IGCSE Physics 2.3 Thermal Physics 0625

A wooden wheel can be strengthened by putting a tight circle of iron around it. Which action would make it easier to fit the circle over the wood?

• cooling the iron circle

• heating the iron circle

• heating the wooden wheel and cooling the iron circle

• heating the wooden wheel but not heating or cooling the iron circle

Four thermometers, with their bulbs painted different colours, are placed at equal distances from a radiant heater. Which thermometer shows the slowest temperature rise when the heater is first switched on?

• dull black

• dull white

• shiny black

• shiny white

Some hot water is sealed inside a metal can. The can is in a vacuum in outer space. The hot water slowly cools down. How does the thermal energy escape into space?

• by conduction then convection

• by conduction then radiation

• by evaporation then convection

• by evaporation then radiation

The diagram shows a convection current caused by a piece of ice placed in a beaker of water at room temperature.

Which row correctly compares the temperatures and densities at water points P and Q?

A is for temperature at P and B is for density at P

• A - higher than at Q

  B - higher than at Q

• A - higher than at Q

  B - lower than at Q

• A - lower than at Q

  B - higher than at Q

• A - lower than at Q

  B - lower than at Q

A rod is made of copper and wood joined together.

The rod is heated at the join in the centre for about a minute.

At which labelled point will the temperature be lowest, and at which point will it be highest?

A - Lowest temperature, B - highest temperature

• A - P

  B - Q

• A - P

  B - R

• A - S

  B - P

• A - S

  B - R

An astronaut aboard the International Space Station (ISS) lights a match. Using ideas about convection, what does the flame look like?

• It burns upwards, like a normal flame.

• It burns like a normal flame, but is directed downwards, towards the Earth

• It burns like a normal flame, but is directed sideways, in the opposite direction to the direction the ISS is travelling.

• It burns in a sphere for a short time, before going out.

Ice is trapped by a metal gauze at the bottom of a tube containing water.

The water is heated strongly at the top, but the ice only melts very slowly.

Why does the ice melt so slowly?

• Heat energy always travels upwards.

• Hot water is more dense than cold water.

• Metal gauze does not allow heat to pass through

• Water is a poor conductor of heat.

One end of a rod of copper is placed in hot water.

Thermal energy travels along the rod to make the other end warmer.

What is the behaviour of the copper at an atomic level that accounts for most of the transfer of thermal energy from one end to the other?

• Atoms at the hot end gain kinetic energy and move towards the other end.

• Atoms at the hot end expand, colliding with other atoms and transferring energy.

• Free electrons at the hot end gain energy and move towards the other end, colliding with atoms along the rod.

• Free electrons at the hot end gain energy from the hot water and move directly to the other end.

In a cold country, the ground is covered in snow. There is a pile of black sand outdoors and its temperature is the same as that of the snow. A man sprinkles a thin layer of this sand over the snow.

Why does the black sand help to melt the snow during the day?

• Any thermal energy still left in the sand will melt the snow.

• The black sand is a good absorber of the infrared radiation from the Sun.

• The black sand is a good conductor of thermal energy.

• The black sand lowers the melting point of the snow.

The diagram shows four rods. Each rod is made of a different metal.

Wax is used to attach small metal balls at the rod ends P, Q, R and S.

Each rod is the same size. They are heated uniformly by a Bunsen burner at point X.

As the rods warm up, the wax melts and the balls fall off.

Why does the ball on the silver rod fall first?

• Silver is the best conductor of heat.

• Silver is the worst conductor of heat.

• Silver is the best radiator of heat.

• Silver is the worst radiator of heat.