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97 Cards in this Set
- Front
- Back
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what percent of your body is oxygen atoms?
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65
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rain in the _____ is more ____ than vineger
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eastern united states
acidic |
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becasue of _____ some insects can walk on water
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surface tension
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the iron in a ______ is the same element as _______
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multivitamin pill
the iron in a nail |
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In 1981, the Centers for Disease Control (CDC)
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Began tracking high numbers of otherwise healthy young men who were coming down with extremely rare diseases.
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In 1981, the Centers for Disease Control (CDC)
Began tracking high numbers of otherwise healthy young men who were coming down with extremely rare diseases. Examinations of these patients showed that they all had a failing immune system. |
This condition was caused by the human immunodeficiency virus (HIV).
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HIV
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binds to certain molecules found on cells of the immune system called “helper” T cells.
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what does HIV do?
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The virus kills these cells and wipes out one part of the body’s defenses.
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Take any biological system apart and ...
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Take any biological system apart, and you eventually end up at the chemical level.
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matter
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is anything that occupies space and has mass.
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Matter is found on the Earth in three physical states:
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Solid
Liquid Gas |
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Matter is composed of ...
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chemical elements
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elements
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are substances that cannot be broken down into other substances.
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There are ___ naturally occurring elements on Earth.
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92
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All the elements are listed in the ...
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periodic table.
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atomic number
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number of protons
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mass number
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number of protons plus neutrons
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_____ elements are essential to life.
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Twenty-five
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25 of the elements that are essential to life fourof these ...
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make up about 96% of the weight of the human body.
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Trace elements ...
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occur in smaller amounts.
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Trace elements ...
An iodine deficiency ... |
are essential for life.
causes goiter. |
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Elements can ...
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combine to form compounds.
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compounds
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These are substances that contain two or more elements in a fixed ratio.
Example: NaCl (salt) |
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Each element consists of ...
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one kind of atom.
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An atom is ...
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the smallest unit of matter that still retains the properties of an element.
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Atoms are composed of ...
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subatomic particles.
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what are the subatomic particles of an atom?
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proton
electron neutron |
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A proton is ___
An electron is ____ A neutron is _____. |
positively charged
negatively charged electrically neutral |
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Most atoms have ____
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protons and neutrons packed tightly into the nucleus.
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The nucleus i___
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s the atom’s central core.
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what orbits the nucleus
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The electrons .
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Elements differ___
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in the number of subatomic particles in their atoms.
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_______, determines which element it is.
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The number of protons, the atomic number
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An atom’s mass number is _____
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the sum of the number of protons and neutrons.
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Mass is______
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a measure of the amount of matter in an object.
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Isotopes are _____
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alternate mass forms of an element.
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isotopes have ____
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They have the same number of protons and electrons. But they have a different number of neutrons.
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In radioactive isotopes ___
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The nucleus decays, giving off particles and energy.
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Radioactive isotopes ___
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have many uses in research and medicine.
Example: PET scans |
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Alzheimer’s disease
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It gradually destroys a person’s memory and ability to think.
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why are Doctors now using PET scans
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In an attempt to diagnose Alzheimer’s disease before the onset of symptoms.
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___________can harm living organisms by damaging DNA.
Example: the 1986 Chernobyl nuclear accident |
Uncontrolled exposure to radioactive isotopes
the 1986 Chernobyl nuclear accident |
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Electrons determine ________
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how an atom behaves when it encounters other atoms.
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Electrons ____
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orbit the nucleus of an atom in specific electron shells.
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The number of electrons in the outermost shell _________
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determines the chemical properties of an atom.
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Chemical reactions ______
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enable atoms to give up or acquire electrons in order to complete their outer shells.
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chemical reactions usually result in ________
The atoms are held together by ____ |
atoms staying close together.
chemical bonds. |
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When an atom loses or gains electrons________
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it becomes electrically charged.
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ions
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charged atoms
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Ionic bonds
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are formed between oppositely charged ions.
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A covalent bond
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forms when two atoms share one or more pairs of outer-shell electrons.
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Water is a compound in which the electrons in its covalent bonds are shared unequally.
This causes it to be a _______ |
polar molecule, one with opposite charges on opposite ends.
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The polarity of water results in __________These interactions are called ______
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weak electrical attractions between neighboring water molecules.
hydrogen bonds. |
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Cells constantly __________
Such changes in the chemical composition of matter are called ________ |
rearrange molecules by breaking existing chemical bonds and forming new ones.
chemical reactions. |
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Chemical reactions include:
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Reactants, the starting materials
Products, the end materials |
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Chemical reactions cannot __________
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create or destroy matter
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chemical reactions only _____
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rearrange matter
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Life on Earth began ______and evolved there for _______
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in water
3 billion years. |
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Modern life still _______
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remains tied to water.
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Your cells are composed of _____water.
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70%–95%
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why is earth habitable?
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The abundance of water
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________explain most of water’s life-supporting properties.
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The polarity of water molecules and the hydrogen bonding that results
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water's life supporting properties are ...
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Water’s cohesive nature
Water’s ability to moderate temperature Floating ice Versatility of water as a solvent |
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Water molecules stick together as a result of ______
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hydrogen bonding.
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cohesion
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Water molecules stick together as a result of hydrogen bonding.
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Cohesion is vital for _____
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water transport in plants.
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Surface tension is ____
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the measure of how difficult it is to stretch or break the surface of a liquid.
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what do Hydrogen bonds do?
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give water an unusually high surface tension.
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Because of hydrogen bonding, _______
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water has a strong resistance to temperature change.
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Heat is ______
Temperature ______ |
the amount of energy associated with the movement of the atoms and molecules in a body of matter.
measures the intensity of heat. |
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Water can ______
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absorb and store large amounts of heat while only changing a few degrees in temperature.
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When water molecules get cold, _____
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they move apart, forming ice.
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A chunk of ice has ______than an equal volume of liquid water.
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fewer molecules
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why does ice float.
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The density of ice is lower than liquid water.
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what do most substances do as they cool?
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Most substances become denser
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_____ also becomes denser, to a point
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Water
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water becomes denser but ....
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reaches maximum density at 4oC, and expands as it cools below that point
expands even further upon freezing |
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liquid water
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hydrogen bonds constantly break and reform
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ice
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stable hydrogen bonds hold molecules apart, making ice less dense than water
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Since ice floats_____
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ponds, lakes, and even the oceans do not freeze solid.
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what would happen if bodies of water could freeze?
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Marine life could not survive
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A solution ________
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is a liquid consisting of two or more substances evenly mixed.
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The dissolving agent in a solution is called _____
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the solvent.
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The dissolved substance in the solution is called _______
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the solute.
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When water is the solvent, ___________
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the result is an aqueous solution.
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Acid
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A chemical compound that donates H+ ions to solutions.
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Base
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A compound that accepts H+ ions and removes them from solution.
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To describe the acidity of a solution, _____________
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we use the pH scale.
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Buffers
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are substances that resist pH change.
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what do buffers do?
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accept H+ ions when they are in excess.
They donate H+ ions when they are depleted. |
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Buffering is ________
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not foolproof.
Example: acid precipitation |
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what created an environment that made life possible?
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Chemical reactions and physical processes on the early Earth created an environment that made life possible.
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Earth began as a ______about ____years ago.
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cold world
4.5 billion |
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what eventually happened to the planet?
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The planet eventually melted from heat produced by:
Compaction Radioactive decay Impact of meteorites |
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The first atmosphere was probably composed of _______
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hot hydrogen gas.
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hot hydrogen gas
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This gas escaped because the gravity of Earth was not strong enough.
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A new atmosphere was formed from _____________
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the gases belched from volcanoes.
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