Definitions [20]
Chemical properties of matter tell us how a substance changes when it interacts with other substances. These properties describe how matter reacts and forms new substances. When a chemical change happens, the matter changes into something new. The atoms in a substance rearrange themselves, and a new substance is formed. For example:
- When wood burns, it turns into ash and smoke.
- When iron is exposed to air and water, it forms rust.
Examples of Chemical Properties:
- Flammability: This describes if a substance can burn. For example, wood is flammable because it can catch fire.
- Reactivity: This tells us how a substance reacts when mixed with others. For example, if you mix vinegar with baking soda, they react to create bubbles.
- Rusting: Some metals, like iron, will form rust when they come in contact with water and air.
- Acidity and Basicity: Some substances are acidic (like lemon juice), while others are basic (like soap). Acids and bases can react with each other to form new substances.
Define the term matter. What is it composed of?
- Matter is defined based on its physical and chemical structure. It occupies space and has mass, particularly as opposed to energy.
- Atoms and molecules are the building blocks of matter, consisting of positively charged protons, neutral neutrons, and negatively charged electrons, respectively.
Define the term matter.
The matter is defined as anything that has mass and takes up space. The matter is found in solid, liquid and gas.
Define the following term of Atom .
Atom — An atom is the smallest part of an element that takes place in a chemical reaction.
Define the following term of Matter .
Matter—Anything that has mass and occupies space is called matter.
Define matter.
Anything that has mass and occupies space is called matter.
Define the emulsion. Give one example.
An emulsion is a colloid in which minute droplets of one liquid are dispersed in another liquid which is not miscible with it. Examples are milk and butter.
Define interconversion of states of matter.
The process by which matter changes from one state to another and back to the original state, without any change in its chemical composition.
Define matter
Anything that has mass and occupies space is called matter.
Define Triple point.
The triple point of water is that point where water in a solid, liquid and gas state co-exists in equilibrium and this occurs only at a unique temperature and a pressure.
The process of change from one state to another at a constant temperature is called the change of phase.
OR
A transition from one state of matter (solid, liquid, or gas) to another is called change of state.
Define Sublimation.
Sublimation is the process in which a solid changes directly into a gas on heating, without passing through the liquid state.
The change from vapour to liquid phase on liberation of heat at a constant temperature is called condensation (or liquefaction) and the particular temperature at which the condensation occurs is called the condensation point of vapour.
The particular temperature at which vaporisation occurs is called the boiling point of liquid.
The change from liquid to gas (or vapour) phase on absorption of heat at a constant temperature, is called vaporisation.
Define sublimation.
The change of state from solid to gas directly is called sublimation.
The change of a solid substance directly into a gas or vapour without first changing into a liquid is called sublimation.
OR
The change from solid state to vapour state without passing through the liquid state is called sublimation, and the substance is said to sublime.
Define absolute zero.
The temperature at which the pressure and volume of a gas theoretically reach zero is called absolute zero.
Temperature is a parameter which tells the thermal state of a body (i.e., the degree of hotness or coldness of the body). It determines the direction of flow of heat when two bodies at different temperatures are placed in contact.
Define coefficient of linear expansion.
Coefficient of Linear expansion is equal to the change in length of a rod of length 1m when its temperature rises by 1°C.
Key Points
| Property | Solid | Liquid | Gas |
|---|---|---|---|
| Mean molecular separation | ~3–5 Å | ~3–10 Å | >5 Å |
| Particle arrangement | Tightly packed, regular | Loosely packed, irregular | Highly irregular |
| Particle movement | Fixed positions, cannot move freely | Moves a small distance within liquid | Continuous random motion |
| Shape & volume | Definite shape and volume | Takes shape of container, definite volume | Takes shape and volume of container |
| Intermolecular space | Very small | Moderate | Large |
| Effect of temperature | Small volume change | Moderate volume change | Significant volume change |
| Compressibility | Practically incompressible | Slightly compressible | Highly compressible |
| Example | A piece of iron | Water, spirit, oil | Air |
- A change of state occurs when heat exchange causes a substance to transition between solid, liquid, and gas phases.
- Temperature remains constant during a phase change because heat energy changes molecular arrangement (potential energy), not molecular speed (kinetic energy).
- The heating curve has flat plateaus at the melting point (0 °C) and boiling point (100 °C) for water, with rising slopes in between.
- If no heat flows between two bodies in contact, they are said to be at the same temperature, even though their thermal energies may be different.
- The S.I. unit of temperature is kelvin (K), and absolute zero (0 K) is the temperature at which molecular motion ceases.
- Metals are mostly solids at room temperature; mercury and gallium are exceptions and exist in liquid form.
- Metals have a shining surface called metallic lustre, which may decrease due to oxidation or reaction with gases.
- Malleability allows metals to be beaten into thin sheets (gold and silver are highly malleable), and ductility allows them to be drawn into wires (gold is the most ductile).
- Metals are good conductors of heat and electricity, with silver and copper being excellent conductors.
- Most metals are hard with high melting and boiling points, but alkali metals (sodium, potassium) are soft and low‑melting, and metals are sonorous, producing sound when struck.
