7C: Heat & Temperature Flashcards
It is a hot day and your family decides to have ice cream with dinner. You walk the 30 min to the store to get 1 L of ice cream. Knowing that it will melt before you get back, you need to make a plan to get the ice cream home in its solid state. What would you do? Why?
Answers will vary.
What does the word sustainable mean?
Sustainable means that something can remain the same, maintained or continued for a long period of time/forever.
What is heat energy and how is it measured?
Energy that flows from matter of a higher temperature to matter of a lower temperature.
- It is measured in Joules (J).
What is particle model of matter?
Model that explains the behavior of solids, liquids, and gases.
What are the 4 main points of the particle model of matter?
- All matter is made up of tiny particles
- These particles are always moving
- The particles have space between them
- Adding heat causes the particles to move faster
List what happens when a gas heats up, or when it gets cooled off.
When the gas is heated, its particles speed up. When it is cooled, its particles slow down.
What is kinetic energy?
The energy of movement; particles that make up matter have kinetic energy because they are always moving.
What is volume?
Volume refers to the amount of space occupied by matter; milliliters(mL) and liters (L) are common units of volume.
-Volume can also be measured in cm, feet, etc.
What is thermal energy?
Total kinetic energy of the particles in a substance. The faster the particles are moving, the more kinetic energy is present.
What is temperature?
A measurement how hot or cold matter is.
What is the difference between heat, temperature, kinetic energy and thermal energy?
Heat: the energy that transfers from one substance to another because of differences in kinetic energy.
Temperature: measurement of how hot or cold matter is.
Kinetic Energy: the energy of movement (usually particles)
Thermal Energy: Total kinetic energy of an object/matter.
What are two specific ways that matter can change its volume when heated or cooled?
Expansion & Contraction
What is expansion?
An increase in volume; matter expands when heat energy is added.
What is contraction?
The decrease in volume; matter contracts when the heat energy is removed.
When water is frozen, does it expand or does it get smaller?
Water is unique because it expands when it is frozen/cooled.
Explain what has happened: A large area of concrete is poured as a single slab to create a new outdoor basketball court for our school. The work is done in August before the new school year starts. A very cold winter follows. When spring comes and you and your friends want to use the court, younotice several large cracks in the concrete. It looks like the concrete will need replacing.
The concrete has cracked due to the forces applied during expansion during the spring/summer, and contraction during the winter months. Since concrete is a solid it has a fixed volume and does not react well to changes in kinetic energy.
Explain what has happened: You are working on your bike on a hot summer afternoon. You need to replace a metal bolt, and you find that it fits inside a metal nut. Leaving most of your tools and the bike sitting in the sun, you take a break for an hour. When you come back, you pick up the bolt and find that it’s hot to the touch. You grab the right size of metal nut that has been sitting in the shade. It doesn’t fit. You use an identical nut that had been sitting in the sun, and it fits.
The sun has caused the metal to expand.
When the metal was in the shade it stayed the same/contracted slightly.
***Welders will use this principle to adjust the gaps between pieces of metal. If the gap is slighlty too large they will heat up the metal to cause it to expand and close the gap off.
Train tracks span great distances. Spaced many metres apart are small gaps between the rails. What might happen if the gaps weren’t there?
If they gaps were absent, then any time it was hot outside and the metal expanded the traintracks would probably malfunction, bend/warm, or be dangerous.
Explain what has happened: After getting caught in a summer thunderstorm, you decide to make yourself a mug of hot chocolate. The biggest mugs are in your kitchen freezer, chilled and ready for lemonade on the next hot day. You take one, noticing that the thick glass is covered with a light layer of frost. As you pour the boiling water into the mug, you hear and see it crack.
The extremely high temperature of the water caused the frozen mug to crack because it applied too much heat too quickly. The rapid change in kinetic energy of the particles caused the mug to break.
What is thermal expansion?
The expansion of a substance caused by an increase in thermal energy, causing the particles to move faster and farther apart..
What are the three methods of heat transfer?
- Conduction
- Convection
- Radiation
True or False? All 3 methods of heat transfer (conduction, convection, and radiation), rely on the movement of particles.
False. Both conduction and convection rely on the movement of particles to transfer heat energy. Radiation does not.
What is conduction? Can you provide an example?
The flow of energy between substances that are in contact.
Ex:
- Metal spoon gets hot while sitting in hot soup
- Water boils in pot because the metal pot is being heated by the flame/burner below.
In regards to conduction, what is the only way that heat can transfer?
From an area of greater kinetic energy, to an area of lower kinetic energy.
