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zalisa [80]
3 years ago
10

Role of a student in protecting environment

Biology
1 answer:
MariettaO [177]3 years ago
8 0
Making sure there's minimal litter and pollution around our daily lives? :)
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2. List three sources of error that could account for the differences between your values for the enthalpy of fusion of water an
Dvinal [7]

1 trial :  nothing is given for result comparision - so we have no idea if it's a mistake.

2nd trial : The results can be compared - if varies, one may go wrong, but which one?

3rd trial : If 3rd result is different from 1st and 2nd, it is unreliable.

calculating enthalpy of fusion. M, C and m,c = mass and specific heat of calorimeter and water, n, L = mass and heat of fusion of ice; T = temperature fall.

L = (mc+MC)T/n.

c=4.18 J/gK. assuming copper calorimeter , so C=0.385 J/gK.

1. M = 409g, m = 45g. T = 22c, n = 14g

L = (45*4.18+409*0.385)*22/14 = 543.0 J/g.

2. M = 409g, m = 49g, T = 20c, n = 13g

L = (49*4.18+409*0.385)*20/13 = 557.4 J/g.

3. M = 409g, m = 54g, T = 20c, n = 14g

L = (54*4.18+409*0.385)*20/14 = 547.4 J/g.

(i) Estimate error in L from spread of 3 results.

Average L = 549.3 J/g.

squared differences average (variance) = (6.236^2+8.095^2+1.859^2)/3 = 35.96

standard deviation = 5.9964

standard error = SD/(N-1) = 5.9964/2 = 3 J/g approx.

% error = 3/547 x 100% = 0.5%.

(ii) Estimate error in L from accuracy of measurements:

error in masses = +/-0.5g

error in T = +/-0.5c

For Trial 3

M = 409g, error = 0.5g

m = 463-409, error = sqrt(0.5^2+0.5^2) = 0.5*sqrt(2)

n =(516-463)-(448-409)=14, error = 0.5*sqrt(4) = 1.0g

K = (mc+MC)=383, error = sqrt[2*(0.5*4.18)^2+(0.5*0.385)^2] = 2.962

L = K*T/n

% errors are

K: 3/383 x 100% = 0.77

T: 0.5/20 x 100% = 2.5

n: 1.0/14 x 100% = 7.14

% errors in K and T are << error in n, so ignore them.

% error in L = same as in n = 7% x 547.4 = 40

The result is (i) L= 549 +/- 3 J/g or (ii) L = 550 +/- 40 J/g.

Both are very far above  334 J/g, so there is at least one systematic error  

e.g: calorimeter may not be copper, so C is not 0.385 J/gK. (If it was polystyrene, which absorbs/ transmits little heat, the effective value of C would be very low, reducing L.)

Using +/- 40 is best.

However, the spread in the actual results is much smaller

* measurements were "fiddled" to get better results; other Trials were made but only best 3 were chosen.

<h3>Other sources of error: </h3>

L=(mc+MC)T/n is too high, so n (ice melted) may be too small, or T (temp fall) too high - why?

* we have assumed initial and final temperature of ice was 0c, it may actually have been colder, so less ice would melt -which explain small values of n

* some water might have been left in container when unmelted ice was weighed (eg clinging to ice) - again this could explain small n;

* poor insulation - heat gained from surroundings, melting more ice, increasing n - but this would reduce measured L below 334 J/g not increase it.

* calorimeter still cold from last trial when next one started, not given time to reach same temperature as water - this would reduce n.

3 0
3 years ago
Which cell organelle is shown by the diagram above?
tatiyna

Answer:

cell membrane

Explanation:

The cell membrane in the diagram consists of lipids, bilayers, and proteins. The lipids, located within the cell membrane, are known as hydrophobic, meaning they are afraid of water. In other words, the lipids keep out the water. Whereas the bilayer, otherwise known as the phospholipid bilayer, is attracted to water. While the proteins simply enable molecules and other microscopic parts travel within and out the cell membrane, through the protein.

8 0
2 years ago
Are Fungi beneficial or harmful? Explain
Nata [24]

Answer:

Honestly it depends...

Explanation:

I would say overall fungi are beneficial because they feed on dead organic matter. They recycle most of the carbon and release nutrients to be used by other organisms. They are also used for medicinal purposes. Not to mention yeast is a fungus and bread is yummy.

But certain fungi are deadly if ingested or linked to plant and human diseases. Also mold is a fungus and nobody likes mold.

6 0
2 years ago
What is a sagebrush's adaptations ? <br><br><br><br> help
Ostrovityanka [42]

Answer:Like many species of the coastal sage scrub, California sagebrush has adapted to summer drought by becoming dormant or semi-dormant during dry months. Winter-spring leaves are feathery and thin and support high rates of photosynthesis; consequently they also have high rates of water loss.

Explanation:

7 0
3 years ago
Forensic scientists who study possible forgeries and questioned documents are often called what?
Ber [7]
Forensic scientists who study possible forgeries and questioned documents are often called forensic or legal linguists.
Forensic linguistics is a branch of linguistics that deals with such illegal kinds of documents so as to solve a certain crime. 
3 0
3 years ago
Read 2 more answers
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