Temperature and Thermal Energy

Objectives Describe three temperature scales Contrast temperature and heat (thermal energy)

Review of matter Matter is made up of particles called atoms. These particles are always in motion even if the object they make up isn’t moving.

Review of kinetic energy Kinetic energy = energy of motion All particles of matter have kinetic energy. The faster particles move, the more kinetic energy they have.

Q. The particles of hot cocoa move faster than those of cold chocolate milk. Which drink has particles with greater kinetic energy? A. The hot drink has particles with greater kinetic energy.

Temperature Temperature is the measure of the average kinetic energy of the individual particles in the object.

Temperature Scales Three scales for measuring temperature Kelvin (K) Celsius (degrees C) Fahrenheit (degrees F)

Absolute Zero Absolute zero – no more energy can be removed from matter The Kelvin scale is defined so that zero on the Kelvin scale is absolute zero.

Kelvin Scale Temperature scale used in scientific research Units on the Kelvin scale are called kelvins Any temperature on Kelvin scale can be changed to Celsius by subtracting 273

Kelvin Scale Absolute zero: 0 Water freezes at 273 Water boils at 373

Celsius Scale Most common temperature scale used in most of the world Absolute zero: -273º C Water freezes at 0º C Water boils at 100º C

Fahrenheit Scale Most common temperature scale in U.S. Absolute zero: -460º F Water freezes at 32º F Water boils at 212º F

Thermal (Heat) Energy Thermal energy is the total energy of moving particles of matter. The more particles a substance has at a given temperature, the more thermal energy it has.

Q. A large pot of hot cocoa has the same temperature as a small cup of cocoa. Do the containers have the same thermal energy? A. No. The large pot has more thermal energy than the small cup of cocoa.

Scientific Definition of Heat Heat is thermal energy moving from a warmer object to a cooler object. Warmer Cooler

3 Ways that Heat is transferred. Conduction Convection Radiation

Conduction Heat is transferred from one object to another by direct contact. Ex – pot on a stove, log on the fire

Convection Heat is transferred by the movement of currents within a liquid or gas. Convection Currents!! Ex- heating a room, boiling pot of water

Review of Density of Liquids Recall that a less dense liquid will float on top of a more dense liquid

Convection Currents Heated liquid or gas rises because it’s less dense Cooled liquid or gas flows into place under heated liquid or gas because it’s more dense This creates circular motion known as convection current.

Examples of Convection Currents Transfer heat throughout a building Birds ride updrafts where warm air is Produce global winds that form Earth’s weather

Drawing-Conduction/Convection Draw a kettle of boiling water on a burner. Label the convection currents and the path of heat conduction.

Radiation A transfer of heat energy by electromagnetic waves. Ex – sun, campfire, microwave.

Inferring (explaining) Pull some clothes out of dryer as soon as dry Grabbing shirt-no problem, Pants-problem-metal zipper too hot to touch What can you infer about which material conducts thermal energy better?

Heat Moves One Way Warmer object to colder one Heat will flow from one object to another until the objects have the same temperature.

Conductor A material that conducts heat well Ex – metal spoon, wire,

Insulator A material that does NOT conduct heat well. Ex – wood, wool, paper, air, cork,

States of Matter:

Matter Anything that takes up space and has mass. Some properties of matter include hardness, texture, flammability, and color.

States of Matter Solids Liquids Gases Plasma the chemical composition of a substance remains the same, just the arrangement of the particles differ.

Atom The smallest particle of a molecule. Everything that you may experience with your five senses is made up of atoms.

Elements A pure substance that contains only one kind of atom. There have been over 100 basic elements discovered.

The 18 elements in color on the periodic table make up most of the matter in the universe.

Molecule Small particles that make up matter. Atoms make up molecules.

Compounds A compound is a substance made of two or more elements chemically combined in a specific ratio. Examples: water, sugar, carbon dioxide

Mixtures A mixture is made from two or more substances in the same place but not combined as a new material. Parts of mixture keep individual properties. Example: soil (has sand, clay, water, other stuff.

Solutions A solution is a well-mixed mixture. The molecules are mixed up in a completely even distribution.

More on solutions Individual substances are not easily seen in a solution. Example: salt water

Is a solution a mixture and is a mixture a solution?

Mixture vs. Solution Salt in water vs. sand in water The sand sinks to the bottom and is a mixture. The salt dissolves and is spread throughout the water and it is a solution.

Structure of an Equation Reactant + Reactant Product H2 + O2 H2O2 Reactant Reactant Product

Activity You and a group of students will be doing the “Do you lose anything?” activity. Follow the directions and be prepared for a discussion at the end by writing your answers down.

Conservation of Mass The amount of matter in a chemical reaction does not change, so the total mass of the reactants must equal the total mass of the products.

Activity Do the “Still There” activity with a group of people. Write your answers down for a discussion after the activity.

Physical and Chemical Changes Changes in Matter Physical and Chemical Changes

Physical Change A change that alters the form or appearance of a material but does not make the material into a new substance is a physical change.

Water Water in different forms – physical changes Different forms of water – solid (ice), liquid (rain), gas (water vapor) Water is still the same substance in all three forms.

Solid Liquid Gas Liquid Changes of State The physical change from one state of matter to another is called a change of state. Solid Liquid Gas Liquid

Physical Changes Demonstration

Chemical Change A change in matter that produces new substances is called a chemical change. The new substances are made of the same elements as original substance, but now in different combinations.

Chemical Changes

Evidence for Chemical Changes Gas production Changes in properties Color Photosynthesis

Chemical Changes Demonstration