metals and non-metals — Science STD 10 — Question

Which information have been obtained from the study of human evolution?

Explain in short: Chemical communication or hormonal coordination.

What is the meaning of reflex actions? Give examples.

Vishva noticed in a dhaba around 50 bulbs, each of 100 W all were glowing. She calculated the cost of electricity consumed in one hour and told the dhaba owner to reduce the expenses and at the same time save electricity by using CFL bulbs instead of ordinary filament-type bulbs.
(1) What would be the cost of electric energy if 50 bulbs, each of 100 W , are used for one hour? 1 unit costs ₹ 5 .
(2) What is a CFL?
(3) What value did Vishva display in the above case?

Dharmendra is a welder, working at Amit's house. After electric welding done with naked eyes, he used a grinder to smoothen the welding joints. Accidentally, some particle fell into his eye. He was then crying due to pain. Amit took him to an eye hospital by a taxi. The doctor used a device connected to two electric wires to remove the particle from his eye. Dharmendra inquired what happened to his eye and what device did the doctor use to remove the particle from his eye. Amit as a science student of class X explained to Dharmendra and advised him to be careful in future as he had a responsible risky job of welding.
(1) Which particle fell into Dharmendra's eye while welding? What precautions should Dharmendra take while doing electric welding and grinding work?
(2) What device was used by the doctor to remove the particle?
(3) What values do you learn from Amit during this episode?

Explain oxidation and reduction reactions with examples.

An electric iron consumes energy at a rate of 840 W , when heating is at the maximum rate and 360 W , when heating is at the minimum. The voltage is 220 V . What are the current and the resistance in each case?

Did Dobereiner’s triads also exist in the columns of Newlands’ octaves? Compare and find out.