science Flashcards
What are the three ways heat transfers?
Conduction: Heat transfers through direct contact (e.g., a metal spoon getting hot in boiling water).
Convection: Heat transfers through fluids (liquids or gases), causing warm fluid to rise and cool fluid to sink (e.g., boiling water or the air moving in a room).
Radiation: Heat transfers through empty space via electromagnetic waves (e.g., sunlight warming your skin).
What is the difference between temperature, thermal energy, and heat?
Temperature is how hot or cold something is (measured in Celsius, Fahrenheit, or Kelvin).
Thermal Energy is the total energy of all the particles in a substance, including both heat and motion.
Heat is the energy that flows from a warmer object to a cooler one due to temperature difference.
What are the differences between Celsius, Fahrenheit, and Kelvin?
Celsius (°C): Used in most of the world. Water freezes at 0°C and boils at 100°C.
Fahrenheit (°F): Used mostly in the U.S. Water freezes at 32°F and boils at 212°F.
Kelvin (K): Used in science. Starts at absolute zero (0K), where all particle motion stops. 0K = -273°C.
How does thermal energy cause phase changes?
When thermal energy is added or removed, it can cause a substance to change from one state of matter to another (solid, liquid, gas). For example, heating ice causes it to melt into water (solid to liquid), and heating water turns it into steam (liquid to gas).
Why doesn’t temperature change during phase changes?
During a phase change, the added energy goes into changing the substance’s structure (like breaking bonds between particles), not into increasing the temperature. For example, water stays at 100°C while it boils because the energy is used to convert it into steam, not to increase its temperature.
What are the three states of matter?
Solid: Particles are tightly packed and don’t move much (e.g., ice).
Liquid: Particles are close but can move around (e.g., water).
Gas: Particles are far apart and move freely (e.g., steam).
What is sublimation?
Sublimation is when a substance changes directly from a solid to a gas without becoming a liquid first. A common example is dry ice (solid carbon dioxide) turning directly into gas.
What is thermal equilibrium?
Thermal equilibrium happens when two objects are at the same temperature, and no more heat flows between them. For example, if you leave a hot cup of coffee in a room, it will cool down until it reaches the same temperature as the room.
What is thermal expansion and contraction?
Thermal Expansion occurs when a substance expands (gets bigger) as it heats up. For example, a metal rail expands in hot weather.
Thermal Contraction occurs when a substance contracts (gets smaller) as it cools down. For example, water pipes may shrink during cold weather.
To convert Celsius to Kelvin:
add 273
To convert Kelvin to Celsius:
Subtract 273
To calculate thermal energy released by a fuel in a calorimeter:
mass of water x change in temperature x specific heat of water = calories
To calculate the heat of vaporization (the amount of energy needed to turn water into steam):
of grams of water x 540 calories per gram = # of calories
to calculate specific heat:
heat/mass x temp change
to calculate the heat of freezing (the amount of energy needed to melt ice)
80 cal x g
