General Science Mixed Quiz: Set 173

Nitrogen has five electrons in its outer shell and needs three more to complete an octet, so its valency is 3.

The stapedius, only about 1 millimetre long, is the smallest skeletal muscle in the human body. It lies in the middle ear and is attached to the stapes, which is itself the smallest bone of the body.

In rusting, iron combines with oxygen in the presence of water to form hydrated iron oxide, and the addition of oxygen is oxidation.

Luminous intensity is the amount of visible light a source sends out in a given direction per unit solid angle, and its SI base unit is the candela (cd), roughly the light of one ordinary candle.

Quick lime is calcium oxide (CaO), which contains no carbonate, so it gives no carbon dioxide with an acid. Acids release carbon dioxide only from carbonates and hydrogencarbonates: the general reaction is metal carbonate plus acid gives salt, water and carbon dioxide.

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.

This matches the reactivity series, which lists metals from the most to the least reactive. Sodium is near the top: it reacts violently with cold water and is stored under kerosene.

Insulin lowers the level of glucose in the blood by helping the cells take it in and by having the liver store it as glycogen, and a want of insulin or a failure of the body to respond to it causes diabetes mellitus.

At the boiling point, water turns into vapour inside the liquid itself, and these pockets of steam are the bubbles that rise and burst at the surface.

Vitamin A, chemically retinol, is needed to make rhodopsin, the light-sensitive pigment in the rod cells of the retina that lets us see in dim light.

A compound always has a fixed composition by mass, so a variable composition is a property of mixtures, not compounds.

When two heterozygous plants of the first generation are crossed, three quarters of the offspring show the dominant character and one quarter the recessive one, because the recessive appears only when both factors in the pair are recessive.

A rainbow forms because raindrops split white sunlight into its seven colours, and this splitting of light into colours is dispersion.

In 1895, while working with a discharge tube, Roentgen found an unknown radiation that passed through cardboard and flesh but was stopped by bone and metal, and made a screen coated with a fluorescent salt glow.

Water gas is a mixture of carbon monoxide and hydrogen, made by passing steam over red-hot coke. The reaction is C + H2O → CO + H2, carried out at about 1,000 degrees Celsius.

One becquerel is one disintegration per second, and it is the SI unit of the activity of a radioactive source, named after the discoverer of radioactivity.

Fungi have no chlorophyll, so they cannot make their own food by photosynthesis.

Photosynthetic bacteria have no chloroplasts; their pigments sit on infoldings of the cell membrane that form vesicles or sacs, often called chromatophores.

When muscles run short of oxygen, the pyruvate formed from glucose is converted into lactic acid instead of being broken down fully.

The truth is the reverse: hepatitis B has a safe, effective vaccine, while hepatitis C has none. The hepatitis B vaccine has been in use since the 1980s and is given to newborns in India under the Universal Immunisation Programme, with the first dose soon after birth.