Vista previa 2 fuera de 14 páginas
Vista previa 2 fuera de 14 páginas
Algunos ejemplos de esta serie de preguntas de práctica
1.
Describe what is meant by an element
Respuesta: pure substance that contains only atoms
2.
Describe what is meant by a mixture
Respuesta: two or more elements not chemically combined
3.
Describe what is meant by a Compound
Respuesta: Two or more elements chemically combined
4.
Describe what is meant by a molecule any elements joined together
Respuesta: any elements joined together
5.
What is Filtration and describe the method
Respuesta: - Sperating a insoluble solid from a liquid - Method - pour solution through a funnel with filtration paper . the liquid will run down the funnel into the beaker whilst the remains (solids) will be left in the funnel stopped by the filtration paper
Algunos ejemplos de esta serie de preguntas de práctica
1.
Describe the arrangement/movemt of particles in a solid?
Respuesta: - Extremely hard to compress this is because the particles in a solid are packed together in a regular pattern with almost no space between particles - They have a fixed shape and cannot flow from place to place this is because in a solid the particles can only vibrate on the spot and cannot move.
2.
Describe the arrangement/movemt of particles in a liquid?
Respuesta: - Extremely hard to compress this is because the particles are still close together with not many spaces between them - They can flow from place to place unlike solids. this is because the particles in a liquid can move
3.
Describe the arrangement/movemt of particles in a gas?
Respuesta: - Extremely easy to compress that is because the particles in a gases are widely spread - Gases spreadout and fill the space of the container this is because the particles in a gas move quickly and randomly
4.
How can we change a solid to a liquid?
Respuesta: process of melting, in order for this to happen we need to put energy, we use this energy to break the forces of attraction between the particles in a solid allowing the particles to freely move
5.
What is ionic bonding?
Respuesta: Ionic bonding is bonds that have electrostatic attraction. When oppositely charged ions form an ionic bond you get an ionic compound. This happens between a metal and non metal
Algunos ejemplos de esta serie de preguntas de práctica
1.
Principle of conservation of mass
Respuesta: during a chemical reaction, matter is not created or destroyed, the atoms are simply rearranged
2.
To calculate the % of an element in a compound we use ...
Respuesta: ((No of atoms of the element x mass of element)/Mr )x 100
3.
a mole is ...
Respuesta: An amount of a substance that contains exactly 6.02 X 10^23 particles
4.
Avagadro\'s number
Respuesta: 6.02 x 10^23, the number of atoms or molecules in 1 mol
5.
Avagadro\"s number is defined by ...
Respuesta: The mass of Avagadro\'s number of atoms or molecules is equal to the relative atomic mass / relative formula mass in grams
Algunos ejemplos de esta serie de preguntas de práctica
1.
Which method must be used to extract metals more reactive than carbon from their ores (metal oxides)?
Respuesta: Electrolysis
2.
What type of reaction is occuring when electrons are transferred?
Respuesta: REDOX (reduction and oxidation) reaction. This is where one chemical is oxidised and another is reduced at the same time.
3.
When a particle is reduced, what two things might have happened to it?
Respuesta: It could have gained electrons or lost oxygen.
4.
When a particle is oxidised, what two things might have happened to it?
Respuesta: It could have lost electrons or gained oxygen.
5.
In a redox reaction, what mnemonic can be used to remember what happens?
Respuesta: OILRIG - oxidation is loss, reduction is gain (of electrons).
Algunos ejemplos de esta serie de preguntas de práctica
1.
What is the pH scale?
Respuesta: A scale that measures how acid/alkaline a solution is. A neutral substance has a pH of 7 (e.g. pure water). The lower the number the more acidic the solution. The higher the number the more alkaline the solution.
2.
In what two ways can we measure the pH of a solution?
Respuesta: 1) Use an indicator - a dye that changes colours at certain pHs. 2) Use a pH probe/ meter, which gives a digital pH and is more accurate than an indicator.
3.
What are wide range indicators?
Respuesta: Mixtures of dyes that gradually change colour e.g. universal indicator.
4.
What type of reactions occurs between acids and bases (or alkalis?)
Respuesta: Neutralisation reaction. Acid + Base --> Salt + water e.g. Hydrochloric acid + Copper oxide -> Copper Chloride + water
5.
What is the ionic equation for a neutralisation reaction?
Respuesta: H+(aq) + OH-(aq) -> H2O(l)
Algunos ejemplos de esta serie de preguntas de práctica
1.
What is an exothermic reaction?
Respuesta: A reaction that causes a rise in temperature to surroundings- it releases energy
2.
What is an endothermic reaction?
Respuesta: A reaction that causes a decrease in temperature in the surroundings-it takes in energy
3.
If a reversible reaction if exothermic in one direction what will it be in the reverse direction?
Respuesta: Endothermic
4.
What must happen for bonds to be broken in a chemical reaction?
Respuesta: Reacting particles must collide with sufficient energy
5.
What happens in a chemical reaction?
Respuesta: Atoms are rearranged as old bonds are broken and new bonds are formed
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