Five key points of partial theory
That all matter is made up with tiny particles that have empty spaces between them
Different substances are made up of different kinds of particles
Particles in constant random motion
Particles move faster as temperature increases
Particles attract each each other
Example of “That all matter is made up with tiny particles that have empty spaces between them”
When you spray perfume, the scent spreads through the air — this happens because perfume particles move through the empty spaces between air particles.
Example of “Different substances are made up of different kinds of particles”
Water is made of H₂O particles, while carbon dioxide is made of CO₂ particles — they’re different substances because their particles are different.
Example of “Particles in constant random motion”
Dust floating in sunlight moves around randomly because air particles are constantly bumping into it — showing that particles never stop moving.
Example of “Particles move faster as temperature increases”
When water is heated, it starts to boil — the water particles move faster as the temperature rises, causing bubbles and steam.
Ex of “Particles attract each each other “
Water droplets stick together on a leaf because the water particles attract each other — this attraction is what causes surface tension.
Pure substance vs mixture
Pure substance is only made of one type of particle
Mixture is made of two or more different particles combined together
Pure substance
Pure substance is only made of one type of particle
Mixture
Mixture is made of two or more different particles combined together
What is alloy
An alloy is a mixture of two or more metals (or a metal and another element) combined to make a stronger or more useful material.
What is the difference between physical and Chemical properties
• Physical Properties: Can be observed without changing the substance.
➜ Example: color, melting point, density.
• Chemical Properties: Describe how a substance changes into a new one.
➜ Example: flammability, rusting, reacting with acid.
What does Ductile, malleability, luster, viscosity, hardness, conductivity mean?
Ductile- Can be stretched into thin wires (ex: copper wire
Malleability - Can be hammered or rolled into thin sheets
Luster-How shiny a substance is (metals have high luster).
Viscosity-How thick or resistant a liquid is to flow (honey = high viscosity, water = low).
Hardness-How well a substance resists being scratched or dented (diamonds are very hard).
Conductivity- How well a substance lets heat or electricity pass through it (metals conduct well).
Difference between quantitative and qualitative properties.
Give examples of each
Quantitative properties: Can be measured with numbers.
Examples: Mass = 50 g, Length = 2 m, Temperature = 37°C
Qualitative properties: Describe characteristics; cannot be measured with numbers.
Examples: Color = red, Texture = smooth, Smell = sweet
Difference between physical and chemical change, vs. characteristic physical properties
- How do you know? AND Provide examples?
Physical change: Changes form, no new substance.
Example: Melting ice, tearing paper
Chemical change: Makes new substance.
Example: Rusting iron, burning wood
Characteristic physical properties: Identify substance without changing it.
Example: Density, melting point
how to find Protons/neutrons/electrons
• Protons = Atomic number
• Electrons = Atomic number (same as protons in a neutral atom) • Neutrons = Mass number − Atomic number
What is the difference between element and compound
Element: Made of only one type of atom.
Example: Oxygen (O), Hydrogen (H), Iron (Fe)
Compound: Made of two or more different elements chemically combined. Example: Water (H₂O), Carbon dioxide (CO₂), Salt (NaCl)
What are the Theories of the atom?
Democritus,
• Democritus (400 BCE) said all matter is made of tiny, indivisible particles called “atomos”, meaning “uncuttable.”
• He believed atoms were solid, indestructible, and always moving.
• His idea was philosophical — not based on experiments.
What are the Theories of the atom? Aristotle,
• Aristotle did not believe in atoms.
• He thought all matter was made of four elements: earth, water, air, and fire.
• He believed matter was continuous and could be divided forever.
• His idea was accepted for a long time because he was a respected philosopher.
What are the Theories of the atom? Dalton,
• John Dalton (1803) proposed the first scientific atomic theory.
• All matter is made of tiny, indivisible atoms.
• Atoms of the same element are identical; atoms of different elements are different.
• Atoms combine in fixed ratios to form compounds.
• Atoms cannot be created or destroyed in chemical reactions — only rearranged.
What are the Theories of the atom?, Rutherford (Chadwick)
• Ernest Rutherford (1911) discovered the nucleus using the gold foil experiment.
• Atoms have a small, dense, positively charged nucleus.
• Electrons move around the nucleus.
• Most of the atom is empty space.
What are the Theories of the atom? Bohr
• Niels Bohr (1913) proposed that electrons move in fixed orbits (energy levels) around the nucleus.
• Electrons can jump between energy levels by absorbing or releasing energy.
• His model explained the line spectra of hydrogen.
What makes up an atom?
- Protons – Positively charged particles found in the nucleus (center) of the atom.
- Neutrons – Neutral particles (no charge) also found in the nucleus.
- Electrons – Negatively charged particles that move around the nucleus in energy levels or shells.
Where are electrons, protons and neutrons found in an atom?
protons and neutrons in nucleus
electrons orbit around in shells
What is an isotope? Can you give an example
Two or more forms of an element with the same number of protons but different number of neutrons
