Matter and Materials - Grade 7 Science Free MCQ Test with solutions

• 0°C is the freezing point of water, which is the temperature at which water turns from liquid to solid (ice).
• 100°C is the boiling point of water at standard atmospheric pressure (1 atm), which is the temperature at which water turns from liquid to gas (steam).

Thus, the correct answer is B: 100 degree Celsius.

So, the correct analogy is:

0°C : Freezing point of water :: 100°C : Boiling point of water

• Love, Smell, and Thoughts are abstract concepts or feelings that are not tangible and cannot be physically touched or seen.
• Almonds, on the other hand, are a tangible, physical object — a type of nut that can be seen, touched, and eaten.

Therefore, Almonds is the odd one out because it is the only physical object in the list.

• Sublimation is the process where a substance changes directly from a solid to a gas without passing through the liquid phase.
• Carbon dioxide (CO₂) is known to sublime at atmospheric pressure. It changes directly from solid dry ice (solid CO₂) into gas without becoming liquid.

Other substances listed:

• Salt: Does not sublime. It melts into a liquid before evaporating.
• Water: While water can evaporate (liquid to gas), it does not sublimate under normal conditions.
• Air: Is a mixture of gases and does not undergo sublimation.

Thus, Carbon dioxide is the substance that is able to sublime.

• Liquids can freeze: When a liquid is cooled below its freezing point, it changes into a solid. For example, water turns into ice when it freezes at 0°C.
• Solids can freeze: While solids are already in a frozen state, they can still undergo further solidification under certain conditions (e.g., solidifying a molten metal).
• Gases can freeze: Gases can condense and then freeze into a solid if cooled to extremely low temperatures. For example, carbon dioxide can freeze into dry ice (solid CO₂) under the right conditions.

Thus, all of the above statements are correct.

• Chemical change: Baking a cake involves the mixing of ingredients and the application of heat, which causes chemical reactions (e.g., the rising of the batter due to gas production, the browning of sugar, etc.). These reactions result in new substances being formed, making it a chemical change.
• Irreversible change: Once the cake is baked, it cannot be reversed back to its original ingredients. The changes that occur during baking (like the transformation of raw batter into a solid cake) are permanent, making it an irreversible change.

Thus, the correct answer is Both (a) & (c).

• Sublimation is the process where a substance changes directly from a solid to a gas without passing through the liquid phase. A common example is dry ice (solid carbon dioxide), which sublimates directly into carbon dioxide gas at room temperature.
• Evaporation refers to the process where a liquid turns into a gas, usually at the surface of the liquid.
• Melting is the process where a solid turns into a liquid.
• Heating is a general term for the application of heat but does not specifically describe the phase transition.

Therefore, the correct answer is Sublimation.

• Melting of ice is a physical change because it involves a change in the state of matter (from solid to liquid) without changing the chemical composition of the substance. When ice melts, it becomes water, but it's still H₂O.
• Breaking of glass is also a physical change. The glass is broken into smaller pieces, but its chemical composition remains unchanged.
• Baking of cake is a chemical change, as new substances are formed through chemical reactions during baking (e.g., the reaction between flour, sugar, and heat).

Thus, the correct answer is D: Both (a) and (c).

• Solid has a definite shape and volume. The particles in a solid are tightly packed together, which gives it a fixed shape and volume.
• Liquid has a definite volume but no definite shape. It takes the shape of the container it is in.
• Gas has neither a definite shape nor a definite volume. Gas expands to fill the entire space of the container it occupies.

Thus, the correct answer is A: Solid.

• Solid has both a definite shape and a definite volume.
• Liquid has a definite volume but no definite shape. It takes the shape of the container it is in, but the volume remains constant.
• Gas has neither a definite shape nor a definite volume. It expands to fill both the shape and the volume of its container.

Thus, the correct answer is B: Liquid.

• Melting is the process in which a solid (ice) changes into a liquid (water) upon heating.
• Evaporation refers to the process where a liquid turns into a gas.
• Condensation is the change from a gas to a liquid.
• Freezing is the process where a liquid turns into a solid.

So, the correct answer is C: Melting.