chemistry topic 1 2 nd 3 flashcards

What happens to particles when heated or cooled?

Heating: particles gain energy and move faster. Cooling: particles lose energy and move slower.

How do gas particles behave?

Gas particles move randomly and freely, colliding with each other and the container.

What happens to temperature during melting or boiling, and why?

Temperature stays constant because energy is used to overcome forces between particles.

What happens during freezing and condensation?

Freezing: liquid to solid. Condensation: gas to liquid.

What is diffusion?

Net movement of particles from high concentration to low concentration.

What three factors affect the speed of diffusion?

Temperature, particle size and state of matter.

What is an element?

A pure substance containing only one type of atom.

What is a compound?

Two or more different elements chemically bonded in a fixed ratio.

What is a mixture?

Two or more substances physically mixed but not chemically bonded.

What are the charges and locations of protons, neutrons and electrons?

Proton: +1, in the nucleus. Neutron: 0, in the nucleus. Electron: -1, in shells.

What are atomic number and mass number?

Atomic number = number of protons. Mass number = protons + neutrons.

How do you calculate the number of neutrons?

Neutrons = mass number - atomic number.

What is the difference between a neutral atom and an ion?

A neutral atom has equal numbers of protons and electrons. An ion has gained or lost electrons.

What is the electron arrangement for the first 20 elements?

First shell 2, second shell 8, third shell 8, fourth shell 2.

What are valence electrons?

Electrons in the outer shell.

What are isotopes?

Atoms of the same element with the same number of protons but different numbers of neutrons.

What is ionic bonding?

Electrons are transferred; oppositely charged ions attract.

What are three properties of ionic compounds?

High melting points; conduct electricity when molten or dissolved; do not conduct when solid.

What is covalent bonding?

Non-metal atoms share pairs of electrons.

What are the properties of simple molecular substances?

Low melting and boiling points; usually do not conduct electricity; weak forces between molecules.

What is metallic bonding?

Positive metal ions are attracted to delocalised electrons.

What are four properties of metals?

Conduct heat and electricity; malleable; usually have high melting points; usually strong.

What is a chemical formula?

A formula showing which elements are present and how many atoms of each are in a substance.

What is the difference between a molecular formula and an empirical formula?

Molecular formula = actual number of each type of atom. Empirical formula = simplest whole-number ratio.

What are reactants and products?

Reactants are the starting substances. Products are the substances made.

What is the difference between a word equation and a symbol equation?

A word equation uses substance names. A symbol equation uses chemical symbols and formulae.

What is a balanced chemical equation?

An equation with equal numbers of each type of atom on both sides.

What is the law of conservation of mass?

Mass is conserved; atoms are not created or destroyed in a chemical reaction.

What are the four state symbols?

(s) solid, (l) liquid, (g) gas, (aq) dissolved in water.

What is an ionic equation, and what are spectator ions?

An ionic equation shows the particles involved in a reaction. Spectator ions are unchanged and can be left out.

What is neutralisation, and what is its ionic equation?

Acid + base -> salt + water. Ionic equation: H+(aq) + OH-(aq) -> H2O(l).

What are Ar and Mr?

Ar = relative atomic mass. Mr = total of the Ar values in a formula.

Calculate the Mr of CO2. (C=12, O=16)

Mr CO2 = 12 + (16 x 2) = 44.

What are reacting masses?

Calculations involving the masses of reactants and products in a chemical reaction.

What is a mole, and what is the Avogadro constant?

A mole is an amount of substance. Avogadro constant = 6.02 x 10^23 particles per mole.

Calculate the moles in 36 g of H2O. (Mr=18)

Moles = mass / Mr = 36 / 18 = 2 mol.

Calculate the number of molecules in 2 moles.

Particles = moles x 6.02 x 10^23 = 2 x 6.02 x 10^23 = 1.204 x 10^24 molecules.

What is the molar gas volume at RTP? Calculate the moles in 48 dm3 of gas.

At RTP, 1 mole of gas occupies 24 dm3. Moles = gas volume / 24 = 48 / 24 = 2 mol.

What is concentration? Give the two concentration formulae.

Concentration is the amount of solute in a given volume. Concentration (g/dm3) = mass (g) / volume (dm3). Concentration (mol/dm3) = moles / volume (dm3).

What is titration, and what are the basic calculation steps?

Titration finds an unknown concentration using a solution of known concentration. Calculate known moles, use the balanced equation ratio, find unknown moles, then calculate unknown concentration. Titre = volume added from the burette.

How do you calculate an empirical formula?

Divide each element's mass by its Ar. Divide all answers by the smallest. Convert to the simplest whole-number ratio.

How do you calculate a molecular formula?

Divide the Mr by the empirical formula mass to find the multiplier. Multiply every subscript in the empirical formula by that multiplier.

What are percentage yield, percentage composition and percentage purity? Give their formulae.

Percentage yield = (actual yield / theoretical yield) x 100. Percentage composition = (total Ar contribution of the element in the formula / Mr) x 100. Percentage purity = (mass of pure substance / total sample mass) x 100.

Calculate Mr of CaCO3. (Ca=40, C=12, O=16)

40 + 12 + (16 x 3) = 100.

Calculate the moles in 48 g of oxygen. (Mr=32)

48 / 32 = 1.5 mol.

Calculate the gas volume of 3 moles at RTP.

3 x 24 = 72 dm3.

Calculate the concentration of 0.5 mol in 0.25 dm3.

0.5 / 0.25 = 2 mol/dm3.

Calculate the percentage purity if 9 g of a 12 g sample is pure.

(9 / 12) x 100 = 75%.

Calculate the percentage of oxygen in H2O. (Mr=18, O=16)

(16 / 18) x 100 = 88.9%.