Answer:
d). A catalyst lowers the activation energy for a chemical reaction.
Explanation:
From the given choices, it is true that a catalyst lowers the activation energy for a chemical reaction.
The activation energy is the energy barrier that must be overcome before a chemical reaction can occur.
Some reactions have very high activation energy and would not occur without the introduction of a catalyst.
The catalyst brings the reactants into contact by removing the energy deficiency in the system.
1. Change in temperature
2. Odour being produced
3. Gas bubbles being formed
4. Solid precipitate is formed
5. Permanent change in colour
6. Light is being produced
Answer:
The tundra!
Explanation:
It is the only biome that has an average winter temperature of -26 degrees Celsius, gets 12-20 inches of rain per year, and has grazing caribou!
Hope this helps!
Answer:
Rusting is a chemical change while breaking down of ricks may just be due to mechanical weathering of rocks
Explanation:
Rusting is a chemical reaction. Rust refers to hydrated iron III oxide. This substance is soft and flakes easily hence making the iron soft and brittle. The entire process of rusting is an electrochemical reaction set up with water as the electrolyte.
Mechanical weathering is the process of breaking big rocks into smaller pieces. The process usually occurs near the surface of the earth. The cool nights and hot days always cause rocks to expand and contract. This movement can cause rocks to crack and break apart. The entire process is a physical process.
Hence rusting makes iron brittle and flake by a chemical process while mechanical weathering break rocks in pieces by a physical process.
