Physics - Kinetic theory Flashcards
What is force, area and pressure measured in?
Force - Newtons
Area - meters squared
Pressure - pascal (1 pascal = 1 Newton/meters squared)
How is pressure increased?
To increase pressure, increase the force or reduce the area the force acts on.
How is pressure decreased?
To reduce pressure, decrease the force or increase the area the force acts on.
What is Charles’ law?
Charles’ Law states that if a gas is heated up and the pressure does not change, the volume will. So, for a fixed mass of gas at a constant pressure, volume ÷ temperature will remain the same.
What is Boyles law?
Gas at a constant temperature = pressure × volume. So, increasing pressure means that volume will decrease providing that the temperature remains constant.
What happens if we change the temperature of a fixed volume of gas?
When the temperature is increased, the gas particles move faster and the collisions become harder and more frequent. This means that the pressure also increases.
When the temperature is decreased, the gas particles move more slowly and the collisions are less hard and less frequent. This means that the pressure also decreases.
Eventually at absolute zero, which is -273°C, the molecules stop moving and the gas does not exert any pressure at all.
What is the coldest temperature possible? Why?
Absolute zero (-273°C) is the coldest temperature possible. At absolute zero, all the particles in a substance stop moving. They have no energy left to lose, so the substance cannot get any colder.
Conversion between the scales of °C and kelvin?
-temperature in degrees Celsius (°C) = temperature in Kelvin - 273
-temperature in Kelvin = temperature in degrees Celsius (°C) + 273
What happens when a substance is heated?
-its internal energy increases
-the movement of its particles increases
-bonds between particles break when a substance melts or evaporates, or sublimes -to form a gas from a solid
What happens when a substance is cooled?
-its internal energy decreases
-the movement of its particles decreases
-bonds between particles form when a substance condenses or freezes, or sublimes to form a solid from a gas
Why are heat and temperature not the same thing?
-Temperature is a measure of how hot something is.
-Heat is a measure of the thermal energy contained in an object.
-Temperature is measured in °C, and heat is measured in J
What is specific heat capacity?
The specific heat capacity of a substance is the amount of energy needed to change the temperature of 1 kg of the substance by 1°C. Different substances have different specific heat capacities.
What happens to the temperature during a change of state?
The temperature stays the same when a solid is melting, a liquid is boiling or a liquid is freezing during a change of state.
What is the specific latent heat?
The specific latent heat of a substance is a measure of how much heat energy is needed to melt or boil it. It is the energy needed to melt or boil 1 kg of the substance.
What is an experiment Investigating the latent heat of water?
-An electrical heater is used to melt ice for several minutes.
-The electrical energy used is calculated by multiplying the power of the heater by time.
-The mass of water melted is recorded and the relationship between energy input and mass is calculated.
-The amount of heat needed to change one kilogram of ice (the latent heat) is then determined.
