rajpurkar/squad huggingface dataset:
Title: Glass

Addition of lead(II) oxide lowers melting point, lowers viscosity of the melt, and increases refractive index. Lead oxide also facilitates solubility of other metal oxides and is used in colored glasses. The viscosity decrease of lead glass melt is very significant (roughly 100 times in comparison with soda glasses); this allows easier removal of bubbles and working at lower temperatures, hence its frequent use as an additive in vitreous enamels and glass solders. The high ionic radius of the Pb2+ ion renders it highly immobile in the matrix and hinders the movement of other ions; lead glasses therefore have high electrical resistance, about two orders of magnitude higher than soda-lime glass (108.5 vs 106.5 Ohm·cm, DC at 250 °C). For more details, see lead glass.

Question: What makes glass melt at a lower temperature?
Answer: lead(II) oxide

Question: How much less viscous is lead glass compared with soda glass?
Answer: 100 times

Question: Pb2+ causes lead glass to have what?
Answer: high electrical resistance

Question: Lead oxide makes it easier to dissolve what?
Answer: other metal oxides
Title: Glass

There are three classes of components for oxide glasses: network formers, intermediates, and modifiers. The network formers (silicon, boron, germanium) form a highly cross-linked network of chemical bonds. The intermediates (titanium, aluminium, zirconium, beryllium, magnesium, zinc) can act as both network formers and modifiers, according to the glass composition. The modifiers (calcium, lead, lithium, sodium, potassium) alter the network structure; they are usually present as ions, compensated by nearby non-bridging oxygen atoms, bound by one covalent bond to the glass network and holding one negative charge to compensate for the positive ion nearby. Some elements can play multiple roles; e.g. lead can act both as a network former (Pb4+ replacing Si4+), or as a modifier.

Question: What components of glass for networks?
Answer: silicon, boron, germanium

Question: What type of components change the network's shape?
Answer: modifiers

Question: What type of component can both make and change networks?
Answer: intermediates

Question: What type of chemical attachment connects ions to the network?
Answer: covalent bond
Title: Glass

The alkali metal ions are small and mobile; their presence in glass allows a degree of electrical conductivity, especially in molten state or at high temperature. Their mobility decreases the chemical resistance of the glass, allowing leaching by water and facilitating corrosion. Alkaline earth ions, with their two positive charges and requirement for two non-bridging oxygen ions to compensate for their charge, are much less mobile themselves and also hinder diffusion of other ions, especially the alkalis. The most common commercial glasses contain both alkali and alkaline earth ions (usually sodium and calcium), for easier processing and satisfying corrosion resistance. Corrosion resistance of glass can be achieved by dealkalization, removal of the alkali ions from the glass surface by reaction with e.g. sulfur or fluorine compounds. Presence of alkaline metal ions has also detrimental effect to the loss tangent of the glass, and to its electrical resistance; glasses for electronics (sealing, vacuum tubes, lamps...) have to take this in account.

Question: What component gives glass the ability to conduct electricity?
Answer: alkali metal ions

Question: How can glass be prevented from corroding?
Answer: dealkalization

Question: What types of ions does typical glass have?
Answer: alkali and alkaline earth ions

Question: Reaction with what causes dealkalization?
Answer: sulfur or fluorine compounds

Question: What can alkaline ions in glass harm, in addition to electrical resistance?
Answer: loss tangent
Title: Glass

New chemical glass compositions or new treatment techniques can be initially investigated in small-scale laboratory experiments. The raw materials for laboratory-scale glass melts are often different from those used in mass production because the cost factor has a low priority. In the laboratory mostly pure chemicals are used. Care must be taken that the raw materials have not reacted with moisture or other chemicals in the environment (such as alkali or alkaline earth metal oxides and hydroxides, or boron oxide), or that the impurities are quantified (loss on ignition). Evaporation losses during glass melting should be considered during the selection of the raw materials, e.g., sodium selenite may be preferred over easily evaporating SeO2. Also, more readily reacting raw materials may be preferred over relatively inert ones, such as Al(OH)3 over Al2O3. Usually, the melts are carried out in platinum crucibles to reduce contamination from the crucible material. Glass homogeneity is achieved by homogenizing the raw materials mixture (glass batch), by stirring the melt, and by crushing and re-melting the first melt. The obtained glass is usually annealed to prevent breakage during processing.

Question: What material is useful in glassmaking because of its slow evaporation?
Answer: sodium selenite

Question: What containers are used for melting?
Answer: platinum crucibles

Question: Why are different materials used in a lab than are used in factory production?
Answer: the cost factor has a low priority

Question: What is the reason for crushing the glass and melting it again?
Answer: homogeneity

Question: Why is glass annealed?
Answer: to prevent breakage
Title: Glass

In the past, small batches of amorphous metals with high surface area configurations (ribbons, wires, films, etc.) have been produced through the implementation of extremely rapid rates of cooling. This was initially termed "splat cooling" by doctoral student W. Klement at Caltech, who showed that cooling rates on the order of millions of degrees per second is sufficient to impede the formation of crystals, and the metallic atoms become "locked into" a glassy state. Amorphous metal wires have been produced by sputtering molten metal onto a spinning metal disk. More recently a number of alloys have been produced in layers with thickness exceeding 1 millimeter. These are known as bulk metallic glasses (BMG). Liquidmetal Technologies sell a number of zirconium-based BMGs. Batches of amorphous steel have also been produced that demonstrate mechanical properties far exceeding those found in conventional steel alloys.

Question: Who coined the term "splat cooling"?
Answer: W. Klement

Question: What are thick alloys made in layers called?
Answer: bulk metallic glasses

Question: What does Liquidmetal Technologies use for their alloys?
Answer: zirconium

Question: What type of metal makes better alloys than traditional steel?
Answer: amorphous steel

Question: At what university was Klement a student?
Answer: Caltech
Title: Glass

In 2004, NIST researchers presented evidence that an isotropic non-crystalline metallic phase (dubbed "q-glass") could be grown from the melt. This phase is the first phase, or "primary phase," to form in the Al-Fe-Si system during rapid cooling. Interestingly, experimental evidence indicates that this phase forms by a first-order transition. Transmission electron microscopy (TEM) images show that the q-glass nucleates from the melt as discrete particles, which grow spherically with a uniform growth rate in all directions. The diffraction pattern shows it to be an isotropic glassy phase. Yet there is a nucleation barrier, which implies an interfacial discontinuity (or internal surface) between the glass and the melt.

Question: Who showed that q-glass could be produced from a melt?
Answer: NIST researchers

Question: What shows that there is an inner surface between glass and melt?
Answer: nucleation barrier

Question: What is q-glass?
Answer: an isotropic non-crystalline metallic phase

Question: What kind of microscope shows that q-glass grows as separate particles?
Answer: Transmission electron
Title: Glass

Glass-ceramic materials share many properties with both non-crystalline glass and crystalline ceramics. They are formed as a glass, and then partially crystallized by heat treatment. For example, the microstructure of whiteware ceramics frequently contains both amorphous and crystalline phases. Crystalline grains are often embedded within a non-crystalline intergranular phase of grain boundaries. When applied to whiteware ceramics, vitreous means the material has an extremely low permeability to liquids, often but not always water, when determined by a specified test regime.

Question: What word means that ceramics don't absorb liquids?
Answer: vitreous

Question: What hardens glass-ceramics?
Answer: heat treatment

Question: What materials do glass ceramics have a lot in common with?
Answer: non-crystalline glass and crystalline ceramics
Title: Glass

The term mainly refers to a mix of lithium and aluminosilicates that yields an array of materials with interesting thermomechanical properties. The most commercially important of these have the distinction of being impervious to thermal shock. Thus, glass-ceramics have become extremely useful for countertop cooking. The negative thermal expansion coefficient (CTE) of the crystalline ceramic phase can be balanced with the positive CTE of the glassy phase. At a certain point (~70% crystalline) the glass-ceramic has a net CTE near zero. This type of glass-ceramic exhibits excellent mechanical properties and can sustain repeated and quick temperature changes up to 1000 °C.

Question: How high of a temperature change can glass-ceramics handle?
Answer: 1000 °C

Question: Because of their heat resistance, glass-ceramics are especially suitable for what?
Answer: countertop cooking

Question: What is the most economically significant property of glass-ceramics?
Answer: impervious to thermal shock

Question: What ingredients give glass-ceramics its useful heat tolerance?
Answer: lithium and aluminosilicates

Question: What proportion of crystalline ceramics yields a product with a CTE of around 0?
Answer: ~70%
Title: Glass

Mass production of glass window panes in the early twentieth century caused a similar effect. In glass factories, molten glass was poured onto a large cooling table and allowed to spread. The resulting glass is thicker at the location of the pour, located at the center of the large sheet. These sheets were cut into smaller window panes with nonuniform thickness, typically with the location of the pour centered in one of the panes (known as "bull's-eyes") for decorative effect. Modern glass intended for windows is produced as float glass and is very uniform in thickness.

Question: What were the areas at the center of an old sheet of glass called?
Answer: bull's-eyes

Question: In early 20th century glass production, the glass was thickest at what part of the sheet?
Answer: the center

Question: Currently window glass is made as what?
Answer: float glass

Question: How was the bull's-eye used?
Answer: for decorative effect
Title: Glass

The observation that old windows are sometimes found to be thicker at the bottom than at the top is often offered as supporting evidence for the view that glass flows over a timescale of centuries, the assumption being that the glass has exhibited the liquid property of flowing from one shape to another. This assumption is incorrect, as once solidified, glass stops flowing. The reason for the observation is that in the past, when panes of glass were commonly made by glassblowers, the technique used was to spin molten glass so as to create a round, mostly flat and even plate (the crown glass process, described above). This plate was then cut to fit a window. The pieces were not absolutely flat; the edges of the disk became a different thickness as the glass spun. When installed in a window frame, the glass would be placed with the thicker side down both for the sake of stability and to prevent water accumulating in the lead cames at the bottom of the window. Occasionally such glass has been found installed with the thicker side at the top, left or right.

Question: What was the benefit of installing glass with the thick side at the bottom, in addition to avoiding water accumulation?
Answer: stability

Question: Who used to make window panes?
Answer: glassblowers

Question: What is the name for the glassmaking method that involved spinning it into sheets?
Answer: crown glass process

Question: The thickness at the bottom of glass panes was once taken as evidence that glass had features of what state of matter?
Answer: liquid

Question: When does glass stop moving like a liquid?
Answer: once solidified
Title: Glass

In physics, the standard definition of a glass (or vitreous solid) is a solid formed by rapid melt quenching. The term glass is often used to describe any amorphous solid that exhibits a glass transition temperature Tg. If the cooling is sufficiently rapid (relative to the characteristic crystallization time) then crystallization is prevented and instead the disordered atomic configuration of the supercooled liquid is frozen into the solid state at Tg. The tendency for a material to form a glass while quenched is called glass-forming ability. This ability can be predicted by the rigidity theory. Generally, the structure of a glass exists in a metastable state with respect to its crystalline form, although in certain circumstances, for example in atactic polymers, there is no crystalline analogue of the amorphous phase.

Question: How is "glass" defined in physics?
Answer: a solid formed by rapid melt quenching

Question: What is the tendency to make a glass when cooled called?
Answer: glass-forming ability

Question: What must happen quickly for glass to form?
Answer: cooling

Question: What predicts glass-forming ability?
Answer: rigidity theory
Title: Glass

Some people consider glass to be a liquid due to its lack of a first-order phase transition where certain thermodynamic variables such as volume, entropy and enthalpy are discontinuous through the glass transition range. The glass transition may be described as analogous to a second-order phase transition where the intensive thermodynamic variables such as the thermal expansivity and heat capacity are discontinuous. Nonetheless, the equilibrium theory of phase transformations does not entirely hold for glass, and hence the glass transition cannot be classed as one of the classical equilibrium phase transformations in solids.

Question: What does glass not have, leading some to think it is a liquid?
Answer: first-order phase transition

Question: What theory isn't completely valid for glass?
Answer: equilibrium theory of phase transformations

Question: Transition in glass is comparable to what?
Answer: a second-order phase transition
Title: Glass

Although the atomic structure of glass shares characteristics of the structure in a supercooled liquid, glass tends to behave as a solid below its glass transition temperature. A supercooled liquid behaves as a liquid, but it is below the freezing point of the material, and in some cases will crystallize almost instantly if a crystal is added as a core. The change in heat capacity at a glass transition and a melting transition of comparable materials are typically of the same order of magnitude, indicating that the change in active degrees of freedom is comparable as well. Both in a glass and in a crystal it is mostly only the vibrational degrees of freedom that remain active, whereas rotational and translational motion is arrested. This helps to explain why both crystalline and non-crystalline solids exhibit rigidity on most experimental time scales.

Question: Atomically, glass is similar to what?
Answer: a supercooled liquid

Question: What acts like a liquid but is under the freezing temperature?
Answer: A supercooled liquid

Question: Despite its atomic structure, cooled glass acts like what?
Answer: a solid

Question: In cooled glass, what types of movement stop?
Answer: rotational and translational
Title: Renewable_energy_commercialization

Public policy and political leadership helps to "level the playing field" and drive the wider acceptance of renewable energy technologies. Countries such as Germany, Denmark, and Spain have led the way in implementing innovative policies which has driven most of the growth over the past decade. As of 2014, Germany has a commitment to the "Energiewende" transition to a sustainable energy economy, and Denmark has a commitment to 100% renewable energy by 2050. There are now 144 countries with renewable energy policy targets.

Question: What drives the wider acceptance of renewable energy technologies?
Answer: Public policy and political leadership

Question: Denmark has a committment to 100 percent renewable energy by what year?
Answer: 2050

Question: How many countries now have renewable energy policies?
Answer: 144
Title: Renewable_energy_commercialization

Total investment in renewable energy (including small hydro-electric projects) was $244 billion in 2012, down 12% from 2011 mainly due to dramatically lower solar prices and weakened US and EU markets. As a share of total investment in power plants, wind and solar PV grew from 14% in 2000 to over 60% in 2012. The top countries for investment in recent years were China, Germany, Spain, the United States, Italy, and Brazil. Renewable energy companies include BrightSource Energy, First Solar, Gamesa, GE Energy, Goldwind, Sinovel, Trina Solar, Vestas and Yingli.

Question: How much was the total investment in renewable energy in 2012?
Answer: $244 billion

Question: Why did the total investment in renewable energy go down in 2012?
Answer: dramatically lower solar prices

Question: What  six were the top countries for investment in recent years?
Answer: China, Germany, Spain, the United States, Italy, and Brazil
Title: Renewable_energy_commercialization

EU member countries have shown support for ambitious renewable energy goals. In 2010, Eurobarometer polled the twenty-seven EU member states about the target "to increase the share of renewable energy in the EU by 20 percent by 2020". Most people in all twenty-seven countries either approved of the target or called for it to go further. Across the EU, 57 percent thought the proposed goal was "about right" and 16 percent thought it was "too modest." In comparison, 19 percent said it was "too ambitious".

Question: Who has shown support for ambitious renewable energy goals?
Answer: EU member countries

Question: What group polled the 27 EU member states in 2010?
Answer: Eurobarometer

Question: The goal was to increase the share of renewable energy in the EU by 20 percent in what year?
Answer: 2020
Title: Renewable_energy_commercialization

By the end of 2011, total renewable power capacity worldwide exceeded 1,360 GW, up 8%. Renewables producing electricity accounted for almost half of the 208 GW of capacity added globally during 2011. Wind and solar photovoltaics (PV) accounted for almost 40% and 30% . Based on REN21's 2014 report, renewables contributed 19 percent to our energy consumption and 22 percent to our electricity generation in 2012 and 2013, respectively. This energy consumption is divided as 9% coming from traditional biomass, 4.2% as heat energy (non-biomass), 3.8% hydro electricity and 2% electricity from wind, solar, geothermal, and biomass.

Question: By the end of 2011, total renewable power capacity worldwide exceeded what number?
Answer: 1,360 GW

Question: Renewables contributed what percentage to our energy consumption?
Answer: 19 percent

Question: Renewables contributed what percentage to our electricity generation?
Answer: 22 percent
Title: Renewable_energy_commercialization

During the five-years from the end of 2004 through 2009, worldwide renewable energy capacity grew at rates of 10–60 percent annually for many technologies. In 2011, UN under-secretary general Achim Steiner said: "The continuing growth in this core segment of the green economy is not happening by chance. The combination of government target-setting, policy support and stimulus funds is underpinning the renewable industry's rise and bringing the much needed transformation of our global energy system within reach." He added: "Renewable energies are expanding both in terms of investment, projects and geographical spread. In doing so, they are making an increasing contribution to combating climate change, countering energy poverty and energy insecurity".

Question: Who was the UN under-secretary in 2011?
Answer: Achim Steiner

Question: Between what years did worldwide renewable energy capacity grow at rates of 10 to 60 percent annually?
Answer: 2004 through 2009

Question: Who is Achim Steiner?
Answer: UN under-secretary general
Title: Renewable_energy_commercialization

According to a 2011 projection by the International Energy Agency, solar power plants may produce most of the world's electricity within 50 years, significantly reducing the emissions of greenhouse gases that harm the environment. The IEA has said: "Photovoltaic and solar-thermal plants may meet most of the world's demand for electricity by 2060 – and half of all energy needs – with wind, hydropower and biomass plants supplying much of the remaining generation". "Photovoltaic and concentrated solar power together can become the major source of electricity".

Question: Which group projected that solar plant may produce most of the world's electricity within 50 years?
Answer: International Energy Agency

Question: Photovoltaic and solar-thermal plants may meet most of the world's demand for electricity by what year?
Answer: 2060

Question: Photovoltaic and solar-thermal plants may meet how much of the world's energy needs by 2060?
Answer: half
Title: Renewable_energy_commercialization

In 2013, China led the world in renewable energy production, with a total capacity of 378 GW, mainly from hydroelectric and wind power. As of 2014, China leads the world in the production and use of wind power, solar photovoltaic power and smart grid technologies, generating almost as much water, wind and solar energy as all of France and Germany's power plants combined. China's renewable energy sector is growing faster than its fossil fuels and nuclear power capacity. Since 2005, production of solar cells in China has expanded 100-fold. As Chinese renewable manufacturing has grown, the costs of renewable energy technologies have dropped. Innovation has helped, but the main driver of reduced costs has been market expansion.

Question: Who led the world in renewable energy production in 2013?
Answer: China

Question: Since what year has production of solar cells in China expanded 100-fold?
Answer: 2005

Question: What is the main driver of reduced costs?
Answer: market expansion
Title: Renewable_energy_commercialization

Renewable energy technologies are getting cheaper, through technological change and through the benefits of mass production and market competition. A 2011 IEA report said: "A portfolio of renewable energy technologies is becoming cost-competitive in an increasingly broad range of circumstances, in some cases providing investment opportunities without the need for specific economic support," and added that "cost reductions in critical technologies, such as wind and solar, are set to continue." As of 2011[update], there have been substantial reductions in the cost of solar and wind technologies:

Question: What is getting cheaper as a result of technilogical change?
Answer: Renewable energy technologies

Question: As of what year have there been substantial reductions in the cost of solar and wind technologies?
Answer: 2011

Question: What group stated that "cost reductions in critical technologies, such as wind and solar, are set to continue?"
Answer: IEA