Chapter 4 Temperature and Heat

All Matter is Made of Moving Particles All matters is made up of atoms, and atoms are always in motion, even if the objects themselves do not change their position. The motion of these tiny particles gives the object energy.

The Kinetic Theory of Matter The Kinetic Theory of Matter states that all of the particles that make up matter are constantly in motion. Solid: Particles in solids are held tightly together but are always in motion. Liquid: Particles in liquids slide by one another and are always in motion. Gas: Particles in gases are completely free to move and are always in motion.

Temperature and Kinetic Energy Particles move at different speeds have different kinetic energies Temperature is a measure of the average kinetic energy of all the particles in an object. Particles Move Fast Particles Move Slow

Temperature and Kinetic Energy We experience the connection between temp. and energy everyday. For example: On a cold day, you warm your hands by putting them near a fire. The added energy makes the particles in your hand move faster.

Temperature Measured In two common scales, temperature is measured in units called, degrees (°) Farenheit: 32°- Freezing; 212°- Boiling Celsius: 0°C- Freezing; 100°C- Boiling A thermometer is used to measure temperature

Liquid Thermometers Liquid-filled thermometers measure how much the liquid expands in a narrow tube as the temperature increases. Mercury is dangerous to handle so many thermometers today are filled with alcohol instead.

Thermal Expansion The property that makes liquid-filled thermometers work is called thermal expansion. Example: Construction engineers often have to take thermal expansion into account because steel and concrete both expand with increasing temperature. The Gateway Arch p. 108

Why does water warm up so slowly? As Compared with Butter and Oil? Because more energy Is needed!

Heat is Different from Temperature Do Not Confuse the them! Temperature is the measure of the average kinetic energy of all the particles in an object.

Flow of Energy Ice Cube in a bowl- At first different temperatures then they have the same temperature. Energy flows from the particles in the warmer bowl to the particles in the cold ice and, later, the cooler water. If energy flowed the opposite direction—from cooler to warmer---the ice would get colder in the bowl and bowl would get hotter! THAT NEVER HAPPENS!

Thermal Energy When energy flows from a warmer object to a cooler object, the thermal energy of both of the objects changes. Thermal Energy- the total random kinetic energy of particles in an object.

Measuring Heat The most common unit of heat measurement are the calorie and the joule One calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1°C. The joule (J) is the standard scientific unit in which energy is measured. One calorie is equal to 4.18 joules.

Calorie or calorie? Calorie with a big “C” is referring to nutrition. It is actually one kilocalorie or 1000 calories. This means that 1 Calorie in food contains enough energy to raise the temperature of 1 kilogram of water by 1°C. So, each Calorie in food contains 1000 calories of energy.

Calorimeter How do we know how many Calories are in a food? We use a calorimeter to see how much energy is released through heat.

Calories Big Mac- 530 Calories Hardee’s- http://www.shapefit.com/hardees.html Pizza Hut- http://www.pizzahut.com/Nutrition.aspx Taco Bell- http://www.calorie-counters.net/taco_bell.html

Burn It! http://www.asd.k12.pa.us/documents/press/Wellness%20chart%20--%20How%20Long%20Does%20It%20Take%20To%20Burn%20100%20Calories.pdf

Some Substances Change temperature more easily than others

Specific Heat The amount of energy required to raise the temperature of 1 gram of a substance by 1°C is the specific heat value. So, each substance absorbs a different amount of energy in order to show the same increase in temperature. Page 113 (Graph)

Do You Know? 1) Which of these substances has the highest specific heat?      (a) Sample A      (b) Sample B      (c) Sample C      (d) Sample D Answer: A

Specific Heat and Mass Thermal energy depends on the object’s mass. Which mass of water has more thermal energy?

Review How is temperature related to heat? Heat transfers energy because a temperature difference exist. What units do we use to measure heat? Calorie and Joule Describe specific heat The amount of energy that 1 gram of a substance needs to absorb to increase in temperature by 1°C.

Energy Moves as Heat in Three Ways Conduction Convection Radiation

Is this a good conductor?

Conduction The process that moves energy from one object to another when they are touching physically.

Conductors Some materials transfer the kinetic energy of particles better than others. Conductors are materials that transfer energy easily. The pot handle is a poor conductor

Insulators Materials that conduct heat slowly or poorly are called insulators Glass, wood, plastic and rubber are poor conductors (good insulators) Nearly all liquids including water are poor conductors (good insulators) Gases, including air are poor conductors,e.g., wool feels warm because it traps a lot of air A fridge has insulation material round it to keep it cold – reduces amount of heat conducted to inside from the warmer room

Convection Convection is the movement of gases or liquids from a cooler spot to a warmer spot. If a soup pan is made of glass, we could see the movement of convection currents in the pan. The warmer soup moves up from the heated area at the bottom of the pan to the top where it is cooler. The cooler soup then moves to take the warmer soup's place. The movement is in a circular pattern within the pan (see picture above).

Convection Cycle 1. Warmer, less dense air is pushed up by cooler, denser air. 2. When air cools, it becomes more dense and starts to sink. 3. Sinking air moves under warmer air, pushing it upward.

Radiation The energy that travels as electromagnetic waves which include visible light, microwaves, and infrared light. When radiation from the Sun is absorbed, energy is transferred through heat.

Insulators Energy is always being transferred between objects at different temperatures. Insulators are used to control and slow the transfer of energy from warmer to cooler objects. Insulators work by trapping the energy.

This is Gus at Central Park Zoo

Insulators

4.3 Review What are 3 ways energy can be transferred through heat? Convection, conduction, radiation How are conductors and insulators different? Conductors easily transfer energy, but insulators do not.