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4. (a) A student placed three different sized cubes of agar jelly into separate beakers containing the same concentration of hydrochloric acid - Edexcel - GCSE Biology - Question 4 - 2020 - Paper 1

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4. (a) A student placed three different sized cubes of agar jelly into separate beakers containing the same concentration of hydrochloric acid. The cubes contained ... show full transcript

Worked Solution & Example Answer:4. (a) A student placed three different sized cubes of agar jelly into separate beakers containing the same concentration of hydrochloric acid - Edexcel - GCSE Biology - Question 4 - 2020 - Paper 1

Step 1

Calculate the distance diffused by hydrochloric acid in one second.

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Answer

To find the distance diffused by hydrochloric acid in one second, we take the distance from the edge of cube B to the pink area, which is 3 mm. Since the cubes were in the acid for 120 seconds, we calculate:

Distance per second=Total distanceTotal time=3 mm120 s=0.025 mm/s\text{Distance per second} = \frac{\text{Total distance}}{\text{Total time}} = \frac{3 \text{ mm}}{120 \text{ s}} = 0.025 \text{ mm/s}

Thus, the distance diffused by hydrochloric acid in one second is 0.025 mm.

Step 2

Give one improvement the student should make to this investigation to confirm their results.

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Answer

One improvement the student could make is to repeat the experiment multiple times to ensure the results are consistent. This repetition can help identify any anomalies or variations in the diffusion results.

Step 3

Devise a method, using cubes of agar jelly, to investigate how temperature affects the rate of diffusion.

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Answer

  1. Prepare cubes of agar jelly containing a pink indicator.
  2. Set up water baths at different temperatures (e.g., 5°C, 20°C, 40°C, 60°C).
  3. Place a cube in each water bath and start a timer.
  4. Observe the diffusion and measure the distance the color has changed over a set period (e.g., 5 minutes).
  5. Record all measurements and repeat for reliability.
  6. Analyze the results to observe the correlation between temperature and the rate of diffusion.

Step 4

Which is the correct description of the movement of a substance by active transport?

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Answer

The correct answer is A) against a concentration gradient using energy. Active transport requires energy to move substances from an area of lower concentration to an area of higher concentration.

Step 5

What is the percentage of preventable cases of cancer that are caused by tobacco?

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Answer

From Figure 8, tobacco accounts for 37% of preventable cases of cancer in 2015. Therefore, the answer is B) 37%.

Step 6

Calculate the number of preventable cases of cancer caused by alcohol.

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Answer

To find the number of preventable cases of cancer caused by alcohol, we first look at the percentage of cancer cases attributed to alcohol from Figure 8, which is 7%.

We can calculate:

Number of cases=Total cases×Percentage of alcohol100\text{Number of cases} = \text{Total cases} \times \frac{\text{Percentage of alcohol}}{100}

Thus:

Number of cases=163440×7100=11441.8\text{Number of cases} = 163440 \times \frac{7}{100} = 11441.8

Rounding to the nearest whole number, the number of preventable cases of cancer caused by alcohol is approximately 11442.

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