Carbon and its Compounds — Science STD 10 — Question

Where would the image be formed by a convex mirror if the object is placed:

1. Between infinity and pole of the mirror?
2. At infinity?

Draw labelled ray-diagrams to show the formation of image in both the cases.

Draw a diagram to show the magnetic field lines around a bar magnet.

How do unicellular organisms perform excretion?

The atomic numbers of three elements A, B and C are given below:

Element	Atomic Number
A	5
B	7
C	10

1. Which element belongs to group 18?
2. Which element belongs to group 15?
3. Which element belongs to group 13?
4. To which period/ periods do these elements belong?

State the law which governs the amount of heat produced in a metallic conductor when current is passed through it for a given time. Express this law mathematically.

Bases should not be kept in active metal container. Why?

Describe the extraction of zinc metal from its sulphide ore (zinc blende). Write equations of the reactions involved.

Why are aqueous solutions of ionic compounds able to conduct electricity?

When a person breathes in air, the air enters into his body through an organ Ahaving two holes B in it. The air then passes through pharynx and larynx and enters into a tube C. The tube C divides into two smaller tubes D at its lower end. The two smaller tubes are attached to two respiratory organs E. Each smaller tube divides inside the organs E to form a large number of still smaller tubes called F. The smallest tubes F have air-sacs G at their ends in which gaseous exchange takes place in the body of the person. What are A, B, C, D, E, F and G?

Why do muscles change their shape in response to a nerve impulse?