Explanation

Materials like cadmium and mercury are harmful and can cause serious health issues, so they are called toxic substances.

Toxic means poisonous or dangerous to living organisms.

Explanation

As ice cream melts, it absorbs thermal energy from the surroundings, but its internal thermal energy decreases as it changes from solid to liquid.

This is a physical change.

Explanation

Tulips, lilies, daffodils, and onions reproduce through bulbs, which are underground storage organs.

Bulbs store food and help the plant survive unfavorable conditions.

Explanation

The nucleus is the control center of the cell, regulating all cellular activities, including growth and reproduction.

It contains the cell’s genetic material (DNA).

Explanation

In an endothermic reaction, energy is absorbed, so the products have more energy than the reactants.

This results in a temperature drop in the surroundings.

Explanation

Bleaching powder is synthesized by reacting chlorine gas with calcium hydroxide (Ca(OH)₂).

The chemical formula of bleaching powder is Ca(OCl)Cl.

Explanation

Reactivity is a chemical property that describes how easily a substance undergoes chemical change.

It indicates how a substance reacts with others to form new substances.

Explanation

In dicot seeds, cotyledons store nutrients that nourish the growing embryo.

They often also help in the early stages of photosynthesis after germination.

Explanation

Nitrogen is the most extensively used nutrient for field crops as it promotes leaf and stem growth, especially in cereals.

It is essential for photosynthesis and overall plant development.

Explanation

Heavy water, also known as Deuterium Oxide (D₂O).

It is used as a neutron moderator in nuclear reactors.

Due to its ability to slow down neutrons without absorbing them.