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Describe the way in which the normal heart beat is initiated and controlled

The heart muscle is myogenic , which means that it can contract without any input from the nervous system. The stimulus for the muscle to contract originates from a group of specialised cardiac cells, the si...
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Explain how a change in one of the determinants of supply could lead to a decrease in the price of rice.

Supply is the quantity of a certain product that a producer is willing and able to supply into a market at a given price, in a given time period. Consider the market for rice: an abnormally fruitful harvest ...
JZ
Answered by Julia Z. • Economics tutor
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A shop sells bags of crisps in different size packs. There are 18 bags of crisps in a small pack (£4), 20 bags of crisps in a medium pack (£4.99) and 26 bags of crisps in a large pack (£6). Which size pack is the best value for money?

You can use the price of each pack and divide it by the number of bags of crips to get the price per packet, the one with the lowest price per packet will be the best value for money. The small packet cost £...
KG
Answered by Kahina G. • Maths tutor
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Explain why chlorine (Cl2) is a gas at room temperature, but sodium chloride (NaCl) is a solid at room temperature.

The different states at room temperature occur as a result of differences in the bonding and structure of chlorine and sodium chloride. In chlorine, there are covalent bonds between individual atoms which le...
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Answered by Julia Z. • Chemistry tutor
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Why does an atom have no overall charge?

An atom has no overall charge because each element has the same number of protons and electrons. Protons have a +1 charge, and electrons have a -1 charge, these charges cancel out if there is the same amount...
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Answered by Kahina G. • Chemistry tutor
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