a unit of energy widely used to measure the chemical energy in food. It is equal to the amount of heat energy required to raise the temperature of 1 gram of water 1°C and is equivalent to 4.184 joule. Some confusion exists when this term is used in the context of food where the kilocalorie is also used, but is often written as Calorie or Cal. One Calorie (or ‘large’ calorie - capital C) is equal to one kilocalorie (or 1000 calories – small c).
Capillaries are the smallest of a body's blood vessels which connect arteries and veins. They are important for the exchange of gases, such as oxygen and carbon dioxide, and other substances between the blood and cells. The walls of capillaries are very thin and are often composed of only a single layer of cells. This allows molecules such as oxygen and water and waste products such as carbon dioxide and
urea to pass through them. This property of capillary walls is critical to the role that the circulatory system has in collecting and transporting different substances to and from different parts of our bodies.
A characteristic is a distinguishing feature or quality of an organism that helps to define, identify or describe it.
A chemical bond is a non contact force holding atoms together in a combined state. This force may result from the attraction of opposite charges (ionic bond), the magnetic and electrical attraction of shared electrons (covalent bond), or a combination of these attractions.
Chromosomes are thread-like bodies, usually x shaped and usually found in pairs in the nuclei of living cells. They carry genetic information that determines the inherited characteristics of an organism. Chromosomes consist of deoxyribonucleic acid (DNA) and proteins and each chromosome can be regarded as comprising a number of genes. Each species can be characterised by the number of chromosomes that its cells contain, for example, humans usually have 46 chromosomes per cell (23 pairs).
The circulatory system contains the blood vessels (arteries, veins and capillaries) and heart which moves blood throughout the body. Among other things this system provides oxygen and nutrients to cells and aids them in the removal of waste products, fighting infection and general repair.
A closed system is a continuous predetermined or prescribed pathway. It may be useful to think of the analogy of trains on a railway line where the trains move around the same track and goods can be transported around the pathway. In the human body the circulatory system is an example of a closed system. The blood travels along a defined, closed pathway of tubular blood vessels comprising a complex system of arteries, capillaries and veins. The blood is contained within this connected system and circulates continuously, never leaving this pathway. Some invertebrate animals such as molluscs, arthropods (such as insects and spiders) have an 'open' circulatory system where organs are bathed in a surrounding fluid which is not contained by tubular vessels. In such an open circulatory system there is no predetermined pathway and there is no distinction between blood and other tissue fluid.
A colloid is formed by the suspension of droplets of liquid or solid particles which are small enough to be kept in constant motion by the molecular movement of the suspending medium. The particles may be suspended in either a liquid or a gas and will not settle out of suspension under the action of gravity alone. Examples are smoke, milk, mayonnaise, whipped cream and aerosols.
Combustion describes the process of burning (rapid oxidation) in which oxygen is chemically combined with a fuel to release energy in the form of light and heat. Combustion occurs in the gaseous state for example, when a candle or wooden log is burning, for example, the reaction (and hence the flame) is always just above the fuel. The variation in ignition temperatures of different fuels reflect the different temperatures needed to get either the fuel or (in cases such as wood) decomposition products of the fuel into the gas state.
any material that does allow electricity to flow through it easily because the electrons in their atoms are able to easily from atom to atom. Most metals are very good conductors. A poor electrical conductor is said to be a good electrical insulator.
A compound is formed by the combination of two or more atoms from different elements in a fixed proportion. The elements in a compound combine to lose their individual properties and to form a substance with new physical and chemical properties.
The application of a compression force to an object causes it to become squashed or compacted. Some solid materials like stone and ceramics are able to withstand very large compressive forces with very little measurable deformation which make them a suitable building material for the construction of high walls and columns.
A concentrate is a mixture that has had the majority of its base component, or solvent, removed. Typically this will be the removal of water from a solution or suspension such as the removal of water from fruit juice. The term is also used to describe the removal of much of the unwanted solid matter from a mined ore. The benefit of producing a concentrate is that this reduces the weight of the ore for transportation.
The term consumer is used in biology to refer to an
organism that cannot produce its own sources of energy, but feeds on other living organisms. Animals and parasitic plants would be considered consumers. In a food chain, herbivores (animals that eat green plants) are primary consumers and carnivores (that eat herbivores or other carnivores) are secondary consumers.
Continuous view of matter
A continuous view of matter advocates that matter remains divisible into smaller and smaller quantities which continue to maintain the physical and chemical properties of the original sample. This view stands in contrast to the particulate model of matter that advocates that matter is constructed from tiny particles called atoms which are not divisible without the loss of their chemical properties. A continuous view of matter also commonly does not recognise any empty space in matter.
Is the standard unit of electric charge and can be either positive or negative. It is equal to the amount of charge contained on 6.25 X 1018 electrons or the amount of charge that flows past a point in a conducting wire when a current of 1 amp flows for one second.