Management of Natural Resources — Science STD 10 — Question

A silvery-white metal X taken in the form of ribbon, when ignited, burns in air with a dazzling white flame to form a white powder Y. When water is added to powder Y, it dissolves partially to form another substance Z.

1. What could metal X be?
2. What is powder Y?
3. With which substance metal X combines to form powder Y?
4. What is substance Z? Name one domestic use of substance Z.
5. Write a balanced chemical equation of the reaction which takes place when metal X burns in air to form powder Y.

Name the main organs of the human digestive system in the order they participate in the process of digestion. Describe how digestion of carbohydrates and proteins take place in our body.

What does a soda-acid type fire extinguisher contain? How does it work?
Explain the working of a soda- acid fire extinguisher with the help of a labelled diagram.

While conducting experiments to study the effect of various stimuli on the plants, it was observed that the roots of a plant X grow and bend towards two stimuli A and B but bend away from a third stimulus C. The stem of the plant X, however, bends away from stimuli A and B but bends towards the stimulus C. The stimulus B is known to act on the roots due to too much weight of the earth. Keeping these points in mind, answer the following question:

1. What could stimulus A be?
2. Name the stimulus B.
3. What could stimulus C be?
4. The branches of a fallen tree in a forest grow straight up in response to two stimuli. What could be these two stimuli out of A, B and C? Also name these two stimuli.

Construct ray diagrams to illustrate the formation of a virtual image using:

1. A converging lens, and.
2. A diverging lens.

When a human female reaches a certain age then vaginal bleeding occurs for a few days after regular time intervals.

1. What is this process known as (i) in scientific terms, and (ii) in everyday language?
2. At what approximate age this process starts in human females? When is the human female said to have attained at this stage?
3. After how much time is this process repeated? For how many days does this process usually last?
4. What does the onset of this process in human females signify?
5. At which particular event in the life of a human female does this process stop temporarily but start again?
6. At which approximate age of human female does this process stop permanently?

An object 4.0cm in size, is placed 25.0cm in front of a concave mirror of focal length 15.0cm.

1. At what distance from the mirror should a screen be placed in order to obtain a sharp image?
2. Find the size of the image.
3. Draw a ray diagram to show the formation of image in this case.

A camera fitted with a lens of focal length 50mm is being used to photograph a flower that is 5cm in diameter. The flower is placed 20cm in front of the camera lens.

1. At what distance from the film should the lens be adjusted to obtain a sharp image of the flower?
2. What would be the diameter of the image of the flower on the film?
3. What is the nature of camera lens?

Suppose you have three concave mirrors A, B and C of focal lengths 10cm, 15cm and 20cm. For each concave mirror, you perform the experiment of image formation for three values of object distance of 10cm, 20cm and 30cm. Giving reason answer the following:

1. For the three object distances, identify the mirror/ mirrors which will form an image of magnification - 1.
2. Out of the three mirrors identify the mirror which would be preferred to be used for shaving purposes/ makeup.
3. For the mirror B draw, ray diagram for image formation for object distances 10cm and 20cm.

An object is kept at a distance of 100 cm from each of the above lenses. Calculate the

1. Image distance and
2. Magnification in each of two cases.