Chemistry Term 1 Flashcards
What are the three different states of matter?
gas, liquid, solid
Describe the arrangement and movement of particles in gas
- Particles are far apart and have low densities
- Gas particles move very rapidly and in random directions
Describe the arrangement and movement of particles in liquid
- Particles are close together and are more dense than gas
- Particles move slowly and at random
Describe the arrangement and movement of particles in solid
- Particles are close together and like liquids, are denser than gases
- Particles vibrate only in fixed positions
State properties of a solid
- Solids have a fixed shape and cannot flow as particles cannot move from place to place.
- Solids cannot be compressed or squashed as the particles are close together and have no space to move into
- Increasing the temp. causes the particles to vibrate quicker
State properties of a liquid
- A liquid is a pure substance and should not be confused with a solution
- Liquids flow and take the shape of their container as the particles a can move around each other
- Liquids cannot be compressed or squashed as the particles are close together and have no space to move into
State properties of a gas
- Gases flow and take the shape of their container as the particles can move quickly in all directions
- Gases can be compressed or squashed as particles are far apart and have space to move into
What are the changes in state between solid and liquid
solid to liquid = melting
liquid to solid = freezing
What are the changes in state between liquid and gas
liquid to gas = evaporation / boiling
gas to liquid = condensation
What are the changes in state between solid and gas
solid to gas = sublimation
gas to solid = deposition
How does pressure affect the states of matter?
If pressure is increased enough a gas will liquefy. This is because particles are moved close enough for bonds to be formed between the particles
How does temperature affect states of matter?
Energy, as heat, is added to break the bonds and to allow particles to move more freely. A change of state occurs when enough bonds are broken to allow a change in position and movement of particles.
What is the difference between evaporation and boiling?
In evaporation, the particles gain enough energy, they move apart, and form a gas. Bubbles do not form as vapour pressure is less than atmospheric pressure. In boiling there are still particles gaining energy, however, the vapour pressure is equal to the surrounding atmospheric pressure.
What is the kinetic theory of an ideal gas?
An attempt to explain the observable properties of gas
1. Gases are made of particles in constant random motion
2. The particles move very fast and collide with each other and the walls of their container with perfectly elastic collisions (they bounce but lose no energy)
3. The particles are negligible in size compared to the spaces in between them
4. There are no attractive or repulsive forces in between the particles
5. The average kinetic energy of the molecules is proportional to the temperature of the gas
No real gas shows all these properties. The gases with the smallest molecules e.g. hydrogen, helium approach ideal behaviour compared to heavier ones
What temperature is absolute zero, and what happens at this temperature?
-273°C or 0 K. When this temperature is reached, all particle motion stop. There is no temperature lower than absolute zero as particles cannot have negative motion.
What is gas pressure?
Gas pressure is the result of collisions of gas particles with the walls of the container. If the number of gaseous particles are doubled, the gas pressure is doubled
What are exceptions to kinetic theory of gases?
At high pressures, the gas particles are close together so the volume of the container will have to be reduced to produce the very high pressures. The intermolecular forces between the gas molecules are strong enough to affect the collisions of the molecules and pull them away from the walls of their container. This reduces the pressure exerted on the container’s wall.
Under very low temperatures, gas particles no longer have enough kinetic energy to overcome the attractive forces between them as the particles are moving very slowly.
Explain Brownian motion
Particles in both liquid and gases move randomly. They do this because they are bombarded by other moving particles in the fluid. Larger particles can be moved by light, fast-moving molecules.
What evidence is there for Brownian motion?
When smoke particles are viewed under a microscope they appear to ‘dance around’ when illuminated with a light beam at 90° to the viewing direction. This is because the smoke particles show up by reflected light and ‘dance’ due to millions of random hits from the fast moving air molecules. This is called ‘Brownian Motion’
What is diffusion?
Diffusion is the random movement of liquid and gas particles from regions of high concentration to regions of low concentration.
What are the three chemical factors that affect rates of diffusion?
- Molecular mass - Heavier particles diffuse more slowly while lighter particles move quicker.
- Temperature - the rate of diffusion increases with increase in temperature as the particles gain more kinetic energy and move faster.
- Concentration gradient - This is the difference between the two areas the liquid or gas molecules are diffusing down. The greater the difference, the faster the rate of diffusion.
Describe diffusion in gases compared to liquids
The natural rapid and random movement of the particles in all directions means that gases readily ‘spread’ or diffuse.
Diffusion of gases is faster than in liquids as there is more space for them to move into.
List most accurate apparatus for measuring volume from pipette, burette and measuring cylinder
Measuring cylinder, Pipettes, Burettes
Define a solute
A dissolved substance
Define a solvent
A substance which dissolves a solute
Define miscible liquids
Liquids that are completely soluble in each other
Define immiscible liquids
Liquids that are not soluble in each other
Define a solution
Mixture that appears to have one substance
Define a suspension
A mixture where two or more parts can be seen
Define an element
Something which contains atoms of the same type (all atoms have the same number of protons)
Define a compound
Something which has two or more types of atoms which are chemically bonded together
Define a mixture
A substance of two or more types of atoms that are not chemically bonded together
Define a molecule
Two or more atoms that are covalently bonded together
Explain filtration
Separates insoluble solids from a liquid. The mixture is poured through filter paper with tiny pores. The solid remains on the filter paper, while the liquid falls through
Explain Decanting
It is used to separate two immiscible liquids. The denser of the two liquids would move to the bottom, while the less dense liquid will remain on the top. You can then separate by either pouring the top liquid out, or you can use a separating funnel to tap out the denser liquid.
Explain Chromatography
Used to separate a mixture of substance into their components. The solutes are blotted onto a line drawn with pencil on a piece of chromatography paper. This is placed in a solvent such as water or ethanol. As the solvent rises up the paper, the substance separates out into individual components. Parts which are the most soluble move further up the paper, while least soluble move very little. Final distance is measured, called the solvent front. This is used to measure Rf value which is compared to a database which has Rf values for many substances.
Explain Evaporation
Is used to obtain a solute from a solvent. This is done by vaporising the liquid from the solid. Only the solid is obtained.
Explain Simple Distillation
Separating two liquids using their boiling points. Liquid with the lower boiling point evaporates first, rises and travels through a condenser where it is cooled using cold water. The gas condenses into a liquid which can be collected. Simple distillation can also be used to separate a dissolved solute from a solvent, and obtain the solvent.
