Bull Type)
(a) How do you describe so many substances
around us in one word?
(h) Are invisible substances like gases or air
also constitute matter?
(c) What about certain feelings like love, hate,
security, smell?
(d) Why?
Answers
Answer:
Explanation:
Physical nature of matter: Matter is a substance
which occupies mass and space. Its presence may
or may not be felt. Air is matter but smell, hate,
love or security which are felt are not matter. Further matter is particulate, i.e., it is not continuous
but made up of tiny particles.
Characteristics of matter: Particles of matter have
space between them. They are constantly moving.
These interact and diffuse into one another. Diffusion decreases from gases to liquids to solids.
States of matter: The particles of matter attract
each other. This attraction is called intermolecular
force of attraction. Depending on the magnitude
of intermolecular forces, a matter may exist as
solid, liquid or a gas. The gap between particles
increases from solid to liquid to gas.
A solid has a definite shape and a definite volume and
is rigid, has boundary, has negligible compressibility.
A liquid has a definite volume but no definite shape,
has boundary but not rigid.
A gas has no shape, no boundary and no fixed volume.
Change of state of matter: A solid on heating
changes into a liquid which changes into gas on
further heating. On cooling, reverse process takes
place. On heating, kinetic energy of particles
increases which is responsible for change of state
of matter.
Latent heat: At the melting point, temperature
becomes constant, though heat is supplied, till
whole of solid melts. Similarly during heating of
liquid, at the boiling point, temperature remains
constant. These are respectively called latent heat
of fusion and vaporisation.
Sublimation: In some cases, matter changes directly from solid state to gaseous state and vice
versa without changing into liquid state.
Effect of pressure: On increasing pressure,
particles of matter come closer and they move
apart on reducing pressure at a given temperature.
Thus increasing pressure liquifies a gas. Similarly
solid becomes liquid at lower pressures.
Evaporation: Particles of matter are always
moving and at different speeds. (We measure
average speed). In case of liquid, when particles
having higher kinetic energy reach the surface,
break away by the forces of attraction of other
particles and get converted into vapours. This
phenomenon gives rise to cooling of water in
earthenwares. The rate of evaporation increases
with temperature, surface area, speed of wind and
decreases with humidity
Explanation:
how do you describe so many substances around us in one word ?