Kinetic Energy: Particle Movement & Temperature

• Internal energy depends on the forces between particles in a substance, which can be attractive or repulsive.
• Particles will push apart when they are compressed
• At longer distances the forces pull the particles back together.
• These forces act like a spring.
• Work stores energy when a spring is stretched by forces.
• Particles of less mass will cause the temperature to increases more per joule
• Particles with more mass will cause the temperature to increase less per joule

Particle Kinetic Energy

• Depends on the mass whereby the greater the mass the more energy is required to increase their speed.
• Transferring the same amount of energy by heating will increase the speed of the vibrations of particles with less mass to a greater amount .
• Some materials have strong forces between particle while some have weaker forces between particles
• Stronger forces make it more difficult for the particles to vibrate faster
• Energy transferred does not raise the temperature as much if forces between particles are strong.
• Potential energy in the bonds between the particle increases when they are further apart, meaning the temperature does not increase by as much for each joule of energy transferred.

Specific Heat Capacity

• Specific heat capacity means it is harder to increase the temperature of some materials than others.
• Aluminium's specific heat capacity is 921 J/kg/°C, while iron's is 460 J/kg/°C.
• It takes more than twice as much energy to increase the temperature of aluminium compared to iron. Specific heat capacity differences are due to particle masses and the forces between them.

Experiment: Comparing Rock Samples

• Measure the greatest increase in water temperature, the rock sample with the greatest specific heat capacity can be determined.

Definition of Keywords

• Specific heat capacity is the change in internal energy when the temperature of 1kg of the material changes by 1°C. Internal energy is the sum of kinetic and potential energy of the particles something is made of.
• Kinetic energy is the energy an object has because of its motion.
• Potential energy is the energy an object has because of its position and the forces acting on it.

Factors Affecting Thermal Energy Storage

• Temperature, where the higher the temperature, the more energy is stored.
• Mass, where the greater the mass, the more energy is stored.
• Type of material.
• The higher the specific heat capacity, the amount of energy stored will be more for the same mass and temperature.

Density

• Volume of regular solids can be calculated from measuring their dimensions.
• Dimensions are measured in Vernier callipers or a micrometer.
• Mass can be found using scales.
• The volume of a sphere is V = 4/3πr3, where r is the radius (diameter ÷ 2).
• The volume of a cuboid is V = l x w x h.

Measuring density of Liquids

• Measuring liquids uses a top pan balance and measuring cylinder.
• Measure of Volume in liters
• Measure of weight in Kg

Measuring the Density of Solid Objects

• Measuring solid objects uses a displacement can and scales.
• Volume found via displacement can.

Defining Density

• Density = mass / volume
• Density is measured in kilograms per cubic meter (kg/m³) or grams per cubic centimeter (g/cm³).
• Mass is measured in kilograms (kg) or grams (g).
• Volume is measured in cubic meters (m³) or cubic centimeters (cm³).
• Mass stays the same when state changes
• Density changes because the mass per unit volume changes

Insulating Buildings

• Insulating buildings reduces heat exchange with the air outside, and the amount of fuel required to keep them warm in winter and cool in summer.
• Materials like fiberglass, foam board and spray foam help reduce heat transfer in walls, floors, attics and roofs.
• Various methods include floor, wall/cavity, and loft insulation
• Double glazed windows reduce heat exchange between inside and outside, and draught excluders stop air exchanging under doors. Thick curtains insulate windows at night.
• Heat can escape through walls, windows, roof, and floor.

Task

• The walls are the most heated part, and the corners of the house are the coldest parts.
• Assuming the house has a uniform temperature, better insulation will reduce the loss.
• The best insulated parts are the walls, while the worst insulated parts are the roof and corners.