Science

Solid

A state of matter characterized by having both a definite shape and a definite volume.

Liquid

A state of matter that maintains a definite volume but adapts to the shape of its container.

Gas

A state of matter that has neither a fixed shape nor a fixed volume, expanding completely to fill its container.

Phase change

A reversible physical transition of a substance from one state of matter to another without altering its chemical composition.

Condensation

The transition of matter from a gas phase into a liquid phase as thermal energy is removed.

Melting

The phase change in which added thermal energy transforms a solid into a liquid.

Freezing

The phase change in which a liquid transitions into a solid as thermal energy decreases.

Vaporization

The transition of a substance from the liquid phase into the gaseous phase, occurring via boiling or evaporation.

Temperature plateau

A flat interval on a heating or cooling curve where temperature remains constant because added or removed energy is used solely for the phase change.

Boiling point

The specific temperature at which a liquid rapidly transitions into vapor throughout the bulk of the liquid at a given pressure.

Freezing / Melting point

The specific temperature at which the solid and liquid phases of a pure substance coexist in thermodynamic equilibrium.

Quantitative observation

Data obtained by numerical measurement or counting, represented using numbers and units.

Qualitative observation

A descriptive observation based on physical characteristics, sensory details, or appearance without numerical values.

Characteristic property

A physical or chemical attribute that is unique to a specific substance and independent of sample size, used for substance identification.

Density formula

$D = \frac{M}{V}$, representing the ratio of an object's mass to the volume it occupies.

Precision

The degree of agreement, repeatability, or consistency among repeated independent measurements of the same quantity.

Accuracy

The closeness of an experimental measurement to the true or accepted reference value.

Percent error equation

$$\text{Percent Error} = \frac{\text{Experimental} - \text{Actual}}{\text{Actual}} \times 100$$

Law of Conservation of Mass

A fundamental scientific principle stating that total mass cannot be created or destroyed within a closed system during a physical or chemical process.

Scientific law

A generalized, evidence-based statement that describes an observed pattern or universal behavior in nature under specific conditions, often expressed mathematically.

Mixture

A material composed of two or more distinct substances that are physically intermingled without chemically bonding, retaining their individual properties.

formula of calculating density of liquid

• Measure Mass (\(m\)) using "weighing by difference":

1. Weigh an empty, clean, dry beaker on a balance.

2. Pour the liquid into the beaker and weigh it again.

3. Subtract the mass of the empty beaker from the total mass to get the mass of the liquid:

\(\text{Mass\ of\ liquid}=\text{Mass\ of\ beaker\ +\ liquid}-\text{Mass\ of\ empty\ beaker}[0.6.9]\)

• Measure Volume (\(V\)): Pour the liquid into a graduated cylinder and read the volume at eye level (at the bottom of the meniscus).

• Calculate: Divide the liquid's mass by its volume (\(\rho = \frac{m}{V}\)

formula of calculating density of gas

Gases expand and change volume drastically with shifts in temperature and pressure, so gas density is usually calculated or measured under specific conditions using the ideal gas law or displacement. [1, 2]

• Method 1 (Experimental/Displacement): Capture the gas (for example, via a chemical reaction or gas collection tube) to measure its mass change and the volume of the displaced gas or container. [1]

• Method 2 (Using the Ideal Gas Law):
  Gas density can be calculated theoretically if you know the molar mass (\(M\)) of the gas, the pressure (\(P\)), the temperature (\(T\) in Kelvin), and the ideal gas constant (\(R\)):
  \(\rho =\frac{P\cdot M}{R\cdot T}\)

  • Note: Unlike solids and liquids, increasing a gas's pressure increases its density, while increasing its temperature decreases its density. [1]