Revision 1a

The diagram shows a helium atom.

Which particles in the helium atom have approximately the same mass?

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The table shows information about four different compounds.

Which compound contains ionic bonds?

• A

• B

• C

• D

Answer explanation

Compound D contains ionic bonds, which typically form between metals and nonmetals due to the transfer of electrons. The other compounds likely consist of covalent bonds, which involve sharing electrons.

A girl uses a rule to measure the length of a metal rod. Because the end of the rule is damaged, she places one end of the rod at the 1 cm mark as shown.

How long is the metal rod?

• 43 mm

• 46 mm

• 53 mm

• 56 mm

Answer explanation

The girl measures from the 1 cm mark. The rod extends to the 4.6 cm mark on the rule, which is 3.6 cm beyond the 1 cm mark. Therefore, the length of the rod is 3.6 cm or 36 mm, making the total length 46 mm.

A child is standing on the platform of a station, watching the trains.

A train travelling at 30 m/s takes 3 s to pass the child.

What is the length of the train?

• 10 m

• 30 m

• 90 m

• 270 m

Answer explanation

The train's speed is 30 m/s and it takes 3 seconds to pass the child. The distance covered in that time is speed × time = 30 m/s × 3 s = 90 m. Therefore, the length of the train is 90 m.

Which of the following statements is correct?

• Mass and weight are different names for the same thing.

• The mass of an object is different if the object is taken to the Moon.

• The weight of a car is one of the forces acting on the car.

• The weight of a chocolate bar is measured in kilograms.

Answer explanation

The weight of a car is indeed one of the forces acting on it, specifically the force due to gravity. The other statements are incorrect as mass remains constant regardless of location, and weight is measured in newtons, not kilograms.

The masses of a measuring cylinder before and after pouring some liquid are shown in the diagram.

What is the density of the liquid?

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In which of these situations is no resultant force needed?

• a car changing direction

• a car moving in a straight line at a steady speed

• a car slowing down

• a car speeding up

Answer explanation

A car moving in a straight line at a steady speed experiences balanced forces, resulting in no net force. In contrast, changing direction, slowing down, or speeding up requires a resultant force.

Which of the following is not necessary when using a measuring cylinder to measure the volume of a quantity of water?

• making sure that the measuring cylinder is vertical

• making sure that your eye is level with the liquid surface

• reading the bottom of the meniscus

• using the largest measuring cylinder possible

Answer explanation

Using the largest measuring cylinder possible is not necessary, as accuracy is more important than size. The other options ensure precise measurement by minimizing parallax error and reading the meniscus correctly.

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Four different mixtures of gases are made.

Which diagram represents a mixture containing only elements and no compounds?

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