chapter 4 Flashcards
(17 cards)
What is a physical change?
A change that doesn’t alter the substance itself. Only appearance changes.
Example: Melting ice, ripping paper.
What is a chemical change?
A change where new substances are formed and the atoms are rearranged.
Example: Burning wood, baking a cake.
What are 5 signs of a chemical change?
- Gas released
- Heat/light produced or absorbed
- Colour change
- Precipitate forms (solid)
- New smell or fizzing
What’s the Law of Conservation of Mass?
Matter can’t be created or destroyed. Mass of reactants = mass of products.
How do you balance a chemical equation?
- Count atoms on both sides
- Use coefficients to match them
- Don’t change subscripts!
- Make sure all atoms are equal on both sides
What’s the difference between a subscript and a coefficient?
- Subscript: How many atoms in a molecule (H₂O → 2 H, 1 O)
- Coefficient: How many molecules (2H₂O → 4 H, 2 O)
What is stoichiometry?
Using balanced equations to calculate amounts of substances, like a recipe!
What is an endothermic reaction?
A chemical reaction that absorbs heat from the surroundings (feels cold).
What is an exothermic reaction?
A chemical reaction that releases heat into the surroundings (feels hot).
What is a neutralization reaction?
Acid + Base → Water + Salt
Example: HCl + NaOH → H₂O + NaCl.
What is a combustion reaction, what does it need?
A combustion reaction is a chemical reaction where a fuel reacts with oxygen, releasing heat and light (energy).
It always produces carbon dioxide (CO₂) and water (H₂O).
✅ Needs:
1. Fuel (like wood, gas, candle wax)
2. Oxygen (O₂)
3. Ignition temperature (heat/spark to start it)
What is cellular respiration?
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy
Glucose + oxygen → energy for your body.
What is photosynthesis?
6CO₂ + 6H₂O + Energy → C₆H₁₂O₆ + 6O₂
Plants use sunlight to make glucose + oxygen.
What are the 3 types of nuclear radiation?
- Alpha (α): Low, stopped by paper
- Beta (β): Medium, stopped by foil
- Gamma (γ): High, stopped by concrete
What is nuclear fission?
Splitting a nucleus into smaller parts, releases lots of energy (chain reaction).
What is nuclear fusion?
Two small nuclei combine to make a larger one. Happens in the sun.
What is half-life?
The time it takes for half a radioactive to decay.
