The Particle Model and States of Matter
Name the three states of matter.
Solid, liquid and gas
Blowing up a balloon is this type of change: physical or chemical?
Physical, because no new substance is formed
In a chemical reaction, the starting substances are called this.
Reactants
Reactions that release heat to their surroundings are called this.
Exothermic
This part of a scientific report states the purpose of the experiment.
The aim (research question)
This state of matter has a fixed shape and a fixed volume, and its particles can only vibrate.
Solid
Name any three of the six indicators of a chemical change.
Colour change, temperature change, gas or bubbles, new substance or precipitate forming, disappearance of a substance, sound or light
What do the state symbols (s), (l), (g) and (aq) stand for?
Solid, liquid, gas and aqueous (dissolved in water)
An instant cold pack feels icy cold when activated. Is the reaction exothermic or endothermic?
Endothermic, because it absorbs heat from the surroundings
A testable statement that is accepted or rejected after the experiment is called this.
A hypothesis
Why can a gas be squashed (compressed) easily, but a liquid cannot?
Gas particles are far apart with lots of empty space, whereas liquid particles are already close together
Ice melting, wood burning, sugar dissolving. Which one is a chemical change, and what is the evidence?
Wood burning. New substances form, and heat and light are given off
Identify the reactants and the product: Magnesium + Oxygen → Magnesium Oxide
Reactants: magnesium and oxygen. Product: magnesium oxide
Name the type of reaction where a substance reacts with oxygen and releases heat and light, and name the two products usually formed when methane undergoes it.
Combustion. Carbon dioxide and water
What is the difference between quantitative and qualitative results? Give an example of each.
Quantitative results are numbers, such as data tables and graphs. Qualitative results are descriptions of observations, such as colour change or annotated images
Explain what happens to the particles when ice melts into water.
The particles gain energy and move faster, so they break out of their fixed positions and can slide past each other. The particles themselves stay the same, only their movement changes
Explain why a colour change usually means a chemical change has taken place.
The substance has changed its chemical structure to produce the new colour, which means a new substance has formed
State the Law of Conservation of Mass and explain why the atoms on both sides of an equation must match.
Mass cannot be created or destroyed. Atoms are only rearranged, so the number and types of atoms stay the same from start to end
Explain, using particles, why increasing the temperature speeds up a reaction.
Particles move faster, so collisions are more frequent and more energetic, which makes successful reactions more likely
The conclusion of a report has three parts. Name them.
Claim, evidence and reasoning
Steam is cooled until it becomes ice. Name the two changes of state in order and describe what happens to the particles' energy, movement and spacing.
Condensation (gas to liquid), then freezing (liquid to solid). The particles lose energy, move more slowly and get closer together, until they are only vibrating in fixed positions
When potassium iodide and lead nitrate are mixed, a solid appears. Name this solid, explain why this shows a chemical change, and say what the reaction produces.
The solid is a precipitate (lead iodide). A new substance has formed because the atoms were rearranged, so it is not just mixing. The reaction also produces potassium nitrate
Read the equation: 2Na (s) + 2H2O (l) → 2NaOH (aq) + H2 (g). Name the reactants and products, and say which product is a gas and which is dissolved in water.
Reactants: sodium and water. Products: sodium hydroxide and hydrogen. Hydrogen is the gas (g) and sodium hydroxide is dissolved in water (aq)
Explain how a catalyst speeds up a reaction, and what happens to the catalyst itself.
It provides an alternative pathway with a lower activation energy, so more particles have enough energy to react. The catalyst is not used up and is unchanged at the end
A group finds that crushed chalk reacts faster with acid than a whole piece. Write the reasoning for their conclusion.
Crushing increases the surface area, so more particles are exposed to collide with the acid. There are more frequent collisions, so the reaction rate increases