10.1 Temperature, Heat and Thermal Energy

Physics 11 Name:______Date: ______Unit 10 Thermal Energy 10.1 Temperature, Heat and Thermal Energy

According to the ______, all matter is made up of tiny particles, which are constantly moving. The particles molecules or atoms attract each other to some extent. The particles can move in a number of ways: they can move in straight lines (between collisions); they can rotate;

and they can vibrate

What makes something cold or hot? Particles in an object are ______, hence they have ______. An object with faster moving particles has more kinetic energy.______The overall energy (in the motion of the particles) of an object is called the ______

When thermal energy is transferred from one material to another material, the amount of energy transferred is called ______The way we describe how hot or cold a body is, relative to some well-chosen standard, is to use a number we call the ______

Temperature: ______. Temperature depends on the ______1.0kg 2.0kg

If both steel blocks have the same temperature, their average kinetic energy is the same. The 1.0kg block has half the thermal energy as the 2.0kg block… It’s half as massive.

Measuring temperature (thermometer): On the Celsius scale, this temperature would be approximately ______. This temperature is called ______. On another temperature scale called the ______scale, after British physicist Lord Kelvin (1824-1907), absolute zero is assigned a value of 0 K. On this scale, the unit for temperature is not called a degree, but instead a kelvin (K). Therefore , ______. A Kelvin is the same size as a Celsius degree. This means that a temperature of 0oC would be equal to 273 K. Water boils at 100oC, or 373 K. To

scientists, the Kelvin scale is useful because ______Celsius: A scale based on water. When water freezes / ice melts, we say it’s 0ºC When water evaporates / water vapour condenses, we say it’s 100ºC How hot can we go? … no one knows… atoms pushing the speed of light??? How cold can we go? … -273.15 ºC

At -273.15ºC, particles stop moving… there is no kinetic energy. Kelvin: same as Celsius… just shifted. 273.15ºC = 0 K “absolute zero” TK  TC  273.15 Convert 20ºC to K.

Convert 50K to ºC.

Changing Temperature

How do you change the temperature of something? …add energy (heat)? How much? Increasing the temperature of 1.0kg of substance by 1K (or 1ºC) requires a specific amount of energy. How do we know what this amount is?... experimentation.

Measuring Thermal Energy The amount of thermal energy in an object will depend on several factors.  First, it depends on the ______, of the object.  Second, it depends on the ______, of the object.  Third, it depends on ______in the object. Different materials have different capacities for holding thermal energy. One material that has an exceptionally high capacity for holding thermal energy is water.

This amount of energy is called the ______.

______

Table 12.1 Specific Heat Capacities

Substance J/kg/Co Substance J/kg/Co water 4200 steam 2100 methyl alcohol 2400 aluminum 920 ethylene glycol* 2200 glass 840 ice 2100 iron 450 kerosene 2100 copper 430 (*antifreeze) lead 130

Since the specific heat capacity, c, is the amount ______that must be transferred to raise the temperature of one kilogram by one Celsius degree, then ______, where ∆E is the energy transferred, m is the mass of material, and ∆T is the change in temperature. Or, ______

Eg. Water requires 4180J of energy to raise 1.0kg by 1 Kelvin (or 1 degree Celsius). The amount of energy (heat) lost or gained is given by:

EH  mCT m = mass of substance (kg) C = heat capacity (J/kg·K) ∆T = change in temperature (K)

Example 1: A 0.40kg block of iron is heated from 295K to 325K. How much heat had to be transferred?

Example 2: How much heat must be transferred into 5.0 kg of water to raise its temperature from 20oC up to 97oC?

Solution:

Example 3: If 25 kJ of heat is transferred to 50.0 kg of water initially at 20.0°C, what will the final temperature of the water be?

Solution p.280 #5,6