Chapter 1 Flashcards
(21 cards)
What is a substance
One type of material. Elements and compounds are substances. One type of particle
What is sublimation
Changing state directly from a solid to a gas
What is an atom
Smallest part of an element
What is a molecule
More than one atom chemically joined together, either several of the same atoms or two or more different atoms
What did Robert brown discover
Using pollen grubs, he observed how they moved in water. They seemed in motion. He originally believed it was because they were living, but using dead plants proved this wrong. Provided valuable evidence for later scientists
What is the name of what Brown discovered
Brownian motion
What did they discover about gas and liquids
They appeared to have invisible always moving particles
Any further evidence for particles
When dissolving a solid, particles break off and spread to create a solution
What’s in soundproofing foam?
Part gas part solid. Pockets of gas trapped in a solid material.
Aerosols?
Some are tiny pieces of solid suspended in a gas, others are tiny liquid droplets suspended in gas like deodorant cans. Move as a result of Brownian motion.
What are coronavirus aerosols?
Covid breath particles mix with air, making an aerosol, allowing it to remain for a long time. Someone else breathing in this aerosol will then likely be infected.
Sublimation
On snowy mountains, on dry days some snow directly turns to water vapour therefore subliming.
Heating iodine crystals results in sublimation, iodine does not have a pure liquid state, only liquid in a solution
What is iodine used for
Forensics use it to identify fingerprints
Dry ice
Solid carbon dioxide, has no liquid form.
Used to store vaccines
What is the name of change of state from solid to gas
Sublimation
Name of change from gas to solid
Deposition
Energy transfers
To melt or boil a substance, the reaction will be endothermic. Energy is transferred from the surroundings to overcome the forces and allow the solid bonds to break. The temperature of the surroundings therefore decrease.
In exothermic reactions, like freezing, energy is transferred to the surroundings, increasing the temperature of the surroundings
Different melting points
Substances have different melting points depending on the strength of the forces holding the particles together
Models in science
Idea that explains observations and helps in making predictions. The particle model is an example of this
Strengths of particle model
Helps explains things, like why water takes the shape of its cup also explains changes of state and helps to make predictions
Limitations of the particle model
Simpler than reality, not exactly the same, never perfect, every particle appears to be a solid sphere, whereas in reality they are different shapes particles aren’t solid not all predictions corrective
