Science Semester 1 Flashcards
What is the nucleus?
It is a small and very dense particle, consisting of protons and neutrons, which are held together by a very large nuclear force. The nucleus makes up almost all of the mass of an atom.
What are protons?
Protons are particles which have a positive electric charge.
What are neutrons?
They share the same mass as protons, and have no electric charge.
What is an electron?
Electrons orbit the Nucleus. Electrons have a negative electric charge.
In symbols, isotopes are represented as A/Z E, where:
A = The mass number; the sum of protons and neutrons in nucleus. Z = The atomic number; the number of protons in the nucleus E = Chemical symbol.
All atoms of a particular element have the same number…
Of protons.
How did Lord Rutherford find out that the atoms in solid gold are mostly empty space?
Lord Rutherford’s atom model was based on experiments in which he fired time positive alpha particles at very thin sheets of gold foil. Most particles went straight through the sheet, where the rest were reflected by a small, positively-charged nucleus. Most atoms carried through because it was empty space.
The number of neutrons in atoms of the same element is different, because such atoms have the same numbers but different mass numbers. Atoms of the same element with different mass numbers are called
Isotopes.
In most atoms, the protons and neutrons found in the nucleus are held together very strongly. The nuclei of these atoms are said to be
Stable.
If neutrons and protons are not held together strongly, the nuclei is therefore
Unstable
Isotopes that are unstable decay to form other elements. These isotopes are said to be
Radioactive, and are called radioisotopes.
Isotopes that ustable are
Radioisotopes.
Natural radioactivity is
Radioactivity emitted from matter without energy being supplied to atoms. There’s 50 isotopes that emit radioactivity naturally,many exist in air, water, and living things in the ground.
Most radioactive isotopes (about 2,000 in total) are made radioactive artificially by
Bombarding their atoms with protons and neutrons.
Energy emitted by radioactive substances is called
Nuclear radiation, because it comes from the nucleus.
Alpha particles are
Helium nuclei that contain two protons and two neutrons, Alpja particles a
Are positive,y charged. They cannot travel easily through materials and can be stopped by a sheet of paper or human skin. Cannot damage outside, but if inhaled, can cause serious damage.
Beta particles are
The same side and mass of electrons, and can have a negative or positive electric charge and can travel at speeds as high as 99% of the speed of light. Beta particles can penetrate human skin and can damage living tissue, but they cannot penetrate thin layers of plastic, wood or aluminium.
Gamma rays are
BURSTS OF energy released after alpha or beta particles are emitted. Gamma rays travel at the speed of light and are highly penetrating. They can cause serious and permanent damage to living tissues and can stopped only be a thick shield of lead or concrete.
The nuclei of different radioactive substances decay at different rates, Some radioisitopes decay in a few seconds, while others take thousands of years. The time taken for half of all the nuclei in a sample of a radioisotope to disintegrate of decay is known as its
Half-life.
There are 3 naturally occurring isotopes of uranium; uranium-238, uranium-235 and uranium-234. Each of the isotopes spontaneously decay spy. Producing alpha particles and gamma rays. Half-lives can vary from milliseconds to billions of years. The half-live of each of the uranium isotopes are more than a billion years. If isotopes have 1 half life, it has 1/2 of its life remaining. 2=1/4, 3=1/8…
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Clearly describe the use of radioisotopes in radiometric dating.
Geologists make use of radioisotopes to determine the age of rocks and fossils. This technique is called radiometric dating.
Clearly describe the use of radioisotopes in nuclear power.
For example, uranium is converted to uranium dioxide, and then sealed in fuel rods. The uranium undergoes a fission reaction on the reactor when neutrals are fired at the radioactive uranium, causing the uranium nuclei to split and form 2 new elements, releasing heat energy. This energy boils water to convert water to steam.
Clearly describe the use of radioisotopes in the treatment of cancer.
There are 2 ways.
External Radiotherapy, which involves radiation being directed at the cite of cancer by a linear accelerator, This is the name of machines used to deliver radiation at the source of cancer.
Brachytherapy (internal radiotherapy) involves placing isotopes inside the body at the cite of cancer.
Clearly describe the use of radioisotopes in the diagnosis of diseases.
Radioactive substances may be injected into the body to detect or identify the cause of disease, some radioisotopes can be used to obtain images. Gamma rays emitted by these radioisotopes produce these images, PET scans (Pesitra, Emission Tomography) use cameras surrounding the patient to detect gamma rays coming from radioisotopes injected into the body.
What causes radioactivity?
Naturally, where radioactivity is emitted from matter without energy being supplied to its atoms.
Most radioactive isotopes are made radioactive artificially by bombarding their atoms with sub-atomic particles like protons and neutrons.
Clearly describe the use of radioisotopes in preserving food.
Food in sealed containers can be preserved by exposing it to gamma radiation. This radiation kills the micro-organism in the food and keeps it from spoiling.
How do chemical reactions take place?
Chemical reactions take place when the bonds between atoms are broken and new bonds are formed, creating a new arrangement of atoms and atleast 1 new substance.
What are some observable changes to show a chemical reaction has taken place?
Change in colour, formation of gases (which can be seen)m or a new solid, or perhaps even just an odour.
What is the Law of Conservation of Mass?
A law which states that matter can’t be destroyed or created during chemical reactions.
What is the Law of Constant Proportions?
A law chick states that a comlound, no matter how it’s formed, always contains the same relative amount of each element.
The new substances that are formed during a chemical reaction are called:
Products.
The original substances before a chemical reaction takes place are called:
Reactants.
What possible sources of energy can be used to start a reaction?
Energy sources include electrical currents, beams of lights, flames.
What is an endothermic reaction?
Chemical reactions in which energy is absorbed from the surroundings. Endothermic reactions are cold from this.
What is an exothermic reaction?
A chemical reaction involving heat being created and sent outwards from the reaction place.
Who was Alfred Nobel, and what was he famous for?
Alfred Nobel was a chemist and physicist, who was famous for investing in dynamite, an explosive which released large amount of energy and gas, exerting great pressure.
Explain how an airbag works.
The rapid inflation I’d an airbag is the result of an explosive exothermic chemical reaction. The reaction is triggered by an electronic device in the car that detects any sudden change in speed or direction of the car. The bag fills with a harmless gas, and when the occupants move forwards or sideways into the bah, they push the gas out of the airbags through tiny holes in the nylon, The airbag is usually totally deflated by the time the car comes to rest.
Explain why the chemical process that takes place in an icepack containing ammonium chloride is not a chemical reaction.
Ammonium chloride + water -> Ammonium Chloride in solution. Although the chemical bonds are broken in this process, it’s not a chemical reaction because no new substances are formed.
In the human brain, the cerebrum has key roles in what?
Thinking processes, such as having conscious thoughts, problem solving, decision making, memory, language, and learning.
In the human brain, the cerebral cortex is what?
The outside layer of tightly-packed neurons covering the celebrum.
The human brain, the cerebellum is responsible for what?
It is responsible for balance, coordinates movement, and has a role in speech, language, memory, and learning.
In the human brain, what does the brain stem do?
The brain stem (or medulla) regulates your life support systems, such as heart rates breathing, and blood pressure.
In the human brain, what is the frontal lobe responsible for?
Decision making, planning, working memory, and higher order thinking.
In the human brain, what is the temporal lobe responsible for?
Hearing, explicit memories, words, and pictures.
In the human brain, what is the parietal lobe responsible for?
Sensory information, motor functions, and spatial awareness.
In the human brain, what is the occipital lobe for?
Vision, pictures, colours, and movement.
What is Homeostasis?
Where the internal environment in which the cell lives needs to be kept constant. Temperature, pH, and concentrations of Ions, glucose, water and carbon dioxide need to be within a particular range.
What is the stimulus-response model?
Where receptors detect responses to create change to correct uneven conditions.
(Stimulus)->(Receptor)->(Control Centre)->(Effector)->(Response)
Define negative feedback reactions.
A response which goes in an opposite direction to the stimulus.
(BLOOD LEVELS TOO HIGH: Lower Blood Levels.)
(BLOOD LEVELS TOO LOW: Raise Blood Levels.)
What is Glucagon, Glycogen and Glucose?
If the receptor detects lack of blood levels, the hormone Glucagon is released. This breaks down glycogen to become glucose.
What is a positive feedback reaction?
Where the response goes in the same direction, and has a positive effect on the stimulus.
What does the Nervous System and Endocrine System do?
It involves the message being sent as a nervous or electrical impulse along a neutron and then as a chemical message (neurotransmitter) across the gaps (synapses) between them.
The endocrine system uses only chemical messages (hormones) transported throughout the circulatory system to its target cell.
What is the central nervous system?
The CNS consists of the brain and spinal cord. Messages are sent through the spinal cord to the brain, or the brain to the spinal cord.
What is the peripheral nervous system?
Neurons which connect the central nervous system to the rest of the body.
Your endocrine system is composed of
Endocrine glands which secrete chemicals, known as hormones, into the bloodstream.
Define thermoregulation.
Where the endocrine and nervous system work together to maintain body temperature. They work with the hypothalamus (in the brain); the body’s “thermostat”.
What is the thyrotropin hormone?
This hormone, released from the Hypothalamus, regulates many body activities.
What is the growth hormone?
Most body activities. Growth hormones can also be called the “master gland”. They’re released from the Piuuitary gland.
What is the thyroxine hormone?
A hormone from the Thyroid glan which regulates metabolism and growth.
What is the Cortesol hormone?
A hormone from the Adrenals gland which regulates metabolism and response to stress.
What is the Insulin hormone?
A hormone from the Pancreas glan which regulates blood glucose concentration.
