Some students observe four different lab investigations. The students record their observations in a table. Investigation
Observations
1
A beaker of water is
heated on a hot plate. Bubbles form in
the water, and steam is given off.
2
Oil is added to a beaker of water. Oil forms a layer on top
of the water
3
Sand and iron filings are mixed in a beaker. A magnet is
then used to separate the iron filings from the sand.
4
A piece of chalk is placed in a beaker of vinegar Bubbles
form as a gas is given off.
Which investigation most likely involved a chemical reaction?

Number 4 is an example of a chemical reaction

Explanation:

heThe chalk is reacting with the vingear which is creating a new substance. The new substance is the gas that the reaction gives off.

h let me think

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.