Atoms and Elements
Name the smallest particle of an element that retains its properties.
An atom
In a solution, what are the substance dissolved vs. the substance doing the dissolving.
Solute (dissolved) and solvent (does the dissolving)
Type of change that produces no new substance, e.g. melting ice.
A physical change
Greek scientist who shouted 'Eureka!' after using water displacement to test a crown's purity.
Archimedes
Name the vertical column vs. a horizontal row of the periodic table.
Column = group; row = period
Name the negatively charged particle that orbits the nucleus.
An electron
Term for a solution that's dissolved as much solute as it can at that temperature.
Saturated
Name two signs of a chemical reaction, other than colour change.
Any two of: gas produced, temperature change, precipitate formed, odour, light produced
A metal block has mass 50 g and volume 25 cm3; calculate its density.
D = m/v
D = 50/25 = 2g/cm3
In a food chain, organisms that produce their own food using sunlight are called this.
Producers
Atomic number counts these particles; add neutrons and you get the mass number.
Protons
Separation technique using boiling point differences, e.g. for ethanol and water.
Distillation
In "magnesium + oxygen -> magnesium oxide", identify the reactants and the product.
Reactants: magnesium and oxygen; Product: magnesium oxide
Why can gases be compressed easily, but liquids and solids cannot?
Gas particles have large gaps to squeeze; liquid/solid particles are already packed tightly
In a series circuit, what happens to the rest of the circuit if one globe blows?
All the other globes go out too, since the circuit is broken
Sodium has 11 protons and 11 electrons. Why is it electrically neutral?
The positive charge of the protons balances the negative charge of the electrons.
Why does sugar dissolve faster in hot tea than in cold tea?
Hot water particles have more energy and move faster, so they collide with and break apart the sugar more quickly
When copper carbonate forms copper oxide and CO2 gas (CuCO3 -> CuO + CO2), it appears to lose mass. This still obeys the law of conservation of mass. How?
The CO2 gas escaped unmeasured — total mass (solid + gas) is actually conserved
Perfume sprayed in one corner of a room can be smelled across the whole room a few minutes later. Explain why, using particle theory.
The perfume's gas particles have kinetic energy and move randomly in all directions, spreading out and mixing with the air particles until they're evenly distributed (diffusion)
Name the energy transformations, in order, when a battery-powered torch is switched on.
Chemical energy -> electrical energy -> light energy (and heat energy)
What do you call an atom after it loses an electron and becomes positively charged?
An ion (cation)
In distilling salt water, why does the water evaporate first and leave the salt behind?
Water has a much lower boiling point than salt, so it vaporises first while the salt remains solid
Burnt magnesium oxide weighs more than the original magnesium. Why doesn't this break the Law of Conservation of Mass?
(Hint: 2Mg + O2 -> 2MgO)
The magnesium combined with oxygen from the air, adding mass — none was created
A sealed gas canister's pressure rises in sunlight, with no gas added. Why, using particle theory?
Heating gives particles more kinetic energy, so they hit the container walls harder and more often
Only around 10% of the energy at one trophic level in a food chain is passed on to the next. Explain where the rest of the energy goes.
Most of it is lost as heat through respiration, movement, and other life processes, or is lost as waste/undigested material, before it can be passed on