Science Review Quiz

Does stirring a solution always increase the rate at which a substance dissolves?

• true

• false

Answer explanation

Stirring a solution can help distribute solute particles, but it doesn't always increase the rate of dissolution. Factors like temperature and solute size also play significant roles, making the statement false.

Which property would best help separate a mixture of salt and iron filings using a magnet?

• Color

• Magnetism

• Particle size

• Texture

Answer explanation

Magnetism is the key property that allows for the separation of iron filings from salt, as iron is magnetic while salt is not. Using a magnet will attract the iron filings, effectively separating them from the mixture.

What happens when sugar dissolves in water?

• It remains solid and floats on top.

• It breaks down and mixes evenly with the water.

• It stays solid and sinks to the bottom.

• It changes water color but remains separate.

Answer explanation

When sugar dissolves in water, it breaks down into smaller particles and mixes evenly, creating a homogeneous solution. This is why the correct answer is that it breaks down and mixes evenly with the water.

Tags

NGSS.MS-PS1-2

Which method will dissolve salt in water the fastest?

• Adding whole salt crystals to cold water without stirring

• Adding crushed salt to hot water and stirring

• Adding whole salt crystals to hot water and stirring

• Adding crushed salt to cold water without stirring

Answer explanation

Adding crushed salt to hot water and stirring increases the surface area and temperature, allowing the salt to dissolve faster compared to other methods, which either lack stirring or use whole crystals.

Tags

NGSS.MS-PS3-4

NGSS.MS-PS3-3

Which mixture can be separated by picking out different colors?

• Mixed nuts

• Colored beads

• Mixed bolts and screws

• Different sizes of sand

Answer explanation

Colored beads can be easily separated by picking out different colors, as they are distinct and visually identifiable. In contrast, mixed nuts, bolts, and screws do not have clear color distinctions, and different sizes of sand cannot be separated by color.

Which two phase changes occur when heat is removed?

• Melting and evaporation

• Condensation and freezing

• Freezing and melting

• Evaporation and condensation

Answer explanation

When heat is removed, substances undergo phase changes that release energy. Condensation occurs when gas turns into liquid, and freezing occurs when liquid turns into solid. Thus, the correct answer is condensation and freezing.

Tags

NGSS.MS-PS1-4

Which pair is incorrectly matched as soluble or insoluble?

• Sugar and water

• Salt and oil

• Flour and water

• Vinegar and oil

Answer explanation

Vinegar and oil are incorrectly matched as vinegar is polar and mixes with water, while oil is non-polar and does not mix with vinegar. The other pairs are correctly matched as soluble or insoluble.

Select the example of a mixture of solids.

• Fruit salad

• Trail mix

• Fruit juice

• Vegetable soup

Answer explanation

Trail mix is a mixture of various solid ingredients like nuts, dried fruits, and sometimes chocolate, making it a clear example of a mixture of solids. In contrast, fruit salad and vegetable soup contain liquids, and fruit juice is a liquid.

Which factor speeds up the dissolving process?

• Decreasing temperature

• Increasing surface area

• Changing the color of the substance

• Adding more solvent

Answer explanation

Increasing surface area speeds up the dissolving process because it allows more solute particles to interact with the solvent at once, enhancing the rate of dissolution. Other options do not effectively increase this interaction.

True or false: Conducting multiple trials in an experiment increases the reliability of the results.

• true

• false

Answer explanation

True. Conducting multiple trials helps to minimize the impact of random errors and variability, leading to more consistent and reliable results in an experiment.