General Science Mixed Quiz: Set 13

A rise of 27°C is a rise of 27 K, because one degree Celsius and one kelvin are exactly the same size.

It states that the upthrust on a body dipped fully or partly in a fluid equals the weight of the fluid the body pushes aside.

Find each mass from F = ma, add the masses, then divide the same force by the total. The first block gives m1 = 5 ÷ 10 = 0.5 kg and the second gives m2 = 5 ÷ 20 = 0.25 kg.

In diamond every carbon atom is joined to four other carbon atoms by strong covalent bonds. These bonds point towards the corners of a tetrahedron and build a rigid three-dimensional network that runs through the whole crystal.

The ball falls from 10 m but rises back only 2.5 m, so it keeps one quarter of its energy and loses three quarters.

Calcium oxychloride (CaOCl2) is bleaching powder, and the chlorine it releases removes colour from cotton and linen in the textile industry.

Pressure is thrust per unit area, so its unit is one newton per square metre, and this unit is named the pascal after Blaise Pascal.

Mature red blood cells, or erythrocytes, lose their nucleus before they enter the blood. Losing the nucleus, and the mitochondria too, leaves more room for haemoglobin, the iron-rich protein that carries oxygen, and gives the cell its flexible biconcave disc shape, which lets it squeeze through narrow capillaries.

Heat is a form of energy in transit, so it is measured in the same unit as work and energy, the joule, which is one newton metre.

Air always moves from a region of higher pressure to one of lower pressure, so it flows out of the lungs only when the pressure inside them rises above that of the outside air.

Loudness and frequency are two different properties of sound. Loudness depends on the amplitude of the vibration, that is how far the vibrating part moves from its rest position, while frequency is the number of vibrations made in one second and is measured in hertz.

Each human kidney has about one million nephrons, and every nephron begins with a cup-shaped Bowman's capsule that encloses a knot of capillaries called the glomerulus.

Potential difference between two points of a circuit is the difference in electric potential between them, and it equals the work done in moving a unit positive charge from one point to the other.

The medulla oblongata is the breathing centre of the brain, which is why we keep breathing even while asleep. It is the lowest part of the hindbrain and joins the brain to the spinal cord.

Argon is a noble gas whose outer shell already holds eight electrons, so it has no room to take another one easily; adding an electron would mean starting a new shell, and energy has to be supplied rather than released.

The lens of the eye is made mostly of water and special proteins called crystallins, packed in a very regular order that keeps the lens clear so light can pass straight through to the retina.

Melting and boiling only have to break the weak forces between the molecules, not the strong bonds inside them, so little heat is needed.

Sulphur dioxide dissolves in water to give sulphurous acid, a weak acid with the formula H2SO3, by the reaction SO2 + H2O to H2SO3.

Silver is a noble metal and does not combine with oxygen even when it is heated strongly. Metals react with oxygen according to their place in the reactivity series.

Moss, or Funaria, and Marchantia, a liverwort, are bryophytes, the group called the amphibians of the plant kingdom because they live on land but need water for reproduction.