GPS  S8S8P2 Students will be familiar with the forms and transformations of energy.  d. Describe how heat can be transferred through matter by the collisions of atoms (conduction) or through space (radiation). In a liquid or gas, currents will facilitate the transfer of heat (convection).

Heat vs. Temperature  Temperature is the measurement of the average kinetic energy of particles in an object.  Heat is a flow of energy from an object at a higher temperature to an object at a lower temperature.

 Temperature depends on particle movement.  All particles in matter have kinetic energy.  Temperature is the measurement of the average kinetic energy of particles in an object.

 SI unit for temp. is the Kelvin  a. K = C (10C = 283K)  b. C = K – 273 (10K = -263C)  Thermal Energy – the total of all the kinetic and potential energy of all the particles in a substance.

Thermal energy relationships a. As temperature increases, so does thermal energy (because the kinetic energy of the particles increased). b. Even if the temperature doesn’t change, the thermal energy in a more massive substance is higher (because it is a total measure of energy). b. Even if the temperature doesn’t change, the thermal energy in a more massive substance is higher (because it is a total measure of energy).

6. Specific Heat a. Some things heat up or cool down faster than others. Land heats up and cools down faster than water

Heat and Thermal Energy  Question: In which direction does heat always transfer energy?  Think about an ice cube in a bowl on a table.

 First, the ice cube and table have different temperatures.  The ice cube melts and the water that comes form the ice will eventually have the same temperature as the bowl.  This temperature will be lower than the original temperature of the bowl but higher than the original temperature of the ice cube.  Why do the bowl and water end up with the same temperature?

 The particles in the ice cube and the particles in the bowl continually bump into each together and energy is transferred from the bowl to the ice.

 Heat is always the transfer of energy from an object at a higher temperature to an object at a lower temperature.  So, energy flows from the particles in the warmer bowl to the particles in the cold ice and later, the cold water.

HEAT FLOW Heat can flow in one of two directions:Exothermic To give off heat; energy is lost from the system: (-q)Endothermic To absorb heat; energy is added to the system: (+q)

Measuring Heat  Calorie – the amount of energy needed to raise the temperature of 1 g of water by 1 0 C.  Joule (J) is the standard scientific unit in which energy is measures.  One calorie = 4.18 joules

Specific Heat a. Some things heat up or cool down faster than others. Land heats up and cools down faster than water

b. Specific heat is the amount of heat required to raise the temperature of 1 kg of a material by one degree (C or K). 1) C water = 4184 J / kg C 2) C sand = 664 J / kg C This is why land heats up quickly during the day and cools quickly at night and why water takes longer.

Why does water have such a high specific heat? Water molecules form strong bonds with each other; therefore it takes more heat energy to break them. Metals have weak bonds and do not need as much energy to break them. water metal

How to calculate changes in thermal energy Q = m x  T x C p Q = m x  T x Cp Q = change in thermal energy m = mass of substance  T = change in temperature (Tf – Ti) Cp = specific heat of substance

HEAT CAPACITY & SPECIFIC HEAT HEAT CAPACITY: HEAT CAPACITY: The quantity of heat needed to raise the temperature of a substance one degree Celsius (or one Kelvin). q = C p  T SPECIFIC HEAT: SPECIFIC HEAT: The quantity of heat required to raise the temperature of one gram of a substance by one degree Celsius (or one Kelvin). q = s x m x  T.

Sample problem 1  A g piece of iron absorbs joules of heat energy, and its temperature changes from 25°C to 175°C. Calculate the specific heat capacity of iron.

Sample Problem 2  A copper ornament has a mass of kg and changes from a temperature of C to C. How much heat energy did it gain?

A calorimeter is used to help measure the specific heat of a substance.

Energy moves as heat in three ways: 1. Conduction 2. Convection 3. Radiation

 What is happening in the photographs?

Conduction  Moves energy from one object to another when they are touching physically.  Conductors are materials that transfer energy easily.  Insulators are poor conductors. Example: Styrofoam cups

Convection  The process that transfers energy by the movement of large numbers of particles in the same direction within a liquid or gas.  As the kinetic energy of particles increases, the particles spread out over a larger area.  This causes a decrease in density.

 So, convection occurs when a cooler, denser mass of the gas or liquid replaces a warmer, less dense mass of the gas or liquid by pushing it upward.

Example  Warm water is dense than cold water so the warm water is pushed upward as cooler denser water moves underneath.

Radiation  Energy that travels as electromagnetic waves which include visible light, microwaves, and infrared light.  Consider the sun. It transfers energy to your skin causing the particles on your skin to increase in movement which you detect as an increase in temperature.

 When radiation is emitted from one object and then is absorbed by another, the result is often a transfer of energy through heat.  All objects radiate energy.

 All three can transfer from warmer to cooler objects but only radiation can travel through empty space i.e. sun to Earth.