indicators include universal indicator and red cabbage indicator.

Question 16

Base/reactions

Answer 16

A base (or alkali) is a substance that releases a hydroxide (-OH) into a solution. They have a pH of 8-14 and will turn red litmus paper blue-purple.

Question 17

Indicator

Answer 17

Indicators are substances whose solutions change colour due to changes in pH. Other examples of indicators include universal indicator and red cabbage indicator. E.g. Litmus paper

Question 17

Atom

Answer 17

Atoms are the building blocks of matter, the thing from which everything is made. Atoms have three key particles inside of them:
protons, neutrons electrons

An atom that is neutral does not have an overall charge. When an atom is neutral, the number of electrons = the number of protons.

Question 18

Electron

Answer 18

Have negative charge, sits outside of the nucleus, is very light and

Question 19

atomic number

Question 20

Isotope

Answer 20

Isotopes are variations of the same element which have more neutrons than usual, so have a different atomic weight.

Question 21

How to find neutrons in chemical symbol?

Answer 21

mass number – atomic number

Question 22

What is the units for atomic mass?

Answer 22

Amu Atomic Mass Units

Question 23

how to find number of neutrons

Answer 23

= Atomic mass – Atomic number

Question 24

Atomic mass

Answer 24

The atomic mass of a particle is given by the number of protons + neutrons and will always be the bigger number.

Question 25

Ion

Answer 25

Sometimes atoms gain or lose electrons which gives them an overall charge. It also means that the number of electrons is not the same as the number of protons. An atom that has an overall positive charge or an overall negative charge is called an ion. example: Hydrogen Ion H+ * The hydrogen atom has lost one electron which results in an overall positive charge of 1. * Therefore, there are more protons than electrons.

Question 26

physical change

Answer 26

No new substance is being produced The substance changes shape, size (gets bigger or smaller), state (into solid, liquid or gas) or it mixes with another substance. Physical changes can be easily reversed. Examples: Shredding paper, cutting hair, chopping wood, breaking an egg.

Question 27

Chemical change

Answer 27

A new substance has formed, and the old substance disappears. If something has changed colour, produced a gas, formed a precipitate, or released energy (heat), then it has gone through a chemical change. Examples: Digestion, fruit rotting, photosynthesis, charging a battery.

Question 28

chemical change

Answer 28

Chemical changes are chemical reactions. In a chemical reaction, new substances are formed, and the original substances disappear. The original substances are called reactants, and the new substances are called products. For example, carbon combines with oxygen gas to create carbon dioxide. We can represent chemical equations using a word equation: Carbon + Oxygen gas -> Carbon Dioxide

Question 29

The law of conservation of mass

Answer 29

The law of conservation of mass states that, like energy, mass can neither be created, nor destroyed. This can be seen in a chemical reaction where the weight of the reactants and the products are the same.

Question 30

Exothermic reactions

Answer 30

*Releases heat. *The reactants have more energy than the products, and energy is released into the surroundings as heat/light. *Examples: combustion reactions

Question 31

Endothermic reactions

Answer 31

* Absorbs heat. * The products have more energy than the reactants and they need more energy to complete the reaction, so will draw energy in from the environment. * Examples: photosynthesis

Question 32

Combustion

Answer 32

Combustion occurs when something (usually a hydrocarbon) reacts with oxygen gas, burning or exploding as it does so. An example of the reaction is: Hydrocarbon + oxygen gas --> carbon dioxide + water + heat/light

Question 33

Complete and incomplete combustion

Answer 33

When there is excess oxygen, we say that the combustion is complete. Although sometimes the oxygen supply is restricted, and this is incomplete combustion. These reactions are still exothermic, but they do not release as much heat/light as complete combustion does. Incomplete combustion reactions are 'dirty' because they produce carbon, which is left behind as soot, charcoal or smoke.

Question 34

neutral solutions

Answer 34

pH of 7

Question 35

Acid and metal reactions

Answer 35

-acids can corrode metals which: Acid + Metal -> Salt +Hydrogen Gas (e.g., Hydrochloric Acid + Magnesium -> Magnesium Chloride + Hydrogen Gas) A common real-life example of an acid reaction is when antacids neutralise stomach acid to prevent things like heartburn.

Question 36

acid and carbonate reactions

Answer 36

Acid + Carbonate -> Salt + Water + Carbon Dioxide (eg, hydrochloric acid + Calcium carbonate --> calcium chloride + water + carbon dioxide) - Acid molecule release hydrogen ions and has pH of less than 7 - carbonate ion is CO3 2- -when the base is a carbonate, the reaction between it and an acid will produce carbon dioxide and water

Question 37

acid and base reactions (neutralization reactions?

Answer 37

Acids and bases neutralize each other when mixed. The products are salt and water Acid + Base -> Salt + Water (e.g., Nitric Acid + Potassium Hydroxide -> potassium nitrate + water)

Question 38

To predict the salt that is formed when an acid reacts with a carbonate/metal/base

Answer 38

a. identify the metal b. identify the ion formed once the acid has lost its hydrogen atom c. put the two together. Example: Nitric acid + potassium oxide --> salt + water Use the table to determine the name of the salt formed? Acid Ion Nitric Acid -->Nitrate Hydrochloric Acid -->Chloride Sulfuric Acid -->Sulphate 1. Potassium is the metal 2. Nitrate is the ion 3. Therefore, the name of the salt is Potassium nitrate.

Question 39

Predict the salt

Answer 39

The name of the salt produced = name of metal Infront of name of ion formed once the acid loses its hydrogen

Question 40

Common ions

Answer 40

nitric acid --> nitrate hydrochloric acid --> chloride sulfuric acid --> sulfate

Question 41

Photosynthesis

Answer 41

Photosynthesis is an incredibly important reaction which occurs in plant cells, without which, life on earth would not exist. Photosynthesis takes carbon from the atmosphere and converts it into oxygen. It has the following formula: Carbon Dioxide + Water -> Oxygen + Glucose

Question 42

Respiration

Answer 42

Respiration is another incredibly important reaction which allows our bodies to use oxygen to make energy. It utilizes the following formula: Oxygen + Glucose -> Carbon Dioxide + Water

Question 43

Comparisons between photosynthesis and Respiration

Answer 43

Photosynthesis: makes glucose uses carbon dioxide makes oxygen gas uses water endothermic requires chlorophyll occurs only in the chloroplasts of green plants shuts down at night Respiration: uses glucose makes carbon dioxide uses oxygen gas makes water exothermic does not need chlorophyll occurs in the mitochondria of cells of all living things happens continuously (day and night)

Question 44

negative feedback loop

Answer 44

Stimulus -> receptor -> signal -> response -> homeostasis restored

Question 45

radiation

Answer 45

- Radiation is released from radioisotopes, which are isotopes that release radioactive particles. The protons and neutrons in the atom’s nucleus are shifting constantly, and sometimes a particle is expelled. Three main kinds of particles can be expelled by radioisotopes: - Alpha particles – equivalent to a helium nucleus (2 protons, 2 neutrons), and are only emitted by very heavy atoms (atomic weight greater than 100) - Beta particles – equivalent to an electron - Gamma waves – electromagnetic radiation instead of a particle, move incredibly quickly. We can also classify the particles based on their penetrance – how easily they can be stopped by an obstacle. It is important to understand this, as you need to have the right protection.

Question 46

Types of radiation and penetrance

Answer 46

Alpha particles are the weakest, and can be stopped by something like paper.\ Beta particles are next, and are a little stronger, but can still be stopped by something such as wood. Gamma particles are the strongest, and can penetrate through everything except thick metal or lead.

Question 47

half life

Answer 47

Radioisotopes become less harmful over time as they decay. We measure decay in half-life, which is unique to the radioisotope. For example: - Randon-222 has a half-life of 4 days - Iodine-131 has a half-life of 8 days So, every 4-days for Randon and every 8-days for Iodine, the amount of material present will halve. We measure half-life through graphs like this: essentially: time it takes for half radioisotopes to decay.

Question 48

homeostasis

Answer 48

self-regulating process by which an organism tends to maintain stability while adjusting to conditions that are best for its survival.

Question 49

combustion word equation

Answer 49

Combustion occurs when something reacts with oxygen gas, burning or exploding as it does so. The 'something' is usually a hydrocarbon. The reaction looks like: Hydrocarbon + oxygen gas --> carbon dioxide + water + heat/light