Test: Nature of Matter: Elements, Compounds, and Mixtures - Class 8 MCQ

Compounds play a vital role in innovation and science because they allow for the creation of new substances with unique properties that can be applied in medicine, agriculture, and technology, leading to advancements in these fields.

A compound is characterized by having a fixed composition and unique properties that differ from those of its constituent elements. For instance, water (H₂O) has different properties than hydrogen and oxygen, the elements that form it.

When substances combine to form a compound, their properties change, resulting in a new substance with unique characteristics. For example, sodium and chlorine combine to form sodium chloride, which is different from both elements.

Matter is defined as anything that has mass and occupies space. This includes all physical substances, like solids, liquids, and gases. Understanding matter is fundamental to studying the physical world and its properties.

The key difference is that homogeneous mixtures have a uniform composition throughout, meaning the components are indistinguishable, while heterogeneous mixtures consist of visibly different substances that can be easily separated.

Elements consist of only one type of atom and cannot be broken down into simpler substances by chemical means. Each element has unique properties and is represented on the periodic table.

Heterogeneous mixtures can be separated by physical means because their components remain distinct and can be identified separately. For example, a mixture of sand and salt can be separated using water and filtration.

An alloy is a mixture of two or more metals that typically have distinct properties. For example, bronze is an alloy made from copper and tin, which enhances the material's strength and durability compared to its constituent metals.

A mixture is defined as a combination of two or more substances where each substance retains its own properties and does not chemically react with the others. This means that the components can often be seen and separated easily. For example, a salad is a mixture of various vegetables, each maintaining its own characteristics.

When calcium hydroxide (lime water) reacts with carbon dioxide in the air, it produces calcium carbonate, which forms a milky solution. This is a classic experiment demonstrating the presence of carbon dioxide in the air.

A mixture is not a pure substance; it consists of two or more different substances combined together. In contrast, elements and compounds are classified as pure substances because they contain only one type of particle.

Saltwater is a homogeneous mixture because the salt dissolves in water, creating a uniform solution where the individual components cannot be distinguished. In contrast, vegetable soup or trail mix contains visible separate parts that can be identified.

The primary reason for separating mixtures in scientific contexts is to obtain pure substances that can be studied or used in further applications. For example, scientists might separate salt from seawater to analyze its purity.

Metals are characterized by their malleability and ductility, which means they can be shaped into sheets or drawn into wires without breaking. This property makes metals very useful in construction and manufacturing.

Pure substances are defined as materials that contain only one type of particle throughout their composition. This means they cannot be separated into other substances by physical methods. Examples include distilled water and pure metals like gold.

Gold is an example of a native mineral because it occurs naturally in its elemental form. Other examples include silver and copper. In contrast, quartz and calcite are compound minerals made of two or more elements.

Graphene Aerogel is primarily made from carbon, which gives it unique properties such as being extremely lightweight and highly porous. This material is used in various applications, including environmental cleanup and energy-saving technologies.

The Air Quality Index (AQI) is used to measure and communicate the levels of various pollutants in the air, providing information about air quality and its potential health effects on the population. A higher AQI indicates poorer air quality and higher health risks.

Nitrogen is the primary component of air, making up about 78% of the atmosphere. While oxygen and carbon dioxide are also present, nitrogen is the most abundant gas in air.

Dissolving sugar in water is an example of a physical change because the sugar can be recovered by evaporating the water, and no new substances are formed. In contrast, burning wood and cooking an egg involve chemical changes.