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raketka [301]
3 years ago
12

Fossil fuels have been used for years as a source

Biology
1 answer:
VMariaS [17]3 years ago
3 0


The best answer is (1)

Fossil fuels are commercially available as an energy source.

They are very easy to find. More and more extractions of fossil fuels is going on everyday. With advancement in science and  technology, the refineries and extraction procedures have improved a lot. This makes their availability even better.

Fossil fuels are also easily combustible. Most combustion engines need to be powered with little amount of fuel to produce large amount of energy. Very large amounts of electricity can be  generated  from fossil fuels.

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Which of the following examples of an ecological study involves the ecosystem level of organization?
Shalnov [3]
As I know, the effects of human activities on biogeochemical cycling are <span>examples of an ecological study involves the ecosystem level of organization.</span>
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3 years ago
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.

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3 years ago
Dance that provides honey bees information about both the direction and distance of food:
liq [111]

Answer: WAGGLE DANCE is the dance that provides honey bees information about both the direction and distance of food.

Explanation:

Honey bees are flying insects that helps in the pollination of plants as they collect nectar and pollen from plants for food. As the name implies, they are known for the production of honey.

The honey bee dance helps in social organization of the honey-bees which is established by the living of all individuals within the colony and they show the mutual cooperation among the members of the colony, and exhibit the overlapping genera­tions.

WAGGLE DANCE is the dance that provides honey bees information about both the direction and distance of food for the colony. It consists of two phases:

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2 years ago
What are the mode of feeding in different organism​
Crazy boy [7]

Answer:

A= 2

B=4

C=3

D=1

Explanation:

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How do eukaryotic plant and animal cells differ from one another?
Ber [7]

Answer:

The eukaryotic plant animal cells are differ having some cell organelles in it.

Explanation:

The first difference is the cell wall, which is present in all eukaryotic plants. It gives shape and rigidity to the plants. But all the animal cell the outer covering is cell membrane. They lack cell wall.

All the plant cell have chlorophyll pigment. It helps them to photosynthesis. In animal cell, chlorophyll molecule are absent. So they depend on plants for their food.

The eukaryotic plant cell more space is occupied by the vacuoles. It stores food and water for the plants. However, animal cells have no vacuole or if present, it is very small in size.

All animal cells have lysosomes, which help in digestion of various materials in the cell. Plants does not contain lysosomes.

Besides this organelles all other structure of plant and animals are similar. They both have nucleus, DNA, cytoplasm, mitochondria, etc.

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