Curds are a dairy product obtained by curdling (coagulating) milk with rennet or an edible acidic substance such as lemon juice or vinegar, and then draining off the liquid portion. The increased acidity causes the milk proteins (casein) to tangle into solid masses, or curds. The remaining liquid, which contains only whey proteins, is the whey. In cow’s milk, 80% of the proteins are caseins. Milk that has been left to sour (raw milk alone or pasteurized milk with added lactic acid bacteria or yeast) will also naturally produce curds, and sour milk cheese is produced this way. Curd products vary by region and include cottage cheese, quark (both curdled by bacteria and sometimes also rennet) and Indian paneer (milk curdled with lime juice). The word can also refer to a non-dairy substance of similar appearance or consistency, though in these cases a modifier or the word curdled is generally used.

Correct Option: B

Curds are a dairy product obtained by curdling (coagulating) milk with rennet or an edible acidic substance such as lemon juice or vinegar, and then draining off the liquid portion. The increased acidity causes the milk proteins (casein) to tangle into solid masses, or curds. The remaining liquid, which contains only whey proteins, is the whey. In cow’s milk, 80% of the proteins are caseins. Milk that has been left to sour (raw milk alone or pasteurized milk with added lactic acid bacteria or yeast) will also naturally produce curds, and sour milk cheese is produced this way. Curd products vary by region and include cottage cheese, quark (both curdled by bacteria and sometimes also rennet) and Indian paneer (milk curdled with lime juice). The word can also refer to a non-dairy substance of similar appearance or consistency, though in these cases a modifier or the word curdled is generally used.

Oxalic acid is an organic compound with the formula H2C2O2. It is a colourless crystalline solid that dissolves in water to give colourless solutions. It is classified as a dicarboxylic acid. In terms of acid strength, it is much stronger than acetic acid. Oxalic acid is a reducing agent and its conjugate base, known as oxalate , is a chelating agent for metal cations. Typically, oxalic acid occurs as the dihydrate . Ingestion of oxalic acid through skin contact or orally is dangerous. Oxalic acid’s main applications include cleaning or bleaching, especially for the removal of rust, e.g. Bar Keepers Friend is an example of a household cleaner containing oxalic acid. About 25% of produced oxalic acid is used as a mordant in dyeing processes. It is used in bleaches, especially for pulpwood. It is also used in baking powder.

Correct Option: C

Oxalic acid is an organic compound with the formula H2C2O2. It is a colourless crystalline solid that dissolves in water to give colourless solutions. It is classified as a dicarboxylic acid. In terms of acid strength, it is much stronger than acetic acid. Oxalic acid is a reducing agent and its conjugate base, known as oxalate , is a chelating agent for metal cations. Typically, oxalic acid occurs as the dihydrate . Ingestion of oxalic acid through skin contact or orally is dangerous. Oxalic acid’s main applications include cleaning or bleaching, especially for the removal of rust, e.g. Bar Keepers Friend is an example of a household cleaner containing oxalic acid. About 25% of produced oxalic acid is used as a mordant in dyeing processes. It is used in bleaches, especially for pulpwood. It is also used in baking powder.

Copper occurs naturally as native copper and was known to some of the oldest civilizations on record. It has a history of use that is at least 10,000 years old, and estimates of its discovery place it at 9000 BC in the Middle East; a copper pendant was found in northern Iraq that dates to 8700 BC. There is evidence that gold and meteoric iron (but not iron smelting) were the only metals used by humans before copper. The history of copper metallurgy is thought to have followed the following sequence: 1) cold working of native copper, 2) annealing, 3) smelting, and 4) the lost wax method. In southeastern Anatolia, all four of these metallurgical techniques appears more or less simultaneously at the beginning of the Neolithic c. 7500 BC. However, just as agriculture was independently invented in several parts of the world (including Pakistan, China, and the Americas) copper smelting was invented locally in several different places.

Correct Option: A

Copper occurs naturally as native copper and was known to some of the oldest civilizations on record. It has a history of use that is at least 10,000 years old, and estimates of its discovery place it at 9000 BC in the Middle East; a copper pendant was found in northern Iraq that dates to 8700 BC. There is evidence that gold and meteoric iron (but not iron smelting) were the only metals used by humans before copper. The history of copper metallurgy is thought to have followed the following sequence: 1) cold working of native copper, 2) annealing, 3) smelting, and 4) the lost wax method. In southeastern Anatolia, all four of these metallurgical techniques appears more or less simultaneously at the beginning of the Neolithic c. 7500 BC. However, just as agriculture was independently invented in several parts of the world (including Pakistan, China, and the Americas) copper smelting was invented locally in several different places.

Metals typically consist of close-packed atoms, meaning that the atoms are arranged like closely packed spheres. Two packing motifs are common, one being body-centered cubic wherein each metal atom is surrounded by eight equivalent atoms. The other main motif is face-centered cubic where the metal atoms are surrounded by six neighboring atoms. Several metals adopt both structures, depending on the temperature. In a metal, atoms readily lose electrons to form positive ions (cations). Those ions are surrounded by de-localized electrons, which are responsible for the conductivity. The solid thus produced is held together by electrostatic interactions between the ions and the electron cloud, which are called metallic bonds. a conductor is a material which contains movable electric charges. In metallic conductors such as copper or aluminum, the movable charged particles are electrons (see electrical conduction). Positive charges may also be mobile, such as the cationic electrolyte(s) of a battery, or the mobile protons of the proton conductor of a fuel cell. Insulators are non-conducting materials with few mobile charges and which support only insignificant electric currents.

Correct Option: A

Metals typically consist of close-packed atoms, meaning that the atoms are arranged like closely packed spheres. Two packing motifs are common, one being body-centered cubic wherein each metal atom is surrounded by eight equivalent atoms. The other main motif is face-centered cubic where the metal atoms are surrounded by six neighboring atoms. Several metals adopt both structures, depending on the temperature. In a metal, atoms readily lose electrons to form positive ions (cations). Those ions are surrounded by de-localized electrons, which are responsible for the conductivity. The solid thus produced is held together by electrostatic interactions between the ions and the electron cloud, which are called metallic bonds. a conductor is a material which contains movable electric charges. In metallic conductors such as copper or aluminum, the movable charged particles are electrons (see electrical conduction). Positive charges may also be mobile, such as the cationic electrolyte(s) of a battery, or the mobile protons of the proton conductor of a fuel cell. Insulators are non-conducting materials with few mobile charges and which support only insignificant electric currents.

Most of us think as glass as a solid material, but it is actually a super cooled liquid. Molecular units have a disordered arrangement yet still have sufficient cohesion that mechanical rigidity is produced. Glass was first made in the Middle East, approximately during the third millennium BC. Early uses were primarily for vessels or decoration. Glass did not come into use for windows until the first century AD, and was made at that time by casting or hand blowing the glass. Today, glass is a highly engineered material with many different varieties and countless uses. There is float glass, annealed glass, wired glass, tempered glass, safety or laminated glass, leaded glass, heat absorbing glass, low e glass, etc. Supercooling is the process of chilling a liquid below its freezing point, without it becoming solid.

Correct Option: C

Most of us think as glass as a solid material, but it is actually a super cooled liquid. Molecular units have a disordered arrangement yet still have sufficient cohesion that mechanical rigidity is produced. Glass was first made in the Middle East, approximately during the third millennium BC. Early uses were primarily for vessels or decoration. Glass did not come into use for windows until the first century AD, and was made at that time by casting or hand blowing the glass. Today, glass is a highly engineered material with many different varieties and countless uses. There is float glass, annealed glass, wired glass, tempered glass, safety or laminated glass, leaded glass, heat absorbing glass, low e glass, etc. Supercooling is the process of chilling a liquid below its freezing point, without it becoming solid.