Types of Matter
What type of matter contains only one type of atom?
An element
What must a particle model show to represent a compound?
Different atoms bonded together.
Is freezing water a physical or chemical change?
Physical.
Which type of reaction absorbs heat?
Endothermic
Are most metals found on the left or right side of the periodic table?
What makes a compound different from an element?
A compound contains different atoms chemically joined
In a particle diagram of a mixture, how are particles arranged?
Mixed together but not bonded.
Name five indicators of a chemical change.
Gas production, colour change, temperature change, new substance, precipitate.
Which type of reaction releases heat?
Exothermic
What does the atomic number tell you?
The number of protons.
Explain why a compound cannot be separated physically but a mixture can.
Compounds have atoms chemically bonded in fixed ratios, so only chemical reactions can separate them. Mixtures aren’t chemically bonded, so physical methods (like filtering or evaporation) work.
A particle model shows identical pairs of atoms and separate single atoms of a different type. Explain why this diagram represents a mixture.
It contains more than one type of particle, and they are not bonded to each other, so the substances remain separate.
Magnesium reacts with acid and bubbles appear.
Explain why this is evidence for a chemical change.
Bubbles show a gas is forming, proving a new substance is produced, which only happens in chemical changes.
A thermometer drops from 24°C to 11°C during a reaction.
Identify the reaction type and explain the heat transfer.
Endothermic — it absorbs heat from the surroundings, lowering the temperature.
How did the discovery of subatomic particles change scientists’ ideas about atoms?
It showed atoms have structure and helped explain why elements behave differently.
Brass is made by melting copper and zinc together. The final material looks like one uniform metal. Explain why is brass (Cu3Zn2) considered a mixture, not a compound?
Brass is a mixture because the copper and zinc particles are only physically mixed, not chemically bonded together. Even though the mixture looks uniform, the atoms do not join in fixed ratios and keep their own properties. This means brass can be separated physically and does not form a new substance, so it is a mixture, not a compound.
A diagram shows:
• single atoms of one colour
• bonded identical atoms of the same colour
• bonded different-coloured atoms
Explain what each particle represents and classify the whole sample.
Single atoms = element
bonded identical atoms = molecule of an element
bonded different atoms = compound
Together (not bonded), the sample is a mixture.
Burning magnesium produces bright light and white powder.
Explain why this is a chemical change using particle ideas.
Magnesium atoms react with oxygen to form a new substance (magnesium oxide), proving particles rearranged.
One reaction warms the surroundings; another cools them.
Explain which is exothermic and which is endothermic using energy movement.
Exothermic releases heat to surroundings; endothermic absorbs heat from surroundings.
Explain how Mendeleev organised his periodic table and why it was considered scientific progress.
He arranged elements by atomic mass and predicted undiscovered elements; when these were found, it proved his model showed real patterns.
A student claims that if a substance contains different atoms, it must be a compound. Explain why this is not always true.
Different atoms only form a compound when they are chemically bonded. If the atoms are mixed but not bonded, even if they are different types, the substance is a mixture. Bonding, not appearance or atom types, determines classification.
Explain why particle diagrams are useful for determining whether a substance is an element, compound, or mixture.
Because diagrams clearly show atom types and bonding. Identical atoms show an element, different bonded atoms show a compound, and multiple unbonded particle types show a mixture.
A teacher melts sugar, then heats it until it turns brown and smokes.
Explain which stage is physical and which is chemical, and why.
Melting is physical because particles stay the same; browning/smoke is chemical because new substances and gases form.
Explain how energy transfer in both endothermic and exothermic reactions affects the temperature of the surroundings.
Endothermic absorbs heat, reducing particle motion and lowering temperature; exothermic releases heat, increasing particle motion and raising temperature.
Describe Moseley’s discovery of atomic number and explain why it led to the modern periodic table.
He showed elements should be arranged by proton number, which fixed inconsistencies and grouped elements correctly by properties.