The West African Senior School Certificate Examination (WASSCE) is a standardized test taken by students in West Africa to certify their completion of secondary education.
One of the subjects covered in the examination is Integrated Science, which encompasses various scientific fields such as biology, chemistry, physics, and earth science.
Try your hands on the following questions;
Question 1
A group of students conducted an experiment to investigate the rate of photosynthesis in plants. They placed a plant in a transparent container filled with water and covered it with a glass plate. They then measured the volume of oxygen produced by the plant at intervals of 5 minutes. The results are shown in the table below:
| Time (min) | The volume of oxygen produced (cm³) |
|---|---|
| 0 | 0 |
| 5 | 0.3 |
| 10 | 0.8 |
| 15 | 1.2 |
| 20 | 1.4 |
| 25 | 1.5 |
a) Calculate the rate of photosynthesis in the plant between 10 and 15 minutes.
b) Explain the relationship between the rate of photosynthesis and light intensity.
c) State two factors other than the light intensity that affect the rate of photosynthesis.
Explanation:
a) To calculate the rate of photosynthesis between 10 and 15 minutes, we need to find the change in the volume of oxygen produced over that time period. The change in volume is 1.2 – 0.8 = 0.4 cm³. Therefore, the rate of photosynthesis is 0.4/5 = 0.08 cm³/min.
b) The rate of photosynthesis is directly proportional to light intensity up to a certain point, beyond which it levels off. This is because photosynthesis requires light to power the process, but too much light can damage the plant.
c) Other factors that affect the rate of photosynthesis include temperature, carbon dioxide concentration, and the availability of nutrients such as water and minerals.
Question 2
A student investigated the properties of a certain metal. She measured the mass of the metal and its volume and found that it had a density of 6.5 g/cm³. She also found that the metal did not react with hydrochloric acid or with water.
a) Identify the metal and explain how you arrived at your answer.
b) Explain what is meant by the term “density” and how it is calculated.
c) State two other properties that could be used to identify a metal.
Explanation:
a) Based on the fact that the metal did not react with hydrochloric acid or water, we can rule out metals such as magnesium, zinc, and aluminum. Since the metal has a relatively high density of 6.5 g/cm³, it is likely to be a transition metal such as iron, copper, or silver.
b) Density is the mass of a substance per unit volume. It is calculated by dividing the mass of the substance by its volume, using the formula: Density = Mass/Volume.
c) Other properties that could be used to identify a metal include its melting point, boiling point, color, and reactivity with other substances.
Question 3
A student is studying the structure of a leaf under a microscope. She observes that the leaf has numerous stomata on the underside.
a) Explain the function of stomata in plants.
b) Describe the structure of typical stomata.
Explanation
a) Stomata are small openings on the surface of leaves that allow plants to exchange gases with the environment. During photosynthesis, plants take in carbon dioxide through stomata and release oxygen. At the same time, stomata also allow plants to release excess water vapor through a process called transpiration.
b) Typical stomata consist of two guard cells that surround a small pore. The guard cells are kidney-shaped and contain chloroplasts. When the plant needs to release water vapor, the guard cells become turgid and the pore between them opens. When the plant needs to conserve water, the guard cells become flaccid and the pore closes.
Question 4
A farmer notices that his tomato plants are wilting even though the soil is moist. He suspects that the plants are not getting enough water due to excessive transpiration.
a) Describe one method the farmer can use to reduce transpiration in his tomato plants.
b) Explain how the method you described in part (a) can help reduce transpiration in plants.
Explanation:
a) One method the farmer can use to reduce transpiration in his tomato plants is to cover the plants with a plastic sheet.
b) The plastic sheet will create a microclimate around the plants that is more humid than the surrounding environment. This will reduce the rate of transpiration because there will be less of a difference in water potential between the leaves and the surrounding air.
In addition, the plastic sheet will reduce the amount of air movement around the plants, which will also help to reduce transpiration.
These easier Section B WASSCE standard questions are designed to test the basic understanding of scientific concepts and principles. By practicing these types of questions, students can improve their fundamental knowledge and prepare themselves for the WASSCE examination.
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