Chapter 2 the chemical basis of life

quiz 2

What is an atom?

The smallest unit of matter that retains the properties of its element.

Define an element.

Matter made of one type of atom, e.g., hydrogen, helium, oxygen.

How many elements does the human body need to survive?

25 elements.

What are molecules?

Particles composed of more than one atom.

What are compounds?

Substances consisting of two or more different elements, e.g., sodium chloride (NaCl).

Give an example of a compound and its constituent elements.

Sodium chloride (NaCl) is made of sodium and chlorine.

What is the definition of a chemical?

A substance with constant composition and characteristic properties.

What is the difference between natural and synthetic chemicals?

There is no difference in properties; both have the same molecular composition.

What are alkali metals?

Shiny, soft, highly reactive metals with 1 outer electron.

What is the most abundant element in the universe?

Hydrogen.

What are alkaline earth metals?

Metals with 2 outer electrons, somewhat reactive under standard pressure.

What are triels?

Elements with 3 outer electrons; boron is the hardest among them.

What is the significance of carbon?

An essential element of biology, found in graphite and diamonds.

What are pnictogens?

Elements with 5 outer electrons, including nitrogen and phosphorus.

What are chalcogens?

Elements with 6 outer electrons, including oxygen and sulfur.

What are halogens?

Elements with 7 outer electrons, highly reactive and electronegative.

What defines noble gases?

Elements with 8 outer electrons that do not readily interact with most elements.

What are transition metals known for?

Lustrous metals with good electrical and thermal conductivity.

What are lanthanides and actinides?

Rare earth metals; lanthanides are used in semiconductors, actinides are radioactive.

What is the role of trace elements in the body?

They are critically important despite making up a small part of the body.

What can iodine deficiency cause?

Goiter, miscarriages, poor growth, and mental impairment.

What is the purpose of adding fluoride to water?

To decrease the incidence of cavities.

What does the CDC list as one of the great public health achievements of the 20th century?

Water fluoridation.

What is the effect of recommended levels of fluoride on children's cognition?

Children exposed to these levels exhibit modestly better cognition in secondary school.

What are some sources of iodine?

Seafood, kelp, dairy products, and dark leafy greens.

What is the significance of iron in the diet?

Iron deficiency affects about 2 billion people worldwide.

How can iron deficiency be combated?

By adding iron to foods, taking supplements, and improving diet.

What are the three main subatomic particles that make up an atom?

Protons, neutrons, and electrons.

What charge does a proton have?

A proton has a positive charge.

What charge does an electron have?

An electron has a negative charge.

What charge does a neutron have?

A neutron has no charge (neutral).

What is the atomic nucleus?

The center of the atom, containing protons and neutrons.

What is an ion?

An atom with an unequal number of protons and electrons.

What defines an element?

An element is defined by its number of protons, known as the atomic number.

What is the mass number of an atom?

The sum of the number of protons and neutrons in the nucleus.

What is an isotope?

Isotopes are elements that have the same number of protons but different numbers of neutrons.

What is a stable isotope?

An isotope that will never spontaneously break down into other elements.

What is the stable isotope of hydrogen called?

Deuterium (1 proton, 1 neutron).

What is a radioactive isotope?

An unstable isotope that spontaneously gives off particles and energy.

How can radioactive isotopes be used in medicine?

Doctors inject patients with short-living radioisotopes to monitor physiological processes or find cancers.

What is a half-life?

The time it takes for half of a sample of a radioisotope to decay into a daughter product.

Which radioisotope is commonly used to date organic objects?

Carbon-14.

What is the geologic time scale based on?

Radioisotope dating of igneous rock layers.

What does the law of superposition state?

Rock layers get older the deeper you descend.

What are index fossils?

Fossils that have a widespread geographic distribution but existed for a short period of time.

What is the difference between absolute ages and relative ages in dating fossils?

Absolute ages provide precise ages, while relative ages indicate whether a fossil is older or younger than others.

How old is the Earth estimated to be?

About 4.5 billion years old.

How long have humans existed?

For around 300,000 years.

What determines an atom's chemical properties?

The distribution of electrons.

What are electron shells?

Different energy levels where electrons are arranged around an atom.

How many electrons can the inner shell of an atom hold?

2 electrons.

What is the maximum number of electrons the outer shell of carbon can accept?

4 electrons.

What are noble gases?

Elements like helium, neon, and argon that do not normally form bonds with other atoms.

What is an ionic bond?

A chemical bond resulting from the transfer of electrons from one atom to another, creating ions.

What is a covalent bond?

The equal sharing of electrons between atoms.

What defines organic molecules?

Molecules that contain carbon-hydrogen or carbon-carbon bonds.

What is the significance of electronegativity?

It is the tendency of an atom to attract electrons to form chemical bonds.

What is a non-polar covalent bond?

A bond where atoms share electrons equally and carry no partial charge.

What characterizes a polar covalent bond?

Molecules with regions having different charges due to unequal sharing of electrons.

What happens in table salt during ionic bonding?

Chlorine strips an electron from sodium, resulting in oppositely charged ions.

What is a hydrogen bond?

A weak bond where a slightly positive hydrogen atom is attracted to a slightly negative atom in another molecule.

How many hydrogen bonds can one water molecule form?

Up to four other water molecules.

What is cohesion in the context of water?

The tendency of water molecules to stick together.

What is adhesion?

The clinging of one substance to another.

What is surface tension?

A measure of how difficult it is to break or stretch the surface of a liquid.

How does water's hydrogen bonding affect temperature?

Hydrogen bonds must be broken for temperature to rise, causing water to heat up slowly.

What is evaporative cooling?

The process where the surface becomes cooler as the highest energy molecules transition to gas.

Why does ice float on water?

Ice is less dense than water due to its crystalline structure formed by hydrogen bonds.

What is a solution?

A liquid consisting of a uniform mixture of two or more substances.

What is a solute?

A substance that is dissolved in a solution.

What is a solvent?

The solution in which a solute is dissolved.

What is an aqueous solution?

A solution where the solvent is water.

What are reactants in a chemical reaction?

The starting materials that undergo change.

What are products in a chemical reaction?

The final materials produced by the reaction.

Why is water essential for chemical reactions?

It facilitates collisions between molecules, which is necessary for reactions to occur.

How does water's high specific heat capacity benefit the environment?

It allows water to absorb a lot of energy without changing its temperature, moderating Earth's climate.

What happens when electricity is applied to a solution?

Ions migrate towards the oppositely charged rod, e.g., Cl- towards the positive rod and Na+ towards the negative rod.

What is an electrolyte?

A substance that dissolves in water to form ions.

What differentiates weak electrolytes from strong electrolytes?

Weak electrolytes release just a few ions in solution, while strong electrolytes dissociate nearly completely into ions.

What ions are commonly found in sports drinks?

Ions such as Na, K, Mg, and Ca, along with sugar and fluids.

Why do many people avoid drinking tap water?

Due to safety and purity concerns.

Which agency oversees the regulation of tap water?

The Environmental Protection Agency (EPA) under the Safe Water Drinking Act.

What is one benefit of tap water?

It is filtered, disinfected, and often contains fluoride to prevent tooth decay.

What is the pH scale used for?

To measure the acidity or basicity of a solution.

What pH range indicates an acidic solution?

A pH of 0-6.

What pH is considered neutral?

About pH 7, e.g., water and blood.

What happens to biological fluids in response to pH changes?

They contain buffer solutions to minimize pH changes.

What causes ocean acidification?

Increased carbon dioxide dissolving in oceans, forming carbonic acid and lowering pH.

What is a consequence of ocean acidification on shelled organisms?

It causes the dissolution of structures made of calcium carbonate.

What is the significance of water in the search for extraterrestrial life?

Water is integral to life on Earth, so astrobiologists look for signs of water elsewhere.

What was the first unequivocal detection of water vapor on Mars?

Demonstrated in 1963 by spectroscopy using an Earth-based telescope.

What did the Hayabusa2 spacecraft discover on asteroid Ryugu?

Hundreds of thousands of ion signals and fifteen amino acids, indicating an abiotic origin.

What is unique about Jupiter's moon Europa?

It has a surface made of ice and a subsurface ocean of liquid water.

What keeps Europa's subsurface ocean liquid?

Tidal friction, radioactive heating, and possible deep-sea hydrothermal vents.

What organic molecules have been detected on Saturn's moon Enceladus?

Methane, propane, acetylene, formaldehyde, benzene, and larger organic molecules.

What did the 2023 paper on organic molecules in interstellar space find?

Ubiquitous presence of water and formaldehyde in interstellar clouds.

What are self-assembling molecules?

Biological structures that do not require enzymes to facilitate their formation.

What is the definition of life according to NASA?

A self-sustaining chemical system capable of Darwinian evolution.

What are the key characteristics of living organisms?

Composed of cells, grow, reproduce, respond to stimuli, have metabolism, exhibit homeostasis, and undergo evolution.

What is metabolism?

All chemical processes in an organism that consume or produce energy.