How to justify apparatus used for A level biology

Remind me what practical 9 is - I don't teach the specification any longer.

Investigation of the effect of temperature on respiration of yeast using methylene blue which gets reduced to turn from blue to colourless .
my homework was basically . Why did I use the apparatus I did ? And justify the methods I used.
i have no idea where to start and how to approach this

OK - thanks. Yes, I know that practical now.
So, if you're investigating the effects of temperature, you need some way of measuring temperature - hence the apparatus choice of thermometer. However, the marks come in not just saying 'I used a thermometer because I needed to measure temperature' but being more specific about the scale of the thermometer. Thermometers can have a wide scale, from -50°C to 200°C or a very narrow scale, like a human body temperature thermometer which goes from about 35-41°C. Which do you think you'd be best to use for this experiment? What range of temperatures would you predict you will need to measure, given you're measuring enzymatic activity? And note that the narrower the range, the more accurate the thermometer is - so using one with a small range appropriate to the experiment allows you to make more accurate measurements. Does that make sense?

Stopwatch - again, you're measuring an experiment that is basically a rate - an enzyme rate. Rates are obviously amount of product per unit time, so you need a way of measuring time. Just like the thermometer, think about what sort of accuracy you need and justify your choice. Do you need to measure to the nearest 1000th of a second (and, practically, could you do this 'by hand)? If not, what sort of accuracy do you think is warranted for this experiment.

I know that in practice you'll just be given one type of thermometer and one type of stopwatch to actually do the experiment at school, but part of justifying your choice of apparatus involves examining things like scale, resolution etc. So, do this for all the apparatus you've chosen:

1. What do you need to measure?
2. What apparatus exists to measure this quantity?
3. Justify which scale/size apparatus is appropriate to the experiment, or the predicted measurements you'll be making.

DAMN teach me biology sensei!

hahaha

If you ever need help or advice with something, start a thread and quote me in

Thanks will do! Actually could you explain how low/freezing temperatures affect enzymes in enzyme controlled reactions? IDK my textbook doesnt include that it only mentions about high temps and how that denatures the enzymes functions.

sure - is this a level?

yaasss! (ocr a)

Do you do A/AS chemistry at all? I want to lead you to the answer, rather than just give it to you - this will be much more useful to you in the long run.

OK - thanks. Yes, I know that practical now.
So, if you're investigating the effects of temperature, you need some way of measuring temperature - hence the apparatus choice of thermometer. However, the marks come in not just saying 'I used a thermometer because I needed to measure temperature' but being more specific about the scale of the thermometer. Thermometers can have a wide scale, from -50°C to 200°C or a very narrow scale, like a human body temperature thermometer which goes from about 35-41°C. Which do you think you'd be best to use for this experiment? What range of temperatures would you predict you will need to measure, given you're measuring enzymatic activity? And note that the narrower the range, the more accurate the thermometer is - so using one with a small range appropriate to the experiment allows you to make more accurate measurements. Does that make sense?

Stopwatch - again, you're measuring an experiment that is basically a rate - an enzyme rate. Rates are obviously amount of product per unit time, so you need a way of measuring time. Just like the thermometer, think about what sort of accuracy you need and justify your choice. Do you need to measure to the nearest 1000th of a second (and, practically, could you do this 'by hand)? If not, what sort of accuracy do you think is warranted for this experiment.

I know that in practice you'll just be given one type of thermometer and one type of stopwatch to actually do the experiment at school, but part of justifying your choice of apparatus involves examining things like scale, resolution etc. So, do this for all the apparatus you've chosen:

1. What do you need to measure?
2. What apparatus exists to measure this quantity?
3. Justify which scale/size apparatus is appropriate to the experiment, or the predicted measurements you'll be making.

Thanks loads. One quick question though soz soz . In improvements I mentioned that we could use an electric water bath instead due to haand made one is prone to heat loss and the need to control it by adding more hot water decreases the accuracy , is that correct ?

Yes and sure I would prefer that

Good - that helps enormously. So, in chemistry, what factors can determine the rate of a reaction?

presence of cataylst, temperature, concentration/pressure of reactants

Brilliant. And thinking of temperature, what happens when you lower the temperature of the system?