Question

Which of these terms, (i) mixture, (ii) solid, (iii) liquid, (iv) gas, (v) chemical element, (vi) chemical compound, applies to the following substances at room temperature? (a) Gasoline (b) Iodine (c) Water (d) Air (e) Blood (f) Sodium hydrogen carbonate (g) Gaseous ammonia (h) Silicon

Short answer

(a) Mixture, (b) Chemical Element, (c) Chemical Compound, (d) Mixture, (e) Mixture, (f) Chemical Compound, (g) Chemical Compound, (h) Chemical Element.

Step-by-step solution

Classify Gasoline

Gasoline is a combination of different hydrocarbons and additives. At room temperature, it is in a liquid state. Therefore, it is best classified as a mixture since it does not have a fixed composition.

Classify Iodine

Iodine is a pure element found on the periodic table with the chemical symbol 'I.' At room temperature, it exists in a solid state and is categorized as a chemical element.

Classify Water

Water, composed of hydrogen and oxygen (H₂O), is a pure substance with a fixed ratio. It is a liquid at room temperature and is classified as a chemical compound.

Classify Air

Air is a mixture of different gases, primarily nitrogen and oxygen, along with minor components. It is homogeneous at room temperature and thus classified as a mixture.

Classify Blood

Blood is a complex mixture containing cells, plasma, and various proteins. It is best categorized as a mixture due to its varied and complex composition.

Classify Sodium Hydrogen Carbonate

Sodium hydrogen carbonate, known commonly as baking soda, has the formula NaHCO₃. It is a pure chemical compound composed of sodium, hydrogen, carbon, and oxygen atoms.

Classify Gaseous Ammonia

Ammonia is a compound consisting of nitrogen and hydrogen with the formula NH₃. At room temperature, it exists as a gas, making it a chemical compound.

Classify Silicon

Silicon is an elemental substance found on the periodic table with the symbol 'Si.' At room temperature, it is solid, and thus it is classified as a chemical element.

Key concepts

Mixture

A mixture is composed of two or more substances that are combined physically but not chemically bonded. This means each component maintains its own identity and properties even when mixed. The substances in a mixture can be separated by physical means, such as filtration, distillation, or evaporation. Mixtures can be homogeneous, meaning the composition is uniform throughout, or heterogeneous, where the composition can vary within the mixture.

Some common examples of mixtures include:

• Air - a homogeneous mixture of gases like nitrogen and oxygen.
• Gasoline - a homogeneous liquid mixture of various hydrocarbons.
• Blood - a heterogeneous mixture containing cells and plasma.

Mixtures are versatile and exist in various states of matter, like solids, liquids, and gases.

Chemical Element

A chemical element is a pure substance that cannot be broken down into simpler substances by chemical means. Each element is defined by the number of protons in its nucleus, known as the atomic number. Elements are the building blocks of matter and are organized in the periodic table based on their properties.

Here are some examples of chemical elements:

• Iodine (I) - At room temperature, iodine is a solid.
• Silicon (Si) - This element is also solid at room temperature and is widely used in electronics.

Elements are capable of forming compounds by participating in chemical reactions where they can either share or exchange electrons.

Chemical Compound

A chemical compound consists of two or more elements chemically combined in a fixed ratio. Compounds have a constant composition and can be broken down into their elements through chemical reactions.

Chemical compounds include:

• Water (H₂O) - A liquid compound made of hydrogen and oxygen in a 2:1 ratio.
• Sodium hydrogen carbonate (NaHCO₃), commonly known as baking soda, composed of sodium, hydrogen, carbon, and oxygen.
• Ammonia (NH₃) - A compound consisting of nitrogen and hydrogen gases.

Compounds differ from mixtures because their individual components lose their original properties and adopt new characteristics defined by the compound.

States of Matter

States of matter refer to the distinct forms that different phases of matter take on. The primary states of matter are solid, liquid, and gas, and each state has unique characteristics based on particle arrangement and energy.

Attributes of different states of matter:

• Solids - Particles are closely packed in a fixed arrangement; solids have definite shape and volume, like iodine and silicon.
• Liquids - Particles are loosely connected, allowing liquids to flow and adapt to the shape of their container; they have definite volume but no definite shape, such as water and gasoline.
• Gases - Particles are far apart and move freely; gases have neither definite shape nor volume, filling any container they occupy, like gaseous ammonia and the components of air.

These states can change from one to another with considerable energy, in processes like melting, freezing, condensation, and evaporation.