5.A Properties of Substances
What is the melting point of ice?
0°C
What is the boiling point of water?
100°C
What unit is used to measure weight?
Newtons (N)
What force opposes motion and slows objects down?
Friction and drag
What is the melting point of glass and silver?
Silver: 962°C
Glass: 1710°C
Name a material that is a good thermal conductor.
Metal
Where does evaporation occur in a liquid?
Only on the surface
What scientist discovered the idea of gravity?
Sir Isaac Newton
Describe the speed of a bicycle that has balanced forces acting on it.
It moves at a constant speed.
If a wooden ball and an iron ball of the same size are placed in water, which one will sink and why?
The iron ball will sink because it has a larger mass and weight.
Describe a scenario where you would choose a material that is a poor thermal conductor.
When making the handle of a cooking pot, using a poor thermal conductor like wood or plastic keeps the handle cool enough to touch, preventing burns.
Describe two key differences between boiling and evaporation.
Boiling is a fast process that occurs throughout the liquid at a specific boiling point, while evaporation is a slow process that happens only at the surface and can occur at any temperature.
Why does an astronaut weigh less on the Moon than on Earth?
Because the Moon has less gravity than Earth.
What force pulls objects downward?
Gravity
How does changing the shape of an object affect its ability to float?
Increasing surface area increases upthrust, making it more likely to float.
What materials should wires and their covering be made up of, and why is each material chosen?
Wires should be made of a good electrical conductor, like copper, to allow electricity to flow easily. The covering should be made of a good electrical insulator, like plastic or rubber, to prevent electric shocks and protect users.
What happens to the particles in evaporation and boiling?
In both evaporation and boiling, particles gain energy and move faster. In boiling, particles throughout the liquid gain enough energy to break free, while in evaporation, only surface particles escape gradually.
If a person has a mass of 65 kg, what is his weight on Earth? (Gravity = 9.8 N/kg)
637 N
Which force increases when a submarine rises to the surface of the water?
Upthrust
If two forces are pushing a stationary object in opposite directions with the same force, what will happen to the object?
It will remain stationary because the forces are balanced.
What causes a change of state in a substance?
When substances gain heat or lose heat
Why can water boil at a temperature lower than 100°C in a pressure cooker?
Inside a pressure cooker, the pressure is higher, allowing water to reach temperatures above 100°C without boiling, which cooks food faster.
Ali's mass on Earth is 55 kg. How much will it be on the moon?
It will stay the same.
Explain what happens to an object if forces acting on it become unbalanced.
It will change speed, direction, or start moving if it was stationary.
What force acts on a flying bird moving at a constant speed?
The force of lift, which opposes gravity, and the force of thrust, which opposes drag, allow the bird to move at a constant speed.