Elements, Compounds and Mixtures — Important Questions

Brass (copper and zinc)

Step 1: A homogeneous mixture is one in which all components are uniformly distributed throughout its volume and cannot be seen separately. Step 2: Brass is an alloy — a homogeneous mixture of copper and zinc that are melted and mixed together. Their composition is uniform throughout, and the two metals cannot be seen separately. Step 3: Sand and water is a heterogeneous mixture — sand particles are visible and settle at the bottom; the components are not uniformly distributed. Step 4: Oil and water is a heterogeneous liquid-liquid mixture — oil and water do not mix (immiscible) and form separ

Difference in rates of adsorption of components on a stationary phase

Step 1: Chromatography works on the principle that different components of a mixture have different abilities to get adsorbed (attached) to a surface. Step 2: In paper chromatography, there are two phases — the stationary phase (filter paper) and the mobile phase (solvent like water or alcohol). Step 3: When the solvent (mobile phase) moves up the filter paper (stationary phase), it carries the dissolved components of the mixture along with it. Step 4: Components that are more soluble in the solvent travel farther up the paper, while components that are less soluble or more strongly adsorbed t

An element that shows properties of both metals and non-metals

Step 1: Elements are classified into four types: metals, non-metals, metalloids, and noble gases, based on their properties. Step 2: Metalloids (also called semi-metals) are special elements that show some properties of metals AND some properties of non-metals — they lie on the border between metals and non-metals in the periodic table. Step 3: For example, Silicon (Si) is a metalloid. Like metals, it has a lustrous appearance and is a hard solid. Like non-metals, it is a poor conductor of electricity in its pure form (though it acts as a semiconductor). Step 4: Option D describes noble gases

Salt dissolves, sawdust floats, sand settles at the bottom

Step 1: To predict what happens, we must consider the individual properties of each component in water. Step 2: Salt (NaCl) is soluble in water — it dissolves completely to form a salt solution (a homogeneous mixture). Step 3: Sand is an insoluble solid that is much denser (heavier) than water — it sinks and settles at the bottom of the container (sedimentation). Step 4: Sawdust is made of wood and is lighter (less dense) than water — it floats on the surface of the water. Step 5: This observation is the basis for separating this three-component mixture: first decant the salt solution + sawdus