P6: Molecules and Matter Flashcards
What is the equation for density?
Density (kg/m^3) = Mass / Volume
What is density and how can it be found?
• The density of a substance is its mass per unit volume.
• Can be found by using balance to find mass of an object, if it is regular you can use measurements to find the volume.
• For a liquid use a measuring cylinder to find the mass and volume.
Describe the method of how to find the density of an irregular object?
- Measure and record mass of object using a balance/weighing scale.
- Fill a eureka can with water and let any excess water flow out of the spout.
- Gently place object into water and collect any water displaced in a beaker positioned under the spout.
- Carefully pour this water into a measuring cylinder to find the volume of the water, which is equal to the volume of the object.
- Use the equation Density = Mass/Volume to find the density.
What are the characteristics of solids, liquids and gases?
Solids: Fixed shape/volume, doesn’t flow, high density, particles vibrate.
Liquids: flows, no fixed shape, fixed volume.
Gases: Flows, no fixed shape or volume, low density, easily compressed.
What is the conservation of mass?
When a substance changes state, the number of particles in the substance is unchanged, so the mass is also the same.
What is internal energy?
Energy stored in particles within in a system in the form of kinetic (movement) or potential energy (positions relative to each other).
Internal Energy = Kinetic Energy + Potential Energy
What happens as the temperature of a solid increases?
- Kinetic energy is transferred as the solid is heated causing its temperature to increase.
- When the temperature reaches the solid’s melting point, the temperature stays constant until all of the bonds have been broken down and potential energy increases and changes. Particles vibrate more until they have enough energy to break away from their bonds.
- The energy supplied during this change is latent heat.
What is the equation for specific latent heat and what is it?
Specific Latent Heat of Fusion/Vaporisation (J/kg) = Energy / Mass
It is the energy needed to change 1kg of a substance at its melting/boiling point without changing temperature.
What is the equation for pressure?
Pressure (N/m^2 or Pa) = Force / Area
What is gas pressure and what happens if the temperature increases?
• The pressure of a gas in a container is caused by the force of random collisions of gas molecules on the surface.
• When it is heated, the particles gain kinetic energy and move faster with more force, causing pressure to increase.
What is Brownian Motion?
The random, uncontrolled, unpredictable movement of particles in a fluid as they constantly collide with other particles/molecules.
What is Boyle’s law?
That pressure and volume are inversely proportional for a fixed mass of gas at a constant temperature.
Pressure x Volume = Constant
What happens if more particles are added to a fixed volume of gas?
Having more gas particles in the same volume means that more particles are present, so more collisions occur and pressure increases.
What happens if there are a fixed number of particles in a smaller volume?
- Particles collided more frequently and gain momentum.
- Particles have a greater velocity due to rebound velocity, meaning particles collide more frequently with more force.
