rajpurkar/squad huggingface dataset:
Title: Wood

It has been used for thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers (which are strong in tension) embedded in a matrix of lignin which resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs.[citation needed] In a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients between the leaves, other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, or wood chips or fiber.

Question: In addition to being used to build things, what has wood been used for over thousands of years?
Answer: fuel

Question: What kind of strong fibers are part of the composite of wood?
Answer: cellulose

Question: What's the matrix in wood made up of?
Answer: lignin

Question: What one word describes the function wood provides to a tree or plant?
Answer: support

Question: What does wood convey to leaves, roots, and other tissues of a woody plant in addition to water?
Answer: nutrients
Title: Wood

The Earth contains about 434 billion cubic meters of growing stock forest, 47% of which is commercial. As an abundant, carbon-neutral renewable resource, woody materials have been of intense interest as a source of renewable energy. In 1991, approximately 3.5 cubic kilometers of wood were harvested. Dominant uses were for furniture and building construction.

Question: How many cubic meters of growing stock forest are there on the planet?
Answer: 434 billion

Question: What percentage of the Earth's stock forest is commercial?
Answer: 47%

Question: In addition to buildings, what is wood often used to make?
Answer: furniture

Question: About how many cubic kilometers of the vast stock forest's wood were harvested in 1991?
Answer: 3.5

Question: In addition to being carbon neutral, what other adjective describes wood that makes it compelling as a renewable energy source?
Answer: abundant
Title: Wood

A 2011 discovery in the Canadian province of New Brunswick uncovered the earliest known plants to have grown wood, approximately 395 to 400 million years ago. Wood can be dated by carbon dating and in some species by dendrochronology to make inferences about when a wooden object was created.

Question: What year were the earliest plants that grew wood discovered?
Answer: 2011

Question: In which Canadian province were the oldest woody plants found?
Answer: New Brunswick

Question: If dendrochronology can't be used, what method would scientists employ to date wood?
Answer: carbon dating

Question: How many millions of years old were the plants that were discovered in New Brunswick?
Answer: 395 to 400
Title: Wood

People have used wood for millennia for many purposes, primarily as a fuel or as a construction material for making houses, tools, weapons, furniture, packaging, artworks, and paper. The year-to-year variation in tree-ring widths and isotopic abundances gives clues to the prevailing climate at that time.

Question: What has been the primary purpose of wood for millennia other than fuel?
Answer: construction material

Question: What is often made of wood that provides shelter to people?
Answer: houses

Question: For clues about the climate of a place, we can look at variation in isotopic abundances or what other thing?
Answer: tree-ring widths

Question: What could be made out of wood that could be used to fight off attackers?
Answer: weapons

Question: What category of items often constructed from wood does a chair belong to?
Answer: furniture
Title: Wood

Wood, in the strict sense, is yielded by trees, which increase in diameter by the formation, between the existing wood and the inner bark, of new woody layers which envelop the entire stem, living branches, and roots. This process is known as secondary growth; it is the result of cell division in the vascular cambium, a lateral meristem, and subsequent expansion of the new cells. Where there are clear seasons, growth can occur in a discrete annual or seasonal pattern, leading to growth rings; these can usually be most clearly seen on the end of a log, but are also visible on the other surfaces. If these seasons are annual these growth rings are referred to as annual rings. Where there is no seasonal difference growth rings are likely to be indistinct or absent.

Question: Where does wood come from?
Answer: trees

Question: What forms in a tree to increase its diameter?
Answer: woody layers

Question: What is the process of trees growing out to get bigger around called?
Answer: secondary growth

Question: What do many places have four of that would cause growth rings in a tree?
Answer: seasons

Question: If a place has annual seasons, what are the growth rings on the trees there called?
Answer: annual rings
Title: Wood

If there are differences within a growth ring, then the part of a growth ring nearest the center of the tree, and formed early in the growing season when growth is rapid, is usually composed of wider elements. It is usually lighter in color than that near the outer portion of the ring, and is known as earlywood or springwood. The outer portion formed later in the season is then known as the latewood or summerwood. However, there are major differences, depending on the kind of wood (see below).

Question: If a growth ring has differences over one season, would the part nearest the tree's center be narrower or wider?
Answer: wider

Question: What name, besides springwood, is used for the part of a growth ring formed in the beginning of the growing season?
Answer: earlywood

Question: If the opposite of springwood is summerwood, what's the opposite of earlywood?
Answer: latewood

Question: Is earlywood usually lighter or darker than the part of the growth ring that forms later in the season?
Answer: lighter

Question: Is summerwood the inner or outer portion of a growth ring?
Answer: outer
Title: Wood

A knot is a particular type of imperfection in a piece of wood; it will affect the technical properties of the wood, usually reducing the local strength and increasing the tendency for splitting along the wood grain, but may be exploited for visual effect. In a longitudinally sawn plank, a knot will appear as a roughly circular "solid" (usually darker) piece of wood around which the grain of the rest of the wood "flows" (parts and rejoins). Within a knot, the direction of the wood (grain direction) is up to 90 degrees different from the grain direction of the regular wood.

Question: What is the sort of circular imperfection in a piece of wood called?
Answer: knot

Question: What property of wood does a knot usually reduce in the wood around it?
Answer: strength

Question: In what direction is wood often sawn so that a knot appears as a solid circle that the grain flows around?
Answer: longitudinally

Question: Are knots usually lighter or darker than the surrounding wood?
Answer: darker

Question: The direction of grain in a knot can differ by as much as how many degrees from the regular wood?
Answer: 90
Title: Wood

In the tree a knot is either the base of a side branch or a dormant bud. A knot (when the base of a side branch) is conical in shape (hence the roughly circular cross-section) with the inner tip at the point in stem diameter at which the plant's vascular cambium was located when the branch formed as a bud.

Question: Other than the base of a side branch, what tree feature causes a knot?
Answer: a dormant bud

Question: What shape is the knot formed by a side branch's base?
Answer: conical

Question: What measurement of a stem determines a knot's inner tip placement?
Answer: diameter

Question: Because a knot's shape is conical, what shape does a cross-section of it have?
Answer: circular
Title: Wood

During the development of a tree, the lower limbs often die, but may remain attached for a time, sometimes years. Subsequent layers of growth of the attaching stem are no longer intimately joined with the dead limb, but are grown around it. Hence, dead branches produce knots which are not attached, and likely to drop out after the tree has been sawn into boards.

Question: What will the lower limbs of a tree usually do during development?
Answer: die

Question: For what length of time can a dead lower limb stay attached to a tree?
Answer: years

Question: Rather than being joined to the limb that died, where do subsequent layers grow?
Answer: around it

Question: Are the knots that dead tree limbs form attached or not attached?
Answer: not attached

Question: A detached knot will probably drop out of the wood when someone saws it into what?
Answer: boards
Title: Wood

In grading lumber and structural timber, knots are classified according to their form, size, soundness, and the firmness with which they are held in place. This firmness is affected by, among other factors, the length of time for which the branch was dead while the attaching stem continued to grow.

Question: What's the process in which knots are classified called?
Answer: grading

Question: Along with firmness, soundness, and form, what property of a knot is classified?
Answer: size

Question: What property of knots does the amount of time a branch stayed on a tree while the stem kept growing affect?
Answer: firmness
Title: Wood

Knots do not necessarily influence the stiffness of structural timber, this will depend on the size and location. Stiffness and elastic strength are more dependent upon the sound wood than upon localized defects. The breaking strength is very susceptible to defects. Sound knots do not weaken wood when subject to compression parallel to the grain.

Question: What is wood's breaking strength susceptible to? 
Answer: defects

Question: Depending on the placement and size of a knot, what property of structural timber can be affected?
Answer: stiffness

Question: What do stiffness and elastic strength depend on more than defects?
Answer: sound wood

Question: What direction of compression in relation to its grain won't weaken wood with sound knots in it?
Answer: parallel
Title: Wood

In some decorative applications, wood with knots may be desirable to add visual interest. In applications where wood is painted, such as skirting boards, fascia boards, door frames and furniture, resins present in the timber may continue to 'bleed' through to the surface of a knot for months or even years after manufacture and show as a yellow or brownish stain. A knot primer paint or solution, correctly applied during preparation, may do much to reduce this problem but it is difficult to control completely, especially when using mass-produced kiln-dried timber stocks.

Question: What positive visual component can knots sometimes add to decorative pieces?
Answer: interest

Question: What term is used to describe what knots can do to affect the finish of things made from wood even when they've been painted?
Answer: bleed

Question: Is bleed easy or difficult to control?
Answer: difficult

Question: The stain from a knot bleeding is usually brownish or what other color?
Answer: yellow

Question: In what stage of processing does knot primer need to be applied for maximum effectiveness?
Answer: preparation
Title: Wood

Heartwood (or duramen) is wood that as a result of a naturally occurring chemical transformation has become more resistant to decay. Heartwood formation occurs spontaneously (it is a genetically programmed process). Once heartwood formation is complete, the heartwood is dead. Some uncertainty still exists as to whether heartwood is truly dead, as it can still chemically react to decay organisms, but only once.

Question: What's another word for "duramen"?
Answer: Heartwood

Question: What is heartwood naturally resistant to?
Answer: decay

Question: How does heartwood formation occur due to its being genetically programmed?
Answer: spontaneously

Question: What adjective describes fully formed heartwood?
Answer: dead

Question: Despite being considered dead, what can heartwood have one chemical reaction to?
Answer: decay organisms
Title: Wood

Heartwood is often visually distinct from the living sapwood, and can be distinguished in a cross-section where the boundary will tend to follow the growth rings. For example, it is sometimes much darker. However, other processes such as decay or insect invasion can also discolor wood, even in woody plants that do not form heartwood, which may lead to confusion.

Question: In what part of a tree's cross-section is heartwood visible?
Answer: growth rings

Question: What simple color distinction can heartwood have that makes it stand out from living wood in a tree?
Answer: darker

Question: Along with insect infestation, what process can discolor wood and make it look like heartwood?
Answer: decay

Question: What kind of plants never form heartwood?
Answer: woody

Question: What is the living wood in a tree called?
Answer: sapwood
Title: Wood

Sapwood (or alburnum) is the younger, outermost wood; in the growing tree it is living wood, and its principal functions are to conduct water from the roots to the leaves and to store up and give back according to the season the reserves prepared in the leaves. However, by the time they become competent to conduct water, all xylem tracheids and vessels have lost their cytoplasm and the cells are therefore functionally dead. All wood in a tree is first formed as sapwood. The more leaves a tree bears and the more vigorous its growth, the larger the volume of sapwood required. Hence trees making rapid growth in the open have thicker sapwood for their size than trees of the same species growing in dense forests. Sometimes trees (of species that do form heartwood) grown in the open may become of considerable size, 30 cm or more in diameter, before any heartwood begins to form, for example, in second-growth hickory, or open-grown pines.

Question: What term is interchangeable with "sapwood"?
Answer: alburnum

Question: Is sapwood the younger or older wood in a tree?
Answer: younger

Question: What essential liquid is the sapwood tasked with carrying around a tree?
Answer: water

Question: How much of the wood in a tree is sapwood at some point in its life?
Answer: All

Question: Does a tree growing quickly out in the open have thinner or thicker sapwood for its size than the same kind of tree in a dense forest?
Answer: thicker
Title: Wood

The term heartwood derives solely from its position and not from any vital importance to the tree. This is evidenced by the fact that a tree can thrive with its heart completely decayed. Some species begin to form heartwood very early in life, so having only a thin layer of live sapwood, while in others the change comes slowly. Thin sapwood is characteristic of such species as chestnut, black locust, mulberry, osage-orange, and sassafras, while in maple, ash, hickory, hackberry, beech, and pine, thick sapwood is the rule. Others never form heartwood.

Question: If a tree starts forming heartwood right away, will its sapwood layer be thin or thick?
Answer: thin

Question: What property of heartwood that has nothing to do with how important it is to trees got it its name?
Answer: position

Question: Does a beech tree usually have thin or thick sapwood?
Answer: thick

Question: Does a sassafras tree typically have a thin or thick sapwood layer?
Answer: Thin

Question: Would a thin or a thick sapwood layer be found in a pine tree?
Answer: thick
Title: Wood

No definite relation exists between the annual rings of growth and the amount of sapwood. Within the same species the cross-sectional area of the sapwood is very roughly proportional to the size of the crown of the tree. If the rings are narrow, more of them are required than where they are wide. As the tree gets larger, the sapwood must necessarily become thinner or increase materially in volume. Sapwood is thicker in the upper portion of the trunk of a tree than near the base, because the age and the diameter of the upper sections are less.

Question: What part of a tree is the cross-sectional area of the sapwood approximately proportional to?
Answer: crown

Question: Are more rings necessary if they're narrow or wide?
Answer: narrow

Question: As a tree grows bigger, if the sapwood layer doesn't increase in volume, what will it become?
Answer: thinner

Question: In what part of the tree trunk is the sapwood layer thinnest?
Answer: near the base

Question: Along with the smaller diameter of the upper trunk, what factor leads to thinner sapwood higher up a tree?
Answer: age
Title: Wood

When a tree is very young it is covered with limbs almost, if not entirely, to the ground, but as it grows older some or all of them will eventually die and are either broken off or fall off. Subsequent growth of wood may completely conceal the stubs which will however remain as knots. No matter how smooth and clear a log is on the outside, it is more or less knotty near the middle. Consequently, the sapwood of an old tree, and particularly of a forest-grown tree, will be freer from knots than the inner heartwood. Since in most uses of wood, knots are defects that weaken the timber and interfere with its ease of working and other properties, it follows that a given piece of sapwood, because of its position in the tree, may well be stronger than a piece of heartwood from the same tree.

Question: What usually covers the whole trunk of a very young tree?
Answer: limbs

Question: What evidence of the stubs of the limbs a tree loses can always be seen in the wood?
Answer: knots

Question: In a very old tree, are you more likely to find a lot of knots in the heartwood or the sapwood?
Answer: heartwood

Question: What hides the stubs of a tree's lost limbs from being visible later in its life?
Answer: Subsequent growth

Question: Since knots are defects that weaken lumber, would the heartwood or the sapwood from the same tree be stronger?
Answer: sapwood
Title: Wood

It is remarkable that the inner heartwood of old trees remains as sound as it usually does, since in many cases it is hundreds, and in a few instances thousands, of years old. Every broken limb or root, or deep wound from fire, insects, or falling timber, may afford an entrance for decay, which, once started, may penetrate to all parts of the trunk. The larvae of many insects bore into the trees and their tunnels remain indefinitely as sources of weakness. Whatever advantages, however, that sapwood may have in this connection are due solely to its relative age and position.

Question: What do broken limbs and deep wounds open a door for in a tree?
Answer: decay

Question: Decay can spread to all of what part of a tree?
Answer: the trunk

Question: What growth stage of insects bore holes into trees?
Answer: larvae

Question: What part of a tree often stays impressively sound even when hundreds or thousands of years old?
Answer: inner heartwood

Question: What evidence do some insect larvae leave in a tree forever?
Answer: tunnels
Title: Wood

If a tree grows all its life in the open and the conditions of soil and site remain unchanged, it will make its most rapid growth in youth, and gradually decline. The annual rings of growth are for many years quite wide, but later they become narrower and narrower. Since each succeeding ring is laid down on the outside of the wood previously formed, it follows that unless a tree materially increases its production of wood from year to year, the rings must necessarily become thinner as the trunk gets wider. As a tree reaches maturity its crown becomes more open and the annual wood production is lessened, thereby reducing still more the width of the growth rings. In the case of forest-grown trees so much depends upon the competition of the trees in their struggle for light and nourishment that periods of rapid and slow growth may alternate. Some trees, such as southern oaks, maintain the same width of ring for hundreds of years. Upon the whole, however, as a tree gets larger in diameter the width of the growth rings decreases.

Question: In what stage of its life does a tree usually grow the fastest?
Answer: youth

Question: As a tree ages, do its growth rings usually get wider or narrower?
Answer: narrower

Question: What part of a tree opens and spreads out more as it matures?
Answer: crown

Question: Is wood production of a tree lessened or increased as it ages?
Answer: lessened

Question: Along with nutrients, what do trees growing in forests have to compete for?
Answer: light
Title: Wood

Different pieces of wood cut from a large tree may differ decidedly, particularly if the tree is big and mature. In some trees, the wood laid on late in the life of a tree is softer, lighter, weaker, and more even-textured than that produced earlier, but in other trees, the reverse applies. This may or may not correspond to heartwood and sapwood. In a large log the sapwood, because of the time in the life of the tree when it was grown, may be inferior in hardness, strength, and toughness to equally sound heartwood from the same log. In a smaller tree, the reverse may be true.

Question: When a big tree is cut up, will the pieces of wood differ or all be the same?
Answer: differ

Question: In a large log, will the heartwood or sapwood usually be stronger and tougher?
Answer: heartwood

Question: If you need really hard, strong wood from a small tree, would it likely be better to use the heartwood or sapwood?
Answer: sapwood

Question: Besides big trees, what trees are more likely to have a range of different kinds of wood?
Answer: mature
Title: Wood

In species which show a distinct difference between heartwood and sapwood the natural color of heartwood is usually darker than that of the sapwood, and very frequently the contrast is conspicuous (see section of yew log above). This is produced by deposits in the heartwood of chemical substances, so that a dramatic color difference does not mean a dramatic difference in the mechanical properties of heartwood and sapwood, although there may be a dramatic chemical difference.

Question: When trees have a visible difference in color between sapwood and heartwood, which is darker?
Answer: heartwood

Question: What is deposited naturally in heartwood that changes its color?
Answer: chemical substances

Question: Is the color difference between heartwood and sapwood usually very subtle or conspicuous?
Answer: conspicuous

Question: What type of properties of heartwood and sapwood is often the same even if their colors are very different?
Answer: mechanical

Question: Although heartwood and sapwood might be similar mechanically, if their colors are very different, what other type of difference would they have?
Answer: chemical
Title: Wood

Some experiments on very resinous Longleaf Pine specimens indicate an increase in strength, due to the resin which increases the strength when dry. Such resin-saturated heartwood is called "fat lighter". Structures built of fat lighter are almost impervious to rot and termites; however they are very flammable. Stumps of old longleaf pines are often dug, split into small pieces and sold as kindling for fires. Stumps thus dug may actually remain a century or more since being cut. Spruce impregnated with crude resin and dried is also greatly increased in strength thereby.

Question: What type of tree has resin that makes it stronger when it dries?
Answer: Longleaf Pine

Question: What's the funny name for resin-saturated heartwood?
Answer: fat lighter

Question: What is fat lighter practically impervious to in addition to termites?
Answer: rot

Question: If spruce is shot full of crude resin and dried, which of its properties is increased?
Answer: strength

Question: Since it's highly flammable, what do people often use little pieces of longleaf pine tree stumps for?
Answer: kindling