Why does density vary from one substance to another substance?

Assertion: The mass of a substance is constant whereas its weight may vary from one place to another. Reason : Mass of a substance is the amount of matter present in it while weight is the force exerted by gravity on an object.

Why do some substance exist as solids?

Give one word for the following : A substance which reacts with another substance

Define relative density of a substance.

Why are symbols and formulae of substances important ?

The chemical substance P is made and secreted by the meristematic tissue at the tip of stem (or shoot) of a plant. The chemical substance P is responsible for a phenomenon Q in plants in which the stem bends towards the source of light. The same chemical substance P has an opposite effect on the root of a plant. It causes the root of a plant to bend away from the source of light in a process called R. What is the general name of the chemical substance like P ? Name another substance which belongs to this class of chemical substances.

How does nerve impules travel from one neuron to another ?

Which of the following statements are true for pure substances? (i) Pure substances contain only one kind of particles. (ii) Pure substances may be compounds or mixtures. (iii) Pure substances have the same composition throughout. (iv) Pure substance can be exemplified by all elements other than nickel.

When a ray of light enters from one medium to another having different optical densities, it bends. Why does this phenomenon occur ?

Why is desorption important for a substance to act as good catalyst?