Physics Revision - P6 - Molecules and Matter

What is density, what are the units, what is the equation for density?

1. It is defined as the ratio of a substance's mass to its volume. Density indicates how compact or tightly packed matter is within a given volume.

2. Its units are kg / m³

3. D = m/V

Describe how to measure the density of a regular solid.

Geometrical Method: Use a ruler or Vernier calipers to measure the dimensions of the solid (length, width, height). Calculate the volume using the formula: volume = length x width x height. Measure the mass using a digital balance. Density = Mass/Volume

Describe how to measure the density of an irregular solid.

Water Displacement Method: Fill a measuring cylinder with a known volume of water, record it as V₁. Tie the solid object with a thread and gently lower it into the water, record the new water level as V₂. Measure the mass of the solid. Use the density formula: Density = Mass / V₂.

Describe how to measure the density of a liquid.

Mass Measurement: Use a mass balance to measure the mass of the liquid. Measure the volume of the liquid using a graduated cylinder. Calculate the density using the formula: Density = Mass / Volume.

Describe the different properties of solids, liquids, and gases.

Solids have a definite shape and volume, liquids have a definite volume but take the shape of their container, and gases have neither a fixed shape nor volume.

What is the density like in Solids, Liquids and Gases?

1. In solids, molecules are tightly packed together in a fixed, orderly arrangement, which is due to strong intermolecular forces.

2. In liquids, the molecules are still close together but can move past one another, allowing for flow and a definite shape.

3. In contrast, gases have molecules that are far apart and in constant, random motion, with weak intermolecular forces.

Solid to liquid - Increasing or decreasing energy?

1.Increasing

2.Gas to liquid - Increasing or decreasing energy?

2.Decreasing

2.Liquid to gas - Increasing or decreasing energy?

2.Increasing

Liquid to solid - Increasing or decreasing energy?

1.Decreasing

What state change requires more energy - Solids to liquids or liquids to gases?

Liquids to gases

Why does the state change from liquids to gases require more energy to occur than solids to liquids?

Because in order to go from liquids to gases all bonds must be broken which takes a lot of energy whereas when you go from solids to liquids only a few are broken meaning less energy is needed.

What is Internal energy?

It is the total energy contained within a system due to the motion and interactions of its particles, including atoms and molecules. It is the sum of all the microscopic energies inside a substance, kinetic and potential.

What are the two components that make up Internal energy?

1. Kinetic Energy

2. Potential Energy

What is Kinetic Energy?

It is the energy an object possess due to its motion. Kinetic energy increases as the particles move faster, this is to do with the temperature change in the substance.

What is Potential Energy?

The stored energy of an object due to its position. Potential energy of the particles increases as they move apart, this happen when state of substances change.

When a substance is heated, the energy of its particles increases due to an increase in their kinetic energy. This results in a higher internal energy and a higher temperature. The energy change is due to the transfer of energy from the heat source to the particles, which causes them to vibrate more vigorously. As the particles gain energy, they move faster and become less tightly packed, leading to a decrease in the substance's density.

Describe how the energy of the particles of a substance changes when it is heated.

In Specific Latent Heat, what does Specific mean?

Per Kg

In Specific Latent Heat, what does Latent mean?

Hidden

In Specific Latent Heat, what does Heat mean?

Joules

What is another way of saying Specific Latent Heat?

Potential Energy

What is Specific Latent Heat?

The amount of heat energy required to change the state of 1 kilogram of a substance without changing its temperature.

In Specific Heat Capacity, what does Capacity mean?

The amount it can hold

What is another way of saying Specific Heat Capacity?

Kinetic energy

What is Specific Heat Capacity?

The amount of heat energy required to raise the temperature of one unit mass of a substance by one degree Celsius.

What does Specific Latent Heat of Fusion mean?

The amount of heat energy required to change 1 kilogram of a substance from solid to liquid at its melting point without changing its temperature.

What does Specific Latent Heat of Vaporisation mean?

The amount of energy required to convert 1 kilogram of a substance from liquid to gas without changing its temperature.

What is the formulae for Specific Latent Heat in calculations?

Q = M x L

What does the Q mean in Q = M x L?

The heat energy absorbed or released (in joules, J)

What does the M mean in Q = M x L?

The mass of the substance (in kilograms, kg)

What does the L mean in Q = M x L?

The Specific latent heat (in J/kg)

What is a Calorimeter?

It is an insulated device used to measure the heat exchanged in chemical or physical processes, such as melting or boiling, allowing the determination of specific latent heat by measuring temperature changes of a surrounding substance like water.

1. Weigh a known mass of the substance.

2. Place the substance in the calorimeter (for fusion, using ice in water; for vaporization, using a liquid in a calorimeter that can handle steam or boiling liquid).

3. Measure temperature changes if needed.

4. Supply heat gradually and record the energy input (often by electrical heating: Q=I⋅V⋅tQ=I⋅V⋅t, where I = current, V = voltage, t = time in seconds).

5. For melting/boiling processes, note that temperature remains constant; all heat energy goes into the phase change.

How to measure the Specific Latent Heat of ice or water.

Why does a gas exert pressure?

Because its molecules are in constant motion and collide with the walls of its container, transferring momentum during each collision.

Describe how to see evidence of gas molecules moving around at random.

Brownian’s Motion and smoke bouncing of oxygen

What is Boyle’s Law?

Constant = P x V