Explanation

In the lab, oxygen gas is prepared by heating potassium chlorate (KClO₃) in the presence of manganese dioxide (MnO₂) as a catalyst.

MnO₂ speeds up the decomposition of KClO₃ without being consumed.

Explanation

Sand is primarily composed of silicon dioxide (SiO₂), formed when silicon and oxygen combine.

It is a common natural material found in deserts, beaches, and riverbeds.

Explanation

Explanation

Calcium chloride (CaCl₂) is a hygroscopic substance, meaning it absorbs moisture from the air.

It is commonly used as a drying agent in desiccators to keep the environment moisture-free.

Explanation

Casein plastic is made by adding an acid (like vinegar) to milk, which causes the casein protein to form a solid.

This solid can be molded and dried to create a type of early plastic, known as casein plastic.

Explanation

Tin and Nickel both have a silvery-white appearance.

They are corrosion-resistant metals commonly used in coatings and alloys.

Explanation

Dry ice sublimation is a physical change where solid CO₂ directly turns into gas without changing its chemical composition.

Rusting of iron, burning of wood, and cooking of egg are all chemical changes, where new substances are formed.

Explanation

Coagulation is the process where a liquid changes into a semisolid or gel-like state.

It often occurs in biological and chemical systems, such as blood clotting or curd formation.

Explanation

Methyl orange is a pH indicator that turns yellow in alkaline solutions.

In acidic solutions, it appears red, but in basic or alkaline solutions, it changes to yellow.

Explanation

Sublimation is the process where a solid directly changes into gas without becoming liquid.

Dry ice (solid CO₂) undergoes sublimation at room temperature.