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A student wishes to investigate the effect of surface area on the rate of reaction between marble chips and hydrochloric acid. Which variables should he control?

Concentration of HCl, Mass of marble chips (use excess HCl).
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Answered by Alfie B. • Chemistry tutor
5181 Views

Expand the following expression: -5x(x-7)(x+3)

Expansion of the given expression will result in x to the 3rd power, as there are 3 parts involving x, multiplied together. Let's ignore -5x for a second, and multiply the two expressions in brackets (using ...
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Answered by Matas S. • Maths tutor
5677 Views

Describe the changes in forces experienced by a parachutist after they have started falling

Initially, the parachutist will experience a greater downwards force due to gravity which causes them to accelatae downwards. As they accelarate, the upwards force of air resistance will increase. They will ...
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Answered by Iona N. • Physics tutor
3969 Views

How do plants alter the way in which they grow in response to light?

Plants have photoreceptors in the tips of their shoots. If light is detected from a specific direction, the plant will produce auxins which diffuse fown the shoot of the plant. The auxins increase in concent...
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Answered by Iona N. • Biology tutor
3054 Views

How do I simplify a surd?

Take the number that is in the root sign, and change it to 2 numbers multiplied together (we want one of these numbers to be a square number). A square number is 1, 4, 9, 16 etc. Then separate this into two ...
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Answered by Francesca E. • Maths tutor
5195 Views