Chapter 6: Energy

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Chapter 6: Energy Section 2: Temperature Why is temperature important in our lives?

Cooks and preserves our food, warms up our homes. Our body depends on a constant temperature to work properly. We could not leave without heat.

Background information **Matter is made of tiny particles called atoms. Atoms make up molecules. Everything around us, including us, is made of atoms and molecules

** Thermal Energy • Thermal energy is a type of kinetic energy (depends on the motion of molecules). • Thermal Energy is the energy of a system, due to the movement of the molecules in this system • The more movement, the more thermal energy and temperature

Definition of Temperature: Temperature is the measure of the kinetic energy of the particles in an object. **It is a value that describes how hot or cold objects are. **higher temperature - more kinetic energy more thermal energy - (because the molecules move more)

Measuring temperature

Mini Lab Comparing Energy Content

Mini Lab Conclusions – (COPY) • In the cup with warmer water, molecules of water moved faster and the food coloring spread faster • At a higher temperature, molecules have higher kinetic energy and therefore, will move faster.

State of matter and Temperature • A substance will change state of matter (gas, liquid, solid) when we

add or remove temperature from this substance

Higher temperatures, higher kinetic energy, more molecule movement . state of matter changes from a solid to a liquid, from a liquid to a gas

Lower temperatures, lower kinetic energy, less molecule movement . state of matter changes from a gas to a liquid, liquid to a solid.

**We saw in Section 1 that: all types of energy can be transformed into other types of energy. This is also true for thermal energy

• Thermal energy can be converted into mechanical energy by steam engines.

Mechanical energy

**We saw in section 1 that: all types of energy can be transferred from one object to another. The same is valid for Thermal Energy •What is Heat?

Heat • Heat is the transfer of energy from one object to another due to a difference in temperature • Heat is energy in transit • Heat flows from warmer objects to cooler ones, until equilibrium is reached. • Look at Figure 14 page 173

Heat on the Move • Remember: Heat moves from warm places or objects to cooler ones. • This transfer can take place in three ways: • radiation, conduction, and convection. •

Conduction: heat transfer by direct contact Atoms collide and transfer heat Ex: hand warmers Read “Bumping Along” Page 175 and answer the reading check

Convection: common in gases and liquids It is heat transfer by the flow of materials • During convection, the warmer gases or liquids go up and the cooler goes down

Convection in liquids In a pot of boiling water, the warmer, less dense water is forced up as the cooler, denser water sinks. Source of heat

Convection in gases • Some homes are heated by convection. • Textbook figure 19 page 176

Radiation – transfer of heat energy in the form of waves When the wave hits a surface, the heat is absorbed See fig 20 pg 177

Heat is a type of electromagnetic wave, this is the reason why it is transferred by radiation

Types of Materials and Heat

• Conductors – are materials that can transfer heat – Metals • Insulators – are poor conductors of heat and don’t allow the heat to escape. EX. Blankets, down coats….

• What do you feel when you enter in the sea water on a very hot day? • What do you feel when you enter in the sea water when it is dark? Figure 16 – page 174

Lakes, Sea and Air Temperature **During the day – the land is warm because of the sun’s radiation, but the lake is colder than the land. **During the night – there is no sun radiation, so the land cools down,but the lake is still warm *It takes longer for water to warm up or cool down than it does for the air or the land around it.

This happens because water has a high specific heat

**Specific heat **Specific heat is the amount of heat needed to raise of one degree Celsius, one gram of a substance. **Specific heat of a material is it's ability to store heat. *Materials with a high specific heat will warm up and cool down slower than other materials with a low specific heat.

**Water • water is an unusual substance, it must absorb a large amount of heat before its temperature rises by one degree. • We say that water has a high specific heat.