Chemistry Term 1 - Section A ( Principles of Chemistry)

CXC

What is the four main ideas for the particulate theory of matter

1. Particles move in constant, random motion

2. There are forces of attraction between the particles

3. There are spaces between the particles

4. All matter is made of particles

What is Osmosis

Osmosis is the movement of water molecules from a high concentration of water to a low concentration of water through a semipermeable membrane.

Explain how osmosis can be used in real world situations. For example pest control.

Salt can be used to exterminate a pest problem for example snails. Putting salt on a snail creates an isotonic condition. The water from the snail leaves its body to try and balance the water concentration.

What is diffusion

Movement of particles from an area of high concentration to low concentration.

What affects the rate of diffusion

Temperature. The higher the temperature the faster the rate.

What are the three states of matter

Liquids, Solids, Gases.

What are three differences between the states of matter?

Attraction

-Solids have a strong force of attraction

-Gases have little to no force of attraction

-Liquids particles are attracted just not as much as solids. Medium attraction

Energy

Solids have low energy

Liquids have intermediate

Gases have high energy

Shape

Gases don’t have a fixed shape

Liquids don’t have a fixed shape

Solids have a fixed shape

What is sublimation

A change of state from a solid directly to a gas. Some examples are iodine, ammonium chloride

What is Brownian motion

The random motion by small particles suspended in the fluid.

Heating curve

At melting point all the energy is being used to separate the particles.

Cooling Curve

What is solubility

Solubility is the maximum amount of solute that dissolves in a specific amount of solvent.

What is an unsaturated solution

Contains less than maximum amount of solute. Can dissolve more solute.

Where would it be located in a solubility curve

It would be below the line.

Saturated Solutions

Contain the maximum amount of solute that can dissolve. It will have undissolved solute at the bottom of the container.

Where would it be found on a solubility curve

On the line

Supersaturated Solutions

An unstable solution that contains an amount of solute greater than the solute solubility.

What is a homogenous mixture

A homogeneous mixture is a type of mixture where the components are uniformly distributed throughout the mixture.

What is a heterogenous mixture

Not uniform throughout

Solutions

It is a homogenous mixture. Has very small particles. Not visible. Light passes through

Colloids

A heterogenous mixture. Small particles. Not visible.Light scatters- tyndall effect

Suspensions

A heterogenous mixture. Large particles ( Larger than solution and colloids), easily visible. No light passes through. will sediment

Filtration

Used to separate an insoluble solid from a mixture.

Evaporation

Used to remove a solvent from a mixture by being heated or boiled.

Crystallisation

Used to separate a dissolved solid from a solution, when the solid is much more soluble in hot solvent than in cold. Used to purify substances by forming solid crystals

Simple distillation

Simple distillation separates liquids in a mixture by heating and collecting the vapor produced, which is then condensed and collected separately. It works best when the liquids have DIFFERENT boiling points.

When do you use simple distillation

When you want to separate the solvent.

Fractional Distillation

Used to separate two miscible liquids that have close boiling points.

What is the difference between simple and fractional distillation?

simple distillation is suitable for separating liquids with large differences in boiling points, while fractional distillation is more effective for separating liquids with similar boiling points.

What are some separation techniques based on difference in density?

Separation Funnel, Centrifugation, Sedimentation

Separation Funnel

Used to separate two immiscible liquids of different densities. Like oil and water

Sedimentation

If a solid particle is insoluble and is more dense than the surrounding mixture. Then it will fall to the ground.

Centrifugation

Rapidly spinning a mixture of substances at an axis that have different densities

Paper Chromatography

Used to separate substances of different solubilities

What is a mixture

A mixture is two or more substances not chemically combined that can be separated by physical means

What is an element

Simplest form of pure substances. They cannot be broken down into anything else.

What is a compound

Mixture of two or more elements chemically combined. They can be broken down into simple substance by chemical means

When do you use evaporation and crystallisation

Evaporation is used to remove a solvent from a mixture or concentrate a solution. While crystallization is used to purify substances by forming solid crystals from a solution

What does the choice depend on

The choice depends on the specific separation requirements and the properties of the components in the mixture.

What is atomic number

The number of protons found in the nucleus of an atom

what is mass number

The relative mass of atoms

What is an isotope

An atom that has the same amount of protons and electron but different neutrons

What is an radio-isotope

A radioactive isotope

What makes chemical properties

The numbers of valence electrons

What are some uses of Radio- isotopes

Carbon dating, radiotherapy, pacemakers, and nuclear power .

Who introduced the law of triads

Johaan Doebereiner from 1817-1829

Who introduced the law of octaves

John Newlands in 1865

Who arranged elements in increasing atomic mass

Dmitri Mendeleev in 1869

Who arranged elements in increasing atomic number.

Henry Mosely in 1914

What is formed when alkali metals react with water?

A metal hydroxide and Hydrogen

Trend in group 2 - the alkaline earth metals

They react by losing electrons to form positively charged cations.

Trends in group 7- the halogen

They react by gaining an electron to form negatively charges ions called anions. The ease of ionization increases moving up because its closer to the nucleus.

Calculating the relative atomic mass of isotopes

Multiply percentage by the mass of each of them.

Example

75% Cl -35

25% Cl -37

75 x 35 + 25 x 37

100

Anions

- negative charge

When non metals gain electron

Cations

+positively charged

Metals lose electrons

How much electrons do metals usually have on their outer shell

1, 2, or 3

How much electrons do metals usually have on their outer shell

5, 6 or 7

Filtration

Evaporation

separating a soluble solid from a mixture . Examle being sugar and water