rajpurkar/squad huggingface dataset:
Title: Wood

Since the latewood of a growth ring is usually darker in color than the earlywood, this fact may be used in judging the density, and therefore the hardness and strength of the material. This is particularly the case with coniferous woods. In ring-porous woods the vessels of the early wood not infrequently appear on a finished surface as darker than the denser latewood, though on cross sections of heartwood the reverse is commonly true. Except in the manner just stated the color of wood is no indication of strength.

Question: Which of the wood in a growth ring is usually darker?
Answer: latewood

Question: Which property of a tree's wood that gives clues about its strength and hardness can be judged by it's color?
Answer: density

Question: What category of trees show this difference greatly?
Answer: coniferous

Question: What type of woods might sometimes appear to have darker earlywood on a finished surface?
Answer: ring-porous

Question: With the exception of earlywood/latewood difference in some types of trees, how much of an indication of strength is a wood's color?
Answer: no indication
Title: Wood

Abnormal discoloration of wood often denotes a diseased condition, indicating unsoundness. The black check in western hemlock is the result of insect attacks. The reddish-brown streaks so common in hickory and certain other woods are mostly the result of injury by birds. The discoloration is merely an indication of an injury, and in all probability does not of itself affect the properties of the wood. Certain rot-producing fungi impart to wood characteristic colors which thus become symptomatic of weakness; however an attractive effect known as spalting produced by this process is often considered a desirable characteristic. Ordinary sap-staining is due to fungal growth, but does not necessarily produce a weakening effect.

Question: What condition does an abnormal color usually indicate in wood?
Answer: diseased

Question: What other property can you assume of wood that is diseased?
Answer: unsoundness

Question: What causes the black checked pattern in the wood of western hemlocks?
Answer: insect attacks

Question: What animals cause the reddish-brown streaks of color in hickory wood?
Answer: birds

Question: What's the name for the pretty coloring effect caused in some wood by rot-producing fungi?
Answer: spalting
Title: Wood

In heartwood it occurs only in the first and last forms. Wood that is thoroughly air-dried retains 8–16% of the water in the cell walls, and none, or practically none, in the other forms. Even oven-dried wood retains a small percentage of moisture, but for all except chemical purposes, may be considered absolutely dry.

Question: What does wood retain in its cell walls despite being air-dried?
Answer: water

Question: Air-dried wood keeps up to what percentage of the water in its cell walls?
Answer: 16

Question: What kind of dried wood retains a small quantity of water but is considered absolutely dry?
Answer: oven-dried
Title: Wood

The general effect of the water content upon the wood substance is to render it softer and more pliable. A similar effect of common observation is in the softening action of water on rawhide, paper, or cloth. Within certain limits, the greater the water content, the greater its softening effect.

Question: Often the water in wood makes it more pliable and what else?
Answer: softer

Question: What material sometimes used for dog chews reacts similarly to wood because of its water content?
Answer: rawhide

Question: What material we use to write or print on, like wood, becomes softer and more pliable when wet?
Answer: paper

Question: When water content increases within certain limits in wood, does is have a less or greater softening effect?
Answer: greater

Question: What type of action does water create in cloth?
Answer: softening
Title: Wood

Drying produces a decided increase in the strength of wood, particularly in small specimens. An extreme example is the case of a completely dry spruce block 5 cm in section, which will sustain a permanent load four times as great as a green (undried) block of the same size will.

Question: What will drying often increase in wood?
Answer: strength

Question: What color is also used interchangeably with "undried" for wood?
Answer: green

Question: What type of wood can hold four times as much of a load when dried?
Answer: spruce
Title: Wood

The greatest strength increase due to drying is in the ultimate crushing strength, and strength at elastic limit in endwise compression; these are followed by the modulus of rupture, and stress at elastic limit in cross-bending, while the modulus of elasticity is least affected.

Question: What type of "ultimate" strength is one of the two types increased the most by drying wood?
Answer: crushing

Question: What property of wood is least affected by drying?
Answer: elasticity

Question: Is strength at elastic limit in endwise compression or stress at elastic limit in cross-bending increased more by drying wood?
Answer: strength at elastic limit in endwise compression

Question: Is the strength of the modulus of rupture or elasticity increased more when wood is dried?
Answer: modulus of rupture
Title: Wood

Wood is a heterogeneous, hygroscopic, cellular and anisotropic material. It consists of cells, and the cell walls are composed of micro-fibrils of cellulose (40% – 50%) and hemicellulose (15% – 25%) impregnated with lignin (15% – 30%).

Question: Along with hygroscopic, cellular, and anisotropic, how is the material of wood described?
Answer: heterogeneous

Question: What does wood consist of?
Answer: cells

Question: What part of wood's cells are composed of cellulose and hemicellulose?
Answer: walls

Question: What makes up 40-50% of the cell walls in wood?
Answer: cellulose

Question: What substance is hemicellulose impregnated with?
Answer: lignin
Title: Wood

In coniferous or softwood species the wood cells are mostly of one kind, tracheids, and as a result the material is much more uniform in structure than that of most hardwoods. There are no vessels ("pores") in coniferous wood such as one sees so prominently in oak and ash, for example.

Question: What type of cells makes up most wood cells in coniferous trees?
Answer: tracheids

Question: Are hardwood or softwood species more uniform in structure?
Answer: softwood

Question: What are the visible vessels in hardwoods commonly called?
Answer: pores

Question: What hardwood that starts with the letter "O" would have pores?
Answer: oak

Question: Besides oak, what's an example of a hardwood with prominent pores?
Answer: ash
Title: Wood

The structure of hardwoods is more complex. The water conducting capability is mostly taken care of by vessels: in some cases (oak, chestnut, ash) these are quite large and distinct, in others (buckeye, poplar, willow) too small to be seen without a hand lens. In discussing such woods it is customary to divide them into two large classes, ring-porous and diffuse-porous.

Question: Is the structure of hardwood simple or complex?
Answer: complex

Question: What handles most of the water conduction in hardwoods?
Answer: vessels

Question: Are the vessels in chestnut wood large or small?
Answer: large

Question: In wood from a willow tree, what would you need to use to see the tiny vessels?
Answer: a hand lens

Question: Besides ring-porous, what's the other class hardwoods are often divided into?
Answer: diffuse-porous
Title: Wood

In ring-porous species, such as ash, black locust, catalpa, chestnut, elm, hickory, mulberry, and oak, the larger vessels or pores (as cross sections of vessels are called) are localised in the part of the growth ring formed in spring, thus forming a region of more or less open and porous tissue. The rest of the ring, produced in summer, is made up of smaller vessels and a much greater proportion of wood fibers. These fibers are the elements which give strength and toughness to wood, while the vessels are a source of weakness.[citation needed]

Question: What species of hardwood are hickory and mulberry trees?
Answer: ring-porous

Question: In what season do the growth-rings of ring-porous species form with larger vessels localized?
Answer: spring

Question: In what season does the part of the growth-ring with smaller vessels form in ring-porous species?
Answer: summer

Question: What fibers does the summer's section of growth-ring have more of?
Answer: wood fibers

Question: Along with strength, what property do wood fibers lend to wood?
Answer: toughness
Title: Wood

In diffuse-porous woods the pores are evenly sized so that the water conducting capability is scattered throughout the growth ring instead of being collected in a band or row. Examples of this kind of wood are alder, basswood,[citation needed] birch, buckeye, maple, willow,and the Populus species such as aspen, cottonwood and poplar. Some species, such as walnut and cherry, are on the border between the two classes, forming an intermediate group.[citation needed]

Question: What kind of woods have pores that are uniformly sized?
Answer: diffuse-porous

Question: What species do aspen, cottonwood, and poplar trees belong to?
Answer: Populus

Question: With walnut, what's another tree in the intermediate group?
Answer: cherry

Question: What capability is spread through the growth ring in ring-porous species?
Answer: water conducting

Question: Is maple wood diffuse-porous or ring-porous?
Answer: diffuse-porous
Title: Wood

In temperate softwoods there often is a marked difference between latewood and earlywood. The latewood will be denser than that formed early in the season. When examined under a microscope the cells of dense latewood are seen to be very thick-walled and with very small cell cavities, while those formed first in the season have thin walls and large cell cavities. The strength is in the walls, not the cavities. Hence the greater the proportion of latewood the greater the density and strength. In choosing a piece of pine where strength or stiffness is the important consideration, the principal thing to observe is the comparative amounts of earlywood and latewood. The width of ring is not nearly so important as the proportion and nature of the latewood in the ring.

Question: What kind of softwoods often have significant differences in their earlywood and latewood?
Answer: temperate

Question: Is latewood denser or less dense than earlywood?
Answer: denser

Question: Does strength come from the walls or cavities of wood cells?
Answer: walls

Question: Are the cell walls of earlywood thick or thin?
Answer: thin

Question: What general size are the cavities in the cells of very dense latewood?
Answer: very small
Title: Wood

If a heavy piece of pine is compared with a lightweight piece it will be seen at once that the heavier one contains a larger proportion of latewood than the other, and is therefore showing more clearly demarcated growth rings. In white pines there is not much contrast between the different parts of the ring, and as a result the wood is very uniform in texture and is easy to work. In hard pines, on the other hand, the latewood is very dense and is deep-colored, presenting a very decided contrast to the soft, straw-colored earlywood.

Question: Comparing a heavy and a lightweight piece of wood from a pine, which would have a greater proportion of latewood?
Answer: heavy

Question: What feature of a piece of pine with more latewood would be more clear and pronounced?
Answer: growth rings

Question: What type of tree has very little contrast between parts of its growth rings?
Answer: white pines

Question: Is white pine easy or difficult to work with because of its texture?
Answer: easy

Question: What kind of pines have very deep, darkly colored hardwood that stands out against the light earlywood?
Answer: hard pines
Title: Wood

It is not only the proportion of latewood, but also its quality, that counts. In specimens that show a very large proportion of latewood it may be noticeably more porous and weigh considerably less than the latewood in pieces that contain but little. One can judge comparative density, and therefore to some extent strength, by visual inspection.

Question: Having a high proportion of latewood isn't all that matters; what else is important?
Answer: quality

Question: What can we judge in wood just by looking at it?
Answer: comparative density

Question: What property of wood could we project some indication of by looking at its density?
Answer: strength

Question: What could we call some specimens with a high proportion of latewood that explains why they weigh less than specimens with much less latewood?
Answer: porous
Title: Wood

No satisfactory explanation can as yet be given for the exact mechanisms determining the formation of earlywood and latewood. Several factors may be involved. In conifers, at least, rate of growth alone does not determine the proportion of the two portions of the ring, for in some cases the wood of slow growth is very hard and heavy, while in others the opposite is true. The quality of the site where the tree grows undoubtedly affects the character of the wood formed, though it is not possible to formulate a rule governing it. In general, however, it may be said that where strength or ease of working is essential, woods of moderate to slow growth should be chosen.

Question: What facet of wood is affected to some degree by the place where the tree grows?
Answer: character

Question: If you want wood that's easy to work with, what kind of growth would you want the tree to have?
Answer: moderate to slow

Question: What species of tree can be said to growth ring proportions that aren't determined just by their rate of growth?
Answer: conifers

Question: What counterpart of earlywood are scientists still trying to explain the formation of?
Answer: latewood

Question: While there is some relationship between where and how a tree grows, what can't anyone formulate to govern it?
Answer: a rule
Title: Wood

In ring-porous woods each season's growth is always well defined, because the large pores formed early in the season abut on the denser tissue of the year before.

Question: What kind of woods always have very clearly marked seasonal growth?
Answer: ring-porous

Question: What size pores form early in ring-porous woods' growing season?
Answer: large

Question: When does the denser tissue the new pores abut come from?
Answer: the year before
Title: Wood

In the case of the ring-porous hardwoods there seems to exist a pretty definite relation between the rate of growth of timber and its properties. This may be briefly summed up in the general statement that the more rapid the growth or the wider the rings of growth, the heavier, harder, stronger, and stiffer the wood. This, it must be remembered, applies only to ring-porous woods such as oak, ash, hickory, and others of the same group, and is, of course, subject to some exceptions and limitations.

Question: Ring-porous hardwoods have a clear relationship between their properties and what other factor?
Answer: rate of growth

Question: Is harder, heavier wood indicated by narrower or wider growth rings?
Answer: wider

Question: What kind of wood with a name that starts with "H" is a ring-porous hardwood?
Answer: hickory

Question: If the growth rings are wider, was the growth of the tree slower or more rapid?
Answer: more rapid

Question: What is the only kind of wood that will definitely be harder and stronger when it grows faster?
Answer: ring-porous
Title: Wood

In ring-porous woods of good growth it is usually the latewood in which the thick-walled, strength-giving fibers are most abundant. As the breadth of ring diminishes, this latewood is reduced so that very slow growth produces comparatively light, porous wood composed of thin-walled vessels and wood parenchyma. In good oak these large vessels of the earlywood occupy from 6 to 10 percent of the volume of the log, while in inferior material they may make up 25% or more. The latewood of good oak is dark colored and firm, and consists mostly of thick-walled fibers which form one-half or more of the wood. In inferior oak, this latewood is much reduced both in quantity and quality. Such variation is very largely the result of rate of growth.

Question: Which specific type of wood within ring-porous woods have more fibers to make it strong?
Answer: latewood

Question: When there is less latewood, what is diminishing?
Answer: breadth of ring

Question: Does slow or rapid growth make relatively porous, light wood?
Answer: slow

Question: What kind of oak has just 6-10% volume of large vessels in the log?
Answer: good

Question: What kind of fibers are in the latewood of good oak, making it very firm?
Answer: thick-walled
Title: Wood

Wide-ringed wood is often called "second-growth", because the growth of the young timber in open stands after the old trees have been removed is more rapid than in trees in a closed forest, and in the manufacture of articles where strength is an important consideration such "second-growth" hardwood material is preferred. This is particularly the case in the choice of hickory for handles and spokes. Here not only strength, but toughness and resilience are important. The results of a series of tests on hickory by the U.S. Forest Service show that:

Question: What term is sometimes used for wood with wide rings?
Answer: second-growth

Question: Do young trees grow more quickly in open stands or in a closed forest?
Answer: open stands

Question: What property is important to manufacturers who use "second-growth" hardwood?
Answer: strength

Question: What specific kind of "second-growth" hardwood is often used to make handles and spokes? 
Answer: hickory

Question: What organization tested hickory to find out about its properties?
Answer: U.S. Forest Service
Title: Wood

In the diffuse-porous woods, the demarcation between rings is not always so clear and in some cases is almost (if not entirely) invisible to the unaided eye. Conversely, when there is a clear demarcation there may not be a noticeable difference in structure within the growth ring.

Question: What kind of wood often has ring divisions that can't even be seen by looking at it?
Answer: diffuse-porous

Question: In diffuse-porous woods, if the demarcation between rings is obvious, what type of difference within the ring might not be?
Answer: structure

Question: What adjective describes how our eyes function without a tool like a microscope to help?
Answer: unaided
Title: Wood

In diffuse-porous woods, as has been stated, the vessels or pores are even-sized, so that the water conducting capability is scattered throughout the ring instead of collected in the earlywood. The effect of rate of growth is, therefore, not the same as in the ring-porous woods, approaching more nearly the conditions in the conifers. In general it may be stated that such woods of medium growth afford stronger material than when very rapidly or very slowly grown. In many uses of wood, total strength is not the main consideration. If ease of working is prized, wood should be chosen with regard to its uniformity of texture and straightness of grain, which will in most cases occur when there is little contrast between the latewood of one season's growth and the earlywood of the next.

Question: What kind of wood has all similarly sized vessels?
Answer: diffuse-porous

Question: What rate of growth in a tree will make the wood from it stronger than trees that grow very slowly or very quickly?
Answer: medium

Question: The capability of diffuse-porous woods to carry what substance is spread out in the growth ring?
Answer: water

Question: What division of trees are diffuse-porous woods more similar in growth rate to than ring-porous woods?
Answer: conifers

Question: Does uniformity of the texture and grain of wood usually result from much or little contrast between earlywood and latewood?
Answer: little
Title: Wood

Structural material that resembles ordinary, "dicot" or conifer wood in its gross handling characteristics is produced by a number of monocot plants, and these also are colloquially called wood. Of these, bamboo, botanically a member of the grass family, has considerable economic importance, larger culms being widely used as a building and construction material in their own right and, these days, in the manufacture of engineered flooring, panels and veneer. Another major plant group that produce material that often is called wood are the palms. Of much less importance are plants such as Pandanus, Dracaena and Cordyline. With all this material, the structure and composition of the structural material is quite different from ordinary wood.

Question: What's another term used for "conifer" wood?
Answer: dicot

Question: What type of plants produce material that is referred to as "wood" even though it is technically not?
Answer: monocot

Question: What monocot plant produces "wood" by the same name that's often used for flooring and veneer?
Answer: bamboo

Question: While we call bamboo "wood," what botanical family does it belong to?
Answer: grass

Question: Along with bamboo, what's the other monocot that's a major source of so-called "wood"?
Answer: palms
Title: Wood

The single most revealing property of wood as an indicator of wood quality is specific gravity (Timell 1986), as both pulp yield and lumber strength are determined by it. Specific gravity is the ratio of the mass of a substance to the mass of an equal volume of water; density is the ratio of a mass of a quantity of a substance to the volume of that quantity and is expressed in mass per unit substance, e.g., grams per millilitre (g/cm3 or g/ml). The terms are essentially equivalent as long as the metric system is used. Upon drying, wood shrinks and its density increases. Minimum values are associated with green (water-saturated) wood and are referred to as basic specific gravity (Timell 1986).

Question: Which property of wood reveals the most about its quality?
Answer: specific gravity

Question: In addition to lumber strength, what important indicator of wood's quality can be determined using specific gravity?
Answer: pulp yield

Question: What measurement is expressed in mass per unit substance?
Answer: density

Question: When wood dries and shrinks, what happens to its density?
Answer: increases

Question: When wood is described as "green," what does "green" mean?
Answer: water-saturated
Title: Wood

Wood density is determined by multiple growth and physiological factors compounded into “one fairly easily measured wood characteristic” (Elliott 1970).

Question: Along with growth, what kind of factors determine the density of wood?
Answer: physiological

Question: Into how many characteristics are the factors of wood combined?
Answer: one

Question: What author called wood's density "fairly easily measured"?
Answer: Elliott
Title: Wood

Age, diameter, height, radial growth, geographical location, site and growing conditions, silvicultural treatment, and seed source, all to some degree influence wood density. Variation is to be expected. Within an individual tree, the variation in wood density is often as great as or even greater than that between different trees (Timell 1986). Variation of specific gravity within the bole of a tree can occur in either the horizontal or vertical direction. :)

Question: What should be anticipated because of the many factors that influence wood's density?
Answer: Variation

Question: What specific type of growth has an effect on the density of wood?
Answer: radial

Question: Which part of a tree can have vertical or horizontal variation in its specific gravity?
Answer: bole

Question: Variation in what measurement is sometimes greater within one tree than from one tree to another?
Answer: density

Question: What tiny object's source plays a role in determining wood density?
Answer: seed