Chem paper 2 (c6 and c7)

1. Measuring the speed of a reaction that produces a gas can be carried out using a mass balance

2. As the gas is released, the mass disappearing is measured on the balance

3. The quicker the reading on the balance drops, the faster the reaction

4. If you take measurements at regular intervals, you can plot a rate of reaction graph and find the rate quite easily (see page 107 for more)

5. This is the most accurate of the three methods described because the mass balance is very accurate. But it has the disadvantage of releasing the gas straight into the room

1. This involves the use of a gas syringe to measure the volume of gas given off

2. The more gas given off during a given time interval, the faster the reaction

3. Gas syringes usually give volumes accurate to the nearest cm3, so they're quite accurate. You can take measurements at regular intervals and plot a rate of reaction graph using this method too. You have to be quite careful though

1. If one of the reactants is a solid, then breaking it up into smaller pieces will increase its surface area to volume ratio

2. This means that for the same volume of the solid, the particles around it will have more area to work on

amount of reactant used or amount of product formed/ time

states that atoms, ions, and molecules must collide in order to react

Enzymes are biological catalysts

1. A catalyst is a substance that speeds up a reaction, without being used up in the reaction itself. This means it's not part of the overall reaction equation

2. Different catalysts are needed for different reactions, but they all work by decreasing the activation energy needed for the reaction to occur. They do this by providing an alternative reaction pathway with a lower activation energy

the minimum amount of energy required to start a chemical reaction

a state in which opposing forces are balanced

1. As the reactants react, their concentrations fall

If the equilibrium lies to the right, the concentration of products is greater than that of the reactants. If the equilibrium lies to the left, the concentration of reactants is greater than that of the products.

1. the temperature

2. the pressure (this only affects equilibria involving gases)

3. the concentration of the reactants and products

States that if a stress is applied to a system at equilibrium, the system shifts in the direction that relieves the stress.

1. You can record the visual change in a reaction if the initial solution is transparent and the product is a precipitate which clouds the solution (it becomes opaque).

2. You can observe a mark through the solution and measure how long it takes for it to disappear

1. Measuring the speed of a reaction that produces a gas can be carried out using a mass balance.

2. As the gas is released, the mass disappearing is measured on the balance.

3. The quicker the reading on the balance drops, the faster the reaction.

4. If you take measurements at regular intervals, you can plot a rate of reaction graph and find the reaction quite easily.

5. This is the most accurate of the three methods described because the mass balance is very accurate. But it has the disadvantage of releasing the gas straight into the room.

1. This involves the use of a gas syringe to measure the volume of gas given off.

2. The more gas given off during a given time interval, the faster the reaction.

3. Gas syringes usually give volumes accurate to the nearest cm3, so they're quite accurate. You can take measurements at regular intervals and plot a rate of reaction graph using this method too.

1. Start by adding a set volume of dilute hydrochloric acid to a conical flask.

2. Now add some magnesium ribbon to the acid and quickly attach an empty gas syringe to the flask.

3. Start the stopwatch. Take readings of the volume of gas in the gas syringe at regular intervals.

4. Plot the results in a table.

5. Now you can plot a graph with time on the x

1. These two chemicals are both clear solutions. They react together to form a yellow precipitate or sulphur.

2. Start by adding a set volume of dilute sodium thiosulphate to a conical flask.

3. Place the flask on a piece of paper with a black cross drawn on it.

4. Add some dilute HCl to the flask and start the stopwatch.

5. Now watch the black cross disappear through the cloudy sulphur and time how long it takes to go.

saturated hydrocarbon with the general formula CnH2n+2, for example, methane, ethane, and propane

unsaturated hydrocarbon which contains a carbon

When a substance burns with a good supply of oxygen the products are carbon dioxide and water.

the reaction used in the oil industry to break down large hydrocarbons into smaller, more useful ones

A mixture of hydrocarbons found underground in rocks formed over millions of years from the remains of sea creatures.

separation of a liquid from a mixture by evaporation followed by condensation

a covalent bond made by the sharing of two pairs of electrons

A resource that cannot be replaced once it has been used.

easily ignited and capable of burning rapidly

hydrocarbons with similar boiling points separated from crude oil

a way to separate liquids from a mixture of liquids by boiling off the substances at different temperatures, then condensing and collecting the liquids

a formula that represents the common structure of all compounds in a single class of chemicals. For example, the general formula of all alkanes is CnH2n+2

a compound containing only hydrogen and carbon

When a substance burns with a poor supply of oxygen the products are carbon monoxide and water.

when some elements or compounds are mixed together and intermingle but do not react together (i.e. no new substance is made). A mixture is not a pure substance

a substance that has had oxygen added to it/ or has lost electrons

describes a hydrocarbon with only single bonds between its carbon atoms. This means that it contains as many hydrogen atoms as possible in each molecule

the breakdown of a compound by heating it

a hydrocarbon whose molecules contains at least one carbon

the resistance of a liquid to flowing or pouring; a liquid's 'thickness'

an atom or group of atoms that give organic compounds their characteristic reactions

a group of related organic compounds that have the same functional group