Everything which occupies some space and has mass is called matter. Example: Air, Wood, H₂SO₄, etc.
There are four states of matter: (i) Solid, (ii) Liquid, (iii) Gas, (iv) Plasma.
Matter in gaseous state does not have definite shape and volume. Gases occupy all available space and have very weak intermolecular forces.
Diffusion is spontaneous mixing up of molecules by random motion and collisions to form a homogeneous mixture. Rate of diffusion depends upon the molecular mass of the gas.
Effusion is the escaping of gas molecules through a tiny hole into a space with lesser pressure. For example, when a tire gets punctured, air effuses out. Effusion depends upon the molecular masses of gases.
Pressure is the force (F) exerted per unit surface area (A), P=F/A. The SI unit of pressure is Pascal (Pa), which is also called Nm². One Pascal (Pa) = 1 Nm².
There are two instruments to measure pressure: (i) Barometer, used to measure atmospheric pressure, and (ii) Manometer, used to measure pressure in the laboratory.
Standard atmospheric pressure is defined as the pressure exerted by a mercury column of 760 mm height at sea level. It is sufficient pressure to support a column of mercury in height at sea level.
Gases are highly compressible due to empty spaces between their molecules.
Gas molecules are always in a state of continuous motion. They can move from one place to another because gas molecules possess very high kinetic energy.
Density is the ratio of mass and volume (m/v). Gases have lower density than liquids and solids. Density of gases is expressed in grams per dm³.
Gas molecules have insignificant intermolecular forces compared to liquids. Therefore, the rate of diffusion of gases is faster than that of liquids.
Pascal is the SI unit of pressure. One Pascal (Pa) = 1 Nm². 1 atm = 101325 Pa.
The density of gases increases by cooling because their volume decreases. For example, at normal atmospheric pressure, the density of oxygen gas is 1.4 g/dm³ at 20°C and 1.5 g/dm³ at 0°C.
Gases have low densities due to light mass and more volume occupied by the gas molecules. That is why gas density is expressed in grams per dm³, whereas liquid and solid densities are expressed in grams per cm³ because liquids and solids are 1000 times denser than gases.
We know that 760 cm Hg = 1 atm. Therefore, 70 cm Hg = 70 / 760 = 0.092 atm.
1 atm = 760 torr. Therefore, 3.5 atm = 3.5 × 760 = 2660 torr.
1 atm = 101325 Pa. Therefore, 1.5 atm = 1.5 × 101325 = 151987.5 Pa.
Boyle's law states that the volume of a given mass of a gas is inversely proportional to its pressure, provided the temperature remains constant.
Robert Boyle (1627-1691) was a natural philosopher, chemist, physicist, and inventor. He is famous for Boyle's law of gases.
No, Boyle's law is only applicable to gases.
No, Boyle's law is only valid at constant temperatures.
If the pressure on a sample of gas is raised three times at constant temperature, the volume will decrease to one-third of its original volume.
J. Charles (1746-1823) was a French inventor, scientist, mathematician, and balloonist. He described how gases tend to expand when heated.
Charles' law, presented by J. Charles in 1789, states that the volume of a given mass of a gas is directly proportional to the absolute temperature if the pressure is kept constant.
The absolute temperature scale or Kelvin scale, introduced by Lord Kelvin, starts from 0 K (absolute zero), which is -273.15°C. It is the temperature at which an ideal gas would have zero volume.
In Charles's Law, pressure remains constant.
The volume of gas decreases with an increase in pressure because pressure and volume are inversely proportional to each other. When pressure increases, volume decreases, and vice versa.
No, the Kelvin scale does not show negative values. 0 K is equivalent to -273°C.
When a gas expands, its temperature will increase because volume and temperature are directly proportional to each other.
Yes, by suddenly increasing the volume of a gas, it results in a cooling effect.
Body temperature is measured in Fahrenheit. Normal body temperature is 98.6°F, which is equivalent to 37°C.
Matter that has an indefinite shape but a definite volume is called a liquid. Examples include water, milk, etc.
Evaporation is the process of molecules escaping spontaneously from the surface of a liquid. It depends on the following factors: (i) Temperature, (ii) Surface area, (iii) Wind speed, (iv) Humidity.
A liquid has a definite volume because the intermolecular forces are strong enough to keep the liquid molecules together, unlike gases.
Density of a liquid can be measured using a hydrometer or by calculating mass per unit volume using a balance and graduated cylinder.
To convert Fahrenheit to Celsius, use the formula: (°F - 32) × 5/9 = °C. For example, to convert 98.6°F to Celsius: (98.6 - 32) × 5/9 = 37°C.
Ice floats on water because it is less dense than liquid water. When water freezes, it expands and becomes less dense.
When the temperature of a gas is increased, its volume expands, which decreases its density because density is the mass divided by volume.
Pressure is the force exerted per unit area. It can be calculated using the formula: Pressure = Force / Area.