Molecular Model IGCSE physics

The size of a balloon increases if the pressure inside it increases.

The balloon gets bigger when it is left in the heat from the Sun. Why does this happen?

• The air molecules inside the balloon all move outwards when it is heated.

• The air molecules inside the balloon are bigger when it is heated.

• The air molecules inside the balloon move more quickly when it is heated.

• The number of air molecules inside the balloon increases when it is heated.

Driving a car raises the temperature of the tyres. This causes the pressure of the air in the tyres to increase. Why is this?

• Air molecules break up to form separate atoms.

• Air molecules expand with the rise in temperature.

• The force between the air molecules increases.

• The speed of the air molecules increases.

The volume of a gas in a sealed syringe is increased. The temperature of the gas does not change. After this change is made, what has happened to the gas molecules in the syringe?

• They move more quickly.

• They move more slowly.

• They hit the syringe walls less often.

• They hit the syringe walls more often.

A cylinder of constant volume contains a fixed mass of gas. The gas is cooled.

What happens to the pressure of the gas and what happens to the kinetic energy of the gas molecules?

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A potato snack packet is taken onto an aeroplane. During the flight the pressure inside the aeroplane changes and the potato snack packet changes shape, as shown in the diagram. Why?

• There are more collisions on the inside of the packet than on the outside.

• It is hotter.

• It is colder.

• The potato snacks are getting bigger.

These statements are about particles in a liquid. Two statements are correct. Tick the boxes next to the two correct statements.

• The particles are in a regular pattern.

• The particles are as far apart as those in a gas.

• The particles are a similar distance apart to those in a solid.

• The particles vibrate about fixed positions.

• The particles move randomly.

The diagram shows workers pouring liquid metal. The metal changes from hot liquid to cool solid. Which of the following is true after the change of state?

• uniform arrangement

• seperation between atoms decreases

• slower moving atoms

• fewer atoms

Which of the following best describes a gas?

• Molecules move around freely and are far apart from each other.

• Molecules are close together.

• Molecules vibrate about fixed positions.

• Molecules increase in size with an increase in temperature.

Which of the following describes a solid?

• molecules are closely packed

• molecules are free to move around from place to place

• molecules are far apart compared to their size

• molecules can only vibrate about a fixed position

• molecules change position randomly

Which of the following is a liquid?

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