Science study flashcards term 2
(32 cards)
What is a chemical change?
A chemical change is when a substance is transformed into a new substance. Atoms are rearranged, and the change is usually irreversible except by another chemical reaction.
What is combustion?
Combustion is the reaction of a substance with oxygen to form an oxide and release energy as heat and light.
How do you test for oxygen gas?
Insert a glowing wood splint into the gas; if it ignites, oxygen is present.
Why do substances burn faster in pure oxygen than in air?
Because the concentration of oxygen is higher in pure oxygen than in air.
What is the general equation for metals reacting with oxygen?
Metal + Oxygen → Metal Oxide
What happens when iron reacts with oxygen?
It forms iron oxide (Fe₃O₄), releasing heat and light. Finely divided iron burns with sparks.
What is rust and how does it form?
Rust (Fe₂O₃) forms when iron reacts slowly with moisture and oxygen.
How do you prevent rust?
Coat iron with paint, grease, zinc (galvanizing), or chromium (electroplating).
What is the general equation for non-metals with oxygen?
Non-metal + Oxygen → Non-metal oxide
What happens when carbon reacts with oxygen?
Burns with a yellow flame, forms carbon dioxide.
Equation: C + O₂ → CO₂
How do you test for carbon dioxide?
Bubble it through clear lime water; it turns milky.
What happens when sulphur reacts with oxygen?
Burns with a blue-purple flame, forming sulphur dioxide (SO₂) with a choking smell.
What is the colour and phase of carbon?
Black solid.
Describe the properties of carbon dioxide.
Colourless, odourless, non-toxic gas.
Observations during carbon combustion?
Yellow flame, heat and light released.
Balanced equation for carbon combustion?
C + O₂ → CO₂
Chemical for testing CO₂?
Clear lime water (Ca(OH)₂)
How do you confirm CO₂ presence?
Lime water turns milky.
What is apparatus A, B, C?
A = gas cylinder, B = combustion spoon, C = base plate.
Function of B?
Holds burning material.
Function of B’s plate?
Seals cylinder to prevent gas escape.
Balanced equation for iron combustion?
3Fe + 2O₂ → Fe₃O₄
Equation for sulphur combustion?
S + O₂ → SO₂
Test for oxygen?
Glowing splint relights.
